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Unread 11-17-2015, 03:38 PM
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Default Re: Vorshlag 2002 BMW E46 325Ci - Daily/Track Car - Project Jack Daniels

continued from above

This is the Catch 22 for most TT-Letter builds... they aren't all equal because only some cars can get to the class P-to-W limits and still have any points left over for adequate tires and other supporting mods.

In a nutshell THAT is was why our TTC classed 92 LT1 Corvette works so well: first we got the adjusted P-to-W modifier for running a 245mm tire (plus 1 point was gained back because that's 10mm below the TTC class starting tire size of 255mm), which moved the P-to-W from 12.0:1 to 11.2:1... but the Corvette could still hit the P-to-W limit of TTC, even with a bone stock LT1 stock motor. This meant we didn't have to burn class points on exhaust or headers or camshaft swaps or intake mods. We spent ALL of our remaining points on suspension changes (springs at 3 points) and tire compound (R7, 10 points), and it worked out pretty well so far. It is rare that this works this way in TT-Letter classes, which means there is a bias for certain car choices for specific classes, which can limit car model diversity and choices for TT competitors.

Let's do those P-to-W calcs "the NASA way" for our TTC Corvette:
  • Weight is at or above the listed minimum weight of 3203 pounds from the base classing
  • That 3203 number is also just above the minimum "competition weight" modifier numbers, which start at 3200
  • We chose a 245mm width DOT legal tire (+0.8 bonus)
  • The stock engine made 284 whp peak (highest of 3 pulls)
  • 3203 / 284 = 11.28:1 (P-to-W) + 0.8 for (245 tire modifier) = 12.08:1
TTC Class "minimum" P-to-W is 12.0:1, which this car is just a hair over. That's what you want to do - aim for the P-to-W limit and find any modifiers you can to help that ratio along the way. Avoid modifiers that hurt, then use your points to run the best tire compound/width and fix any suspension issues, and add aero if you have any points left.

So long story short DO YOUR HOMEWORK up front when building for a class, make sure to CHECK THE MATH, and PAY MORE MONEY to start with the right car. Lastly, YOU GET WHAT YOU PAY FOR, so don't expect to save money by starting with a high mileage heap that needs a bunch of repairs vs a cleaner/lower mileage car that costs more up front. I just wish I could follow my own advice, ha!


The calculations for classing a Letter car was tortuously convoluted. Did you READ all of that crap in the section above?? Look at how much ink was spilled just to explain that a 330 is a better car for TTD than the 325!? The sad thing is I still got it wrong and had to go out and find the right car (330), and I've built a half dozen TT cars for myself and have made worksheets for dozens more for customers, many of which have gone on to be competitive, max point, maxed-out power-to-weight TT Letter cars.

Here is what we feel are the three most important things to winning in a road course setup, specifically TT-Letter classes:

1. Power-to-Weight ratio
2. Power-to-Tire ratio
3. Weight-to-Tire ratio

For NASA-Letter classes we have several things that limit tire width, so we have to keep that in mind. Ideally I'd run a wider tire than we are shooting for here in our TTD E46 330 (245mm) or our TTC Corvette (also 245mm), but the 0.8 P-to-W "bonus" for running 245mm or smaller is too good to pass up.

More tire width will burn up points FAST and we have found that a better tire compound is ultimately more important than running extra tire width, within reason. But if that were not the case, say that TTC became "TT5" (it might someday, read below) and had the ultimate 12:1 P-to-W limit as the lone guiding factor, we'd run more tire width.

Why? A wider tire can make more laps before overheating, lasts longer (wear), and is easier to drive. On the TTC Corvette with the power it makes we can quickly overheat the rear tires, so we use TT strategies to limit laps in any session to 2-3 laps. Running more laps would likely overheat the tires, they get greasy and fall off, then lap times start to slip.

We noticed this running 315mm Hoosier A6 tires on our TT3 Mustang, and after lap 1 the lap times would slow down 1-2 seconds for each successive lap. The tires also liked to run best cold, so that meant the first session of the day was almost always ideal. So it boiled down to one "golden lap" in one "golden session" to shoot for the best time each day, which sometimes made it difficult to get the best lap time out of the car (and subsequently, many of our TT3 records are "soft"). Every once in a while the stars would align, however, like the video below shows.This was 2013, Day 2 at a NASA event at NOLA, when we ran the 315mm tire on the TT3 car.

Day 2, first session, first lap - one shot to get the best conditions

As I mention in the beginning of the video, I knew it would come down to this ONE lap to nail it. It rarely works that way but somehow in that one lap I manged to match the theoretical best lap that the predictive lap timer showed was possible all weekend. That lap record has stood for 2-1/2 years with 3 different NASA groups running the same NOLA course, even after we made the car much faster in 2014 (wider tire, better aero). Since we didn't have any points or tire modifiers on that TT# classed car (the modifiers all go away above max out at 275mm in width for DOT tires), in 2014 we switched to 335mm front and 345mm rear Hoosier A7 tires (with no penalty), which added enough width and heat capacity so so that best laps could be made on lap 1 or lap 2. With the weight that car was run at (3802, to utilize the maximum "competition weight" modifier) it was still easy to overheat the 345mm tire after lap 2 - and that was the biggest DOT tire Hoosier makes.

Just like we used in TT3, up through 2014 the DOT Hoosier A6 was still a fairly low point, attainable tire that was commonly used in TT-letter classes to set track records. This made the "first lap strategies" that much more important in TT-Letter. Thankfully, in 2015, NASA rules makers raised the points up for the Hoosier "A" compound (autocross compound), so much so that it becomes prohibitive to use the A6 or newer A7 compounds. Now the go-to tire for TT-Letter is the more reasonable and less "peaky" Hoosier "Road Race" compound, the R6 and newer R7.

1 ) The following DOT-approved R-compound tires: BFG R1S, Goodyear Eagle RS AC (auto-cross), Hoosier A7, Hoosier Wet DOT (if used in dry conditions—see section 5.6), Hankook Z214 (C90 & C91 compounds only) + 22
2 ) The following DOT-approved R-compound tires: Hoosier A6 + 17
3 ) The following DOT-approved R-compound tires and those with a UTQG treadwear rating of 40 or less not otherwise listed in these rules: BFG R1, Goodyear Eagle RS, Hankook Z214 (C71, C70, C51, C50), Hoosier R7
Kumho V710 + 10
4 ) The following DOT-approved R-compound tires: Hoosier SM7 +9
5 ) The following DOT-approved R-compound tires: Hoosier R6, Hoosier SM6 (note: Continental Tire Sportscar Challenge EC-Dry tires (225, 245, 275) OK) +8
6 ) The following DOT-approved R-compound tires: Toyo Proxes RR, Hankook TD +7
7 ) The following DOT-approved R-compound tires and those with a UTQG treadwear rating over 40: Maxxis RC-1 (ex. Kumho V700, Michelin Pilot Sport Cup & MPS Cup 2, Nitto NT01, Pirelli PZero Corsa, Toyo R888, Toyo RA-1, Yokahama A048, etc) +6
6 ) DOT-approved (non-R-compound) tires with a UTQG treadwear rating of 120-200 (examples: Toyo R1R, Dunlop Direzza Sport Z1 Star Spec, Bridgestone Potenza RE070, Kumho Ecsta XS, Yokohama Advan A046 & Neova
AD08, Hankook R-S3, BFG g-Force Rival) +2
9 ) Non-DOT-approved racing slicks +30 (of any origin—re-caps and re-treads are not permitted)
And while there are many other tire models/compound eligible in TT-Letter class, the points they cost and the lap times they can produce just don't seem to be worth the effort. Even the hot "200 treadwear" tires still cost +2, which makes the points not work in their favor compared to a Hoosier R6 (+8 points) or R7 (+10). ALL other tire compounds seem to fall to the wayside when competition gets serious, at least in TTB-TTD. Toyo, Nitto, Maxxis all seem to be hopelessly uncompetitive at the highest levels of NASA TT. The BFG R-1 (+10) is a close contender to the R7, but it has many fewer sizes to choose from and has NO contingency program for NASA TT. The Hoosier contingency program is pretty solid, and is part of why so many racers just ignore all other options - they are fast and you can win 4 tires in a weekend if you have enough competitors in class.

So once you run the numbers and pick your tire width and compound (which locks in your "tire-to-__" ratios), its now time to maximize the Power-to-Weight ratio. Which is simple.

1. Minimizing Weight
2. Maximizing power

Duh.... right? Ultimately you run the least weight, the most power and the most tire, but that "most of everything" formula isn't allowed in TT-Letter, so we work with what we can maximize. Getting down to the minimum weight published in the Base Class listing is what you strive for (with driver and fuel), as I explained before. Going below that minimum isn't worthwhile due to the points its costs.

Maximizing power is a matter of both luck and skill. "Luck" in that you picked the right car that has plenty of OEM power, or potential to make power without too much effort. "Skill" in the way you utilize the points to modify the things you can to get to the max power allowed for your adjusted P-to-W.

That's it. That's the big 3. The rest (aero downforce and brakes and suspension) are smaller gains, but still significant, and on some cars there are deficiencies you need to fix (poor brakes, suspension issues, etc) that will eat up your TT-Letter class points. I could go on but that's enough, so I hope that made sense. This is the strategry we use.


The TT1/2/3/U (aka: TT#) classes are SO much simpler to build up than TT-Letter. You don't have to worry about NOT doing some upgrade because you ran out of points. Gone are base classings, points for mods and class bumps, the sometimes impossible struggle to max out a car for the classes' power-to-weight limit with no points left for power mods. You also aren't stuck running the minimum base weight - you can do whatever is allowed within the very loose TT# rules to get down to whatever weight you want, so you can always get your TT1, TT2 or TT3 car to the max P-to-W limit. Unless you suck at math or have no budget.

Time Trial 1 (TT1) = “Adjusted Wt/Hp Ratio” equal to, or greater than 5.50:1
Time Trial 2 (TT2) = “Adjusted Wt/Hp Ratio” equal to, or greater than 8.00:1
Time Trial 3 (TT3) = “Adjusted Wt/Hp Ratio” equal to, or greater than 9.00:1

And that list, ultimately, is the main basis for the TT# classes. The P-to-W calculation is 95% of the class rules. Just like the TT-Letter class Appendix B's list of modifiers, TT# has similar modifiers to that ratio, but ultimately P-to-W is your main guide, goal, whatever. You can remove weight to get there, or add power however you want to get there, but your adjusted P-to-W limit is everything.

That's why our TT3 Mustang worked well - we used some modifiers to get it to 8.8:1 (running it very heavy, over 3801 pounds gained us 0.6!), took the aero penalty for TT3 (0.4 this year), maxed out the P-to-W for TT3, and ran it on the biggest DOT tire Hoosier made (345 Hoosier A7), ran LOTS of aero (to the limit of the rules in several places), kick ass suspension, and brakes that were up to the task. We made it easy enough to drive so a schlub like me could win, then just used some strategies to try to get traffic-free laps. We racked up dozens of wins, set 16 track records this way, and didn't pay for tires in almost 3 years, but always ran on sticker sets (from winnings).

This is almost the level of dedication we are bringing to TTD with this E46 build. Getting the 330 makes this a MUCH easier task, but there are other cars in TTD that can and do hit the max P-to-W limit. But to me, none do it as easily as the E46 330....


So that was pretty epic explanation and had ALL of my strategies for maximizing a Time Trial build within NASA. I hope it was worthwhile because it took many seasons to learn these tricks. Remember though, the rules change every year and there are more changes afoot for TT-Letter.

These tricks also apply to the wheel-to-wheel (W2W) crossover series called Performance Touring (PT) and Super Touring (ST). In case you didn't know, TTC-TTF classes share the same competition rules as PTC-PTF, and TT1/2/3/U are the same as ST1/2/3/U. The only real difference are the W2W safety requirements. We often see PT and ST cars jump to TT for more chances to win, too.

I have not always seen eye-to-eye with the National TT/ST/PT Director and rules czar Greg G. I grumbled about TT-Letter class rules when we ran our Mustang in TTB (briefly and poorly) and again with all of the Mystery Internet Protest stuff surrounding our TTC build for my 1992 Corvette. Some of the rules in TT-Letter classes just went against basic racer logic.

This is one of the "dyno tricks" that turbo cars are doing in P-to-W classes

Well I think in the long run Greg is moving the complicated rules of TT-Letter classes to the more simplified TT# set of rules for all classes. That's what I've gathered from recent NASAforum posts by Greg G, and follow up letters to various competitors that have been shared. For 2016 the TT3 class is also getting an adjustment to the P-to-W starting points plus changing the way power is measured (average vs peak), which takes out some tricks turbo engines could do to make the same peak power for a LONG range of RPMs (see image above). These changes will likely propagate to TT1/TT2 in 2017 and possibly to TT-Letter also, at some point. I really like the proposed changes, so kudos to Greg. It is a bold move but a necessary one.

ST1/TT1 = “Adjusted Wt/HP Ratio” equal to, or greater than, 5.50:1
ST2/TT2 = “Adjusted Wt/HP Ratio” equal to, or greater than, 8.00:1
ST3/TT3 = “Adjusted Wt/HP Ratio” equal to, or greater than, 10.00:1

You can read the new proposals here and look for these changes and the Letter classes in general to phase over to new TT# classes in 2017, 2018 and beyond. I think the next TT-Letter class to go is TTB, which will likely become TT4. This happened already in 2013 when TTA merged with TTS and became TT3, so there is a precedent. Trust me, the TT# rules are SO much easier to understand and take out a LOT of the inherent car model advantages. TT# gives you more choices, more paths to the end goal (P-to-W), without fretting over damned points.


Please don't take this long explanation of NASA TT and get turned off. It really is worth it, and all of these rules, modifiers, points, and base classings are used to equalize the cars and differentiate the classes. And for the most part they really do work. It only fails when people don't do the math or understand the rules correctly.

NASA TT has big fields, lots of car diversity, and great contingency payouts

If you are thinking of buildings a car around NASA TT rules and are getting confused, CALL US. Jason and I here at Vorshlag can help, and we can steer you towards the best modifiers and tires to use for a given car and end class goal. That's really what you need to decide up front: what car you want to start with and what class do you want to end up in? Knowing that + the type of tracks you frequent, we can help guide you through the class points, the modifiers, and calculations within calculations to get towards the right selection of parts for tracks in your area.


We still have some initial repairs on the 330 to tackle, but they are much less extensive than the 325. And the 325 is getting the some interior and other bits from the red car, plus some other repairs, so it can be sold for a trouble-free daily driver to someone. I will post a CraigsList ad and link it here when its ready, hopefully in a couple of weeks.

I'm more excited than ever to prep the Hellrot 330 Coupe, as I really like the looks of this car and its better chances at a max P-to-W build. So, what do we call this red thing?

Thanks for reading,
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