I bought a 1995 Miata a month ago now and it was prepped well for AutoX by the previous owner. For me, this is my new AutoX and HPDE track day car. I am retiring my DD '12 Mazdaspeed3 from racing.
Here's the list of mods the car came with:
-FMII Turbo kit - Hydra Nemesis ECU
-FM turbo shield
-FM chassis braces
-Racing flywheel and clutch
-Over-sized Aluminum Radiator
-Tein Flex coilovers with two sets of springs
-3 sets of wheels and tires: track, summer street and snow.
-I'm sure I'm forgetting some stuff.
Anyways, the car was sold to me with some known problems that I have been trying to work out and my biggest concern with the car is the excessive heat from the turbo. Before diving into the heat, let me talk about some of the problems as there may be related issues:
-ECU boost target of 12psi is not met, and the computer seems to be doing nothing to manage boost - all mechanical right now.
-When the car is shut down hot, and restarted immediately or 15 minutes later, it will not idle smooth; revs oscillate from 400-1,500rpm and settle down after 20 seconds to ~800rpm. Behaves much like an low-dampened control system oscillation that overshoots and then smooths out. This can also happen without shutting the car down on a hot day.
-Compression isn't perfect: Cyl #1,2,&4 are about 180psi, Cyl #3 is 160psi. (dry) Leak down test is next on the list.
Those are all the known issues at the moment. Now lets talk about heat. Last night I took the Miata for a short cruise, getting into boost here and there, in 70*F weather. When I got home, I parked, immediately popped the hood, and sat next to the turbo listening... After about 40-60 seconds of silence, I heard the radiator cap release some pressure and coolant in the turbo coolant lines started percolating. To me, it appears like heat is soaking into the coolant from the turbo, and starts to exceed the 16psi cap, so pressure is released and then low enough for the coolant to start to boil.
The cap that came with the car was a 16psi Stant, but the rubber was cracking and it was not holding pressure. I replaced it with a new 16psi Stant 10233 (Napa #703-1712) and pressure seems to be holding. The percolating was much worse with the old cap, so once replaced I flushed the coolant and burped the air out of the system.
Should I be using a higher-pressure cap? Should I do something to make the radiator fans run after shutting down the car?
Two more notes:
1. The under-body panels, the "air diverter" in front of the radiator and the panel under the engine bay are missing. I plan on replacing them to get proper air flow through the radiator while driving.
2. The stock hood is unmodified; no vents or hood risers and still has the rubber seal on the back edge. I bought a second hood and plan to vent the front center between the lights, as it seems to be the consensus on these forums as the best location for an extraction vent.
Sorry for the life story guys, but I thought I should put everything on the table. Out of all this information I've given you, I would like to focus on the heat management. However, if you have some ideas or tips for my other problems, please feel free to share, I just don't plan on solving them in this thread.