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We've got a few ideas in mind to keep pushing the performance of this 2011 Mustang on track. We know some of our TT3 records are soft, so it might be nice to bump them up a bit. And we're running some all new track configurations this year so we could try to nail down some more. But then again, TT2 is faster, and would be challenging to try to compete there in Texas and at NASA East Nationals. We beat some of the TT2 records last year in TT3, and with less weight or more power (or just more development on the TT3 set-up) we could feasibly reset some of those and nail down some wins. And if we went ahead and bumped the red 2011 to TT2 it would be an easy transition to bring the BMW LS1 ST2 car up to speed, accumulating points in the same class all year. Which way to go then?
Where To Race - TT2 or TT3?
Before we start this bench racing section I have to post the new NASA Super Touring rules, revised for 2014. This is the basis for the TT classing and rules, and there are some changes that affect TT2 and TT3.
New 2014 rules: http://www.nasaproracing.com/rules/Super-Touring.pdf
Lots of little changes in the new ST rules, and they look good. I like that the 4 door exemption is being cut in half, as this factor never really hurt most of cars that could come in both 2 or 4 door models.
The E36 BMW 2 door and 4 door chassis weigh almost exactly the same, but the 4 door used to have a +0.4 modifier bonus but now is only +0.2
The new 2014 revised Competition Weight modifier chart for ST, above, is easier to wade through and penalizes the super light cars more (sub 1800 pounds = -2.0 penalty!). I like this since the sub-1800 pound cars with driver aren't really "cars" per se, not by any modern definition. Just for grins here is the old, more complicated Competition Weight modifier chart from the TT rule set, below.
For 2013 the TT3 class was the most popular TT class in the NASA Texas at almost all of the 14 race regional competitions we had last year (and at NASA Nationals). And Vorshlag had a decent set-up there, winning 13 of the 14 regional TT3 races in this car, mostly with the pre-August '13 aero changes and narrower front wheels. We could feasibly develop the car further and do better in TT3 again, but for grins let's see what it would take to make the jump to TT2. At first glance it would seem like the jump would be easy, as it is "only a 1 point weight to power ratio change", going from 9:1 to 8:1. Just lose a few pounds here and there and race it, right? In reality it is much more complicated than that.
First let's back up and analyze our current TT3 setup with respect to power, race weight, and ratio modifiers:
2013 TT3 race weight was
3770 pounds with driver. I'm about 210 with my gear on and we've been using 3/4 tank of fuel to ballast up that weight (and to avoid fuel starvation - I usually go out in each session with a nearly full or totally full tank). Latest DynoJet chassis dyno pull was a best of
419 whp, after we added the new air snorkel, but it made 430 whp in the past (more on that "missing power" in a second). Here's the 2013 and 2014 TT3 ratio calculations:
TT3 Unadjusted Wt/Power Ratio = 9.0
Non-OEM aero =
+0.4 (*penalty) -
note this changed from -0.5 in 2013
Running 3700-3799 pounds = -0.5 (*bonus)
note: we used a +0.6 bonus for 2013
Adjusted Wt/Power ratio = 8.9 (the adjusted limit at this weight was also 8.9 in 2013)
3770 pounds / 419 whp = 8.99 currently
So if you noticed we were a little
over the 8.9 ratio needed at this race weight, almost by 0.1, which is a good bit. This means we could really have run as low as ~3730 pounds at this power level, or run a few hp more on the dyno at 3770, and not get dinged. That is just part of the cushion we like to run, just to stay squeaky clean and legal. As much as others have pushed me to I won't cheat, and I show these ratios and calculations publicly and have our TT classing paperwork at every event for anyone to look at. In 2 years, 20+ TT events, and probably 40 weighings on this car we've missed weight twice, both times by 5 to 7 pounds, and we fixed it shortly after (and ran faster at the proper weight in later sessions).
But how can we get this car down to an "8.0 ratio", to be competitive in TT2? We think there is a
bit of power to be had in the exhaust, as this setup used to make 430 whp and did for quite some time. The catalysts we are running are a few years old, and one of them is smashed a little and might have a busted catalyst matrix, causing some flow restriction. Removing the cats and making a shorter/lighter race exhaust might uncork that 10-12 whp and get the power back to where it was before (from 419 to 430). But other than that there is no more "easy power" to be had. Everything we could do to add 20-30 more hp would cost thousands of dollars (build a race motor) and virtually every bolt-on mod that might be done would just move the rev range up and likely lose as much or more power below 5500 rpms. So let's stick with 430 whp, for the most simplicity, reliability and lowest costs.
3770 pounds / 430 whp =
8.76
Hmm, we're still way off the mark at that power level. What about losing a bit of weight? We think that ditching the over-the-axle exhaust section and the pair of relatively heavy Flowmaster mufflers in favor of a lightweight "dumped" system like we built on the
custom Boss 302-S exhaust we built (see above) could shed as much as 40 pounds off of the current system (see below). We dropped
more than that on the 302-S exhaust. We could also replace the bloody
slip-fit joints from the headers to the exhaust (which always leak just a little and we have to tack weld in place) in favor of proper 3" stainless V-band flanges.
Then there is the rear seat, which when removed would drop another 35 pounds, with hardware. So with exhaust changes and rear seat removed that is the "easy" 75 pounds to lose. All could be quickly undone and involve almost no cost (well the exhaust would take two mufflers, some mandrel bends and about 7-8 hours to fabricate and weld, but who's counting!).
3695 pounds / 430 lbs =
8.59
If we do something about the fuel starvation issues, maybe with a new fuel tank sump or surge tank, that could mean we wouldn't have to run nearly a full tank. We run almost full now, which is 16 gallons, and at 6 pounds per gallon for gasoline
that's 96 pounds. Running only a 20-25 pound fuel load, with a proper fuel tank pick-up, surge tank or even a small fuel cell, might help us drop up to 70 pounds of fuel weight...
3625 pounds / 430 whp =
8.40
We're making some progress but we need a lot more. Let's look at some interior bits that could be removed to drop more pounds. That carpet likely has some hefty insulation under it. It needs to come out and be weighed. And the air conditioning compressor, accumulator and condenser core are not only heavy but the condenser core is blocking air to the radiator. Is there another 90-100 pounds in weight savings here, not even touching the under-dash bits? Could be.
3525 pounds / 430 whp =
8.18
So with a little bench racing we're getting closer to the 8 pounds per hp goal, but
don't forget about the TT modifiers. Since we are moving to TT2 there's no more +0.4
penalty for "non-stock aero" (formerly 0.5), yet there's still a
bonus for running a race weight heavier than 2999 pounds... scroll up to the Competition Weight adjustment chart for that modifier (now a -0.5 bonus, which used to -0.6).
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