Seeking Advice: Time Attack, NA vs. NB2 A better Starting Point?
 

Oh holy MT.net, I have followed your wisdom and knowledge for years and now I come to you once again to show me the light...

Little background, I have a 91 NA w/ FBO NA6 garbage motor on full E85 tuned with a MS3X, (Xidas 800/500 on the way). I have basically followed the MT.net bible thus far by:

1. Learning to tune the car while NA
2. Picking a MS3 over MS2
3. Getting a year of HPDE while learning how to tune suspension and use a Pyrometer correctly
4. Realizing the 1.6L is an inferior motor to any 1.8
5. Taking a year to research turbo stuff before buying a single component etc.

And many more. So you've led me straight and true so far, so here's my question. I am looking to get into competitive time attack with the miata chassis starting with the Gridlife TT series (Street Mod RWD/Track Mod RWD). Basically this entails open engine, open fueling, 2 pieces of major Aero, canards, up to 285 tires, and FI for motors under 4.0L's. Last HPDE my brother screwed up our fenders pretty bad last track day and the paint is chipping, so we are in an odd place in which we can choose to roll/pull the fenders, go with flares, or simply move to an NB2 in order to fit wheels/tires move easily. We are planning to move to a VVT motor w/ Trackspeeds EFR kit regardless of what miata body we are in. The NB2 simply seems like an easier platform to start with, with a stiffer chassis and better drag co-efficient. Also there's less of my messed up custom wiring to go wrong. Planning on running 245/40/15's and 275/35/15's on both. So the questions are such:

1. With all else being equal, given the same exact mods (VVT, EFR, E85, 15x10/15x9, same tires) would an NA or NB2 be quicker around a mid-size circuit?
2. I have moderate mechanical knowledge, but which platform would be the easier one to meet these goals?
3. If money was no object, which would you choose? What if it was an object?

I'm really just trying to figure out if it's worth making the switch. Almost all the mods swap over so that isn't an issue. Thanks for the help, I know MT.net will show me the light as always.

Pic of said car:

Attachment 229878

Prevailing wisdom says the NB is stiffer and aerodynamically superior to the NA. A rollcage and aero rework of the entire body probably negates most of that. The NA is most definitely lighter as well. It will really depend on what the class rules say, what modifications are allowed, etc.

the major disadvantages of the 1.6NA are the drivetrain (engine/diff) and the brakes. For the caliber of competition your proposing to compete in, all of those will be changed.
Is the differential something that can be changed in your class? the 1.6 diff wont handle it.

Otherwise there isn't enough difference to make a chassis swap worthwhile, IMHO.
Fix your wiring regardless.

Time attack has gotten very competitive quickly. Expect to spend big money on big power to keep up. Personally I'd rather start with an abs equipped nb2 sport if starting from scratch (or a c5 zo6 if time attack is my goal).

Nasa TT will still give you a more competitive place to play...

NB no doubt, 01+.. better drive train, brakes, more tire room, stiffer.. need I go on? If personal preference goes out the window then the NB2 is clearly the superior car.

Interesting thread. Something I have pondered as well as the NB shape has suddenly grown on me....

but to my mind most advantages of the NB are negated with replacement race oriented upgrades..... (stands to be corrected and in for hearing of what and why)

brakes replaced - bigger nb brakes become irrelevant.
diff, driveshaft, axles usually replaced with NB items (stronger and better torsen).
extended lower front BJ's - making improved NB front geometry (mostly) irrelevant..(?)
roll cage making any improved oem chassis stiffness irrelevant.

Differences of NB
heavier (?)
more room for bigger tyres
better aero than NA (?)
more engine bay space without pop up headlights
negative to me is ABS brake system.

Assuming building to the limit of the rules for the class, all of the drivetrain and chassis advantages of the NB are irrelevant because there's no limitations in time attack on update/backdate of parts so the NA would run the same stuff (subframes, brakes, engine, diff, etc.), and the cage and chassis stiffening that would be added either way means the NB chassis is heavier without offering much advantage.

If you're not building to the limit of the rules and just looking for the car that comes with more inherent performance (so you're not really in it to win it) then the NB has the edge in the lower tier classes. In the upper tier classes (Where I'd only recommend going if you ARE going to build the car to the limit of the rules) it's a wash between the two because you're allowed to change everything that makes any difference between the two chassis. I'd go so far as to say that the edge is with the NA chassis because it's lighter in a few key areas where you aren't allowed to cut stuff out.

Basically, buy an 1.6L NA for the tub and an NB for the running gear.

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This above.

I have (since XMAS) a 99 NB road car that I couldn't believe how much nicer it was to drive. Actually shocked me given that almost everything is the same bar some tweaks by the factory.

The NA feels vintage in comaprison (to me at least).

It is tempting to move platforms but i'm not sure that any of the nice NB road car traits will stay or in my case even be necessary, given the race car is 90% used on the track.

It pretty much doesn't make any difference at all, and if you're planning on running at the pointy end start planning how you're going to be making big power (to the point of considering a different car altogether).

Thanks for the awesome advice guys. Some great stuff here. We always see threads about "What's the better starting point" etc., but it seems there's little talk about which is better when some of the factors are equalized. Weight vs. Aero + stiffness seems to be the battle now, but like stated I think it'll be a wash. The interesting thing about Gridlife TT rules is they allow a massive range of mods ranging from bone stock cars to tube frame racecars. In my case, I will not be able to run a full cage so chassis rigidity is still a factor. Another factor is the time it'll take to set up another car. I plan to run next year which gives only a little while to buy an NB2, switch my Xidas over and retake all my track/alignment data. Choices choices.

I guess I could throw the possibility of getting a MSM into the mix. (https://www.miataturbo.net/cars-sale...d-miata-93420/)

Just stop yourself there.... NO MSM

sounds like a really fast class for only a rollbar.

OP needs to read the rules more carefully, cage is permitted even in Street Mod.
At any rate, without significant addition in the power department, the car will end up as "also ran"... the rules allow big power, and people will take advantage of that.
OP - the easy way to tell what you're heading into is to compare the class lap times in all the tracks that the series runs and compare to your times in the same track as well as the times that whoever is the local Miata hot shoe runs and see how the car fares.

Looks like a very loose ruleset. That means more to do to the car to get competitive. The guys at the front of the class will be those who read the rules thoroughly and find all the things the rules don't say you can't do and they will do them all.

As Moti said, there is almost no regulation on motor (typical for time attack) even in the lowest class, so you need to figure out a plan to make BIG power if you want to have any chance.

This. If you want to be competitive, you're going to be running all of the boost, and VVT won't make a difference. I'd say the NA might be a better platform.

Though I have no personal experience, I've seen the results of cam tuning on turbo spool, so VVT does make a difference. I remember seeing an Option video from years ago where HKS did a lap time test on their demo R34 GT-R with and without the VVT function operating and it was a measurable difference in turbo response.

Pretty sure Keith did a test on exactly this topic, determined VVT was negligible versus a 99/00 motor when turbo'd. I'll try and dig it up.

VVT makes a huge positive difference in midrange power with a turbo. This has been common knowledge for years in this community.

Here's a link from seven years ago showing how good VVT is.

https://www.miataturbo.net/media-53/...e2/#post554300