my thoughts on running it in next time
remove the turbo exhaust and use a standard exhaust put filters on the carbys and run it in as a normal engine for a few ks
then once its run in then comence putting the turbo system on. may have a better survival rate ....my turbo runs very rich indeed but when it comes on boost it certainly uses a fair chunk of gas ,Id be more inclined to say it was lean and timming .

bad luck kegs aye. just thought i would point out the irony of the title of the thread.

poorly tuned EFI is just as bad as poorly tuned carbs and dissies.

I'll ask again. have you done anything to control the mechanical ignition advance?

fuel being burnt around the rings? aren't the rings designed to be the barrier of the combustion process? There is always fuel/air mixture around the rings - that's what they (compession rings) are for - to hold the explosion (burning fuel) and extreme pressues above them so they can be converted into useful work on the top of the piston...

if it was in any way caused by fuel being burnt around (ie past) the rings, there would be lots of scoring on the piston skirts where the oil was burnt off them...

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or you just fix all the probs right now with EFI.

I dont see heaps of logic in that. I am not saying its wrong. Just dont see how it could happen. Any boosted engine is gonna have blowby under boost.
The ring lands were said to be broken, do they look burned?
Nissan has always been known to overfuel their boosted engines.

The closest logic to that I can think of that, is anything like that is what I have been told from an oldbloke that tunes/messes with alcohol engines.
Guys that run alcohol easily suffer engine problems from bad tuning. The reason being is alcohol is so cold. If they run an engine and it detonates. The next lot of alcohol to enter that cylinder is going to cool the hot metal to quick and cause problems.
Fuel is nowhere near as cold as alcohol, but enough of it will still cool without igniting.

The only way I can see to prevent unburnt fuel from passing the rings, is to ignite it as its entering the cylinder, And that just isnt going to work.

Only real way to know the cause of the problem, is to run/tune the next engine with a good gas analyzer.

i was just talking to jeff taylor he reckons the piston went from overfueling, he said the fuel gets forced past the rings by the boost pressure, and ignites around the ring lands and burns them away, sounds pretty logical tome... dont know what im going to do now, think i need to go searching for someone who knows how to tune dellrtos coz i aint driving it untuned again my pockets are getting worried after one blown engine ....

Silly question, but you are running a rising rate fuel reg, with a return line aye?

mmm turbo territory...still scares me...

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yep, it was caused by detonation. you used black rings, didn't you? on a boosted engine it doesn't take too much detonation to crack them, then the broken pieces work against each other. sometimes they can overlap and crack the piston's headland.

as for what caused the detonation, when an engine is running hot, it will be prone to detonating for sure. It may just have been that, and it took a bit of time before the broken rings actually caused the problem.


Otherwise, as phunk said, its either leaning out under boost, or running too much timing (what have you done to control the advance?), or it could be caused by a hot spot in a combustion chamber - have you done any work to them? sharp edges can cause hot spots, but so can carbon build up.

Like the good Dokta said, Take it for a strap and shut it down at full noise(a "plug chop"), not a real good expierience for the turbo bushes, but still a better way to examine the plugs. Also a bit hard with the engine apart.

Another thing to inspect is the exhaust valves. When the engine runs lean, it creates a lot of heat, the exhaust valves copping a lot of it. How are they looking?

On the dyno with a sniffer is the safest bet.