Just a couple of quick questions:

1.Of all of you that have had engine failures, were the engines in std trim or modded, with the exception of a/f's 7 bb's.

2.If modded, were you all running high pressure oil pumps.

3.Were any of you runnning oil additives.

just something for the brain to think about.

Curious ... why those specific questions ...

just trying to come up with maybe different theory to all the ones that have been posted, hence the specifics.

the standard oil pump is used in wrc and group a engines.

although rebuilt often they dont seem to have a problem with them.

Apparently according to some rally teams it is one of the better designs, and in standard form is supposed to be very reliable and efficient.

I am more concerned about jamming oil pressure relief valves.

So the std oil pump is double a ok for pressures in a modded motor.
but still getting engine failures either on the mains or holed piston.

As for pressure relief valves, if they were opening early, there would be high warrenty claims regarding the oil pump, and if so subaru would have redesign/altered the pump to hopefully erradicate the problem, new lumps would be a high warrenty concern(i.e costly).

Could the the failure rate of engines lay directly with us?

HERE GOES. the scooby lump is a stress item, 250bhp (ave) with about 300lbs of torque from a very compact unit. Due to the stresses and heat produced, subaru have manage to make it probably 90% reliable total volume.
Due to press reliability reviews, we think it's pretty much indestructable.
we buy em, modded em and expect them to be reliable.

By upping the anty, we're heading for melt down, by adding extra stress, we should be treating our cars more in the mode of track/ rally, rather than road.....every 6k service bah bah bah.

If you push em, treat them extra special. total performance doesn't = total reliability.

Flame suit on.

I heard that a standard STI engine sustains over 30% knock. Can anybody confirm this (or not)?

I'd like to add that that's for the STIs sold in France, not sure of the spec variation with a Jap / UK version...

what the hell was all that about? ;)

we all know the subaru has chocolate internals. No one thinks its indestructable, if they do they are fools.

I wasnt talking about oil pressure relief valves opening early, i was talking more about them closing late. Ie, after sustained high speed, they simply do not close down, meanign no oil pressure at the bottom.

there HAVE been a lot of warranty claims for failing big ends, I dont know about holed pistons though. If holed pistons are your concern then why ask about oil additives? I would presume holed pistons to be fuelling related.

This has been discussed at length for years. My conclusion is to isolate what the remedies might be for any of the proposed causes of engine failure and employ them all.

Just trying to provoke a reaction.

As for choccy internals, are they.......or do we expect to much from oe parts?

the relief valve in oil pump, whether opening too early or late would have been fixed...10yrs+ of building turbo lumps.

IMHO, this issue could have been overlooked.

There is a design flaw within, especially when running sustained high load high rpm situations and only subaru will know. the cost of redesign therfore is greater than warrenty claims.

The reason i ask about oil addatives, which nobody seems to run.

Is that the likes of slick 50 could prevent bearing failure, the coating they provdive during the short space of time when oil pressure drops off could be the lumps life saver.

Piston failure can be down to heat, causing pinking, again slick 50 reduces friction, therfore heat.

I'm not saying it's the answer, just a helping hand, with out looking to deep, or costly strenthening of internals (bhp wants depending).

slick 50?


do you not think the companies that make the engine oil would look into such things if they really believed them to be of any value?

I have seen some products that run the engine whilst it is encased in a block of ice, yet it does not seize. I then saw them open the sump on this engine and run it without oil for ten minutes. They then proceeded to tip sand in the combustion chamber and still it ran.

will I be putting this stuff in my engine?

no.

GTB,

You seem to be implying that pouring a few strands of teflon into your oil will do some good... be our guest.

The best you can hope for is that your additive just stays in suspension in the oil, rather than clogging your oil filter.

What it won't do is coat the internal surfaces.

Oil companies rate additives on a scale of 1-4. 1 is useles and harmless, 4 is useless and dangerous.

1 is stuff that is supposed to offer frictionless running, 4 is some of the chlorine based compounds that will actually dissolve the copper in the bearings.

If teflon type coatings were any good, ALL of the oil companies would include them in their mixes or sell them separately.

The reason for mentioning addatives, is that my previous 5 cars have all run slick 50, though non turbo.

1.6ohc, 2.0ohc,1.6 grpA ohv, 2.8v6 and 2.9v6.
Each of these engines having done 40k plus. All having 70k plus on the clock before me, with exception of the 1.6 grpA.

Non have suffered clogged oil filters.
All have run quieter, smoother and cooler. No engine fatalities.

For oil companies to place addatives in every 5ltr tin is costly, considering they are 1 shot treatments every xk. Plus engine oil must remain stable after the addative has dispersed into the engine, effectively you need a 2in1 oil. Again expense.

Have they ever said they don't work, or is cost effectivness?

Has anybody use it in their scooby with bad results?

Again, i didn't say it was the answer, just a helping hand.

p.s shell to buy out penziol, who produce slick 50.....

Well well, anyone putting that stuff into a Scoob is asking for trouble as IT WON'T STAND THE TEMPERATURES. Sorry for being pedantic but there are enough for owners to be concerned about without this sort of comment.

As for oil pumps, I'm with Adam what's the point ...

Bob

DO NOT put ANY additives into your oil until you have read the following linked article SNAKE OIL

It's very long, but a fairly comprehensive and realistic overview of additives.


Mike.

So oil adds are out.

The pumps a dam good design, even though we're a bit suspect on the relief valve closing.

Remove det, coz the ecu is smart enough.

Then hyperthetically

If the engine is running long and hard, the probability of causing bottom end damage is slim, air flow over engine keeping it cool enough, along with coolant.
It could be the drop of to lower speeds, ie thrash, then hit traffic.
Engine temps rise sharply over the next 5-10mins(heat soak), the cooling system gives it its best, but no moving air flow to assit.

With rise in temps within the engine, you could get a build up of tolerances across the mains, closing down the oil ways, not permentally, but enough to cause damage.

As said just another theory.........

You can split the lump, see the damage but can't see why, and there's still plenty of oil pressure.

"With rise in temps within the engine, you could get a build up of tolerances across the mains, closing down the oil ways, not permentally, but enough to cause damage."

How can it close down the oilways??? If the pump is pumping, and assuming no blockage, I dont see how it could be possible for any build up of tolerances to stop oilflow to/from the mains.
I have seen crazier temps on other engines, and they have not had bearing failure, and I think that the cooling system on the subaru does a pretty good job as std. As in any turbo engine, the oil does take abuse, so quality is very important. I wouldnt even use magnatec in my diesel car, let alone a performance car. Dealers use oil that may be available locally at good prices. Im sure that they still charge the customer plenty, and if the engine fails, usually subaru will be picking up the bill anyway. I suspect that a lot of dealer maintained cars, are pretty std, and a lot of owners dont really drive them as they love to be driven. Low quality oil may last for a long time in these cars. If you do drive hard, then buy good oil. Its about the simplest/cheapest thing you can actually do to try and avoid the big end nightmare.

Build up of tolerances, I'm with Stevie, what tolerances, I think you had better read this http://www.scoobynet.co.uk/bbs/thread.asp?ThreadID=29769&Page=1
b4 going too much further, this thread is not even scratching the surface of analysis.

can we please get to the point ...

Surely the design fault is there for all to see - that the ECU can only retard the ignition so far when det is occurring. If det still occurs it neither retards the ignition further nor puts the engine in a "safe" mode.

A lot of engine failures seem to be after prolonged high speed running followed by a period when heat soak can up the inlet temps sky high.

CS ;)

Cap'n sensible

That seems to fit for me.

If, 'for example' high speed running then say 5 minutes for turbo cool down with engine on then say 30 minutes switched off then more high speed running, repeated ?

How would this 'heat soak' affect things and what is the alternative to the procedure above to prevent the big end problems ?

but it isnt consistent.

the failures seem to occur when the cars are slowing down, the only one I know of when the car was stopped after cruising was mine.

Even with a top mount, you dont get heat soak when the car is slowing down as the intercooler will happily get rid of ambient temp from the turbo, and since slowing down, you arent generating mroe heat in the turbo.

Not only that but there seems to be no indication of visible signs of det on failed pistons that I have been told about at least.

All four of my pistons are completely unpitted (a testimony to both R19KET's and Bob's mapping).

Not only that but if coming to a stop or slowing down you are not pushing the performance of the car and you certainly arent running boost. in this circumstance you cane asily get away with running high intake temps as det is not likely to occur.

You can run a car at idle with an intake temp of 80 degrees, the ecu wont be retarding ignition because it is unlikely to hear any det because there is unlikely to be any.

Therefore this is not the obvious answer.

Oh - I liked this idea as a possible answer to my failure

The only bit that I guess will never be answered is why some cars fail and some don't, even if both have been hard driven, but the one that fails has had the best oil, maintenance etc etc etc

capn':
If det still occurs, it drops boost to ~7psi, and this removes almost any chance of knock. So it does have a 'safe' mode.

Anyway, as Adam points out, that doesn't appear to be the problem, at least not in the cases being looked at. They are not under boost at failure. So the question would be - what happens in the engine when slowing from sustained high-speed driving, and why would the problem typically show up after a service.
Personally, I think Adam's oil whatnot not closing when it should do - agitated by gunk dislodged with an oil change? is the most likely looking at the moment. But I don't know enough to really have a valid input... But is there anyway that this sort of thing can be checked? Change the oil, run the car about (casually) for a bit, then wash the gunk out & see if there's anything nasty in there?

Mine failed just after a service as well for what its worth

mark aigin once suggested the idea of a remote oil pressure relief valve. at the moment the current one is bolted to the block and is difficult to get to as part of the oil pump behind the cam cover and cam belt.

i just worry about the prospect of building an aftermarket adaption to what is essentially the most important component protecting the engien from failure, especially when we dont know if the standard one is actually the cause of failure.

saying that, I am incorporating a failsafe into the pectel ecu (or asking pat to) wherein if the rpm is above 2500 and the oil pressure is below 2 bar, it cuts the engine. so even if i cant read the gauges to act fast enough, the ecu can do it for me.

Again i come back to build up of tolerences.

Bare with me.

All engine have upper and lower tolerences of components, ie sizes and componds of materials.

Manufacturing process of engine, from the cast components.

Block mains are drilled, from x machine, then block is then labelled grade a.
This block requires shell pack B.
With c/rod set C.
With crank D.
And piston set E.
etc etc

This process varies from batch to batch, to keep the tolerences in check. There can be up to 4 different grades per component.

If these tolerances are at the upper level, the expansion of rod shells and crank could cause the oil to stop flowing over the journal. The restriction of flow could even start at the crank.

Hence the possibility of a heat soak problem at no.3 three main, after prolong high rpm/load.

Hence no oil pressure drop of as the rest of the is still recieving oil in a normal manner.

Imagine the forces at work to slow a piston to TDC when there is no explosion to help it.....I always close the throttle slowly where possible :)

Richard

this tolerance problem is identical to the manufacturing of all engines by all makes.

Why are we the only ones failing?

and a lack of pressure anywhere in the system will still reduce the overall pressure of the engine as the oil will follow the easiest path, thats how oil pressure relief valves work!

Dealer said that oil with 'Magnatec'- type properties where the molecules are 'charged' (forgive the technical ignorance) would prevent meltdown for longer if oil starvation was a problem.
I was using 15-50 at the time but whether it's wrong or right, I'll go back to what they recommend now !

And - the other clicher here - is why do the same cars, with new blocks, etc., go again? Some have no troubles at all, others go 3 times. Isn't a key thing to be looking at here is what is NOT changed when the engine blows? It seems likely that the problem is being transferred from one engine to the next. There was a suggestion previously that it was the ECU (Subaru suggestion, via can't-remember-who :rolleyes:), but from what I can gather, there is exactly the same failure with other manufacturers' ECUs as well?

who's got an oilpressure gauge fitted?

whats pressure at cold?
whats pressure at hot(normal running)?

GTB, regarding the tolerances. Obviously you have never had an engine apart, to see how the oil actually flows through the engine.