Andy.F

Thanks Scott

ustolemyname??stevieturbo

iTrader: (1)

Perhaps I may be be accusing when it was not through any fault of the owner in that case. But still, that the CAUSE of the failure is known.

Hoppy

I think EvilB has got it. The problem is a combination of many factors. And there are several combinations of factors, not all the same. Hence multiple permutations and no clear conclusions. From previous threads, these are the factors that stood out for me. Comments welcome

STi's need a regular supply of high octane fuel, eg 97 RON plus octane booster minimum. Every time.

Induction kits can compromise the delicate MAF sensor.

Wrong oil is bad. Change it every 3/4,000 miles. Observe filter filling and cranking procedure before firing up.

Always drive on light throttle until oil is fully up to temp.

After a service, if an enthusiastic mechanic has not observed the above oil change procedure and then takes the car for thrash around the bypass when full of cold oil, the bearings can pick up.

Stock internals don't like high revs. Sustained high revs are risky. Sustained high revs and high speed (120-plus) where TMIC efficiency is compromised is heading for trouble as inlet temps rise (usually unnoticed).

Subaru's decision to position the intercooler above the engine and right next to the turbo was not a smart move.

And the straw that breaks the camels back: some or all of the above followed by a high-speed drive. Stop for fuel or whatever and inlet temps soar due to heat-soak (again, unnoticed). Boot it up the road and then bang.

In short, driving a cheap Jap saloon with 300bhp has its drawbacks

Best regards,

Richard.

ustolemyname??stevieturbo

iTrader: (1)

After stripping my engine, I think the reason for big end failure is fairly obvious ( in my eyes anyway ) Looking at the crankshaft oilways.
No 1 big end is fed from Main journal No1
Mo 4 big end is fed from mian journal no5
Nos 2+3 big end are fed from main journal 3 ( centre main )

It doesnt take a genius to figure out the maths as to which has the most oil flow, considering all the oil galleries and drillings seem to be the same diameter.
This was basically confirmed by GGR, when I phoned to enquire about their billet crankshaft they do. It has oil drillings, feeding from Main journals 1,2,3,4 to the big ends, as opposed to just 1,3,5. This also requires the use of different main bearings to accomodate the oil supply to the big ends. They say they do nt drill the rear journal no 5, as this is the weakest point on the crankshaft, and is no longer necessary due to the other drillings provided or supplying oil to the big end journals.

It just looks like bad design on subarus part, as Any I have seen have destryed No 3 big end. On mine it was No3, but also No2 was on its way out too, and the centre main thrust and main faces were also bad. Its just trying to feed too many places, they all got starved. I might look to see if I can enlarge these oilways any to help the oil, supply, as I cant afford the GGR crankshaft.

Andy.F

This sounds similar to the ZZR 1100 Kawasaki engine. Tuners of that unit designed an additional oil feed into the centre main bearing, to supply the two bigends it was feeding.
This was done externally via braided hose from the end of the oil gallery feeding an 'uppipe' through the sump into the bearing cap.

It looked a bit of a bodge but it totally eliminated big end failures under racing conditions.

mrkimpreza

1 MY99
2 1,5
3 77000 (km)
4 Detonation caused hole in piston and damaged cylinder #2
5 end feb. 2002
6 25000 (km)
7 Subaru Dealer vdboon Holland
8 BP Visco 3000
9 don't know
10 ehh ???
11 ehh ???
12 RON98, no addictives
13 evening
14 PPP, downpipe, K&N 57i, approx 250-260 bpp
15 1,2 - 1,3b max
16 It's my daily driver. Normally keep it under 3500rpm. Always drive it warm (15 min) and let it idle / cool 1 to 2 minutes. When it's trashed its trashed till 7000rpm in all gears (but 5th).
17 trashing it, detonation came at 6500-7000rpm in 4th gear
18 7000rpm
19 don't know. Don't drive topspeeds often and certainly not held
20 see above

Mark

TonyBurns

iTrader: (3)

Mark, what oil where you using? Mineral or fully synthetic and which grade, ie 5w30

Tony

johnfelstead

It's common practice in racing engines to use crossdrilled cranks, but we are talking production cars with not a lot of stress here, the standard oilways are fine for a not highly modified engine.

After driving my STi for 2 weeks, i am convinced a large amount of failures will be down to the fuel pickup design, it's apauling. Until i can sort out an anti surge solution i am not cornering hard below 1/2 tank of fuel as i can feel it losing supply. I dont think most people would notice this until it's severe, i tend to be quite sensitive to small power changes myself.

A question to add is how much fuel was the fuel tank, had you been cornering hard with the tank below 1/3 full before it failed.

As to MAF's, my engine is staying on the standard Subaru filter as i dont want to go down the MAF bulk buy route!

Adam M

If it was a number 2/3 oil feed problem, then there would be as many no.2 failures as there are number 3 failures, but people seem to think number 3 is the big problem.

This simply isnt true.

I have seen more number 4 failures than anything else.

If 2 and 3's supplies were restrictive and not capable of supplying, would we see increased oil pressure?

cos I dont.

Andy.F

Valid point John. Thing with det is that the piston may not fail at time of det but just be weakened. A few heat cycles / high RPM later it can fail for no 'apparent' reason

ustolemyname??stevieturbo

iTrader: (1)

All the failures I have come across, and hear of, are No3. Drivers side rear.
Subaru cranks do appear to be cross drilled as standard.

mrkimpreza

That's precisely what happened with my engine. Got bad detonation at 6500-7000 rpm in 4th gear at Saterday. At cold startup Sunday I got piston slap when cold (5 minutes). Except for that cold 5 minutes it run fine, till thursday then piston blew.

@tony: BP Visco3000 is non synthetic 10W40 (I think)


Mark.

Sheepsplitter

Does detonation cause piston slap?
I thought that was just a manufacturing problem or piston mismatch issue.

ustolemyname??stevieturbo

iTrader: (1)

The I highly doubt it was piston slap you heard, more like a broken piston. 2 completely different things. Piston slap isnt really something to worry about. ( Unless you have just rebuilt your engine with the wrong size of pistons...then you should worry!!!! )

swaussie

Just to re-open the debate and add another "possibility" I found this at http://www.streetrodstuff.com/Articles/September_2000/Engine_Basics_III.php

"In the same vein, an engine running at full throttle may be happy due to a rich WOT air/fuel ratio. Throttling back to part throttle the mixture may be leaner and detonation may now occur. Bingo, the piston overheats and scuffs, the engine fails but the postmortem doesn't consider detonation because the failure didn't happen at WOT."

Adam M

I have just specced up a custom crank fro farndon, should I be asking for cross drilling then?

I am not convinced by this shared oil supply problem, but if I am having the thing made, is there any reason why I shouldnt go for cross drilling?

I assume cross drilling means that there is a continuous oil feed through the whole crank, so oil is supplied from all main bearings to all big ends. Can someone correct me if I am wrong, and possibly indicate what they would do in my position.

Andy.F

Crossdrilling AFAIK is referring to the big end journal having two oil feeds at 90 degrees to the OEM drilling which is radially inwards toward the main bearings.
The benefits are - Improved (twin) oil feed to each big end bearing. improved oil pressure retention due to less centrifuging effect at high rpm. Marginally more bearing CSA at TDC.

Crossdrilling alone will not cure the '2 fed from 1' Subaru crank lubrication issue.

I would take advice from Farndon in your position. They are the experts

Ivor_the_engine_ChooChoo!

I drilled out the oilways in my block, and enlarged the centre main oilway on the crank, at least now its a bigger hole feeding 2 big end journals, which should balance out the flow a bit. So far it hasnt broke!
For those engines that have died, what was the condition of the other bearings in the engine? If it was an oilflow problem relating specifically to the centre main 2-1 issue ( which I do mostly believe ), then obviously both the big ends 2+3 will show damage. But then the other bearings could still be OK in comparison. If it is a major oil supply/quality problem, then surely all the bearings will show signs of damage.

cwal1

My STI 5 engine blew a month or so ago and ALL bearings are gone. 2 big end bearings have collapsed and fragmented, all crank bearings deeply scored and worn. 1 piston slightly det melted, 1 conrod snapped and twisted sending the piston into the head and valves, another conrod very, very hot and partially siezed to the crank, 2 cracked heads, knackered turbo, damage to the block within which the conrod broke, lots of impact damage to the crank cases, impact damage to the sump.

The oil pressure relief valve was siezed completely open and is assumed to be the most likely cause of the failure.

Still at least the clutch didn't break !!

Chris.

dowser

Jesus Chris - you have my condolences, at what revs did it let go?

Richard

UkLegacyT

cwal_1

where is the pressure relief valve located? is it in the oil pump housing?

cheers
ian

Gez

I havent experienced a blown engine (Thank god), but out of interest i spoke to Roger Clark Motorsport. They have built quite a few scooby engines minly due to failure. All the above faults were mentioned ie craked pistons, snapped rods etc. What the chap told me was that with every engine that was opened there was always something different that had failed not leading to a common fault ie failure due to det etc. What he did notice though was that in 99% of the cases oil pump relief valve was always faulty. Detonation due to fuel quality etc is common but a dodgy oil pump only speeds thongs up. Roger Clark Motorsport have designed a new oil pump which has cured the problem.
Hope this has helped.

Cheers

Gez

UkLegacyT

cheers gez

will contact roger clark motorsport to find out more about the redesigned pump.

thanks
ian

Gez

Not a problem UKLegacy! Im willing to invest in one if it will protect my engine from blowing to smithereens. As im not so clued up on oil pumps, is it an engine internal job????

Cheers

Gez

UkLegacyT

the pump bolts onto the front of the engine. just a case of removing the front crank pulley, and then the cambelt in order to access it. its held onto the block by about 6 or 7 bolts, cant remember off hand.
easy job really, and one worth doing.
right must go to bed, am knackered.

cheers
ian

cwal1

Richard,

When it went bang it was at 50 mph in top so less than 3000 rpm, but I think the trouble started prior to that. I was on a tight backroad going quickly in front of someone on a GSXR600 when I heard a noise like a blowing exhaust. This didn't bother me too much as I had had the exhaust swapped out and back again for the 1st MOT, so I turned round and just slowly drove home to fix it. I think now that just before I heard this noise the oil pressure had dropped and the noise was a bearing picking up. I've heard big ends before on other cars and this sounded completely different, but it may be because of the all ally engine and the fact that there are no cylinders on top of the block.

Ian, yes I think the relief valave is in the oil pump housing. You can get hold of Roger Clark Motorsport on 01455 828610.

Chris.

TonyBurns

iTrader: (3)

Where abouts is Roger Clark Motorsport??

Tony

cwal1

Tony,

Roger Clark Motorsport is in Desford, about 3 miles from Mallory Park.

Chris.

Adam M

does someone want to ring up then post details of this mod?

I would but cant do it from work.

Gez

Just spoke to Roger Lark Motorsport! Yes the oil pump is a big contribution to to engine failure. There is no set life span for the oil pumps pressure relief valve. What tends to happen is that the valve jams open and everything goes mad after that. Roger Clark have a modifed unit which is a big seller at the moment and only costs £142 plus 2.5 hours labour. The guy didnt want to give too much away but he did say that the pressure relief valve along with some other bits were re-designed - modified. Its a small price to pay for peace of mind the bonus is that when you are having that fitted its recommended that the belts get replaced as they have to come off anyway.
Do i sense a group buy????????

Cheers

Gerry

[Edited by Gez - 9/13/2002 2:22:39 PM]