Going into our very first American Endurance Racing event at Road Atlanta, we didn’t have high hopes. Well, we did, but we didn’t actually expect them to pan out. Our Miata had suffered a catastrophic failure at each of its last two races, and we feared the same fate would befall us again while rac…
Sounds great. Finished with a running car, and sorted out some of the last details.
Ah, the fun of endurance racing a turbo car... Can I give you a nickels worth of free advice? Inconel studs and Stage8 locking nuts for the turbo-manifold housing connections. Once that's fixed, you'll find the next weak point just like we did, so come back to me when you find it and I'll share the fix for that... assuming you haven't beaten me on track that is ;-)
Yea, we are playing the same game with our ghetto charged Lemons Civic, and that exact fix did solve the turbo separating from the manifold adapter.
Gearhead, what issues are you getting now and on what platform? We’re having trouble keeping piston rings in the thing now, working on getting the right specs for that now. Good thing boost is addictive.
What are you using for engine management? My knee-jerk reaction says you probably need to pull a few degrees of timing under boost...
Next separation point (on a RWD anyway) will be the turbo outlet. Mine is a Nissan T25 with the funky 5-bolt outlet which is a PITA for bolts. Ended up changing out to a v-band adapter and some machine work to fit 10mm outlet studs :)
Current unsolved issues are all heat related... I'm on the hairy edge of having enough cooling for the horsepower, and not enough points left to fit the big radiator. More (effective) venting may do it, we'll see.
Hacked stock Honda ecu, we are pulling timing, no evidence of detonation, think we need to widen the ring gaps a bit more, we have a lot of cylinder pressure.
We use a Saab T25 from a 9000 with their very strange flange, but it has been problem free
Cooling, yup. We have a giant radiator and the biggest oil cooler we could fit, plus ducting work. Until that was all done we had to run at about 2/3 to keep it from cooking. Now we can hammer it all day and stay appropriately cool.
Glad your fortunes have improved.
If you are only lasting 45-60 minutes per tank and continue to have mechanical issues, I wonder if an ecotec swap and a fuel cell (to maximize fuel capacity under champcar rules) would be a better way to go?
I'm surprised the failed cooling fan caused an issue on the track. I wouldn't have expected it to run.
Snrub said:I'm surprised the failed cooling fan caused an issue on the track. I wouldn't have expected it to run.
That's what I was going to say; how is a non-functioning fan be a problem at-speed? In the pits, sure, but on-track?
Our Miata clearly needs more ducting, because yes–a cooling fan actually made a difference. It dropped temps from 230 to 215 on track at speed.
And the fuel issue... We have that one figured out, too. But that will be another update. 
Tom Suddard said:And the fuel issue... We have that one figured out, too. But that will be another update.
Fuel cell seemed so obvious when I read this earlier today, that I figured it was outside of the rules.
Glad to see you finished well. Hopefully no hot shot came along and thought they could port out the whole intake manifold and everything. In which case an old timer comes back and replaces the gasket when they aren't looking. Alternatively, you can run a milder tune. Maxxing a turbo 4 on pump gas might be around 17 degrees of timing advance. With a larger lower rpm 4 that might be a little different. Currently trying this brown basmati rice and peas to see if the root canal worked.
Another well known and very successful endurance racing turbo NA Miata team went so far as to remove their fuel cell as the changing fuel load had enough of a weight difference in the small light chassis to cause some handling issues. They have gone back to a stock tank, and usually get 1.5+ hours out of it.
Pay attention to how the fuel return is placed in the tank. If it's not dumping into the little dump, you'll have trouble with starvation.
There's less airflow through the rad at speed than you might think. Fans work. Even NASCARs run fans.
Inconel/Stage 8 parts are heading GRMs way as soon as they give me the address to use :)
The air though the radiator needs to be slowed down so it can absorb heat.
Look at the tiny inlets Nascars run. I think they only run the fans during cautions and pit stops.
It was long thought that more air through the radiator was needed. It has now been found that less is more.
Even dirt track racers have found that indirect air is better. It also keeps the mud out.
Long story short, there should be no need for a fan at racing speed. If the fan helps , then something is wrong.
If the fan helps, then you're cooling better than without it :) I've found that good fans make a massive difference at highway speeds, more than ducting or radiator changes do.
I still say, if a fan helps at highway/racing speed, something is deficient in the cooling system.
Okay. You can say that 
I'm just basing this on experience with a few different Miatas, including one of my own street cars. Perhaps they're fundamentally deficient. But since we're talking about a Miata, it's a reasonable data point.
You're welcome to come by, take the fans off and try to keep that street car cool on the highway. You are allowed to make any changes you'd like. I'd be interested to see what you come up with. I went through a number of different things before hitting on the fans.
Years ago, I used to take the fan off my DD. Only once in heavy traffic did I have any overheating, turned the heater on full blast.
My Saab 96 never had a fan, even in hill climbs. My ZX2SR's fan only came on on the cool down lap and entering the pits.
So, as you say, Miata have deficient cooling systems and need help.
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