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,