Serious heat issue with small turbo and 00 motor
 

So back in jaunary I got the feeling that I really should just park the car till I find or rebuild the engine. Last week I finally got around to pulling the old motor from the car and taking a serious look at it. I replaced the engine in my 95 with this 00 some time ago, at 112k miles. It had around 89k on it, IIRC. I had my modified BEGi kit on that I had purchased from a user on clubroadster. Had the cast manifold, some of the original intercooler pipes but others were replaced with one of the ebay piping kits. Had a Forge BOV, and an ok intercooler. It was big enough, on 90* days I never saw intake temps climb above 115 or so.

Ran for the most part the base wastegate pressure of 5.5 however because of the size of the turbo at my home elevation ide see about 6.5 psi at 7k. On the dyno in ventura I put down 186 whp because after 4500 boost climbed on its own to 7.5 psi at rev-cut. again 7k. It did see some limited time pressures of 10-12-14 and 16 psi, stopping at each level to make sure I'm not lean or detonating, and in winter at 4000ft elevation with temps never above 60* ambient. However I was allways strugling to control detonation on longer durations under boost, and was unsure why even at 0 to 6 atdc. Well ignoring the #4 rob bearing and 4 of 5 main bearings being nearly ready to let go completly, it was pretty bad. 1 and 4 pistons were just fine, re-useable even, no cracks, no skirt scuffing worth mentioning, however 2 and 3 were not so lucky. HEAVY scuffing on the exaust side and all 4 pistons top rings were far from the sharp edge that they should be, rounded like a ball point pen with obvious signs of blow-by. Explains the heavy smoking on throttle lift. I'm guessing this was caused by not only a cast log manifold that concintrates heat on 2 and 3, but a garrett gt2554r turbo not having near the flow needed to sustain more than short bursts of boost without heavy heat and pressure building up in the manifold. Needless to say the turbo, manifold and downpipe are for sale. perfect for someone who likes light-to-light and short squirts on the on-ramps, or maybe autocross. But for extended runs its just too restrictive... Anyone havve similar results or opinions?

Full setup;
gt2554r turbo
BEGi cast manifold
repaired, really crappy downpipe
jackson racing testpipe
2.5" mandrel bent exaust and magnaflow straight through muffler
random conglomeration of FM, BEGi and ebay intercooler stuff
MSPNPgen1
Innovate lc-1
Stock 2000 bp4w
ALLWAYS run on 91 as thats the best I can get with crappy California gas.

wall of text and no mention of AFR

great post, would read again

Sorry lol afrs have been probably too conservative of between 12.5:1 and 12:1 with pre-tuning safe overshots of probably damn near 8:1

12.5:1 and 12:1 arent conservative. Thats the realm of an aggressive turbo tune.

what size injectors do you have?

You're running CA 91 and 12.5 afr and breathing through a teeny 2554 and wondering what's wrong? LOL
What was the timing at peak boost?

While the 2554 and log mani is small and restrictive, neither are that small or restrictive that you can't run 7psi with them efficiently.

Your damaged motor is 100% your fault due to terrible tuning.

11.0 - 11.5 = conservative
12.5 = lean as fuck

I've got a smaller motor and a bigger turbo and i shut it down if it gets much over 12.0 af/r.

11.5-11.8 isnt even "conservative", but it should be safe. That's what I run.

My new setup will be on e85 to prevent my noob ass from blowing it up, although i havnt been able to blow up my current 1.6 yet either.

11.5-11.8 isn't conservative; it's simply what you should be running.

most of the "higher end" car tuners actually tune well in the 10's on pump 91......the only cars that run 12.5 in boost are direct injection cars which are a completely different animal.

The 2554 will make more heat than boost at 14-16psi. You say it was detonating at 0 to 6 degrees AFTER TOP DEAD CENTER of timing? You were probably burning most of your fuel in the exhaust manifold and turbine housing with timing that retarded. Your EGT's had to be through the roof. Detonation was probably caused by the red-hot exhaust valves pre-igniting the mixture.

Seriously, if you don't know what you are doing, take a moment and read a little.

Wow... Ok, guess I've been givin a whole lot of misinformation. Thank you for the responses guys, time to go change my far targets and do some more research! This is why I like miataturbo.... I've been under the impression 13:1 for na and 12:1 12.5:1 for boost is what's safe. Despite the expense Im going to look into an egt setup. Ide ask for some recommended timing baselines, however I'm sure ill find some if I look for them, someone else has probably already asked.

Oh, brain, I'm using 460cc injectors.

Overshoots at 8:1? You trying to wash the oil from the cylinder walls with a fire hose?

You've already got a wideband. Get your AFRs into the correct range first with that. Then you can worry about the additional data an EGT can give you and what to do with it.

I run 12.2:1 on my gt2560 ported @12psi Stock 1.8.

Hasn't blown up yet...

... Yet

How much timing?

I don't understand the question.

How much timing do you run at 12psi at 12.2:1?