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.

.

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

If you can use all that midrange torque its great, in my experience with the kinds of tracks we have in Australia and the tyres most people here run (read: road legal semi slicks) the midrange is usually tuned out anyways at least at part throttle.

Dann

Trackpeed engine and EFR turbo kit, KMiata / E46 trans, E85, Getrag rear or stock housing w/ OSG. For that rule set (no foreign motors allowed) that's the ticket.

More than one way to skin the cat, 2.5L boosted MZR is legal and 700cc bigger.

Always options... and the 2009+ MZR is forged... but I think I'd want to stick to BP in this case where sequentials are out and you need to make a factory option transmission work.. primarly because with the BP there is (finally) a bulletproof trans option whereas the NC box, similar to the NA/NB units, becomes the eventual weak point when going for well over 300whp.

Dear OP,
No doubt keeping the BP is the easy button build, as LFX Ryan points out.

Signed,

Ferrari Moti

Reverse logic (with a twist?) :)

Logic? What's that? ;)

Thanks guys. I took another look at the rules and you can indeed run a full cage as long as it doesn't go past the firewall. Most cars in Street Mod are between 250-400 HP with the high HP one's being a few Mustangs and a Supercharged E46 M3. Right now it doesn't look as competitive as the West Coast stuff yet, but regardless I'm just looking to try something new and continue to have fun. Getting my Xidas corner balanced and aligning in today so hopefully that'll point me in the right direction to be significantly faster than most cars in class in the corners. While I don't think I'll be hugely competitive, I believe a 2100 pound NA with 250-300 whp and aero will be at least semi-competitive given a decent driver.

Hehehe I wish I could go LFX, but I picked up a 2003 VVT with 39K miles for $800 that I couldn't pass up. Plan as of now is to drop in rods, and shoot for 250-300whp.

P.S. Just got your spoiler on, looks amazing. Can't wait to try it out. (Will have before and after track times)

Pics or it didn't happen :D

In stockish form VVT helps midrange. With cams it can do something entirely different. Think of it this way. Without VVT you can optimize a power curve over 1,500-2,000 RPM. With VVT that rpm ban extends to 3,000 RPM. That's makes for a great power curve with or without FI. Helps dig you out of a corner if slightly off the power band for some reason.

In time attack where there are no power caps and virtually no limitations on motor, the only person who has 'enough' power is the one at the top of the podium who set a new track record. Everyone else needs more power.

As someone that has lots of track time at their main track, Gingerman. I gave up on TA. as other have said it's such a HP/ Money game. Miatas are in a tough place. I placed 3rd in the wangfest series street class many moons ago which what eventually turned into Gridlife. My miata was around 1:50s then. got it into the 1:46s a few years later and then sold it to someone running it in Supermiata on the west coast.

Where you at with car development? Lap times at Gman? Faster than spec? I think the spec record is now 1:46-1:47? Crazy to think the fast car is a civic running 1:26s now at Gridlife. I don't see how anyone can compete with that.

IMO I think makes far more sense to build a nasa spec car/ scca car. For a variety of reasons.

I'd keep the NA. In my experience with my NB 100 pound difference is worth 1.5 seconds. in a 140hp NB at Gingerman. NA seem easier to get to a lower weight.

I love the idea of a Miata in Time Attack. You just have to go in to it with eyes open about the challenges you face and the type of car that you need to build to be competitive. Most people are not ready to build that car. They get into TA for fun and then end up disappointed when they realize they can't be competitive with a car not built specifically for the discipline.

Here we have the Superlap Battle each year at Buttonwillow, which is probably the top event for TA in the US. When I look at the podium times for Street, Limited and Unlimited RWD from recent years I see a huge challenge for a Miata, but not insurmountable. An unlimited car needs to be in the lower half of the 40's; sub 1:45 for sure, and limited needs to be well under 1:50... the farther under the better. Possible? Yes. But to give an idea of the challenge, no Miata has ever cracked 1:50 to date. Nobody is going to arrive with their casual Miata build and get on the podium. It will take a ground-up build focused on the class you're taking on where no bolt is left untouched and no allowance in the rules is left unexploited.

Exactly.
Coming with the state of mind of where Miatas normally compete won't take you very far.
Gotta get used to think out of the box, be willing to make big changes, challenge the common thought process and know that the further you go the less answers you'll find to your questions.
Some may find it intimidating, I look at it as a part of the fun.

.

More great info here. Yeah it seems like Gridlife TA is in a really interesting place with 1-2-3 positions being highly contended by cars with 3 widely different drivetrains.

As for the comments about what you need to be competitive I completely agree. My only contention is that with the Gridlife season being so long with so many different tracks (many of which a lot of drivers are familiar with) means that wild things can happen. For instance, the Street Mod RWD class leader is in a Bolt-On E46 M3 with no aero. I'd guess a well setup Miata with similar power to the wheels while weighing ~1000 pounds less with aero would at least be competitive with that. Either way, I'm excited to get a season of real racing under my belt with whatever the result may be.

I say go for it. We won the New Zealand Street Pro (road legal, log book cars) 2 wheel drive class this year AND a Top 10 Shootout from consistency and a really nicely balanced, mid level power to weight vehicle.

It's racing.....Anything can happen. Not to mention the massive learning curve racing/competing puts you in and the experienced gained.

I find too much focus on trying to win isn't much fun, focusing on competing and developing car and driver as best you can and seeing where you get to IS a lot fun......you never know, like us you may very well end up being more competitive than thought. Particularly from mid season on when a lot of the big power cars have broken and others have given up with lack of commitment.

I was trying to say something like this...only true racers have this mindset it has slowly become apparent to me. Nicely said.

Whats times is that e46 M3 running @ gingerman in street mod? I looked it's Brad Yonkers running 1:40.4 I could see davids Kmiata car being close to that. I think he did 37s or 38s on hoosiers but not sure if he's ran it on street tires. He's making 230-250hp NA. It seems doable if you can have 300whp+ and keep the weight under 2100 pounds. Should be well under the 1:40s.