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  • Vorshlag 2006 C6 - PROJECT NEW BALANCE

    Project Introduction - March 26th, 2021: We just bought a 2006 Corvette for Amy to use to at autocross, on track, and on the street. This will be a rules-free build that will be done on a "normal" budget, with an emphasis on both streetability and great on-track manners. While this car might see some use in autocross or time trial, it will NOT be built strictly for those purposes or around any given rule set. Just a "fun buggy" that serves as a back-up car for when our main race cars are down that can actually be driven to events.



    And here it is in all of its 16 year old, used car glory! This is a "narrow body" base model C6, with a 6-speed manual and 45K miles that we bought for $20K. It is bone stock and overall in 98% perfect shape mechanically and about 95% perfect visually. A squeak under hood, a few scratches, and the wheels have some road rash - all things that are easy to fix/replace with parts we had planned.



    Now many of you reading this are likely wondering - why wouldn't we buy a widebody Z06 or Grans Sport if you wanted to get a C6 Corvette for performance use?!? It came down to two things: First was cost. I looked at comparable mileage C6 Grand Sports were more than double ($43K+) and low mileage C6 Z06 cars were higher still ($50K+). I found only higher mileage (usually 120K+) narrow body C6 cars for the same or more costs, and 100% of those were automatics (yuck). It was an easy purchase that we could get on track immediately.



    Second was: low stress. This C6 being a less desirable "narrow body" means we won't be as inclined to "go crazy" and build some wild race car (plus I already have an all carbon widebody C6 Z06 in storage, waiting for a complete build, above). As a relatively low value C6 we won't stress out if it gets a scratch or a tiny bit of cosmetic damage. I try to explain further why we went this route below...

    HISTORY, MODEST GOALS & BUDGET

    Vorshlag started out 16 years ago developing parts for the most flawed cars, and our unofficial motto was "We make your car SUCK LESS." The more terrible the OEM suspension, the more improvement we could offer! Most sporty car models then (as now) were built with McPherson strut suspensions, soft spring rates, inadequate roll stiffness, skinny wheels and tires, and all sorts of other performance compromises.

    This is where we started.... strut suspension cars

    We started out with BMWs and Subarus as the primary targets of our parts development, and that method of attacking the "low hanging fruit" has paid off for the business. I am glad we went that direction, instead of chasing true sports cars that came with MUCH better stock suspension options. And in extreme cases we even swapped in LS engines, which I first stared doing in 2002.

    Cars with terrible suspension are easy to make big improvements on!

    But the year before we started Vorshlag (2004), Amy walked into a GM dealership to look at the then brand new C6 Corvette. This was just days after the new generation Corvette hit the streets, and it was a radical departure from the C5 generation before it (which neither of us liked, since the C5 is the Corvette with Four Asses). She saw a new C6, fell in love, and custom ordered a 2005 Corvette Z51 6-speed in silver. It arrived a few weeks later. It came from the factory with decently wide wheels, world class suspension, and LS2 power - with a 186 mph top speed in stock form.

    This was our 2005 C6 Corvette Z51 - which we ordered new in 2004

    This was her first new car purchase and it was just an amazing car, which she loved. We both autocrossed it a few times (after several years away from that sport) but mostly she drove it to work and loved every minute of it. I hooned it a bit... took it to Houston Raceway Park and ran the 1/4 mile (12.8@112), weighed it on a scale, dyno'd it (355 whp). The wheel offsets needed proved to be a challenge so I bought some 17x11" C4 ZR1 rears and we ran 315/35/17 Hoosiers, which poked like crazy!

    We sold our 2005 Z51 to help pay for a new home + shop, to concentrate on starting Vorshlag in 2005

    But in 2005 when we had just started Vorshlag and had some tough choices to make. Keep a relatively expensive new car / note ($45K) while building an expensive new home with giant attached shop (which we ran Vorshlag out of from 2006-11)? A car we would have trouble applying our Vorshlag fixes to? It did not help the business, and it was a tough choice, but we sold it after 1 year - to a dealer, who paid us sticker price - because NOBODY could get C6 models at the time, and our rare Z51 6-speed no option car was SUPER rare at the time (90% of early C6 models are automatics).

    My main track car (S550 Mustang) was sold. Amy's FR-S is being LS swapped and stuck behind customer cars

    Fast forward 15 years, and after many years of having multiple track and autocross capable cars at any given time, 2020 was a bleak year for racing in the Fair household. We sold my 2018 Mustang (above left) in August 2019 to move onto a more serious S550 race car build, but that stalled out with manpower limitations in our shop and a customer car build backlog. Likewise Amy's 2013 FR-S (above right) was pulled from racing duty in late 2018, but the LS swap work on that car stalled out for the same reasons. So Amy and I haven't raced anywhere in our own cars going on two years! Neither of us like borrowing cars either. We're both going stir crazy NOT competing track or autocross events.

    I have been bumming co-drives for a year in a friend's C5 we used for development

    At an event at Eagles Canyon Raceway a week ago (above), Amy was lamenting our "stalled out" race car builds and declared - "It is time to buy another car, that runs, that I can race RIGHT MEOW." We puzzled over a few ideas while in the drivers lounge with some friends, and Jason here at Vorshlag mentioned this 2006 Corvette he had for sale... Yadda, yadda, yadda.... she bought it!

    Of course, every car we buy for the business has to "earn its keep" here at Vorshlag. 16 years after starting Vorshlag and we are indeed developing parts for more than just "Crappy McStrut" suspension cars. We have even had some success with our products developed for the C5 platform, among other non-strut cars.



    For this narrow body C6 have a small budget for this one, and overall build will be fairly mild - we want to keep this a 100% street legal, nice driving car *that is also track capable* and quick. Goals do NOT include TT track records or some SCCA obscure autocross class rules - just an all around "fun buggy" that she can run "where it fits".



    While Vorshlag is not known as a "Corvette Shop", we still make a number of unique parts for some Corvette models and have worked on a number of C4, C5, C6, and C7 Corvettes over the years (and I have personally owned 5 Corvettes - two C4s and three C6s). For this narrow body C6 there are a number of areas we can improve with our part solutions - which we will prove with track testing, data, and product development.



    Initial plans for this car include the usual Vorshlag upgrades: custom wheels and wide 200TW tires, MCS non-remote coilovers, G-LOC pads on fresh Z51 rotors, adjustable swaybars, maybe seats, and of course a number of new C6 specific "track products" from Vorshlag. We will share the development of the car and these parts in this forum build thread, of course.

    I have driven numerous C4, C5, C6 and C7 Corvettes at Motorsport Ranch on their 1.7 mile CCW course

    Will get a baseline lap in stock form at two race tracks: MSR Cresson and/or ECR. Having driven 500+ laps at MSR in dozens of cars and 1000 laps at ECR (on the old 2.9 mile layout), with dozens of wins and class track records in Time Trial at both locals, these tracks will be best suited for our initial and continued testing on this C6.



    Baseline laps will be done with just with fresh Motul RBF600 brake fluid and stainless brake lines (which the C6 already has). We will go back after each major round of parts changes to chronicle any lap time gains or losses. To help with this testing we purchased a membership at Motorsport Ranch and a membership at Eagles Canyon is coming shortly.

    FIRST INSPECTION & WEIGHING

    On March 25th, 2021 we put the new C6 on the lift for the first time to take a look at the car more closely. Brad wiggled all of the bushings, wheel bearings, noted any leaks or issues. First things we noticed that needed replacement: idler tensioner pulley, engine mounts, oil pan has a slight leak, hood lift struts were shot, and I wanted to do a full oil & filter replacement. We will also swap in fresh plugs (NGK TR6), plug wires (Taylor 10mm), and plug wire heat boots (DEI).

    We also, of course, got an initial weight. And it was a pleasant surprise, and a relief after dealing with 3600 pound pony cars for the last fee years.



    Ideally I like to weigh a car with the fuel tank as empty as possible. This makes it is easier to compare car-to-car weights. Why empty and not full? Because we almost NEVER autocross or track a car on a full tank, but have done those events with low fuel levels (There is no such thing as "good ballast weight"). We run the least amount of fuel needed for the session and/or to prevent fuel starvation. But this one had 5/8ths of a tank when we bought it, and we didn't have a lift clear for very long so we took the weight we could get.

    Now my memory of our 2005 Z51's weight was 3148 lbs, which I weighed at a drag strip in 2005 - but that was 16+ years ago, before we really started Vorshlag, before we owned our own digital scales, and before I began documenting EVERY weight on EVERY car we owned or worked on. Plus, that 2005 Z51 had bigger brakes and wheels than this 2006 "base" car, so maybe that makes up for some of the weight difference? Or maybe my memory isn't 100%...

    continued below
    Terry Fair - www.vorshlag.com
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

  • #2
    continued from above

    WHEEL MEASUREMENT SESSION

    Wheels on this BASE model C6 are pretty narrow: 18x8.5" ET55 fronts and 19x10" ET79 rears. This is what we used to jokingly call the "drag pack" wheels for Corvettes back in the day, and why when we custom ordered Amy's 2005 C6 we made sure to get the Z51 package - which has wider wheels and bigger brakes, among other tweaks. Virtually all modern (C4+) Corvettes come with narrower front wheels and tires than the rear, to ensure "safe" handling - meaning UNDERSTEER. Lawyers are why most cars handle poorly, but that is an easy fix for us!



    There are numerous 18x10" wheels out there that fit this car with a "Square" setup (same width front and rear), and even some 18x10.5" has been done. But our goal here was to measure a narrow body C6 for MAX FITMENT wheels. So Jason and I measured the car, using the stock wheels to go by, and our proven techniques to see what is the theoretical maximum wheel and tire widths on both ends. Then calculated the offsets and put a wheel order together.



    What wheel brand and model will we use? What widths and offsets? Stay tuned and we will show you soon, after a set of custom 3-piece wheels arrive. That's right - this will not be another "Forgestar F14" wheel set for one of our cars, as none of their one piece, flow formed wheels can be built to the offsets needed to fit this car's fender limits. This is with another wheel brand we've been quietly working with, and I want to show off their work. It will likely be the most extravagant purchase for this entire project, but WHEELS MAKE THE BUILD.



    We will make some suspension tweaks to be able to fit these but we WILL NOT be adding the C6 "widebody" fenders to clear bigger tires. Why? Well, after a lively debate internally, we concluded that converting a narrow C6 to the OEM widebody fenders takes a LOT of time and money - which could be better spent on the 3 other shop owned race car builds, not to mention the many customer builds that are demanding all of the hours we can throw at them to be completed.



    And yes, the widebody C6 is my favorite car GM has ever built, so this was not an easy decision to stay narrow body. The wider C6 cars - Z06. Grand Sport, ZR1 - can fit SO much tire under the stock fenders! (see above) But again, our narrow C6 build will be pretty limited on scope and quick to complete, minimizing shop hours and costs. The narrow body C6 is also extremely undervalued and under appreciated in the (still flaming hot) used car market - we aim to see how far we can push one of these, on a budget.

    C6 BRAKE OPTIONS AND UPGRADE PATH?

    I learned a good bit from some recent research, including from this Corvette Forum post. The base C6 non Z51 has the JL9 brakes. The J55 brakes are on the Z51 and later model year F55 option C6. The J56 brakes are the option on both the Z06 and Grand Sport models.J57 is the carbon ceramic brake package on the ZR1 and Z07 Z06 models.
    • JL9 - Front 325mm/12.8"; Rear 305mm/12" (base model)
    • J55 - Front 340mm/13.4"; Rear 330mm/13" (Z51 model)
    • J56 - Front 355mm/14"; Rear 340mm/13.4" (Z06 and GS)
    • J57 - Front 394mm/15.5"; Rear 380mm/15" (ZR1 and Z06/Z07)
    Apparently the front calipers are exactly the same for both the JL9 and J55. The rear calipers of the J55/Z51 have slightly smaller pistons than a rear JL9 caliper in order to maintain the correct front/rear hydraulic bias with the larger rotors of the Z51. Most likely we will convert our base JL9 brakes to the larger Z51 brakes, which is very cost effective.



    All model C6 Corvettes have factory front and rear brake ducting, and I will show more of this in future updates. Amy's JL9 rear brakes (above left) are incredibly small and instead of spending hundreds of dollars on track brake pads for these we will upgrade the rotors and calipers to the similar but larger J55 from the Z51. I will show costs for each mod done to this car and the J55 brake upgrade and refresh will be one of the most affordable upgrades. Going to the J56 brakes (above right) would cost more than 5x as much.

    RELIABILITY MODS

    We want to be able to drive this car to local events. Nothing sucks worse than driving to the track and having something break, with no truck/trailer to bring you home. To proactively prevent some of this drama we will do a number of upgrades to make this car ultra reliable and bulletproof. Two of the things that come to mind are cooling and oil control. With the higher temps we see in Texas and the higher grip we will see with "tires that start with a 3" we are pushing the stock cooling and oil pan beyond their capabilities.

    The factory C6 radiator is a tiny little thing with plastic end tanks, and at 16 years old things are probably starting to get brittle. I know we will tax the limits of the stock cooling system in the Texas summer months, even with a bone stock 6.0L LS2 engine. We will replace the radiator soon with something like this massive DeWitt Pro Series aluminum radiator (below left). They make drop-in replacements that massively improve cooling capacity and efficiency. That is the unit Koenig's C5 has now and it is ROCK SOLID reliable. We recently ran his car at an "autocross" that was actually held on a road course, and with two drivers making 10+ runs back to back, never shutting off for nearly 90 minutes... it sat at 205°F all day (the thermostat opening).



    The other big thing we HAVE to do soon is an Improved Racing oil pan baffle / crank scraper, shown above. Any LS engine has pretty poor oil drain back onto the spinning crank, which turns the oil to foam and burns it under hard use. High G lateral and braking can also slosh oil away from the pump's pickup.

    This car has a "wet sump" LS2 engine - but these can and do last on track IF you keep the oil pick-up submerged in liquid oil at all times (a dry sump isn't "required" for track use, like some people like to insist). A better oil pan baffle is usually all you need, and of course, keeping an eye on the oil level after every track session. The oil pan gasket seems to be leaking on this car right now, so dropping the pan to fix that was already on the list. Adding the baffle isn't much more work when you have the oil pan off.



    We also want to keep an eye on the oil temps. Going to an external oil cooler (like this Derale 10000 series below left, on a customer's endurance CTS-V) would give me a good excuse to replace the "thimble sized" oil filter that all LS engines are stuck with (above right). If we do an oil cooler we will also add an external oil filter with a thermostatic bypass (below right, Improved Racing unit we like to put on lots of cars). That let's us move to a MUCH larger and more effective oil filter.



    We won't jump off into that set of modifications unless the oil temps noted during track driving push us over safe levels (275-300°F max temp is about the limit I go by for reliable oil system use).

    WHAT'S NEXT?

    I have started cleaning things and ordering parts, and of course our new fashion needs. That is enough for an intro post.



    We will setup a time at a local shop to get a baseline wheel dyno test, then at MSR-C to get the baseline laps in on these stock 245/275 all seasons. Then we will write another post after the video and dyno charts plus the initial suspension bits, wheels and tires, and other changes in store.

    Thanks for reading,
    Last edited by Fair!; 04-30-2021, 07:20 AM.
    Terry Fair - www.vorshlag.com
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

    Comment


    • #3
      Project Update for May 4, 2021: It has been about a month since this project began and we have already completed the first two track tests and done one round of mods, with a load of parts ordered for rounds 2 and 3 to follow.



      The C6 was pretty slow on track in bone stock form, and we weren't back at the shop five minutes from that event before we ordered the brake pads and three sets of wheels! One set of wheels was a mistake, but all of these sets do now have a purpose. Let's dive into the work we've done in the past 4 weeks.

      REPAIR & MAINTENANCE WORK

      Any 16 year old car - even one with low miles like this one - is going to need to need some maintenance over the years. The last owner deferred a few things, which is fine - we inspected the car thoroughly at the shop before we bought it, and knew all of that. It wasn't much and we chased down a few parts to get this C6 whipped back into shape.

      FIX THE SQUEAK + ENGINE BAY DETAIL



      There was a squeaking pulley bearing under the hood, so we bought what we thought was the likely culprit - the main serpentine belt tensioner. The hood struts were blown so those were ordered and quickly installed. I also ordered some new NGK spark plugs, Taylor 409 series plug wires, and an oil pan gasket - but we haven't installed these last 3 bits yet. You might see my new jean shorts (jorts) in the pile of parts (above right) - its called fashion!



      Brad replaced the tensioner replacement and hood struts, then I detailed the engine bay after hours. It was just dirty, nothing too nasty in there, and soap and water plus some brushes and water got it all clean - then I got it all shined up with my underhood detail tricks. I have left the LS2 "coil covers" on the engine for now, just to show how stock it still is. The coolant reservoir is a little dingy so I ordered one of those new, which we will install with the full round of radiator upgrades.

      OIL & FILTER + BRAKE FLUID FLUSH

      Driving on track with a purpose means you are pushing the engine beyond the loads seen in a normal daily commute. And this base model has no oil cooler, which might prove to be an issue long term. As such, we didn't skimp on the new oil - Motul 5W50 Ester based synthetic does the trick.



      This particular mix from Motul only comes in this weight, but for the hot and cold weather we see in Texas it works well - and I have used this exact oil on multiple cars and engine platforms. As for the filter, the Wix XP will do just fine.



      This base model C6 doesn't even have much of a power steering cooler - just the "loop cooler" shown above - so we will wrap the power steering cap with a rag and zip tie to catch any fluid that might get by the cap when it first goes on track. We do this on all hydraulic power steering systems, especially on GM cars (which tend to suffer from fluid spillover at track speeds). Turns out that was a good idea, as this was the one fluid that did spew out at both track events (see top right pic) - that was a freshly detailed engine bay so all of the "shiny sports" were power steering fluid. We will flush and add synthetic fluids here and might be adding a real power steering cooler as well.



      The brakes... this was a dilemma. Do we preemptively change to proper track pads or complete the first track test on these "street" pads? Jason said he had installed "the cheapest parts store pads" recently, and they were at full pad depth when we checked. I wanted to get the car on track ASAP for the baseline stock laps, so we left the stock rotors and pads in place and Brad just flushed the (black!) brake fluid for Motul RBF600 (these pads were horrible - this was a mistake).

      REMOVE FRONT LICENSE PLATE

      This is not something meaningful to maintenance or performance, just a styling thing that is is a personal pet peeve of mine. Removing the front license plate is a technical violation of state law here. But this is just a "paperwork violation", and no harm comes to any human being in any way by not running a front plate. Only 31 of the 50 US states require this, so it is not even a consistent law across this country. When I get pulled over for this I will tell the cop I identify as a Louisiana resident! (where it is not required).



      After removing the front plate I assumed there would be two ugly holes in the painted front bumper cover, like there is on most cars fitted with a factory front license plate bracket...



      I was glad to be wrong! There is just some "sticky goo" that was holding the vertical portion in place, and even after 16 years of use it was able to be removed and there wasn't a single scratch on the paint! Way to go GM - one pleasant surprise about this factory front plate bracket. I am an outlaw now, woo! Stay tuned for my 31 state crime spree and impending jail time.

      SEAT TESTING & INTERIOR DETAIL

      At first glance you might look at this car and think, "Sure, those look like sporty, supportive seats." Let me assure you, they are not. This is one of the least supportive seats in any modern sports car I've ever driven on track. The C7 had optional Competition seats that are crazy good, as does the C8, but the C6 generation on back had pretty much "good enough for grandpa" grand touring seats that should be replaced on any seriously tracked Corvette.



      That was the biggest difference when I drove these two cars below - the C6 Z06 had the slightly more sporty versions of the base C6 seats above, whereas the C7 Grand Sport had the amazing, optional C7 Competition seats.



      With both cars on the exact same tires (285/335 Michelin PSS), both driven the same day, and by the same driver (me) - the C7 GS was a full second quicker. And honestly, part of that was the seats.



      It was MUCH easier to drive hard around corners in the optional Competition Sport Seats in the C7 GS. Those seats held me in so much better compared to the C6Z seats, which felt like I was gonna fly outta the damn window. REALLY have to exert a lot of upper body strength and concentration into "holding your body in place" in sub-par seats. The C6 has no such option like the C7 and C8 models do.



      If you have followed any of my Forum Build Threads over the last 20 years, one of my common themes is - I always put fixed back racing seats (and usually at least a 4-point roll bar and harnesses) in every car that I track and/or autocross seriously. Even budget builds, like our GRM $2010 Challenge winning E30 (above right). Part of this is the safety aspect, sure, but mostly it is done as a driver comfort and control upgrade. Having done seat installs for 100+ customers over the last 16 years at Vorshlag, the universal response after the first time they get used on track is, "Wow! I wish I would have done this seat upgrade sooner!" It is a huge change, and is worth actual lap time. Not to mention a way to fend off back & muscle ache after a long session on track.



      Here are two different stock C6 seats we weighed. The power driver's seat from our 2006 is remarkably light at 45.6 pounds (we have weighed many in the 70-80 pound range). It also has power fore-aft and height adjustment, not to mention the tilting backs like all OEM seats. We then weighed a manual adjust seat from the passenger side of my 2007 C6 Z06 (that chassis is in storage) at 40.1 pounds. Also very light, and you can barely see the deeper side bolsters on these seats - which is still not NEARLY enough support. Plus these have no shoulder harness pass-thrus or a anti-sub strap pass-thru, for use with 5/6/7 point harnesses.



      We had Koenig's C5 in the shop altering his Sparco EVO II US seat placement with our prototype C5/C6 seat bracket bases, so we pulled the driver's side out, weighed it and put it into the C6. At 41.0 pounds (with our seat base, side brackets, lap and anti-sub belts, and Sparco EVO II US seat) it would work, but the "step-over" of the lower leg bolsters on these seats is pretty high, and of course there is no seat back tilt function. It was still a bit tall for me at the layback angle for the seat we needed for Koenig to fit his C5 well, and this limitation would definitely affect the seating position needed between Amy's (5'6") driving position and mine (6'3") in the C6. Fixed back seats are also a pain to use every day in a real street car, and often make it hard (or impossible) to use the OEM 3-point retracting seat belts, depending on the seat's lower design aspects.



      After having driven stock C6 seats on track I knew how bad they were, so before we even took the car on track we started to look at some better Tilt Back seats, including several aftermarket versions we had on hand. The first one tested was this Sparco R333 "tuner" tilt back seat, above right. This one fits Amy's torso length well but not mine - it puts the shoulder pass-thrus several inches below the tops of my shoulders, which would compress my spine in a crash with real 6-point shoulder harnesses. That seat choice was right out.



      Next we tried this Corbeau RBR tilt back seat we used to keep in our lobby. We have an older (2015) version of this seat on hand but the basic dimensions haven't changed. The side bolsters for the base (legs) and back (torso) are MUCH deeper than any OEM C6 seat. This is a steel framed / bottom mount seat (like OEMs) that comes in around 25.6 pounds. We put this old, dusty seat in the C6 to test how it fit me and Amy both.



      Having driven with this RBR seat on track I know it works well for that use, even with just a 3-point belt - but it works even better with real harnesses. This one fit in the C6 very well, and as you can see (above right) the shoulder harness slots are above my shoulders, so it will work safely for taller torso heights. Amy noted that they are a little harder to get into/out of with the deep bolsters on the base. But they ARE setup for 5/6/7 point harnesses so it us still a solid choice for a dual purpose street/track car. The one down side - you cannot lean the seat forward past vertical, due to the side bolsters from the seat back and base running into each other - so if you need to get into a back seat, you really can't with these seats.



      After she asked for another seat option I looked up and found this newer Corbeau RRS seat, shown above. This is essentially the same seat as the RBR on the torso section (the updated should harness pass-thrus look remarkably like the C7 sport seats now, and the current RBR has the same update) but with a more OEM like lower base section. The lower won't hold your legs in as well on its own, but will still allow a 5/6/7 point racing harness to be used, which can really holds your body in place when driving on track. It was a compromise seat that will be more friendly to street use (easier ingress/egress), so after Amy picked the material / style she liked and added the optional seat heater on the driver's seat, we ordered the pair. When you are old and/or have back problems, these seat heaters are a real life saver, trust me!



      Whenever we have seats out of any street car we vacuum the carpets, and this was a good time to shampoo them as well. Tons of stuff was found underneath both, and the passenger side carpet had coffee spills that turned the hot water in our carpet shampooin'g vacuum brown. After a few passes with the hot water spray and vacuum, the carpets were clean and it smells like new inside now. We left the car open with a fan blowing on it all night to dry and then Brad put the stock seats back in. The Corbeau RRS seats shown above had a 4-5 week lead time (they just shipped, so almost exactly on time). Will show that install next time, along with a new seat base we will make for these bottom mount seats.

      FANCY FLOOR MATS

      This was a barely needed maintenance / interior upgrade, and might seem a silly thing to even list in this "build". It was just that the $9 parts store floor mats that came in this car were SAD. I found these "officially licensed by GM" mats online for a decent price and took a gamble...



      These Lloyd's Mats are actually very well made, and these were a perfect fit for our C6. I've since found out you can custom order from their website in a number of different colors, 4 carpet thicknesses, with tons of options and embroidery patterns to choose from.



      The black of these mats matches better than the pictures above would seem - it was a photo exposure thing - but I'm very happy with the result. Of course we remove the driver's side floor mat before it is driven on track, even with the OEM "hook mounts" engaged. Don't need a mat slipping under a gas pedal or something like that on track.

      continued below
      Terry Fair - www.vorshlag.com
      2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
      EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

      Comment


      • #4
        continued from above

        TRACK TEST #1 APRIL 9, 2021 - STOCK BASELINE

        With the initial maintenance items handled, some proper oil and brake fluid in the car, and with the C6 in otherwise sad stock form it was time to go to the track to get our Stock Baseline Laps in. This is the target lap we will try to improve on with this build. We utilized Motorsport Ranch in Cresson TX for this round of testing on a member day when they ran the 1.7 mile course in the CCW direction.

        Event Gallery: https://vorshlag.smugmug.com/Racing-...mys-C6-040921/

        I was hoping to get some laps in at ECR on the same stock configuration but our membership there might be delayed a bit. So we will use the MSR 1.7CCW to do all of our testing, for now. As I explain below in more detail I have over 500 laps on this layout over the past 2 decades and it works well as a test track, due to the layout, length, consistent surface condition, and my familiarity with this course.



        Amy and I left for the track around 6:30 am and got there just after 8, with fairly light traffic for a Friday morning. We quickly unloaded the C6 then... realized we had outdated schedule info on when the first cars would go out on track. So we took the time waiting for the track to open to get two cameras installed, the AiM lap timer, then checking fluids and tire pressures. We went out with 31F/30R psi cold pressures - which turned out to be WAY too high.



        We were there the same time as a lot of track friends with much cooler cars. I only barely remember seeing any of these cars out there when we were, as we had our hands full trying to keep this C6 on track while fighting brake fade and of course the REALLY poor stock seats (which were worse than I remembered).



        We went out a bit early in the "8:30 am" sports car session and spent 34 minutes straight driving this car, swapping drivers on pit lane. We had some real concerns - with the brake pads overheating and the oil temps touched 275°F - but we were really watching oil pressure. The digital gauges on the C6 can only show one thing at a time, and while Amy was driving I was looking at that number closely under braking and in corners (by the next test I had enabled the CAN data to log this). I never saw oil pressure dip under 40 psi.



        Click the image above to see the best lap on YouTube. Amy happened to be riding along on that, and I explain why below. Made for some hilarious in-car commentary! She was not having fun riding with me, but she took 6 hot laps when she drove (she is never a good "passenger" on track!) Our AiM DL was only setup to get the basic OBDII data - tachometer, Throttle Position Sensor, and a few other useless things (I had CAN data logging enabled for Track Test #2) plus the g-meter and GPS from onboard the AiM.



        I went out alone for the first stint and the stock brake pads were VERY unhappy, and the 245/275mm all seasons were howling around every corner. I could overheat the brake pads pretty easily, so I had to baby them to get them to cool back down. So I adjusted my driving to not use as much braking - definitely an area we can improve upon for test #2. In my first stint I ran two 1:29.93 laps followed by a 1:29.67, a bit frustrating and very very slow. Amy ran 6 hard laps with me coaching and was finding time - but the brakes were not giving her any confidence. Then we hot swapped for 2 more hot laps with me driving and Amy riding right seat. Bleeding tire pressures down allowed me to drop a solid second from my first stint to a dismal 1:28.743 best lap.



        We tested a new video camera along with the trusty Sony HDR-MV1, and the RoadKeeper dual 1080P vidcam was a roaring success. I will cover more of this in a review next time, but after 2 track events using it I am very happy with the video quality and the dual cameras is a nice feature. There are some quirks and cons, of course, but I will go over those in the review in my next Forum Build Thread Update.

        I was only watching the oil pressure gauge while on track, as scrolling through two screens to see TPMS data is impossible. We stopped to check then bleed down the tire pressures after my first stint. Amy said the fronts and rears were at 45 psi after I came in! I had her bleed those down to 34F/33R psi for her stint, and we bled them down again at the next driver change - when I drove and she rode shotgun with me. Having tire pressures in the right range made a noticeable difference in grip, allowing me to drop nearly a full second in my last stint, even carrying a passenger.



        Those lap times are painfully slow (you can see how they ranked in my "lap list" at the bottom of this post). Sure, both of our driving was pretty rusty, but I felt the rust "breaking loose" on my second stint. My last time on track was here in January of 2020. Amy's last time on track here was in 2018, and she never got into a good groove - when she's comfortable in the same car she's usually in the same second as me (and has NASA TT wins of her own). I tried to get her to go out again in a later session, but there was going to be an hour of waiting (open wheel cars and motorcycles each had 30 min sessions) and she was ready to go. The ineffective brake pads were just not confidence inspiring AT ALL, and I don't blame her. I sure didn't want to drive it like this any more!



        The stopping performance on the random parts store pads was just BAD - two half-serious stops in a row would overheat them. As we swapped drivers in the pits there was smoke POURING off the front brakes (from the lack of airflow while stopped - they heat up). Next lap out the pedal would go to the floor on the first stop, so we had to make cool down laps at both the end and beginning of each stint.

        REPAIRS AND UPGRADES - ROUND #1 MODS

        Looking at the front tires after this event, I am surprised they weren't just shredded on the shoulders, as much as these things were howling and understeering badly. Turns out when you have rock hard 500 treadwear tires, they don't wear super fast. They also didn't make much grip!



        This car had a mix Goodyear, Hankook and Michelin tires when we bought it, with that 30mm spread in front to rear widths (245/275) - which contributed to the serious understeer the car had (per the GM design - to make it safely understeer for the "lowest common denominator" random Corvette buyers). We needed something better - and now.

        INTERIM WHEEL & TIRE UPGRADE

        On previous projects where we have chronicled lap times with major mod levels along the way, we upgraded the tires and sometimes even the wheels right after the baseline stock laps. Sometimes we would add an an "interim" set of wheels and tires that are better than the stock rubber, but not quite the competition set we would end up with. Tires is the biggest early upgrade we can do to any project - as nothing is more important than tires to lap time performance. With the staggered wheel widths it was necessary to upgrade both wheel widths and tire widths. We had an "extreme fitment" set of 3-piece wheels already on order but I needed something to arrive in the next few days, as we wanted to get back out there and improve on the dismal baseline lap time ASAP!



        Unfortunately we didn't have a significant amount of experience creating wheel fitments for the narrow body C6 (we have lots of wheel experience and sales on the C4, C5, widebody C6, and C7). With a 5-6 week wait on our "real" wheels I just wanted to get something "square" - the same widths front and back - and quickly. TireRack is notoriously hard to look for non-stock wheel sizes, but we found two options that looked like they might fit - shown above. The 18x11" OZ was a bit pricey and was a "rear only" C6 fitment that might poke on the front. Instead of taking the chance on a $1400 set of 18x11s that might not fit I went went for the Flow One F4 wheel in 19x10" - also a rear only fitment - for $400 total. I ordered these minutes after returning to the shop after Track Test #1!



        Tire choice was a bit tricky as the "pandemic surge" of parts orders and shipment issues have made for a serious shortage of tire options. This reduced our choices in tires to fit these 19x10" wheels, greatly. Luckily the 275/35R19 size is not super popular in the 200 treadwear tire wars that track folks are fighting, and we got this long lasting Hankook RS-4 in that size - which I have driven on before and really liked. This compound is popular for endurance series events, as it is and not as soft (nor as fast) as the "one lap wonder" 200TW tires - A052, RE-71R, RT-660, Rival S 1.5 and the like.

        The RS-4 wears VERY well on track and this tire should allow us to still get fast laps deep into a session, without having to nurse the tires and shoot for a fast lap quickly before they overheat (like the softer 200TW options - which I treat like a Hoosier A7). There was some concern that the staggered OEM tire heights front to rear might be an issue (the old front tire and new one side by side show this), but it turned out not to be the case.



        There's always a fine line between light wheels and strength, but this flow formed 19x10" wheels weighed about what we expected them to - 21.8 pounds (pretty close to the 21.6 TireRack claims). Sure, an 18" wheel would be lighter and more than tall enough for the base JL9 brakes or just about ANY brakes we might use on this car. But wheel COST and quick AVAILABILITY were key here. These 19x10" wheels were on closeout at $124 retail (minus our shop discount), so it was a very cheap upgrade.



        Surprisingly the stock rear 19x10" wheel and 275 tire was only 1.2 pounds heavier - we normally see a bigger drop over OEM wheels than this when going to aftermarket flow formed wheels. We had TireRack mount and balance the set, but they didn't have the TPMS sensors in stock, so we just had them use normal tire valves. We wanted this set here in a few days, and they made it happen - with one small mistake.



        The math from our previous wheel measuring session (covered in my last post) showed this 19x10" would fit within the envelope Jason had designed on the front, but we still held our breath as they went on. They cleared at full steering lock in both directions and had #NoPoke at both ends. Surprisingly the stock rubber front control arm bushings are so sloppy that when backing up (reverse) at full lock the tires DO rub, ever so slightly. We will address those bushings and their gross deflection in a future round of mods.

        TRACK PAD UPGRADE

        So this is going on a bit of a tangent, but for a purpose. If you have ever ridden with me in an autocross or on track, one thing might jump out at you - I push the tires hard, trying to keep them loaded on the edge of their Friction Circle at all times. As such I tend to brake LATE and HARD, then get the turning phase of the turn going, and start adding throttle as soon as possible (at or before the corner's apex). I never EVER coast - I'm on the gas or brakes at some point at all times, and I always Left Foot Brake if there is no downshift needed for a corner. To me, coasting is the greatest sin when driving on track. When I am right seat coaching someone trying to find lap time, this is where we tend to find the biggest gains - by reducing any time spent coasting. This might not be how you drive, but it is how I do it, and it has worked for me.



        I also transition from gas to brake after a straightaway very quickly (sometimes even abruptly) when entering a corner, then transition to trail braking, then get off the brakes as soon as possible and start feeding throttle. To some, that means I "abuse the brakes". And yes, to those that like to tip-toe and gently squeeze pedals, it seems abrupt - but my driving style (and the way I was taught) was to always keep the tire loaded. "Smooth is Fast" might be your motto, but "Coasting Is Death" is mine. When driving the same car with others and comparing data, I often extract more braking g forces, and sometimes touch the ABS limit on many cars. Nobody can say I am coasting or under-utilizing the brakes.

        Could I drive faster? Sure, I'm not naive - there's always someone that can eek out more time. But after three decades of Time Trial competition, with thousands of laps data logged and analyzed, I've found that pushing the braking as late as possible is some worth lap time, for me, rather than just lifting / coasting or "easing into" the brakes. A good ABS system can cover up any abruptness on the middle pedal, and the tenths gained in braking zones can add up. I have passed a lot of lighter cars under braking after high speed straights, like into T1 or T12 at COTA.



        This long tangent was written because - some people don't "understand" the brake system problems that we have uncovered when I push a car 10/10ths on track. Comments like "These Hawk HP+ brake pads work fine for me!" online are always followed by my question of "yea.... but what are your lap times?" Because driving slowly won't tax the brake system like driving faster will. My point in all of these back-and-forth comments is that NOT EVERYONE USES THE FULL CAPACITY OF THE BRAKES ON THEIR CAR when driving on track. So my driving style tends to use all of the brakes, and can quickly find weaknesses.



        We looked at the C6's brakes before Track Test #1 and they looked fine. Rando parts store pads but at full depth, and the PFC twin piston front calipers looked fine, just needed a flush. After 12 hot laps at MSR in Test #1 (which is a track not known to be hard on brakes) the pads were shot and the front caliper's dust boots had caught fire and mostly burned away (hence the smoke). This isn't alarming or unexpected - I've used to PFC calipers on cars going back to the 1990s, and these dust seals are not what seals the pistons from the fluid. Real race calipers don't even have dust seals.



        While the stopping power of the parts store pads was hilariously bad (as expected), we had planned on getting proper G-LOC track pads after the first test event. I wanted to drive the car first on the stock pads to see what race compounds we needed. Danny at G-LOC rushed built and shipped us a set of R12 fronts and R10 rears. As you can see above, the previously new front pads were 2/3rds worn out in just 12 hot laps. I was pressing the pedal will all of my strength on some stops - but they just don't have the friction capability when hot like real track pads do.



        We staggered the pads one step in compound front to rear - using a harder R12 up front to the slightly less aggressive R10 on the rears. This is a normal technique we do for all manner of cars, based on how weight transfer naturally forces more braking abuse to front brakes versus rears. Now I normally run even more aggressive R16 front and R12 rears (which is also one step front-to-back) on most cars, but I was worried that the more aggressive R16 might be too much for the notoriously finicky Antilock Brake System programming we have noted on dozens of other GM cars. Turns out even these milder pad selections were still too much for that GM ABS...

        TRACK TEST #2 APRIL 18, 2021

        This was our first track test after our first real "performance modifications" to this base model C6 - the stickier tires on wider wheels plus the track worthy brake pads. We had wanted to get a performance alignment before this test but the timing didn't work out. This time Amy and I went out on a Sunday, which was also a member day at MSR on the 1.7 CCW course. The weather was perfect and we had a lot of fun that day getting our laps in.

        Event Gallery: https://vorshlag.smugmug.com/Racing-...Test-2-041821/

        We towed the car in the trailer again - we almost drove it out, but we managed to load the car in under 15 minutes and the truck & trailer is good peace of mind. I drag a lot of tools and electronics out to these events and didn't want to leave something behind by driving the car out. Turns out I left the Canon DSLR camera, so we got no "on track" pics other than cell phone shots.

        continued below
        Terry Fair - www.vorshlag.com
        2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
        EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

        Comment


        • #5
          continued from above

          Since this was a Sunday and we had seen so much traffic on track at the last member day we aimed to get there around 11:30, hoping to get on track before the 12:30 lunch break. Which almost happened, but we got out on track at 12:30-1 pm and again in another session at 2:00-2:30 pm. Between Amy and I we made 23 hot laps this time, without any brake overheating issues. Now we still had brake problems, but that was all a rear lockup situation. That ABS was wigging out any time either of us braked over 1.0 g.



          We saw accelerometer data of around 1.15g (both lateral and braking gs) but the rear tires would lock up quickly in stops over 1.0g, then the car tried to swap ends. Amy (a much smoother driver than me) saw the same issues, so we both had to dial back our braking considerably, especially when compared to other cars we have tracked in the past. Now we might have a sticky caliper piston, or some other mechanical issue - so we are preemptively changing ALL of the calipers and rotors in the next round of mods. I have felt Ice Mode / ABS issues on virtually every GM car I have ever driven on track, including multiple C4/5/6 Corvettes and 5th gen Camaros, so it might just be this issue.



          The video above has more data channels from the CAN data stream, logged via the AiM Solo after I properly uploaded a new firmware versions specifically for the C6. Everything worked except the Steering Wheel Position Sensor. In fact this sensor often breaks on many C5 and C6 cars, so we think this happened - we got a "Service Active Handling" fault at both events. As always drove with both the traction control and active handling control systems turned off, as it is faster on virtually every OEM car than leaving the electronic nannies on.



          We met our friend Jerry out at the track and I chased him for a bit in his C7 Z06, but he was several seconds a lap faster, so I didn't chase him long. It was supposed to rain all day but didn't, and the 63°F ambient temp was perfect. We even saw rainbows in the clouds.



          This time we stuck around longer and drove in 2 different track sessions. My first stint was just 2 laps, to scrub the brand new tires and get them up to temp, and I quickly came in to let Amy bleed the tires down to 33F/31R hot. The understeer was still there but not as pronounced as on the 245/275 All Seasons. There was a LOT of traffic and I was one of the slower folks on track, so I had a lot of aborted fast laps to get out of people's way - and of course a few close calls where the rear tires locked into the big braking zones (T3 and T9 - see track map below). In my second stint in session 1 I made 5 laps and managed a 1:26.428. Then we swapped Amy in for 4 hot laps where I coached.

          We had an hour to kill before our next session where we could go out and we relaxed a bit and Amy and I talked about her comfort level in the car. We made some seat position changes before going out again. Traffic was much lower in session 2 and I went out for an 8 lap stint, running two other 1.26.9 laps back to back. I had a high 1:25 lap on predictive timing while chasing Jerry's C7Z, but a 1.1g stop into T3 nearly sent me off track backwards, so I reset and went for one last blast the next lap - finding another couple of tenths with a 1:26.248 best.

          Amy then went out next for a 5 lap stint where I didn't ride with her, and she had virtually zero traffic - which helped her get into a groove where she dropped TEN seconds from her best laps back on April 9th! She came in beaming, knowing that she was much faster this time. And more importantly, she had a lot of fun - which was the point of this C6 purchase: to get some track time while our other cars are being built and to have a ball doing it.



          While the rear tire lock up issues were unnerving they were not completely unexpected. At least the G-LOC pads never got so hot that the fluid boiled and we never had a long pedal, always had good pad bite - but perhaps too much for this ABS systems. Not a huge problem, and if this persists after the next set of brake upgrades, we have another couple of ABS systems we can swap onto this car. Was hoping we could avoid that, we will see.

          "INTERIM" WHEELS ORDERED (TWICE)

          Remember the "one mistake" I mentioned in the 19x10 wheel and Hankook tire order we made after Track Test #1? Well it was the fact that I did NOT order black wheels, but that's what they sent. And I absolutely HATE black wheels - they disappear and you cannot see what they look like. Just a mass of black.



          I mentioned this to my TR rep and he admitted the error, then sold me another set of these 19x10s in the correct silver color, above. Luckily these were still on closeout and again super inexpensive, plus at I got free shipping this time. I also found some TPMS sensors elsewhere and had the 275 Hankook tires swapped to these silver wheels after just that one event.



          Not a great pic but it was raining all week and that's the best I have for now. Long term these will likely be the "street wheels" we use to drive around on, after these RS-4s have either worn out or heat cycled out. The "real" wheels we custom ordered 6 weeks ago are almost done, and those will be used exclusively for track/autocross use. More on that next time.



          Meanwhile the ugly black wheels will now be getting a set of new Hoosier R7s, which I picked up for a song (old date codes, but stored inside and never mounted so they still have the mold release). The Hoosiers won't go on the car until we have the MCS coilovers on, and then we will test that setup with the 275 RS-4s first and the 295 Hoosiers on identical wheels on the same day. Just couldn't pass up this deal, and its more data in my long term 200TW vs R-compound tire lap comparison testing - which we did extensively for 2 seasons of NASA TT events in our 2018 Mustang in TT2 and TT3 (2018-2019).

          LAP TIMES LIST RANKING AT MSR-C 1.7

          Here is my "leader board" list for laps at Motorsport Ranch Cresson on their 1.7 mile CCW course, and the first two track tests on the C6 are shown ranked inside my videos/times for other cars I've driven here.




          Love this track and have been coming here for 20 years. Their 1.7 mile course (see above) is relatively easy to learn, has a good mix of corners, and is short enough to not have a long out lap and in lap - making for more laps in a 30 minute session. This facility has had consistent paving from when they opened in 2000 until they repaved in 2021 - a month before the recent repave, NASA drivers were still setting new lap records on the "old" asphalt. Having driven before and after the repave, there is no significant change and lap times didn't change - not something you can say for most tracks over 2 plus decades of use.



          We have used this course for setup and testing, and I personally have driven over 500 laps in many different cars here. With this much seat time at the same track I can drive fairly consistent laps, in the same conditions. In the past I have done as many as 15 track tests / competition weekends in a single year on this same 1.7 CCW configuration. MSR has 4 configurations: 1.7 CCW. 1.7 CW, 1.3 mile (see above) and the 3.1 mile layout (combines 1.7 and 1.3 together). We finally got a membership earlier in 2021 so we can do even more testing here. The only track I have more laps at is Eagles Canyon (above right), but they repaved recently and reconfigured (from 2.9 to 3.1 mile) about a year ago, so none of my old laps there are relevant to compare to for current testing. Plus their new 3.1 mile course is a bit long for a small number of laps driven in a given stint - with long out- and in-laps.



          I keep this list updated of my best laps at this track in various cars I have driven, and put this list into most project build threads to show how a particular car is progressing, compared to other cars driven by the same driver - me. Why just my times? Well simply put it keeps the "driver variables" to a minimum.

          I am not claiming to be a great driver by showing "my list" of laps only - far from it, I know I'm a hack - but I have driven 50+ cars at this track and have set 5 or 6 NASA Time Trial lap records here. As "terrible" of a driver as I may be, my laps here tend to be fairly consistent when the tires/brakes/traffic line up, often running multiple laps in a row in the same tenth of a second. That consistency can at least help show a progression of performance for a car over different rounds of modifications driven at different times, even if my times aren't the absolute best that a given car could theoretically do.

          This list of laps shows a spread of times for a range of cars under similar conditions, with both 200TW and Hoosier race tires, as noted. Each time we add a new Track Test for this C6 I will add it in bold into this ranked lap time list:
          • 2013 Scion FR-S, Baseline Stock Lap Time, 215mm tires (Test #1), 8/31/16: 1:31.90
          • 2006 Corvette, Baseline Stock Lap Time, 245/275 all season tires (Test #1), 4/9/21: 1:28.743
          • 2016 Focus RS, baseline stock laps, 235mm MPSS, 6/15/16: 1:27.40
          • 2006 Corvette, G-LOC R12/R10 pads, 275 Hankook RS-4 tires (Test #2), 4/18/21: 1:26.248
          • 2013 Scion FR-S, AST 5100s, camber, bars, BBK, "not fresh" 315mm Rival-S tires (Test #6), 8/25/18: 1:25.978
          • 2001 BMW 330i, NASA TTD prepped, 216 whp, MCS coilovers, camber, 245 Hoosier R7, 3/12/17: 1:23.789
          • 2016 Focus RS, coilovers and camber, 275mm RE-71R, (Test #4) 9/27/16: 1:23.658
          • 2012 Corvette C6 Z06, Carbotech XP10/XP8 pads, 285/335 MPSS, perf alignment, 9/16/16: 1:22.63
          • 2013 Camaro SS 1LE, 305 Hankook RS-3, Bilstein PSS, camber, seats, brake ducting, 430whp, 9/16/16: 1:22.56
          • 1992 Corvette, NASA TTC prepped, LT1, 288 whp, stock shocks, Hyperco springs, 245 R7s, 3/13/16: 1:21.90
          • 2017 Corvette Grand Sport, Z07 aero package, 285/335 MPSS, perf alignment, 9/16/16: 1:21.89
          • 2018 Mustang GT, "sort of" TT3 prepped, 305 RE-71R street tires, 474 whp, 3/10/19: 1:20.348
          • 2018 Mustang GT, "mostly" TT3 prepped, 315 Hoosier R7, 474 whp, 3/10/19: 1:19.2
          • 2011 Mustang GT, NASA TT3 prepped, 335/345 Hoosier A7, 447 whp, aero, 3802 lbs, 3/9/14: 1:17.310
          This C6 is actually a bit slower than we expected, when compared to the red target times above - a nearly stock C6 Z06 and a C7 GS Corvettes that I drove on the same day. Both the C6Z and C7 GS had performance alignments and much wider OEM tires, so that explains some of this deficit - but not all. In the next post we will have more lap testing on our C6, hopefully moving this car's best time up the leader board - eventually ahead of the Spec Miata track record! #LapTimesMatter

          PERFORMANCE ALIGNMENT

          This is something we recommend for anyone to do to their car BEFORE they ever go do their first track event in any given car. The goal for most unmodified cars you want to autocross or track is to add as much negative camber the stock adjustment range allows - because the stock suspension will allow a LOT more body roll than one with a modified suspension. And excess roll allows the tires to wear abnormally fast on the outer shoulders. Adding static negative camber will mitigate this, of course.


          The first autocross in our 2018 GT shredded the OEM tires. Look at that roll! With coilovers/springs/camber it wore the tires GREAT

          We had intended to add a Performance Alignment to this C6 between Track Tests 1 and 2, to show that as part of the lap time progression. Why wait? I wanted the Baseline Stock track test to be the absolute "stockest of stock" for this base model C6, and also why we did that one with the all season tires and random brake pads (but with good brake fluid and oil - I'm not suicidal). As you can see (below left) the C6 had tons of body roll, even on low grip 245/275 all season tires.



          Well timing didn't work out for this to happen until after Track Test #2. Since we moved our shop "out to the country" in 2018 we have been looking for a place nearby with a proper laser alignment rack. We don't own one of these $75-100K alignment racks and it's unlikely we will - because they would never pay for themselves. In our best months we had maybe 3-4 cars aligned using a partner shop (that little use would never pay the note on these machines). At our last shop location we had a nearby shop with a really nice alignment rack and we would take cars there with a list of measurements we wanted. After a while we had trained their crew to do performance alignments to our specs. I was "breaking in a new shop" the week before Track Test #2...


          As a test for a new nearby shop, I had taken my shop truck (above) to check out their abilities on a state of the art alignment rig, and they did a great job. They do 10-12 alignments per day, but on the only open slot we had for the C6 (the day before Track Test #2) they were slammed and couldn't fit us in, so we did BOTH first tests on the crappy stock alignment. That hurt lap times, for sure.



          Looking at the car in stock form (above) we could see that the alignment was as Plain Jane as the rest of the car - it never had a performance alignment, and this is likely as it came from GM sixteen years ago. After we finally got the car aligned we can see the "before" settings were pretty bad: -0.6°/-0.8° camber front and -0.4°/-.6° camber rear. Oof...



          They hit the marks we set for them, but it took them longer to do than they expected. These Corvettes require a lot of shimming on the front suspension to get the camber set. At least track test #3 (later this week!) will have some proper camber, and that alone will help lap times. We will likely dial in more rear camber on the next alignment as well (there are two mods planned in the future that will require new alignments).

          WHAT'S NEXT?

          We have a LOT of things ordered for future rounds of modifications and subsequent track tests. If I have to go to the track once a week to test all of these, well darn, I guess I will do it!



          Brad is in the middle of swapping all of the calipers and rotors for the larger (and different hydraulic piston sized) Z51 bits, shown above. Also the DeWitt radiator, new hoses, lower radiator support (old one is smashed), and more. We should be back on track later this week to see if this makes for any changes in Test # 3.



          There are more planned upgrade parts already here or en route, but those will be for later rounds of mods. The MCS dampers coupled with real spring rates should make a substantial change in handling - and might even help with the rear brake locking situation (old dampers and springs allowing too much rear rise/brake dive?) We will see in the next track test if the Z51 rear caliper hydraulic changes help that situation. We can always "dumb down" the rear brakes by swapping in some really crap rear pads, too. Stay tuned for more!

          Thanks for reading,

          Terry @ Vorshlag
          Terry Fair - www.vorshlag.com
          2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
          EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

          Comment


          • #6
            Terry and Vorshlag Team,
            A couple of observations from corvette track cars over the years, I know you guys know most of this stuff already, but it bears repeating....

            Suspension Bushings are crazy soft on the Vette and only poorly control camber especially once you get a really good tire on there. Delrin kits are available from a couple of suppliers and make a noticeable improvement in feel and control of the contact patch. Bearing kits are available but expensive. Polyurethane is also available, but with the obvious drawbacks....

            Corvette Control Arm camber eccentrics are notorious for slipping, especially on good tires or when torqued to only the factory torque spec like an alignment shop is likely to do... Either crank down on those things or better yet switch to a "camber plate" system that locks out the lower bolts and adjusts alignment using shims on your upper control arms. Added benefit of making alignment adjustments with minimal toe change. A slipped eccentric will really ruin your day....

            The oem single sided C clamp type brake calipers will always taper the pads, necessitating flips and rotations, but eventually the soft aluminum calipers will actually spread and wear very unevenly from top to bottom. The sooner you switch to a fixed caliper system the sooner you can save on pad costs. There are a few fixed caliper systems that use the stock cheap rotors, allowing for frequent inexpensive rotor changes.

            Corvette brake force is electronically distributed. It seems to have a heavy natural rear bias and electronically reduces rear pressure. This is just one more aspect of the overall weirdness of gm brake systems, but there might be improvements to be made by upgrading only the front to add some natural bias especially with a square wheel set up.

            The clutch throwout bearing slave system holds a ton of heat and cooks the fluid, suck out and refill the reservoir often. The oem clutch master cylinder has a lot of problems, adapting to an after market tilton or similar removes the return spring system and makes for a more natural clutch feel and to prevent a sticking clutch pedal.

            Like with your engine oil, replace the power steering fluid with a quality ester based synthetic like Redline, or maybe Motul makes one?

            Vent the hood to get enough airflow, add ducting to the front brakes, add oil cooling, you can see heat is already going to be an issue when the temps go up, after that start watching your trans temps.


            Finally Thanks for all the great content and posts!
            Last edited by Ando; 05-06-2021, 04:22 PM.

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