Vorshlag 2011 Mustang GT + S197 Development Thread

[Thinkkker]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Yea, I have heard a "muffler delete" exhaust on Kent's ESP-prepped S197. Its still pretty loud. With full length headers and a 7500 rpm redline on this Coyote motor, it might get a bit too loud. I don't want to be "that annoying guy with the loud car" at events.

Though at Nats it only just hit over 97dB

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Project update for Nov 22, 2010: I'll start with some replies to questions, some requests for ideas/advice on upcoming mods, then I'll move on to the wheel test I did yesterday on the 18x9 and 18x10 test wheels.

Either allow headers or don't. I don't see how they picked the number 6. Why not 7, 10, or 14? Floorpan stampings and engine combinations can leave plenty or no room at all. Why not use a number that allows most any effort the same opportunity in fitting a long tube header?

Agreed. At least the STX and STU classes can do away with 4 cats and replace them with 2, of any type (not OE/CARB stamped units of the same number as stock, like in ST/STR/STS classes). There are rumbles of making STX/STU adopt the lame cat rules in these lower classes, but that's not until 2012, at the soonest. I hope.

You might consider whether any (muffler) choice greatly increases drone. There are plenty that don't. There are also plenty that do. Maybe I'm getting older, but I much prefer a quieter system that emits a simple, deep, burble, as opposed to an all-out wail.

Yup. I'm old.

Agreed. I've owned many Mustangs over the years that had oppressive exhaust drone, and I'm also getting old. And my wife daily drive's the Mustang (but she's pretty a dedicated racer, so she has mucho tolerance). When I worked at a Mustang tuner shop over a decade ago for a short stint the head tuner there (Sen-Roy, who used to post here a lot) would do tricks with varying the muffler case size on each side of a dual exhaust Mustang. It usually killed the drone. If it gets bad I'll swap out one muffler and try that.

A quick word on coatings....if you coat, don't wrap. (his coater) said it would not help and would not be good longterm for the coating. Check with your coater and see what they say.

Costas
cars and such...

Yea, I think coating and wrapping a stainless header is probably overkill. Now I'm leaning towards just using header wrap on the stainless headers only, and not blowing $250-350 (and weeks of time!) on coating.


http://www.summitracing.com/parts/DEI-010130/

I have this 100' x 2" roll of DEI header wrap in my "shopping cart" as well as stainless steel zip ties, DEI exhaust wrap (for wiring), some long front wheel studs (for potential wheel spacer use up front - see more below), and a pair of these mufflers:


http://www.summitracing.com/parts/FLO-843048/

I did some searching and found, for the first time, real stainless steel chambered Flowmaster Series 44 mufflers. There isn't room for a small/resonator style muffler before the axle, so I might as well go with a "real" chambered muffler out at the rear bumper (these don't have packing that burns/wears out). I don't want this car stupid loud with $600 worth of Burns mufflers and dumps before the axle, either. Sure, it'll cost us a few more pounds to go with a chambered style muffler and full length tail pipes, but these FM 44's are shown to be only 7-8 pounds each (not 13 pounds like the much larger case sized Flowmaster Series 50 I used on my E36 M3). We'll see how they sound, test the sound levels, test the performance hit with and without them on the dyno, and weigh the mufflers before they even go on. These 3" type 44's are smaller than the stock mufflers so they should easily fit in the stock locations. The stock over-the-axle pipes are so compromised and crimped down to clear the panhard support (by inches) that we should hopefully see some small gains here, as well.


Stock muffler case is 15.5" long. The FM type 44 muffler case is 13" long


http://www.summitracing.com/parts/ARP-100-7722/

If anyone has experience with these wheel studs, please chime in. These ARP 1/2-20 x 3.3" long studs show to be made for 2005-2010 Mustangs ("front only"), so its a gamble if they'll fit the 2011. And at $11.36/each they are just a wee bit pricey. Probably not enough market to make it worthwhile to make our on wheel studs, though. We might need these long studs for use with the 18x10" track wheels (see below).

Terry, I really enjoy your perspective. You stated your goals, continue to research, make sound and logical choices, then verify results. Keep up the good work and I hope the car is capable of meeting your demands.

Tob

Thanks - we are always trying new stuff here, and I'm sure some of it won't work and we'll have to back up and try again. I like having the input from lots of experienced racers, because it limits the "dead ends" a good bit.

To save some weight you may be able to get away with just the cats. When I had the '05 GT I had a muffler delete exhaust with stock headers and cats and was never above 93dB at the local autocross course. I know it's a different engine and exhaust configuration but there is also a big difference between 93 and 100 dB.

Yea, I have heard a "muffler delete" exhaust on Kent's ESP-prepped S197. Its still pretty loud. With full length headers and a 7500 rpm redline on this Coyote motor, it might get a bit too loud. I don't want to be "that annoying guy with the loud car" at events.

We have been spinning our car past 7500 with a 8000 rpm limit. The car only picks up power beyond 7000 with a good CAI (we have a JLT) and just an off road H-pipe we see over 400 SAE on the cars we have tuned.

The shop car has; CAI - ported heads - long tube AR headers - X-pipe - resonator delete - flowmaster mufflers - 1 peice DS - RST clutch and flywheel. With SCT software we have gotten as much as 435 RWHP SAE.

Ahh, some real power numbers from an S197 tuner. Thanks for replying. I noticed when we dyno'd the car it wasn't really losing power yet at 6800 rpm, so I could see it gaining a bit more up top with the right tweaks. I'm still planning on an eventual 7500 rpm redline. With the right tire choice (we've been looking at so many) in STX it could mean a 73 mph 2nd gear speed. Virtually assured to never have to shift.

We cannot do the 1-piece driveshaft (the stock unit is a huge 2-piece unit that looks very heavy), ported heads, or the lightweight clutch/flywheel, but the rest is fair game. We need to look at the CAI offerings soon, as I'm getting tired of how quiet, stock and slow this car is already. If anyone has experience with a Cold Air Intake on a 2011 GT, especially with before/after dyno numbers, please chime in. I saw a couple at SEMA already, but many weren't ready yet.



OK, onto the latest round of wheel testing.



The two Enkei test wheels arrived Friday but I didn't get a chance to test them on the GT until Sunday. The 18x9" ET45 FP01 fit fine. This wheel bolted right onto the front and rear, with ample clearance to the caliper and strut (front) and to the inner sheet metal (rear). Even without any camber and this 4x4 ride height the outer lip of the 18x9 wheel fit within the stock fender confines.



As they should - they are almost the same width/offset as the stock 19x9 ET42 wheel. In fact these Enkei 18x9's will be 3mm more inboard than stock, which is good - I like to run narrow track widths for autocross cars when I can, to make slaloms that much easier to navigate. Its worth a little time, as we've seen in testing where we time a car through a set gate length slalom, then again with wider cone offsets by just a few inches. You can see the big end link stud that interferes with some wheel/tire clearance when you push the wheel inboard. If it comes down to it we'll just cut/shorten this stud.



So the 18x10" ET38 Enkei RPF1 wasn't quite as easy to fit. The flatter spokes of the RPF1 didn't clear the caliper on the front, as we kind of expected, and some of you warned about.



Not a huge shock - so I tried it on the rear and it looked good. There's a good 1.5" more inboard room, too.



So back to the front with the RPF1 18x10". I didn't have any 5x4.5" wheel spacers, so I started stacking washers to get the proper clearance. Turned out about 7mm of spacer is all that's needed to clear the caliper with the spokes on the RPF1 up front. Then I counted turns on the lug nuts and had just a hair over 10 threads of engagement... which equates to 1/2" (which is 1 diameter). That's just barely enough, and still only afforded about .040" of clearance at the caliper (but the stock wheel only has about .050" clearance here). Hmm.



Then there was the outer fender clearance. With the already wide 18x10" and now a 7mm spacer. It looks... well, its damn hard to tell if it will clear at full droop and with no camber, even hard to show in pictures. With the stock ride height and stock camber, I'd guess no. But we're going to be lowering the car a LOT (2-3"), which will inherently add negative camber and tire clearance. And then with some more camber adjusted in at the plates, that's more outer wheel clearance we'd be adding.

So for now we'll punt on the 18x10" wheels, and retest this wheel again once we have the car lowered and a 285mm tire mounted to it (I've got plenty of dead Hoosiers in this size we can mount and test with). It looks like we'd need a spacer of some sort, which I can draw up and machine easily enough if it comes to it. So I'll get the longer wheel studs installed, just in case. We'll also get the remaining 3 wheels in the 18x9" set, then order the tires (I'll discuss the size and model in an upcoming post). I'll be buying all of the stuff mentioned in this post in the next 24-48 hours, so if you have suggestions/alternatives, speak up now.

Thanks,

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Update for Nov 19, 2010: Not a lot of "work" to update on here, but we did get the baseline dyno run completed so I figured I'd share that, plus some bench racing on the exhaust, and some more wheel weight testing.

The guys at Dallas Performance were kind enough to squeeze in a quick 3-pull dyno test on our GT late yesterday. This was using their state-of-the-art, 2008 model, Dynojet® "Eddy Current", loaded in-ground 224xLC chassis dyno. They just moved to a new (and massive) location where they've built a dedicated dyno cell. Its as clean as a surgical room in there - and everywhere else in their shop. It is literally the nicest looking, most well equipped tuner/fab shop I've seen in all of Dallas/Ft Worth. They do some amazing high powered builds there, with 1000-1400 whp twin turbo V8s and V10s being the norm.

Our 2011 GT was the first stock Coyote 5.0 powered car they'd dyno'd so far. They told me that the most power they'd seen from a bone stock 2010 Camaro V8 was 345 whp, and a 370 whp pull from a stock 6.1L Hemi Challenger was the highest of any modern, stock "pony car" they have tested to date. Well the numbers from our 2011 GT beat all of those pony cars...

Here's the video & dyno chart (all pulls within 3 whp):


Click for baseline dyno video



We were a little disappointed with the peak 378 whp figure, as we'd seen a number of '11 GTs post 385-395 whp pulls, bone stock. We tried to rationalize the number on the low mileage on the motor (580 miles at the time of the test), or the fact that I drove the car around all day and didn't let it cool down before we dyno'd it (heat soaked), but in reality I screwed up and told them to dyno it in the wrong gear! For consistency and the least drivetrain loss, you typically dyno a car in the 1:1 gear, which is usually 4th gear in most 4, 5 and 6 speed transmissions. All Tremec T56 cars ever built had a 4th gear of 1:1, which is normal. But of course the 2011 GT doesn't have a Tremec, it has the Getrag MT82 6-spd (see the specs on the 6-spd).

6-speed manual transmission (MT82 Getrag) gear ratios:

• 1st = 3.66
• 2nd = 2.43
• 3rd = 1.69
• 4th = 1.32 (oops! We dyno'd in 4th, thinking it was 1:1)
• 5th = 1.00
• 6th = 0.65
• Final drive 3.31:1

So not using 5th might account for maybe... -3-8 whp or so? A small but measurable amount. We'll dyno it in 5th after the next round of mods, and we'll do a 4th vs 5th gear pull to see the difference, then. We have the headers we want to use picked out and we're rounding up parts for the custom after-header system we're going to build in-house so hopefully this won't be too long from now.

We have a ways to go on the 450 whp goal, but I still think its doable. Tuners are finding 10-20 whp on otherwise stock 5.0's, just in air/fuel/spark tweaks, too. DP is looking into getting the software for HPTuners or one of his other tuning packages to be able to tune our car, but I won't bother until after we have the updated I/H/E or at least the underdrive pulleys. Nobody else tunes our cars but Taylor @ DP. He programs powerful yet reliable tunes. We'll raise the rev limit at that time to 7500 rpm, up from the 6800 rpm the car is stuck with now (was supposed to be 7000 stock).

The I/H/E mods (intake/headers/exhaust) currently planned include some sort of aftermarket cold air intake (need to research the various 2011 offerings available) and of course full length headers + custom exhaust. A biggest single gain will likely be found in the headers - the stock exhaust manifolds units are short, tortured messes of tubes. There's a lot of 2011 GT header offerings out there already, but I plan on using American Racing Header's stainless steel full lengths:



Luckily they have some of the best header products on the market and their 2011 GT 5.0 full length header options are amongst the best. They claim a 32 whp increase, using the stock mid-pipe/mufflers/no tuning. So somewhere around 410 whp is what we'd be looking at after installing just their headers, without any tuning or other exhaust mods. The baseline number they had was almost identical to ours, 379 whp, and they reached 411 whp with the headers.

The problem I see with using theirs or anyone's full length header design and catted X-pipe is the location of the converter. Here's the STX/STU specific rule:

STX, STU – Any high flow catalytic converter(s) are allowed, but
must attach within six inches of the original unit. Multiple catalytic
converters may be replaced by a single unit. The inlet of the single
replacement converter may be located no further downstream
than 6” along the piping flow path from the original exit of the final
OE converter.

Here's the stock converter location on our 2011 (there's only 2)



So my thought is to buy the headers, throw some header wrap on them, then mock them up in the car. Take the measurements and see where the cats can be placed. Then we can build our own after-header exhaust with high flow cats further upstream, maybe even modify headers/collectors a bit if needed. We can then push the high flow cat exactly 6" back from the stock unit. Its more work, and less than ideal for ultimate power gains, but its the rules. We'll at least save weight on the custom X-pipe and rear exhaust portions over the pre-made units from the aftermarket, which always use heavier wall tubing.



On the custom X-pipe and after-cat portions of the exhaust system we'll be using thin walled, 20-22 gauge stainless mandrel bends & tubing, with a few V-bands in there to make everything easily removable. I thought briefly about making an aluminum after-cat exhaust, for the lightest possible weight, but the longevity would be severely compromised and it would be significantly louder. Need to keep the tested sound number under 100 dB (SCCA limit), but with cats it shouldn't be a problem. We'll do our own before-and-after exhaust sound tests here, as usual.

Not sure what mufflers to use, yet. Just read Andy Hollis' "Sounding Off" muffler test article in the Dec 2010 issue of Grassroots Motorsports and the best results came from the Burns mufflers, so I cannot ignore those pricey little buggers. I really like Flowmaster's products and tend to use their mufflers on a lot of our builds, but I want to keep it very light and all stainless. With the cats required in STX it won't need as much muffler to meet sound regs as we used in DSP on the E46, so we might go with some sort of lightweight race muffler instead of FM's larger chambered style or the new glass-pack style Hushpower units. Since there's 2 big spots for the stock mufflers all the way at the back, that's likely where we'll end up with ours. Meaning: a full length exhaust (not a dumped/shorter run). If we can use a bullet style muffler we could place them where the stock resonators are, and use turn-downs for a shorter/lighter system.



The first two real "test wheels" purchased for the Mustang also arrived today. Both Enkei wheels were immediately weighed, with some surprising results:



So the 18x10" RPF1 was lighter than the 18x9" FP01. Weird, right? But we knew the FP01 would be heavier in the same size, just a bit surprised that a one inch wider RFP1 would be almost a pound lighter. Still, at 19.3 lbs the FP01 is already at least 7 pounds lighter than the stock wheel.

My wife stole the Mustang today so we'll test fit wheels later this weekend and post up about if/how they fit next time. I have a feeling the more curved spoke FP01 will have substantially more caliper clearance than the flatter spoke RPF1.

OK, I'm going to get back to work. Until next time,

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Talk to Wheel Dude about the Rota DPT. From what I've heard about the 17x9 it's only a 1-2 lbs more than a RPF1. A lot of the time attack guys were/are running them. Turn-In-Concepts was running a set of 17x9 DPTs on their car at Englishtown in 2009.

http://www.wheeldude.com/catalog/pro...oducts_id=5911

They have 18x9 with 42mm and 20mm offset.

Rotas are always going to be heavier than the Volks or Enkeis they are copying. We weighed Matt's 18x9.5" Grids and they weren't light @ 22 lbs.



Not to worry - we have an Enkei FP01 18x9 ET45 arriving today and an 18x10 ET38 RPF1. We'll weigh both shortly...

[Miatamoto]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Talk to Wheel Dude about the Rota DPT. From what I've heard about the 17x9 it's only a 1-2 lbs more than a RPF1. A lot of the time attack guys were/are running them. Turn-In-Concepts was running a set of 17x9 DPTs on their car at Englishtown in 2009.

http://www.wheeldude.com/catalog/pro...oducts_id=5911

They have 18x9 with 42mm and 20mm offset.

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Terry,

The RX-8 uses the same 5x114.3 bolt pattern, and can fit 18x10 wheels pretty easily. SSR made a set of 18x10 or 10.5 +42 (??? i think) Comps at one point - Sipe had a set on his STU RX-8 back in the day.

If the brake clearance issue is radial clearance, good luck with the RPF1. Those wheels are super light and strong for their size due to the barrel design, but that same issue means they usually size for brake clearance like a wheel 1" smaller in diameter (i.e., an 18" RPF1 will have radial clearance like most 17" wheels, etc.)

Mazda uses this same pattern, that figures. It seems all 5 lugs are this size, except GM and Porsche.

Sipe has an 18x10.5" SSR, eh? Hmm... can you find out more? Size and backspacing? I don't have Sipe's contact info, and with him being in STX... don't know if he'd want to share. Not like we'll be a threat, but you know.

I asked McCall what he had on his RX8... he can't remember. It was an RPF1 and we think it was an 18x10 or 18x9.5"? He's going to go back and see if he can find out.

Thanks,

[altiain]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Terry,

The RX-8 uses the same 5x114.3 bolt pattern, and can fit 18x10 wheels pretty easily. SSR made a set of 18x10 or 10.5 +42 (??? i think) Comps at one point - Sipe had a set on his STU RX-8 back in the day.

If the brake clearance issue is radial clearance, good luck with the RPF1. Those wheels are super light and strong for their size due to the barrel design, but that same issue means they usually size for brake clearance like a wheel 1" smaller in diameter (i.e., an 18" RPF1 will have radial clearance like most 17" wheels, etc.)

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Project Update for Nov 17, 2010: We've had a huge amount of responses (some that I've replied to) on the 4 forums where I have posted this thread on so far, so some of this might look familiar on the thread you're reading. Adding the RoadRaceAutoX.com forum was a big boost in ideas/questions (thanks guys).

Autocross and Time Trial Classing - We've had a lot of folks question my sanity on the decision to run STX for SCCA Solo classing. Not sure what this class is? Read the STX rules here on Jason Rhode's STX blog page. Speaking of that...

http://www.rhoadescamaro.com/build/

Go read that blog and see another racer who's bucking the trend in STX - by using a V8 powered RWD solid axle '67 Camaro Z/28! If you thought our build was crazy, he has pretty good reasoning for his similar-yet-different V8 RWD chassis decision there. Now his 1st gen Camaro STX build, when all is said and done, will likely be 300+ pounds lighter than our 2011 GT, so he might really be onto something. And remember: he beat all the Civics in STS back in 2006 using a RWD Nissan 240SX, so don't just assume that being competitive in STX is impossible in a powerful RWD car. He's proven that winning in unconventional cars is possible, if you develop it well enough. Very cool build, mad prop's to J-Rho! We've been tossing ideas back and forth on both of our cars, and he has clued me into some great ideas already.



Also, our foray into the ST category with the S197 Mustang GT isn't unprecedented. We had a Vorshlag tester (KentK) that helped us in the development phase with our S197 camber plates and AST shocks for this chassis. Somehow Hanchey and I convinced him to try it in STU. He ran the same Enkei NT03+M 18x10.5" ET30 wheels (the rears needed more backspacing) we ran on the EVO X, and he had the STU class limit 285mm wide Dunlops, with the above mentioned AST/Vorshlag suspension. It wasn't half bad in the handful of races he ran in STU, against the Texas STU crowd here, but he didn't stick around long enough to develop it. He moved to ESP class, with big 315mm Hoosier A6 tires, where its done well Nationally - and is still doing well there. The prep level he has on the car now would have sure helped his chances in STU, way back when. So for our 2011 GT in STX... sure, its going to take a lot of testing and prep, but we think its got an outside shot at being competitive. Stock for stock, the '11 GT has +100 whp over the '05-10 GT chassis Kent used in STU, too.

For NASA Time Trial use (where we should have better luck using the proposed 450 whp we think we can make in STX legal trim) we'll use a wider wheel (18x10" or 18x10.5") and a wider tire (285mm) with something like 140-200 treadwear. The 2011 GT was just re-classed in NASA from TTC (2005-2010 GT) to TTB (2011 GT), and has a race weight of 3770. We'll have to ballast up to make that, and it will likely end up in TTA with the mods we have planned. Ugh. We'll talk more about TT prep in a later post - we won't have a track test day even planned until after at least the "Stage 2" (AST 4100) suspension and the "big" wheels are on.


Factory undertray has a flip-down trap door over the oil filter. We changed 8 qts of Mobile1 and Wix filter goodness

Wheel Testing - this has been most of what we've done with the GT the past week, other than the initial oil change @ 250 miles (the stock oiling system takes 8 qts of oil - that's kind of encouraging, actually. Went with 10W30 Mobil1 + Wix filter). I started asking about wheel options before we bought the car, back in this massive Corner-Carvers thread about the Coyote 5.0 motor/2011 GT. The beef I brought up there was the lack of wider, lightweight 18" wheels made for the S197. In my early measurements I could see that the standard GT's 18x8.5" and even the '11 Brembo GT's 19x9" (ET42) wheels were small for the size and weight of this car - and there was tons of room for wider wheels going inboard. The stock 19x9" wheels/tires are boat anchors (57.2 lbs per corner!) and the factory 255/40/19 tires are super tall, too (27.2" tall!).


Left: Stock wheel/tire is 57.2 lbs. Right: factory wheel is 19x9" ET42... that's made in China

The problem we quickly noted was that the aftermarket was pushing blingy, heavy, yet narrow wheels for the S197. Most of the Mustang drivers on the non-race forums were choosing cheap, "replica" wheels that are hideously heavy. Or Shelby GT500 wheels (18x9.5"), also very heavy. The only "real S197" direct fit wheel we found in 18x10" that wasn't a Chinese replica was the expensive BBS 18x10" shown below...


Above: The "Boss302R" 18x10" BBS wheel Rehagen sells is 20+ lbs and $637; Its used on some Continental GRAND AM S197 race cars

TireRack lists a bunch of heavy aftermarket stuff for these cars, too: 18x8, 18x8.5", 18x9.5" and a bunch of 19" rubbish - all of it heavy. I won't have a car that uses 19" race tires, no way. There's no reason to have 19" wheels on this car, period. 18"ers clear the brakes, and the tire choices are MUCH better in that diameter, so 18" it is. 19's is simply a styling move, and one I hate. Some of the reason we haven't found many wider 18" options yet, I think, is because the 2011 Brembo package is still "new" and the larger 14" Brembo front brakes are somewhat unknown - not all 18" wheels will clear the big caliper, as we found out.

Where were the Enkeis, Team Dynamics, Volks, WedSports, OZs and the many other lightweight aftermarket wheel options?? Well, digging deeper we noticed that they were all out there, just not listed under the S197 Mustang. Nissan (350Z), Mitsubishi (EVO), Subaru (WRX/STI), and Honda (S2000) all use the same 5 x 4.5" bolt circle (they call it 5 x 114.3mm). And most of the aftermarket wheels use an oversized hub bore, so we can make hub-centric adapter rings to fit the Ford's 70.5mm hub bore. That's good news.



So last week I tried to fit Stuart at AST's 18x10" CCW Classics (6.75" backspacing) from his '05 GT (above, left) onto our '11, but they didn't even come close to clearing the huge front calipers. The Classics aren't known for their awesome caliper clearance, but it did have me a tick worried. Next we pulled an 18x9.5" ET20 (6" backspace) Rota "Grid" Matte Bronze wheel and 275mm tire off of Matt@Vorshlag's 350Z (above, right) to see if that cleared the brakes and fenders, but I had my doubts due to the 20mm offset... (sorry for posting this pic twice, but it is more applicable here/now)


(yes, that is photoshopped to be lowered... this is the actual pic)

That first test was pretty enlightening. The gold wheel didn't look that bad on the car, either, but that was not the point. This Rota 18x9.5" ET20 doesn't fit inside the S197 fenders, as feared; the tire was sticking out past the fenders (about 1/2" out back - see below), but it was a good reference point and let us measure the inboard clearance to the suspension. After measuring the 18x9.5" Rota on the car it looks like we could go inboard by 2.5" in back and over 2" in front... meaning an 18x11" up front and 18x12" in back could just barely fit, if you played your offsets right. With enough camber, rolled front fender lips, and a different style front swaybar end link (more on that later). It should be easy to fit an 18x10 on both ends, though. Backspacing of 7-7.5" on the front and 7.5-8.5" on back looks to be ideal for 10"+ wide wheels, from my measurements.



I then borrowed an 18x9.5" ET45 wheel (a TireRack branded Subaru-fit wheel) with a mounted Dunlop 275/35/18 tire from Paul M's '95 Impreza/STi swap project last weekend. Tested it on the GT this past Sunday and it fit much better than the same size'd wheel in ET20 we tried before (under the fenders at both ends). If I had to choose a street wheel without the need for maximum width/grip or goofy class rules that limit us to little 9" wide wheels, the 18x9.5" ET45 would be the obvious choice for the S197.

So the Subaru/Nissan 350Z fitments are what we ending up searching on, as there seemed to be many more wheel choices from companies like Enkei. Hub bore is different, but like I said, we can make a hub-centric adapter ring. I'm trying to get an 18x9" in at 18 lbs or less, so Enkei is the first obvious option we're looking at (NT03+M, RPF-1 or PF01 models). Matt found an Enkei RPF-1 in 18x9" ET35 (6.4" backspace) which might just barely fit (18.4 lbs), and they also have a PF01 (new for '09) with ET45 (6.77" backspacing) that's sub-19 lbs (the 18x8.5" shows to be "18 lbs", no weight on the 9"). The ET45 will fit inboard better, obviously (nearly identical to the stock '11 Brembo 19x9" ET42 wheel). In the 18x10" size the choices got much slimmer... the most backspacing we could find was 7" (18x10 ET3 for this bolt pattern. So we ordered one of the 18x9" ET45 in the Enkei FP01 and one 18x10 ET38 in the Enkei RPF1 yesterday from TireRack and we'll test fit them when they show up next week and report back.



We talked to the nice folks at Team Dynamics, who were willing to custom make the 5x4.5"/70.5mm hub bore in one of their 18x10 wheels in one of 3 offsets (ET40, 52 and 56 - all Porsche fitments normally in 5-130mm), all of which would fit much better ion the rear but might require a small spacer up front. Weight was the killer - 28.5 lbs for the 18x10s.

Tire height is the next issue. The stock Mustang 255/40/19 tires on the 19" wheels are a staggering 27.2" tall. The 265/35/18 we're thinking of using for STX class is only 25.3" tall, which is a huge difference (for gearing, CG height, etc). Not many choices there, as most of the ST-legal/competitive 265s are all this same size. For the street a closer match to stock is a 285/35/18 tire, which is 25.9" tall. Those probably will go on the 18x10" wheels for street/track use. For a variety of reasons (racer recommendations, price, compound, & sidewall style) we're looking at the Hankook RS-3 tire for initial testing. After being out of ST category for a year a lot has changed... we probably need to test the same sized tire in Yokohama AD08, Dunlop, Kumho XS, and Toyo R1R, if not more. I doubt many/any of these have been tested on a car this heavy, either.



Last night I worked late on SolidWorks and revised our Vorshlag S197 camber/caster plate drawings (rev 3 for all of the main parts), so we're having a short run of these made in steel. It will eventually be released as an aluminum plate, after I have time to add the "Vorshlag" logo, model engraving, hash marks, and crunch the numbers. We'll test the plates on the stock springs/suspension next week, then try it with Eibach lowering springs (I think that's going to likely become a popular and affordable S197 package - Eibach springs and Vorshlag plates). I'll rate the stock '11 GT Brembo spring rates on our Longacre spring rater, too (see this Spring Archive for similar data).

I'll stop there for now. We've got a lot more to share., and keep those suggestions, questions and ideas coming.

Thanks,

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Do you have plans to take advantage of any of the STX Solid-axle suspension allowances? I'm not real familiar with how they work or what advantage they'd give, but I'd think if they help offset the crappy rear end that that would be an important part of the build.

The stock rear suspension set-up looks pretty good, for a solid axle RWD car, from a basic geometry perspective. The 3 link and panhard bar are so much better than the "opposed 4 link/quadra-shock" mess that SN95/Fox3 was stuck with for nearly 3 decades. The S197 rear suspension is much more "Camaro-like" (3rd/4th gen Camaro) than Mustang-like. Not surprisingly it weighs similar to what the 4th gen Camaro did, and can fit similar wheel/tire sizes. And makes similar power. Really, the 2011 is pretty much an updated 4th gen Camaro (what GM should have built, not the 3800 pound parade float with zero visibility and IRS!).



I need to read up on the solid axle allowances in ST*, but I think they are similar to SP, right? Torque arm, panhard, watts link are all allowed. If anything we'll look into the watts link. There's some other tid-bits we have planned on the rear suspension we'll talk about soon as well.

[murph]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Do you have plans to take advantage of any of the STX Solid-axle suspension allowances? I'm not real familiar with how they work or what advantage they'd give, but I'd think if they help offset the crappy rear end that that would be an important part of the build.

[racer7088]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Looks awesome baby T!

[Thinkkker]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

18X11 please! Heck, even bigger!

I think it can be done, maybe with the use of a spacer in front and allow the rear to swallow the rubber. I'll put my name on the list now!

[Fair!]

Re: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build

Terry, just a thought: You have found some rims that would clear the calipers that either come in the right widths but wrong offset or vice-vice versa. Given the volume of the SN197 aftermarket (and its likely growth), I wonder if a company making one of those rims could be talked into producing some with the correct offset and the widths you want. Perhaps a retailer such as Vorshlag could commit to selling and promoting them? Just a thought.

We are looking at the potential for helping design/market a new wheel to fit the S197, yes. It would have to be "significantly different" than the hundreds of other S197 fit wheels out there to be worthwhile... lighter, wider, proper hub bore/bolt circle/caliper clearance without spacers, etc. As we're seeing there are a lot of heavy wheels, and a few Nissan/Honda/Subaru/EVO wheels that can be made to fit these cars, but not any real lightweight wheels that are truly made for the S197 (other than the $637, "20 pound" BBS being sold by Rehagen Racing - see below, right).


Left: D-Force 18x10" wheel is 18.7 lbs and $309 retail. Right: This is the only lightweight 18x10" we could find truly built specifically to fit the S197

There's probably a good place to build say.... an 18x10.5" wheel (under $350 and less than 21 lbs) that would fit the S197 correctly and accept wider than 275mm tires. We'd partner with D-Force Wheels, of course. Then again, as soon as we spent the capital to make this new wheel, a company that sounds like FirePack would just copy it with a Chinese built offering and sell it for $10 less... D-Force is also getting into forged and multi-piece wheels - we'll know more about their added capabilities after the 2010 PRI show next month. The Mustang is one car that really needs a dedicated, racer-owned/run, small wheel company like D-Force in its corner making lightweight racing wheels, and Vorshlag has worked with D-Force intensely since 2007 developing new wheel fitments for the BMW community.

Let me guess......this car will not have an LSx put in?

Ha! For once there is a car out there with a motor worthy enough to NOT need an LSx swap!


Va-goosh!