Legacy GTB

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R19KET

OUCH !!!

Looks like it's been suffering from massive det'/pinging. What do the heads look like.

There are people FAR more knowledgeable than me on the list, but I would expect to see a lot more heat discolouration on the pistons if it were purely down to running lean.

Mark.

johnfelstead

That looks like classic piston crown overheating. Usually caused by too much boost for the fuel available or sustained high speed running.

You havent done a high speed run on an autobahn have you? Holding the car at high speed for any length of time?

The most common cause of this type of failure is the immense heat generated by holding the car at full throttle at high speed, where the drag on the car causes the boost to be held high.

The ring land is always the first point of attack for 2 reasons. Firstly there is a sharp edge for the heat to build on, secondly it is where the thickness of the metal is at its lowest so the heat gets higher there to the point of melting the piston first.

How were you using the car when it failed??

johnfelstead

i see you live in new zealand, not many long roads there are there?

I would put it down to too much boost for the fuel based on your location. Have you been playing with the boost at all?

Legacy GTB

We were about 2 hours into an early morning run up State Highway 1 from Wellington and were making good time, probably sitting at around 140km/hr for the most part. Where the damage occurred we were at around 170km/hr and heading up a 1000ft incline, following an old single turbo Legacy GT.

There was no temperature warning on the guages, the first warning I had was a decelleration due to a loss of power and then clouds of thick smoke. We pulled over immediately and powered off. The rest is a tow truck story. What you have suggested sounds a likely cause, but I'd be concerned that such a car is not capable of a short, quick incline like that without a major meltdown. I'm now thinking of selling and buying a big, lazy, strong and reliable V8 because I'd always be paranoid that it would break again. Apparently technology is no substitute for cubic inches!

Legacy GTB

Oh yes, the car is factory standard in every way, from turbos & boost to the factory exhaust and cat converters.

johnfelstead

170k's is nothing. That should have been fine unless it was a very steep hill and you were holding full throttle at a constant speed because the hill was very steep.

It's more likely a combination of either a very bad batch of fuel (get it lab tested) or you boost control on the engine has failed. There werent any split vacuum pipes on the waste gate solonoid/actuator/turbo feed were there?

Another posibility, did you engine burn oil at all? did you have to keep toping it up? because oil vapour drops the octane of the fuel and in bad cases can lead to this kind of failure.

johnfelstead

just thinking, have you also recently noticed a drop of in low revs performance, because if the primary turbo has failed and is feeding the engine with oil down the inlet, that will of course cause a lowering of the octane rating of the fuel and could lead to a meltdown like yours?

Legacy GTB

No, the car was running like new. The only reason I know this is I drove a 'demo miles only' RSK B4 with the 5 speed before deciding on the auto and apart from a little power difference, the two cars were nearly identical.

The idea that the blown turbo seal has caused the whole problem is fairly likely, because the car showed no warning symptoms at all. Thanks for your ideas on the issue. It's like a nightmare that I can't wake from at the moment and finding a replacement motor seems to be a bit tricky. Any idea if the non-turbo 2.0l motor is useable when I bolt on all of the good bits from my old engine?

CharliePsycho

I've seen this before on an engine that had just been rebuilt. The lunatic (me) went straight out and thrashed it up a hill.

The engine hadn't been run in and basically the first piston ring seized, shattering the edge/top of the piston on 3 out of the 6 pistons.

It wasn't running lean and was in a fine state of (group 1) tune. I just didn't run it in...

I've seen it since on brand new engines (other peoples) so it's not uncommon.

Rich_R

Nito m8 - can u give me a bell - haven't got your number.

Cheers
Rich.

Legacy GTB

Well, we seem to have finally sorted the problem. A faulty knock sensor valued at NZ$130 (GBP40) caused all of this carnage. See

Legacy GTB

Oh yes, and the primary turbo was fine! We assumed damage as so much oil was present in the intercooler and turbo housing. Ahhhh, assumption- the mother of all f__k ups!

NITO

further to what JF was saying re: heat build up at high speeds. I've just come back form the continent and now have an EGT Meter. It's a very interesting and useful gauge. The car is running just under 1.15bar of boost and has an fmic which makes inlet temps 3 degrees over ambient.

The EGT on acceleration is usually around the 800 degrees or so mark. Once you get higher in the rev range, 5k plus it rises. Prolonged running at 110-120mph even on very light throttle can see it almost around the 875-900 mark and a blast to 155mph held for about 30 seconds saw the egt rise to 950 degrees. Apparently STi recommend egt's of no higher than 875degrees and I've been told that around 930deg is the safe maximum. Anything over 1000degrees, 1050-1100 etc means more than likely engine det! I have the warning light on mine flagged at 875degrees and in normal uk usage the most I've had has been around 875-900 so about right. It's interesting to see how it goes so much higher in 5th gear at high revs where the revs are being held in this range. 950 degrees is getting pretty hot and if this sort of speed were to be kept up for a prolonged stretch it's easy to see how damage could be caused, particularly for cars running more than 1.2bar of boost! Oil temp also rises immediately at these speeds. Mine will more than likely need an oil cooler soon due to the fmic blocking airflow to the rad but my oil temp sender is now above the no.3 piston as opposed to in the sump so the temps I see are the absolute maximums in the engine. Since re-locating the sender here temps are approx 15 degrees higher than in the sump. Likewise since fitting the fmic temps are 15 degrees hotter on average than with the tmic. At 155mph temps went from 100-110 to 125. As soon as you back off this comes back down. I also use Castrol RS which is one of the cooler oils.

Just a bit of food for thought!

Nito