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Unread 08-02-2017, 11:24 AM
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Default Vorshlag C6 Corvette Development + Shop Z07 Race Car (Rampage)

Project Introduction - August 2nd, 2017: For some time I have been meaning to create a "development" thread for C6 generation Corvette (2005-2013), to show the parts we have built for and work we have done to these cars at our shop. On July 27th I purchased a 2007 C6 Z06 chassis, so I needed to start a "C6 build thread". Instead of two separate threads this will function as both. From time to time here I might also touch on some C5 and C7 Corvette work, as those generations are similar enough to the C6 that there is some crossover.



We purchased this C6 Z06 chassis for a number of reasons. Like to develop things a proper roll cage for this aluminum chassis, to perfect some new wheel fitments, to test out new engines/components, and eventually to build it into a dedicated road race car. But it is meant to be a test platform for products and techniques as its first priority, as are most of our shop cars.

Snowflake Warning: In this thread I will not be "self censoring" the contents, to make it more palatable for cross-posting into multiple forums like I usually do. Why? Well to be honest most of the car tech forums where I used to share threads on are either dead, broken, have become pay-to-play and just full of shills, or have so little traffic it is not worth the effort. This is written for the Vorshlag forum, but if there are some remaining car forums that are looking for uncensored tech, it will have: water marked pictures, links to products on our website, and rambling posts covering multiple cars. For the first time in 15 years this will be a raw, no-holds-barred post. Easily triggered readers - this thread is not a Safe Space! Remember: I'm not putting a gun to your head and making you read this.



This build and development thread, like everything we do, has the end goal in mind of improved road course and autocross performance, along with additional horsepower. Those are the things we care about are: turning, stopping, and accelerating. We won't be discussing car show upgrades, or stereo tweaks, just things that make a C6 better in competition motorsports use, building/fabricating parts, testing and driving these cars on track.


Left: The C7 Corvette uses an aluminum chassis like the C6 Z06. Right: C6 Z06 on 315F/345R Hoosiers + aero

I will open this first post with the reasons why I have NOT had a C6 Corvette for the past 12 years, then we will cover some basic aspects of the C6 chassis that are noteworthy. I will then veer off into a 2016 track test where I put some laps in a stock '12 C6 Z06 vs a '17 C7 Grand Sport (and a '13 1LE) to get a baseline lap time, which we can compare against when we drive other modded C6 Z06s on track (including our build, some day). Then I will cover the rolling chassis 2007 Z06 we purchased. I will also show some other C6 Corvettes we have worked on and developed parts for in the past several years. I won't cover everything C6 related we have done in my first series of posts today, but will instead insert the various C6 parts and past work into future posts.

SELF-IMPOSED C6 OWNERSHIP BAN

So I initially wrote an eleven paragraph section explaining the reasons why we sold our 2005 C6 Z51 12 years ago - a car that I absolutely loved for its performance - and then I waited until 2017 to buy another. Other than for my own benefit nobody would have cared to read those 11 paragraphs, so I re-wrote that to be extremely brief.

In 2004 my wife saw the C6 at a car show and loved it. We custom ordered a 2005 Corvette Z51 6-speed with no other options, got it within the first month of the C6 debut, drove the heck outta the car for a year, and really enjoyed it. We autocrossed it a bit (on 11" wide wheels with 315 Hoosiers) and that car and I really clicked. In the words of Jim Carrey: "I like it a lot."



After a year of ownership we came to a cross roads: we were building a new house/shop, Vorshlag was just starting to take off, and since the main product we sold at the time was spherical camber plates for McPherson strut cars it didn't make sense to own a Corvette that couldn't use these parts. Since the C6 was brand new and cars were still very scarce we sold it for what we paid for it. It was a tough call but selling that C6 really helped us move Vorshlag forward in 2005. As a result I have been racing "McStrut" cars almost exclusively for the last 12 years. A dozen years of waiting... for another.

WHAT MAKES A C6 CORVETTE WORTHWHILE?

I'm not a "Corvette person", or a devotee to any marque or model. I don't go in for any "car worship", but instead value a car for simple reasons: power, handling, brakes, grip, drive-ability, and weight. I don't really care what badge is on the outside, what "prestige" a car maker has, as long as it delivers the goods. Part of our business is making "hybrid" cars using things like a German chassis, an aluminum GM LS engine, Ford differentials, brakes from South Africa, suspension from Holland, etc. We try to take the best "performance/price" parts from all over the world and put them into one car.



The C6 Chevrolet Corvette happens to have a lot of really good "parts" all in the same chassis, from the factory. And the Z06 model is amped up even further: hydroformed aluminum frame, *carbon fiber bodywork (*some panels), ample tire room, 7.0L 505 hp aluminum V8 with *dry sump oiling (*only a 2 stage pump, but better than a wet sump), decent brakes, and a low drag body shape. It runs low 11 second quarter miles and can do 200 mph top speeds in stock form. The strong, rear mounted transaxle (see below) shifts some weight to the rear, which is always good on a front-engined car. Its relatively light, too.



There are some negatives as well - poor seating position/visibility & limited interior room (making racing seat and cage installation difficult) to name two. Having a composite body that bolts to a full frame is supposedly less efficient than unibody construction. Is that last claim proven? We have a good test in mind to prove or disprove this unibody vs full frame weight theory.

We will compare the final weight of my 2007 C6 Z06 race car build (below left) against a similarly prepped, carbon roof/hood equipped E46 M3 (below right). Both builds are getting large displacement aluminum LS V8s, both will have a 335mm front and 345mm rear tire, both will be caged, and both will get similar aero upgrades. In the end the scales will show which is lighter and which has the better front/rear weight bias. I'm actually pretty excited to see both of these being built side-by-side in our shop.


Which V8 race car will be lighter? The body-on-frame C6 Z06 or the lightened unibody BMW E46 M3?

Every car I have purchased since 2005 has had some business purpose for Vorshlag: as test mule/product development chassis and usually as a marketing vehicle in some form of motorsports competition. I violated the first half of that rule (we don't make any C4 Corvette parts) when I purchased this 1992 Corvette below back in 2014 (Project Dangerzone) - which we built just to prove a theory. Turns out that hunch was well founded and we set several track records in the car, got noticed by NASA officials, and they threw weight at it the next year. Had a lot of fun with that C4 but there were some Corvette specific challenges we had to learn to solve, like the roll cage installation. Landing cage tubes onto a full framed car - while passing through a composite body - was tough.



We want to test our cage building techniques on this Z06 - a car with an aluminum frame, no less. We have seen some sketchy cages done on C6 and C7 aluminum chassis cars and want to see if we can come up with a better solution. So "better cage development" will be one of many goals for this chassis.

BASELINE ROAD COURSE TESTING: STOCK C6 Z06 vs C7 GRAND SPORT!

If you have read any of our other detailed build/development threads you might already know that we do a lot of track testing. From 2008-2015 we did most of our track testing at ECR, but that track has gotten too bumpy. For 2016-17 we have moved our road course testing to the 1.7 mile CCW course at Motorsport Ranch in Cresson, TX (MSR-C). I cannot exactly "baseline test" the 2007 Z06 chassis we bought, as it is in pieces, but I've got the next best thing.


Photo Gallery - Track Test, September 16, 2016: https://vorshlag.smugmug.com/Racing-...C-Test-091616/

On this beautiful Friday morning last September I was lucky enough to be able to drive three cars around MSR-C with an AiM SOLO lap timer and camera in each one. Same day, same track, same driver, similar tires. The first two included a 2013 Camaro 1LE that we modified (see this thread) and the same car owner's newly acquired 2017 Corvette Grand Sport 7-speed manual, which was bone stock and still sporting the dealer's paper tags. These were both owned by our tester Scottish Joe.



The Camaro was on fresh 305/30/19 Hankook RS-3 tires (on 19x11" wheels we spec'd) and the C7 GS was on fresh 285/335 Michelin Pilot Super Sport tires (factory equipped).



I also tested our accountant Jerry's almost bone stock 2012 "Centennial Edition" C6 Z06 Corvette, who has become a product tester for us on two cars now. The Z06 was on fresh 285/335 MPSS tires (same as what came factory equipped, same as the C7), plus it had better brake pads, some additional negative camber up front (-2.0), but it was also otherwise bone stock.



We got there early on a member day and the weather was great in the morning. I managed to get out on course in the Camaro when the course was devoid of traffic - which made for some easy laps where I clocked off some quick ones. This car was on coilovers, camber plates, 19x11" wheels, aftermarket headers, dyno tune, Cobra racing seats and Scroth 6-point harnesses. The Cobra racing seat and harnesses made driving the big 3800 pound Camaro effortless and I wasn't having to "hang on" like I did in the C6 Z06 - which had some of the worst stock seats I'd ever experienced.

Data Logged Track Videos at MSR-C in Vehicles on Street Tires:
https://youtu.be/6Rpepzil8FI - 1:21.89 in the stock 2017 C7 Grand Sport
https://youtu.be/athEpfLRH3o - 1:22.56 in the modded 2013 1LE Camaro
https://youtu.be/1_B2u_fOnww - 1:22.63 in the stock 2012 C6 Z06
https://youtu.be/fpWyzzf-pHk - 1:27.40 in a stock 2016 Focus RS
https://youtu.be/Cs6AF436ykE - 1:31.90 in a stock 2013 Scion FR-S

All three cars I drove that day put down fast track times but each was very different to drive. The Camaro had lots of track specific suspension/brake/power/seat/tire upgrades, so it wasn't exactly a fair fight there. All of these laps listed above were in street going vehicles using 200-300 treadwear street tires and the same AiM SOLO lap timer / data logger and driver. This AiM unit is within 0.1 sec of the AMB timing loop whenever I run NASA Time Trial events here, too.



The Camaro's stock 14.5" Brembo front brakes were upgraded with custom brake cooling that we made, G-LOC pads, and proper Motul fluid. These were absolutely infallible - watch the g-traces in the on-board videos and you can see how I abused them (1.1-1.2g stops on every corner, every lap) and yet never had a hint of fade. The Hankook tires worked great, generating 1.3g lateral in some places, mostly 1.1-1.2g. The brakes on the C6 Z06 and the C7 GS both had larger 6-piston iron brakes with GM's "half measure" semi-directed brake cooling, but both were actually pretty easy to overheat - after my fastest lap in the GS the brakes had massive fade. The brakes were more manageable in the C6 Z06, but that was mostly the pad upgrade - I could overheat them as well.


Left: The C7 GS brake cooling is a "scoop and flap" method. Right: The C6 Z06 has a plastic brake cooling duct

The C6 Z06 had Carbotech brake pads (XP10/XP and better fluid, so it was stopping better than the C7 GS. Other than the brake fade tendencies the $76K Grand Sport was GLORIOUS to drive and the fastest of the three that day. For stock seats the C7's upgrades "sport seats" were pretty good, but still left something to be improved upon. The stock brake pads were complete junk, though. Its hard to imagine how GM could deem these track worthy pads and I could fade them hard in only 2 hot laps.



I drove my fastest laps in the C6 Z06 and the C7 GS with a passenger riding shotgun (nobody would ride with me in the Camaro, ha!), and since I drove the C6 last it was in the hottest temps of the day (94F). It was still surprising that the C6 Z06 - my dream car - put in the slowest lap of the 3 cars I drove that day. Why? Well the stock suspension felt very soft and the car was rolling around like a school bus. The stock seats were downright awful - I felt like I'd slide up the door panel and pop out the side window on every big corner.

Both the C7 Grand Sport and C6 Z06 were on very fresh 285F/335R MPSS tires, so grip wasn't an issue. The C7 GS has different programming on the mag ride shocks and it seemed to corner MUCH flatter than the C6 Z06, which also had mag ride dampers. Again, the C6 Z06 was only 3/4 of a second slower than the C7 GS, but it definitely felt slower in the corners. Power it had for days, brakes were better as well. It was very interesting to drive these cars back to back in their stock forms.

continued below

Last edited by Fair!; 08-02-2017 at 03:32 PM.
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Unread 08-02-2017, 11:45 AM
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Default Re: Vorshlag C6 Corvette Development + Shop Z07 Race Car (Rampage)

OTHER C6 DEVELOPMENT

We have built some C6 parts and done track upgrades on these cars, which I will show in future installments of this development thread. Jerry's C6 Z06 has been going to the track 2-3 times a month for the last year so we get to see how pads, tires and such are wearing on his car.



Of course we weighed his 2012 C6 Z06, above. At 3217 pounds it is about the same as a base C6 Corvette, a touch heavier than the C5 Z06 (3050-3100 is common), yet hundreds of pounds lighter than Joe's C7 GS (below left, 3409) or the yellow C7 Z06 (below right, 3570) automatic we weighed. The C7 GS has a dry-sumped LT1 engine and iron brakes, with identical tire sizes, so its the closest C7 to the C6 Z06.



The C7 got a little bigger, a little more complex, and a good bit heavier than the C6 Z06. Its a bit funkier looking as well, at least to me. All C7 Corvettes have an aluminum frame and carbon fiber bodywork, too. The "non-Z06" C6 has a steel frame and fiberglass body, for what it's worth. My former 2005 C6 Z51 tipped the scales at 3150 pounds, with low fuel load, on a digital scale.

After that September 2016 track test I convinced Jerry to let us test out some better front brake cooling upgrades on his C6 Z06. This has helped extend his brake pad life on track significantly as well as reduce the chance of brake fade on track.



I will talk more about this C6 Z06 brake cooling kit when it is closer to production (we are testing version 2 now). Next time I will also show the Powerbrake 6-piston 350mm front brake upgrade kit we tested on Feras' 2008 C6 Z06, which he races in the Optima Ultimate Street Car series. I drove this car on track recently - which ruined me forever. Feeling how a heavily modded C6 Z06 handled on the same MSR-C surface was eye opening.



Feras' 2008 Z06 also just got a 7.7L stroker aluminum LS engine from our sister shop, Horsepower-Research. I will cover much more about the extensive list of upgrades on his Z06 next time.

VORSHLAG C6 Z06 - PROJECT RAMPAGE

So let's talk about this rolling heap of C6 Z06 parts I recently bought. This 2007 model Z06 was the innocent victim in an elaborate insurance fraud case and it ended up being confiscated. It was so mired in paperwork that the insurance company sent it to auction to be sold as parts.


Some Assembly Required

The damage to the actual chassis was minimal and it actually drove into the body shop I bought it from last year under its own power with every body panel intact. The title was a bit of a mess so it sat and sat, then parts started being "liberated" for use on other C6 Z06 body repairs. From the picture below left (taken 6 months earlier, when I first saw it) it lost the LS3 engine (part of the insurance scam - someone had swapped out the LS7), front fenders, right front inner apron, the hood, front nose, front bumper beam, driver's door, windshield, driver's seat, steering wheel, rear bumper cover, wheels, front upper control arms, rear toe link/tie rod, and both rear fenders. A lot of parts left this car...



It seems like there wasn't much left, and it would be nearly impossible to sell this to anyone who wanted to make a real street car out of this chassis. It didn't even roll. But I spotted it there when I bought another car from this same shop and told him to "Stop stealing parts off my C6!" Eventually I came back and bought what was left to make a race car out of...



I paid a little more than scrap value for this Z06, and honestly I am happy with the purchase. With 3 other race cars and a business to run, I couldn't have afforded to buy a $35-40K+ used C6 Z06 that was a complete car. And with what we have planned, it would be wasting a lot of good street parts. Brad and I fought with loading this car in 103F heat, first getting it onto dollies, then pushing it into my trailer (of course the winch decided to die that day), then we hauled it back to Vorshlag. The whole crew here helped unload it - and once again they thought I was nuts! But I had a vision, and managed to negotiate for a bunch of spare C6 parts the shop had. We filled the truck and trailer with random body parts they donated to the cause - a hood, apron, a door missing the window, some rear fenders, random wheels, and a few other bits.



Once we got it here Aaron got to work getting the rear hatch open. With that unlatched we found the rest of the entire interior, minus one seat and steering wheel. So we'll sell those bits soon to recoup some costs.



We didn't waste any time and the day after we unloaded the car I ordered a new pair of front control arms and rear toe link from the Chevrolet dealership, to replace missing items. Aaron spent 1.27 hours and installed those new suspension bits, bolted on the rear fenders and driver's door, then he installed on the Z06 front wheels and tires we got with the car. It rolls!



Of course I weighed these parts before they were installed. You expected anything less?? There are all sorts of weights we took of various C6 body parts, which I will show in future posts.



Brad got a weight of the Z06 assembled. This is with all of the body panels and hood we got with the car, the full interior (minus the seat/steering wheel), and the transaxle/torque tube... but no motor, nose, or front fenders. We're pulling interior parts out now and will show more of this build up next time.

WHAT'S NEXT?

I wanted to keep this first post short and sweet, and its already grown a bit long. We have already started getting our Z06 lighter by removing unnecessary engine bay wiring, plumbing and reservoirs.



We have also started removing interior and the bolt-on roof panel (below left) in preparation for roll cage layout. The first set of race wheels is being measured for and ordered soon, as one of the "freebie" wheels we got with the car isn't exactly holding air (below right).



I will show more of this shop Z06 race car build-up next time. We don't have a concrete build schedule or detailed plan for it yet so I will share that as it emerges. We have 3 other shop race cars and plenty of customer cars that all need attention, so our Z06 will get worked on as time and budget allows. I will also explain the project name next time, but Archer fans will have already figured it out. #Zima

Thanks for reading,
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Unread 08-02-2017, 12:49 PM
Mark-C Mark-C is offline
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Default Re: Vorshlag C6 Corvette Development + Shop Z07 Race Car (Rampage)

Hey don't forget the C5 autocross car in December doing a 1:22.5!!!
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