continued from above
2017 TTD POINTS BUDGET AND PLANS
Time for some bench racing! Assuming no major rules changes happen to TTD for 2017 (HA!), we have an updated yet flexible build plan laid out for our next round of mods to this 330 for TTD. We will hopefully reach "fully prepped" status before too much of the next season has passed us by. We hope.
A custom long tube header, like this one we built for a customer's tube framed 69 Camaro, is in the works for this 330
There have been a few emails I've sent among the Vorshlag staff and a few trusted gearheads showing where we are on the build (we have excel spreadsheets for every NASA build we have ever done, dreamed up, or helped customers plan out). We have 12 unused points that we don't want to "just use for weight", as running a TT-letter class car under class minimum gets pretty "points spendy" pretty fast. On top of that, your P-to-W ratio never changes, so even when you spend points to "run light" you have to lower your target horsepower to match the lower weight. This is usually only done when you don't know any better or, like in our case in October, have an under-prepped car in between development phases.
A high flow, custom stainless steel, mandrel bent exhaust is also in the plan when we add the header
For 2017 we will ballast back up to 3285 pounds (a 4-point roll bar will make up a chunk of that) and then use the remaining 12 points to take the car to "max prep". I will quickly explain below the points, weights, and power for our car in TTD now and where we are going.
Base classing: TTE* with 3285 lb minimum. That means we have 12 points (19 - 7) to spend in TTE class.
Bumping up one class (+20) gives us a total of 32 total mod points for max TTD prep.
Adjusted Power-to-Weight Goal = 13.45 pounds per hp (we get a 0.8 modifier bonus for 245mm tires)
Target weight with driver = 3285 pounds (we can ballast up to that easily)
Target horsepower = 244 whp (we are at 195 whp now)
Points budget so far:
- Tires: 245mm size (+1) and Hoosier R7 compound (+10)
- Suspension: Swaybars (2), MCS 2-way non-remote shocks (3), and coilover springs (2)
- Brakes: Front "BBK" upgrade (+2)
- Total points spent: 20
Winter power upgrades:
- Custom full length header and full exhaust (+5)
- Vented hood & cold air intake (+1) and custom tune (+0)
- Undertray/ belly pan (forward of axle centerline +0)
- Widen track width (+0) up to 4", and add flares for more tire clearance (+0)
- Total with winter plans: 26
All of these modifications had competitive based reasons, and some of them also had marketing reasons. While the swaybars (+2) and BBK (+2) might seem frivolous (testing/marketing vendor parts), after doing some before/after testing we agreed that both mods were worthwhile. And yes, finding 50 whp with exhaust + cold air + tune will be difficult, but I think we can get pretty dang close. The SpecE46 guys run a terrible E36 M3 factory exhaust manifold, a non-optimal "spec" exhaust, and a conservative tune and get to 220-230 whp. Why can't we find 15 more than that with a REAL header design and a custom tune??
This leaves us with only 6 points (32 - 26) left to spend after we burn the points on exhaust and cold air mods for the winter. The best way to spend those points seems to be aero mods. With the low-ish power goals we know downforce will cost some straight line speed but we hope to make that up in cornering speed and braking improvements. We also have a lot of drag now (no front undertray, front tires poking into air stream, non-vented hood) that we think can be cured with some smart aero tweaks.
Here are all of the relevant TT-Letter aero mods' points (see page 34):
- Custom front splitter (+3)
- Alternate front fascia and/or air dam (+3)
- Undertray/belly pan forward of axle centerline (+0)
- Add canards/winglets, includes portions of an added/modified/replaced fascia that provide a downward force (+2)
- Add or modify side skirts (+2)
- Custom rear diffuser, under 5" verticals (+2)
- Rear wing up to 8" above roof (+4)
- Vented hood (+1, lumped in with cold air)
Of the list of possible aero mods above, I'd originally planned to do a fascia (+3), rear wing (+4), vented hood (+1 with cold air) and splitter (+3). That was only 10 points above our current build, but with the 7 point classing penalty from January 2016 that wrecked some of our aero plans. Now we have to get very stingy on points.
The "air dam / fascia change" is out, as 3 points costs too much for so little gained. Shame, as the "Base Trim Model" E46 front end on the car now is a little beat up. I had already purchased an E46 M3 bumper cover for this car in 2015, before the reclassing. I've also seen Greg rule on front facia changes with points for air dam (3), splitter (3), and canards (2) for a total of 8 points for a bumper cover. Too risky.
Making a worthwhile splitter that only costs +3 point looks nearly impossible, as the bottom of the bumper cover isn't flat. Almost all splitters added in TT-Letter end up taking air dam points (+3) as well, which makes a splitter really cost 6 points - too many, and it would leave us 0 points to balance the rear with any downforce. I have driven a "front biased downforce" car and it was a bit scary at high speeds.
To help cover the protruding edges of the front tires, the 2015 Camaro Z/28 used add-on "tire walls"
I think adding some tire walls to cover the front tires - which already poke out past the front fascia quite a bit and will only get worse with more track width - is a good idea. Tire walls are not listed in the aero section of the TT Letter rules, however. Would they be deemed "air dam" points (+3) or part of fender flares (legal for +0)? I think you could argue these vertical panels could be part of a flare (0 points), if shaped flat and vertical they couldn't be judged downforce adding canards... but that's the unknown, and some of the TT aero rules are written so vaguely here that it only begs for a protest. I doubt we will ever see totally crystal clear rules on all of these aero tricks, so we cannot take the chance.
With only 6 points left, going for a full splitter (+3) and wing (+4) are out, so what about a splitter (+3) & rear diffuser (+2)? That even leaves us a point for wiggle room. But again, can we even make a legal +3 point splitter? Risky.
The problem with a diffuser is - we would need to cut out the spare tire well out of the trunk to make room for the diffuser. Legal? If you look at the pictures above the trunk floor is pretty flat and all of that is dominated by the spare tire well. I would assume the "points" for a diffuser (+2) would seem to "pay" for that change? And spare tire wells are often sacrificed for fuel cells (+0 points), but that's the only place it is spelled out as legal to remove. Risky.
My other fear with this plan is that the front splitter (assuming +3) will overpower the rear diffuser (assuming +2), again making the car have an aero imbalance. After driving that scary ass scenario at Miller in 2013 (above), I never want to have that setup on a car again! We cannot afford to build and test every possible aero iteration, and so many of these run the risk of points protest - we need to make some educated guesses, figure out a "protest proof" setup, and then optimize those choices.
Fender flares need to happen to this car, regardless. We are seeing some tire rub in hard cornering and any time we even touch any curbing. Too risky, we need more room, and flares (+0) would allow us to push the wheels outboard for that +4" track width optimization (+0). We would keep the flares simple - just covering the tops of the tires, no rules pushing there - just like how I flared our blue 330 before.
Our last and possibly wackiest option is adding multiple, massive canards (+2) up front and a full AJ Hartman Aero rear wing (+4). My fear with this setup is too little front downforce having the rear wing over-powering the canards. Oh well, this is the least "risky" with respect to protests so we might just try that.
Last but not least - safety upgrades. We have to get some sort of roll-over protection in this car, and a good place to hang shoulder harnesses from. After debating this back and forth between a full cage, bolt-in 4-point roll bar, and a "back half" caged (custom 4-point roll bar welded in) we think we finally have a solution. We will build and install this over the winter, then finally get some real 6-point harnesses installed.
WHAT'S NEXT?
Whew, that was a monster to write. I better stop while I'm ahead. Well, we did inspect the DME today to see which DME module for BMW-Editor we needed to purchase...
This is an EFI software tuning system that should allow us to custom tune the M54 engine after we have the custom header, new exhaust and cold air installed. Goal is to make 50 more horses (244 whp) on the dyno to max out TTD, or whatever the new number is after they change the rules (inevitably) in January. If we move to "average" power and the P-to-W doesn't change we can make even more peak power. We'll know in about a month.
Cheers,
Leave a comment: