kyle h.

p.s. keep in mind, my engine might have been in boost for a maxium of 20 minutes, not even 10 mintues at a time. the car ran no longer than 20 min with the turbo on, thats counting idle time to warm up and cool down, etc...

i can probably count on my hand how many time the engine went into boost.

Dr.Boost

That's why I can't understand why it blew. I ran a motor one time with NO fuel management. It didn't produce much boost, but it boosted and it would just fall on it's face. Yes, this was stupid, but I was waiting on parts and was just to stupid to keep off the gas. I ran it like that for a few days entering boost very frequently engaging a cel every time. The motor was fine after all of this. No smoke, no loss of compression. I never made it to anywhere near 10psi, but still........
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kyle h.

OK! This has got to be it.


I finally got the clutch working correctly after dropping the tranny this weekend. I also examined the pistons more.

On the #1 piston (which had the lowest compression after the calamity) there was a piece of the ringland which broke out, after i wiggled it off the piston. i was looking at the piston, the groove the ringland had left and there was a clean part (fresh break) and the rest of the broken out section had some carbon build up on it, and when i looked straigh up on the piston, to the edge of the top it was a darkened black color there also.

I've also notices this sohc zc pulls a lot harder at top end than my other one, and the engine, cranking it by hand feels like it has way more compression that my old engine had, before i blew it up.

so im thinking that the pistons were cracked before and the boost with the lean condition just put it over the top and cracked the ringlands a little worse than they were already.

moral of the story, compression test an engine before you put a turbo on it. oh well, live and learn.

88crxSi

detonation is not only caused by ignition, but lean too. running lean means the cyl (and exh) temps are hotter. a hotter mix of fuel/air will ignite easier. compression also plays a factor here. sounds like the combination of 11psi w/ a maz 9.5psi fuel table w/ high compression casued detonation and broke ring lands.

hackish

This fall I implemented boost cut routines for the PM6 map. They were posted up on PGMFI and the maps were sent around to the ghettodyne guys and a few others. I'm not sure if they were ever merged into support with these programs but I deem that feature as being absolutely necessary for anyone running a turbo car. They can and have saved a number of engines.

-Michael

blundar

as implemented, they aren't useful for the HMT crowd pushing the edge of their MAP sensors to start with.

You can say "boosting more than 9.5psi on a stock MAP sensor is BAD" a thousand times and most kids aren't going to listen because they want more boost. If the target boost level exceeds the maximum boost able to be read by the sensor, there is no value to set the boost cut to that will protect the motor while at the same time allowing the target boost level.

The solution to this problem is obvious - MAP sensors that can read more boost than is desired used in conjunction with code that can support the different resolution of the sensor. If the MAP sensor can register more boost than is desired, the boost cut code can (and will) save motors. The boost cut code is active and live in the TE2 ROMs, although I think it may need to be modified slightly to account for the new code handling the MAP sensor.