Are turbo Miatas still a bad choice as a reliable track car?

I love convertibles. I'm also getting ready to begin a new $10k-ish track car build this summer. A convertible track car would be wonderful. Obvious options are the 986 Boxster S (which I would probably not want to drive to work because clients and co-workers would think I'm a prick getting paid way more than I actually am), the AP1 S2000 (which I would probably not want to drive to work because it may not be there anymore when I leave for the day), or a nice $3-4k NA 1.8 or NB Miata with $6-7k of mods including a turbo setup, which I wouldn't be afraid to drive anywhere.

Unfortunately, the general consensus seems to be that turbo Miatas don't hold together on track without a ridiculous amount of work. I know cooling is an issue, and FM has the heavy-duty radiator and oil cooler setups available which alleviate the problem somewhat but I'm not sure if they're a true "solution," and it sounds like there is still plenty of other stuff left to break (transmissions being one example). My plan would be to either get a NA and go Megasquirt with one of the FM basic turbo kits and all of the heavy-duty hardware upgrades and what not, or a NB with the Voodoo box (since I'd need to pass OBD2 emissions with a NB) and also all of the hardware upgrades, and then throw the rest at cooling and suspension work with just enough left to cover a roll bar.

Is this pretty much a recipe for disaster like it always has been? My home track is Road America which is a big, fast track. On top of that the slowest cars you typically see on track are BMW E36s and similar, so a naturally-aspirated Miata is just plain off the table if I want to run with the DE groups there. I'm wondering if a $10k turbo Miata build is a realistic option to keep up, or if I should relent and go the S2000/Boxster route (or give up on the convertible idea entirely and pursue an RSX Type-S, MR2 turbo or one of the other appealing fixed-roof options).

What say ye, turbo Miata duders?

Well, there is the ecotec swap.

But none of us are really sure how the math works on that one.

In all seriousness, with a 10k budget, I would be looking hard at buying a 3/4k miata, driving it out to BC (I think that's where the ecotec guys are), paying 4500 for the turn key swap, and documenting the epic summer tip down road trip across the Canadian Rockies twice.

Leaves you with 2k for suspension, too.

In reply to Robbie:

Unfortunately that $5600 (according to their website) turn key swap leaves you with a stock Miata clutch, cooling, exhaust, etc...the Ecotec swap is novel but I'm not terribly interested in binning the BP, especially if I'm using 50%+ of my budget and still needing more parts to make it track-safe. At that point I'd probably just go with a different car, which I might end up doing anyway. Mostly just interested in hearing about turbo Miata reliability as opposed to other options.

They can be made reliable. The FM cars get beat on all the time and rarely, rarely have problems. I think the big reason for this is that they're being driven with some mechanical empathy and the drivers watch the gauges. They're also really well tuned.

We have lost one trans on track in the past 15 years. Damaged one motor when a waste gate line failed and the driver said "cool, feel all that power!" instead of "uhoh". Our biggest problems are cooling problems, but that's because we're running double sessions on a kart track in dry, thin air with an average air speed of 45 mph. Take them to a "big track", they do fine. Mostly, we just wear them out. The engine in "Igor", a salvage 1999 that's been a track demo car for at least 6 years, is starting to use oil.

Build them a bit conservatively, tune them well and drive using your brain. They'll hold up. A lot of people only do two of the three, and then they have problems.

In reply to Keith Tanner:

What is your opinion on the potential/reliability on track of a NA 1.8 turbo on Megasquirt versus a NB on the Voodoo system? I know the NB has better head flow and a few other positives, but I get the impression that the Voodoo system is not really designed for track-type usage. Obviously a NA with standalone is going to have more flexibility as far as tuning and probably a higher power potential, but I'm not sure if the Voodoo would also work just fine on a car with built water/oil cooling and safe boost levels. In either case 200whp would probably do me just fine.

Coolant reroute so the engine is cooled the way it was originally intended to seems to help a lot. My old miata would over heat if i ran too many back to back "laps" in autox but my friends wouldnt, same car minus reroute. But thats in the south in 100*+ heat and slow speeds. Also oil is responsible for 20% roughly total engine cooling, put a good oil cooler on and it should help as well

If I were chasing cooling problems, I'd be working on aero first. Get more air through the radiator, and that means getting air out of the engine compartment. Also, note that shifting at 6500 instead of 7200 has a fairly dramatic effect on cooling.

Anyhow, NA vs NB isn't a big concern to me. Yeah, the head's a bit better on the NB but it's not enough to make a difference from a reliability standpoint.

The Voodoo isn't the engine management of choice for the hard core track guy. I ran mine on the track when I had that system, but the fuel is essentially open loop and there's nothing being done with timing. 200 whp is at the top end of its capabilities. So I'd say an NA with an MS that was fully and properly set up would be preferable. The MS should have a wideband running in closed loop 100% of the time and should have aggressive knock protection strategies along with proper fuel and timing trims for temperature changes.

Now, the Voodoo is a better choice for street use. You don't have to worry about cold start, AC voltage compensation, all the hard stuff. You also retain OBD-II compliance.

It's possible to build a reliable turbo Miata track car, but it's not cheap. 5-speeds will have a limited life when doing track days at the low-to-mid 200s level. It's not going to instantly fail, but be aware that it won't last forever. Mine did 20-ish track days at that power level before stripping the teeth off third. You can either treat them as a consumable (they're a few hundred each), or you can swap it out for a 6-speed ($800-$100) which will last a lot longer at that level, but will be really annoying with the 4.3 or 4.1 rear end. The 3.6 is the right R&P to use with it, but it's $600 just for the parts.

Save some room in your budget for brakes. At that power level you're going to want something more than high-temp pads & fluid with stock rotors and calipers -- at a minimum the $600 Wilwood kit front with some ducting and sport rears.

Another area that hasn't really been mentioned on cooling is ducting. Unfortunately there really are no off-the-shelf solutions for it, but you're going to want to make sure that every scrap of air that comes in the nose goes through the radiator, rather than sneaking off to the side. Putting the intercooler in there usually means hacking up the factory ducts to the point that they don't seal very well any more, so you need to fab something to replace them. The cooling system also works leaps and bounds better if you're willing to take out the AC so that the condenser isn't blocking the radiator -- are you?

One of the big challenges to building a Miata as a track car as compared to a lot of other things (like the E36 you mentioned) is interior room for safety gear. How tall are you? Getting a 6-foot driver to pass the broomstick test is not easy. It can be done, but it probably means a race seat bolted to the floor with no sliders.

Also consider that for a big fast track like Road America, a high-drag convertible with a short 90 inch wheelbase like the Miata is never going to be the best choice.

I'm of the opinion - not backed up by hard instrumented testing - that too much emphasis is placed on ducting pre-rad, and not enough on post-rad pressure management. It would make for some interesting testing.

There are two aspects to cooling: transferring heat into the coolant and transferring heat from the coolant to the air. The reroute addresses the former, airflow management and radiator design addresses the latter. I used to have a third, but on a sunny Saturday that one has taken a vacation from my brain. I think a 200+ hp Miata is stretching both sides of the system, as the decrease in cooling problems when a lower rev limit is used points to potentially water pump cavitation and we definitely know it's hard to shed that heat. Interestingly, using a controllable electric water pump improved the cooling of an NC but we haven't been able to show that it's improving the cooling on a turbo NB.

Most of the issues that I've seen are with the manifold\turbo\downpipe hardware backing out after being viciously heat cycled. V-bands and inconel studs seem to help, but there are a lot of folks that never quite get it figured out.

Personally, with 10k I'd be looking at either an ecotec or K-series swap. Or just buy an NB, do the tried & true squaretop\RB header\exhaust and be happy with 150whp. Spend the rest on a top shelf suspension.

Our Inconel studs seem to have gone a long way in addressing that. Reports of stud failures have dropped dramatically.

I guess I shouldn't point out that I find it odd that you're worried about overall speed at a High Performance Driving Event.

I'm of the mind that you're there to learn how to drive better within the confines of what you're driving. You'll never "win" an HPDE, though it's possible to lose one.

Also, will you have a backup vehicle in the event your track car gets balled up?

Of course for $10k you might find a Corvette works better for your speed needs. They are faster out of the box and while consumables cost a bit more, they tend to take abuse a bit better.

Stefan (Not Bruce) wrote: I guess I shouldn't point out that I find it odd that you're worried about overall speed at a High Performance Driving Event. I'm of the mind that you're there to learn how to drive better within the confines of what you're driving. You'll never "win" an HPDE, though it's possible to lose one. Also, will you have a backup vehicle in the event your track car gets balled up? Of course for $10k you might find a Corvette works better for your speed needs. They are faster out of the box and while consumables cost a bit more, they tend to take abuse a bit better.

I'm not directly worried about speed, but it's no fun whatsoever to go out every session and point faster cars by for a half hour straight. If that's fun to you, so be it, but IMO that is a very stressful and un-fun experience.

I've run with a few groups here before and I wouldn't want to go out with less than 180HP or so. When quicker cars in your group are hitting a buck fifty on the main straight at Road America, YOU are the safety hazard if you are struggling to go 40MPH slower. Heck, I'm not even sure they would take my money and let me run in something like a stock-ish Miata!

It has been discussed in other threads that the hardware at most HPDEs is getting crazier and crazier and there are really no places for slower cars to run anymore. Unfortunately, that is very much the case with the groups around here. My E46 330ci (a pretty quick car) was in the slowest group with an Audi TT, a Cooper S, a Mazdaspeed3 and a 128i the last event I ran...and Vipers, Z06s, turbo P-cars and the like were absolutely blowing our doors off multiple times per lap. Going out in a car with 110HP is just plain a non-starter. THAT'S why I'm concerned about speed.

Also, nowhere did I say that this would be my only car, I daily a Honda Fit and am looking to build something specifically for track days and the occasional weekend cruise.

calteg wrote: Most of the issues that I've seen are with the manifold\turbo\downpipe hardware backing out after being viciously heat cycled. V-bands and inconel studs seem to help, but there are a lot of folks that never quite get it figured out. Personally, with 10k I'd be looking at either an ecotec or K-series swap. Or just buy an NB, do the tried & true squaretop\RB header\exhaust and be happy with 150whp. Spend the rest on a top shelf suspension.

The 2nd part. Depending on your local track, a well sorted suspension/brakes/tires with that much power in a Miata that's well driven? Will upset a lot of pricey machinery.

Keith Tanner wrote: If I were chasing cooling problems, I'd be working on aero first. Get more air through the radiator, and that means getting air out of the engine compartment. Also, note that shifting at 6500 instead of 7200 has a fairly dramatic effect on cooling.

Would you be willing to expand on the "extraction" part? I know you guys sell hood louvers. Is that what you suggest? If so, how many and where specifically do I need to install them?

"Depending on your local track, a well sorted suspension/brakes/tires with that much power in a Miata that's well driven? Will upset a lot of pricey machinery."

In reply to z31maniac:

At Road America? Not likely.

At RA as your home track you need a better car, or at least a stock car that can handle a bit more speed.

S2000 would do it, the Boxster would as well but the cost of consumables would be high. Seriously a C5 FRC even in stock form would be enough.

NC Miatas are getting to the 8K and under price point now. Also, would a RX-8 work for you?

dyintorace wrote:

Keith Tanner wrote: If I were chasing cooling problems, I'd be working on aero first. Get more air through the radiator, and that means getting air out of the engine compartment. Also, note that shifting at 6500 instead of 7200 has a fairly dramatic effect on cooling.

Would you be willing to expand on the "extraction" part? I know you guys sell hood louvers. Is that what you suggest? If so, how many and where specifically do I need to install them?

Yup, louvers. We actually have some bigger ones from Singular Motorsports that aren't on the site yet, but it's what I use on my own car. There are pressure maps in the louver instructions and the Singular units come with a vinyl layout guide.

Those look nice!

What's the difference between these 2 examples? These seem much more flush:

Than these do:

Just the installation. They come with some trim to cover the cut edges, the green car doesn't have it. The green car also doesn't have the lips ahead of the louvers, which will cut down efficiency.

I put mine on top instead of underneath. Much easier to install, and it's a race car :)

I don't have any empirical measurements, but I can say that the Singular louvers do vent a significant amount of heat. It's easily visible while driving in cooler weather. Here they are on my NA:

I didn't use the Gurney flaps on the initial install, but I will be putting them on when the VVT motor is in the car as they do increase the efficiency of the louvers. I also did not use the rubber trim.

The install is messy, but really the worst part is taking a cutting wheel to a pristine hood...

They also require the removal of a significant amount of under hood bracing. I haven't found that to be a problem so far.

I'll get them up on the FM website tomorrow :)

Roman, any chance I could use that photo?

No problem, Keith.

I can also send you a higher rez version, and some install photos via email if you'd like.