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this happened to my 2.0 liter engine and i'm looking for qualified ideas of the reason and analysis:
engine about 35k km, tuned to stage 2 (cobb, intercooler, 3rd cooler, bigger turbo with max 2bar, exhaust manifold and exhaust etc) since about 10k km.
about 500hp on the dyno and good driveability. did oil change every 2 to 3k km,
operating in a tropical country with temperature average above 30 degree celcius and mostly high humidity. intake manifold temperature always about 40 to 45 degrees celcius.
we have poor fuel quality with max 95 ron / 91 octane, so i always added a bottle of octane booster per refilling. i never drove the tank less than one third.
lastly (before the incident) the engine was going too rich in terms of black smoke under load / shift, but lambda was good at 0.82 and no knock when analyzing the logs. i changed the spark plugs and checked the valves, exhaust valves and plugs were all too black = rich. so i lowered the amount of fuel for ignition slightly and also cam timing.
incident occurred going quick over hills and corners. the last maneuver was a very tight 120 degree right corner, which i did with wot in 2nd (full boost up to 2 bar), but had to release the throttle on the straight because of traffic. i think i heard a clicking or blowing sound at this moment. revs dropped because of traffic to about 3k rpm when i re-opened the throttle slightly. but there was than a very strange engine feeling, like it was running only on several cylinders or missfire (could also be a temporary limp mode, but no error message on display). i released the throttle and clearly heard that there was additional a slight tack-tack sound. i drove some meters slowly to the side in very low rpm to park the car safe. there the sound was still here, but the engine felt normal in about 500 to 1000 rpm. i stopped it immediate after the car reached it's final position and called the workshop to tow it. no smoke, nor any liquids leaking.
the guys at the workshop checked the oil from the filter (see photo) and the sump. in the filter oil there are small (less than 0,5mm) metallic non magnetic particles inside. no magnetic particles in the oilsump.
before they removed the oil, the started the engine and said, the sound was mostly on the right bank (cyl 1 or 2).
than the workshop changed the oil and said that the sound was almost gone...
going to get further dismantled the next days to see the cause - i'm going to update this thread regarding...
maybe i am struggling with this longer than just the last ride. the 'missfire' issue i had some times in middle rev since months because of a non optimal tuning under certain conditions, which got adapted than after some trials. at this time i thought, the missfire issue was created by engine electronics, like a rev limiter, to protect the engine under some specific situations. now i may think that this was already a mechanic thing, like that a shaft or bearing had some unexpected friction.
unfortunate, even with my high frequent oil changes, they workshop had never checked the oil nor the filter before this final issue.
any qualified comments / ideas / suggestions on the issue are very welcome
Just my opinion, but if you actually got 35k km out of that street stretch sort of build, I am impressed. We used to call the extraction of this sort of power from an engine of this size . . . . a Grenade.
so, today i dismantled my old blown engine, after finishing the transplant of the new 2.5l engine (separate thread).
piston 2 and 4 had lower compression, 1 and 3 were normal.
everything inside the engine is fine, all bearings are fine, the rod's are fine.
just piston 4 said: 2.1 bar - enough is enough. and piston 2 wanted to follow him, but much slighter.
the cylinder coating is fine and looks still virgin, just some very little signs of metallic parts in the head of 2 & 4.
strangely one of those plastic blue water channel plugs was broken. have no idea how and why and what that means...
anyhow, the short-block will become a table and the rest goes on sale in parts
as follows some pic's and videos of all 4 pistons.
Interesting. Thanks for sharing. Usually detonation causes failures of the top ring land and piston crown. This looks like something got into the combustion chamber and damaged the piston from there. All the valves are intact? Can you post some pics of the heads?
The 2.0T engine seems pretty robust, especially if we keep it stock (like I will), so happy about that. If I was into tuning, I'd probably do it at the 2.5T level (350hp), but at the GT4RS level seems insane. Ha ha.
here are the heads. only issue is very small dents on 2 & 4 from the piston parts.
at the time of this happening i had 30.5 psi / (=2.1bar) boost pressure with fuel 95 ron (=91 octane, no better fuel available here) plus magnesium based octane booster additive.
the reason was the high boost together with bad fuel and detonation/knock.
i did with my 2.0 max. 2.1bar (30.5psi) and had almost 500hp with it. now with the 2.5 i have max 1.4bar with non-vtg turbo and 490 dyno hp, but it feels much stronger in the middle than the 2.0 - and still on the very safe side
05-23-2024, 12:05 AM
718 2.0 liter blown engine
