NASA TT/ST Thread

[Ewheels]

@Scootsmcgreggor @PaddyPrix there is a S197 guy on TMO who says he fits 4 wheels in the car with a roll bar and no passenger seat. Patrick, I think Frank has done this too. I haven't tried it yet myself but if I can fit 4 wheels, jack, stands, basic tools in the car with roll bar, then I will for sure get rid of the trailer hitch and save myself 36 lbs.
I think it'll be one in the trunk and maybe 3 in the passenger seat area...or possibly one between the down bars and then two in the passenger seat area.

Can anyone chime in on if its better to shed weight or go wider and stickier on tire? I think if I stay TT3 and go to 305 (200tw) at my current weight I am fine, but if I go full sticky race tire I would have to add a little weight or tune a little power out.

Both, lol.
I'm not familiar with SCCA rules but at least in NASA TT, there's no penalty for width of tire so I would use the widest you can fit.
The latest tire rules for NASA allow you to drop more weight (or add more power) if you use less-grippy tires. So an A7 would mean your car is the heaviest and a 300tw tire means you can shed several hundred pounds. That balance is up to you (though typically, A7 is the fastest choice if they are in your budget.)

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[nbjeeptj]

On the car class form for the TT3 cars if you use a tire from 267 to 282 section width you get a .3 HP to weight benefit on your power to weight ratio. That is why I can go so low on my weight at my current HP because I run a 275 tire. If I go wide and sticky I don't get the .3 benefit and my weight is pretty close to min at 3850ish.

Here is the part of the car class form I'm talking about.

 

[Ewheels]

On the car class form for the TT3 cars if you use a tire from 267 to 282 section width you get a .3 HP to weight benefit on your power to weight ratio. That is why I can go so low on my weight at my current HP because I run a 275 tire. If I go wide and sticky I don't get the .3 benefit and my weight is pretty close to min at 3850ish.

Here is the part of the car class form I'm talking about.

Gotcha. I think tires play a larger advantage than weight. In your position, I would go with increased width (305mm) and if you need to ballast up to make minimum weight, then it's a necessary evil.

You'll need to play with the calculator to see what works best for you but I would guess a +1 tire (A052), 305mm width, and you should still have room to lose some more weight even with your added hp.
From what I've seen, A7's always win races even if that means the car is a bit heavier.
I can't afford a $2000 set of tires that last one weekend so I will be utilizing the +1 or +1.6 tire category and play with weight and power from there.


Hope this helps!

 

[Ewheels]

It'll also depend on the tracks you drive at.
Longer straights favor more hp. Tighter tracks will favor less weight.

 

[Scootsmcgreggor]

For you Eric. The downbars on the Watson roll bar are a bit further back but hopefully this configuration could still work. God help you if you get hit on the street with the wheels up front but pretty sure the time on track is still the more dangerous part of the day.

 

[Flyhalf]

Current weight reduction:
Jacking rails: +13.8
Mufflers: -18
SVE Wheels: -36
Engine Cover Removal: -3.4
Sound Tube Removal: -1.3
CB005: +5
Sway Bars: +1
Front Rotors: -2
Rear Rotors: -2
Catch Cans: +2
Misc Brake Cooling Parts: +3
Floors Mats: -2.6
Fire Extinguisher: +5
Rear Seats + Hardware: -60
Trunk Carpet Cover: -5
Tire Inflator: -5
Watson Roll Bar: +58
Curt Hitch Receiver: +36 (to pull a tire trailer, but might be able to fit 4 wheels in car with roll bar still)

Weighed at event: 3957 w/ driver and 1/4 tank gas

Sparco Seat/Harness/Hardware: -20
Passenger Seat Removal: -50
Windshield washer bottle: -9
Resonator: -10

New estimated weight: 3877

I personally want to keep the engine completely stock for reliability purposes, so at my stock 413 whp, I can go as low as 3601 lbs with a +1 tire OR 3750 lbs and add 20 whp. Either way, a lot of weight to lose......or just put some 3R's on and call it a day. I don't think my current skills would fully utilize 3R's though.

3r worth less at ansa cause same points of A7

The front indicators are 7-8lbs for both.
Tires wheels are great for weight loss.same for girodisc (11lbs each)
Coilovers are lighter than OEM stuff.

 

[Ewheels]

Yeeeeess! Seriously wish I tried this before I bought a tire trailer but that's ok, learning experiences were had.

God help you if you get hit on the street with the wheels up front

Sshhhh, we don't talk about that part

3r worth less at ansa cause same points of A7

The front indicators are 7-8lbs for both.
Tires wheels are great for weight loss.same for girodisc (11lbs each)
Coilovers are lighter than OEM stuff.

True but I can't afford A7's so that makes the decision much easier.

 

[Flyhalf]

Yeeeeess! Seriously wish I tried this before I bought a tire trailer but that's ok, learning experiences were had.


Sshhhh, we don't talk about that part




True but I can't afford A7's so that makes the decision much easier.

The difference is less than u think

 

[Ewheels]

The difference is less than u think

One day. I still need much more driver mod before I move to those big-boy tires.

 

[Biggsy]

thanks of creating this thread. I plan to run TT3(hoping that I meet the hp/lbs limit) and must admit I'm a bit confused on the point system. Is there a number of points allowed for each class? I read the rule book but I didn't see anything explaining that. Don't really know what number of points I am trying to target.

 

[Ewheels]

thanks of creating this thread. I plan to run TT3(hoping that I meet the hp/lbs limit) and must admit I'm a bit confused on the point system. Is there a number of points allowed for each class? I read the rule book but I didn't see anything explaining that. Don't really know what number of points I am trying to target.

You just have to be above the minimum power-to-weight ratio for the class. So TT3 is minimum 10:1 but there are modifiers. The big modifiers are weight and tires.
For example: tires may be +1.6, +1.0, +0, or -0.7 modifier. So if your car is exactly at 10:1 and you then choose a +1.0 tire, then your adjusted ratio is now 11:1. That means you can add more power or drop more weight to get you back down to 10:1

(In case it's unclear, they weigh and dyno your car at the events to get actual values. Unlike most lower-budget time attack organizations which use modification point systems to class cars.)

Link to calculator

 

[PaddyPrix]

I will for sure get rid of the trailer hitch and save myself 36 lbs.

I mean, you could also bring some sockets/wrenches and remove it.

The latest tire rules for NASA allow you to drop more weight (or add more power) if you use less-grippy tires. So an A7 would mean your car is the heaviest and a 300tw tire means you can shed several hundred pounds.

That's where you have to collect your data and make that informed choice for. Nobody races in a 300tw tire, because it's not a race tire. Does grip matter on a very fast course with slow turns? Does grip matter on a super slow course with slow turns? I dunno, and that's where the fun comes in. At someplace like ACS, the tire grip doesn't really matter for a heavy car with lots of power, there are 3-4 straightaways for which a +1.6 tire is equally as fast as a 0 tire. Something like Buttonwillow, not enough space to let the power down, so that additional grip comes up big, an extra 3-5mph in each turn will definitely add up.

thanks of creating this thread. I plan to run TT3(hoping that I meet the hp/lbs limit) and must admit I'm a bit confused on the point system. Is there a number of points allowed for each class? I read the rule book but I didn't see anything explaining that. Don't really know what number of points I am trying to target.

Not saying RTFM... buuuuut -- https://drivenasa.com/time-trial/

They have a real nice calculator that you use to start your form and declarations though -- https://form.jotform.com/drivenasa/st-tt-car-classification-form

So from there choose your intended class, and what options you are taking. The 1-2 is different than 3-4, and moreso than 5-6, not that we have a shot in hell of making it. In short, TT is the gateway to ST, and so we're using those rules for classing/mods/weight. So, TT3 is 10:1 power to weight, with each class being off by 2, to TT2 is 8:1, TT4 is 12:1, and so on.

If you're under weight, you're cheating, DQ! If you kick ass and take too many names, they can force you to dyno, or an angry competitor can just the same, and then who is in the wrong pays the dyno fee. If you're over, DQ! Definitely don't want a DQ, as it's 0 points, not dead last, and you cannot use one of your drops against it. Might as well carry just a few extra pounds or add a few extra HP just to allow for dyno variance, or best yet, get your dyno done at the track, so it's on their official dyno which may make or break you. For sure, definitely not the place that gives huge numbers to brag to your friends, because if they're overstated, you're lining up against a guy who is potentially understated, and 10-20rwhp might be enough if all other car and drivers are equal.

But in short, the smaller the number, the better, and you want to get as competitive as you can and just barely make the class limits, because just barely making one class above means you'll likely catch beatings from cars that just barely make theirs.

The baseline is a 3000# race weight (car + fluids + gas + you) as measured as you come off the track, if you're lighter (say, 2400), you get a mod penalty because you brake later and have less to stop and accelerate on what, and if you're heavier (3600), you get a bonus to run more power or better tires to start and stop that boat. More or less, our competition are usually 3000#ish Corvettes WITH SHITTY DRIVERS.

Everybody who races ST/TT has their forms up on the internet, so you can stalk your opponent and try to figure out what makes them tick == https://airtable.com/shrtuIZcugofvmCJZ

For example: tires may be +1.6, +1.0, +0, or -0.7 modifier. So if your car is exactly at 10:1 and you use a +1.0 tire, then your adjusted ratio is now 11:1. That means you can add more power or drop more weight to get you back down to 10:1

It actually goes the other way, which is hard, but 10:1, if you use a +1 tire, then you're technically 9:1 then, because the power is the denominator.

 

[Biggsy]

@Ewheels @PaddyPrix My apologies gentlemen. I should've mentioned that I did see the calculator and played with it a couple times before but I never scrolled back up to see the "min weight' and " max HP" change until just now. I was expected something at the bottom of the page to change/appear. I appreciate you guys still taking the time to reply and answer all questions as always.

 

[Ewheels]

I mean, you could also bring some sockets/wrenches and remove it.


It actually goes the other way, which is hard, but 10:1, if you use a +1 tire, then you're technically 9:1 then, because the power is the denominator.

Sadly, the hitch does not go on and off easily. Otherwise, that would definitely be my plan.

I see how my first post was misleading. Let me clarify...
If you at 10:1 before you make a tire selection, then choose a +1 tire, you will be at 11:1. Then you can shed weight (assuming power is constant) back down to 10:1 adjusted but in reality you will be at 9:1

 

[Flyhalf]

Nasa is simple.
U need to input 3 things.
Class where u wanna be
Your weight.
Your tire.

And he tells you
How much HP max you can have.

Then submit a dyno sheet with SAE5smoothing and calculate average max power. With the 8 top peaks. With 250rpm increments.

I.e. Lets say you top 400whp at 7000rpm
You work around this +-250rpm (like 6750rpm 397 6500@391 7250@398
) /8 =.your average power

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