If the bearings have to much clearance you will most likely to hear it with a hot engine , no load at rpm up to 2500 , it must not be confused with piston slap and will sound more along the lines of a runble to knock .

The oil temp will be diffent throughout the engine , but if you use good oil that is up to the job and change it offten you will go a long way to reducing the chances of failure . Coolant will help reduce temps , but it will take a large change in coolant temps to have an affect , this will not be helping bore wear if the coolant isn't at the right temps .

One thing i have done is fit a pre 96 turbo heat shield plumbing air from the bonet scoop to cool the exhaust shell and bearings/oil for track work .

Interesting thread indeed. It's the first time I've bothered to go through it since with 150 replies it must be interesting!

Just a couple of points to add/re-iterate. All the engine failures I've heard from people I've known have been after high speed runs. I know of an STi2 engine that has recently expired after prolonged high speed running, it wasn't until he slowed down on the slip road that it let go. It's the same story with many cars on here.

This doesn't suprise me in the least. When I was abroad I bought my foot down on the motorway to see what the gauges would report since it's the first real opportunity I've had to do a proper high speed run since having all the gauges up and running. Obviously my car isn't standard so not necessarily representative but I still think the general principles are the same. At around 130mph in 5th the temps started to rise from around the 105deg mark to around 115-120, then by the time I hit 155mph oil temps had gone upto 130 degrees almost straight away, at the same time EGT soared from 800 odd to 955deg all in the space of about 1000rpm increase.

So if mine, a UK car (with an fmic and larger turbo keeping charge temps down, although paradoxically it also means oil temp will be up) with long gearing revving at just over 6k in top, is making egt's of this nature, after less than 30 seconds prolonging this, I backed off at this point as the egt's were still rising then it doesn't suprise me in the least that an STi (with shorter gearing at an 8k rev limit) at anywhere near the red line will be making egt's well in excess of this - is it suprising that they will go boom?

Surely the problem must be down to the oil film breaking down at such high temps and heat soak while at the same time revving at such a high rpm range where it needs the most protection, instead the oil film is breaking down etc. Bear in mind heat soak at these temps, 950+deg in egt's 130+ oil temps and then take into account cars with tmic's small turbos running even higher charge temps.

To summarise, it was certainly an eye opener for me. The way the egt's rose substantially from 5k to 6k in top was impressive and really puts into perspective the strain and amount we are expecting from our engines. For the record I also run Castrol RS which is probably one of the cooler oils anyway and seems to work very well on the scoob.

just my 2p

Rgds
Nito

What characteristics would cause such a massive rise in oil/EGT temps? Are we going well outside of the effective operating envelope of the engine and is something (what?) complaining by no longer providing adequate cooling effect?

Excellent thread: I think this will find the culprit given time and thought.

Nito,

Without wishing to get into another debate, your car isn't really representative.

One of my concerns about going FMIC is the effect it will have on water temp's, and the knock on effect, to oil temps. I think at the very least, an oil cooler should be used in conjunction with a FMIC, and depending on core design, maybe even an uprated rad'.

One possibility for the sudden jump in EGT's, is that even though your car showed the correct fuelling on the RR, there's quite a difference between 100mph + in 4th on the RR, and 155mph + in 5th on the road. It's possible, that a combination of increased boost, standard ignition timing, and all your other mod's, led the car to lean out, and run hot, under the high load conditions.

Try doing a run in 4th, to 6000rpm, and compare the EGT's, oil temps, etc'. It would be interesting to know if it makes any difference.

With reference to bearings, one thing I have noticed, is that whilst the "main" bearings have a groove running around the circumference, for oil flow, the big ends don't. Maybe one of the more knowledgeable, could let us know if there is a logical reason for this, or could a modified big end bearing make the difference.

Mark.

The oil first feeds the mains through oil galleries in the block , the oil travels round the grooved main bearing to supply oil through crossed drilled holes from the main journal in the crank to bigend journal .

It would be of no use having grooved bigend bearings as they need as much surface area as can be to take load .

Eally Chev v8's only had a half gooved bearing and single cross drilled hole , so for one half of a revolution the bigend had No oil pressure http://bbs.scoobynet.co.uk/smile.gif

cheers
Michael South

By way of keeping this one going...

Why would changing the bearings to a different material (eg white metal) help... surely the bearing will only wear when there is physical contact with the other surface and this will only happen at start up or when there is an oil feed or oil integrity problem. So am I right in thinking that a harder bearing will simply keep the engine in one piece a _little_ longer assuming the oil feed or integrity fails, which _might_ help get a rally driver to the end of the rally if they are lucky, but wouldn't really help a road car?

Moray

I was under teh impression that after rebuild, all big end bearings show signs of wear, as they do pick up at some point during their lives (start up?). Would uneven wear mean a variation in pressure across the surface of the bearing, causing a compromise in the integrity of the film in different areas? Clutching at straws but why not?

Bob, If a bearing had spu, cutting off its oil supply, is it possible that the beaing might be in the same orienta\tion after the collapse and wewould be able to see this, or is there such carnage that it would be wishful thinking to expect this?

With reard to what ito has written, how many of the blown engines have shown significant heat damage to indicate leaning out at the top end, and since the piston crown is taking most of the brunt of this, why is it that so many of the failures are from the big ends and not some other part of the chain?

Michael South,

To my knowledge teh 22B was not specific to the 22B, as there are other closed deck 2.2s which appear identical. The americans have a 2.2T closed deck block, which incorporates oil squirters which the 22B does not. Why would subaru create a specific block for their special edition designed for performance without incorporating this feature? doesnt make sense to me, but then, a lot of things dont.

Mark - off the thread!

Re FMIC's - are you therefore saying that this is the wrong way to go? - ie say, keep the top mount and add water injection? - as a bigger radiator and oil cooler start adding to the cost.

Steve, mark doesnt normally log on during the day,

but I know he is not saying this, merely pointing out that he would not fit an fmic, without lokoing at water temps, and considering an oil cooler.

I will certainly be fitting an uprated rad along with my fmic, and if it isnt full width and full height then will be using the area behind the grille for a power steering and oil cooler.

Steve,

I'm certainly not suggesting people shouldn't go for a FMIC. For most people, a FMIC will be more than adequate, for some, those who are looking to extract the most they can from the engine, take things a little further.

Mark.

Moray is mostly right - bearings are designed to resist working loads only when an oil film pressurised by the eccentric rotation of the bearing around the journal is seperating the surfaces. AFAIK, the oil pump simply has to flow enough oil to the bearing to allow the bearing to maintain a sufficiently thick film of oil, and the supply pressure is a secondary factor (subject to pressure differentials across the bearing). If oil flow is insufficient, the hydrostatic pressure in the bearing will not keep the surfaces apart and they will pick up.

Obviously, local heating effects will also reduce film strength and sometimes a fractionally larger clearence (with adequate inflow) will reduce this by reducing the temp rise from inlet to outflow. This has to be balanced against a reduction in the self-pressurisation of the oil film, and its easy to go too far..

The point of this is that a) High revs / load means that more heat is entering the piston crown than can be conducted away through the piston skirt, leading to greater heat in piston, conrods and big ends. Could this result in a change in big end clearences as a result of thermal expansion?. If so, it may be worthwhile to look at either reducing the heat entering the piston crown (ceramic coating?), or improving heat transfer through the piston skirt (thicker than stock ring lands or oil squirters?).

Another possibility is that the oil pump might start to cavitate at high revs if the oil system pressure is too low, and this could be responsible for for an interruption in oil flow to the big ends.

The more that emerges, the more I feel that an oil system or bearing design limitation (maybe a combination of several factors) is at work here... I await Bob's analysis of the data with interest http://bbs.scoobynet.co.uk/smile.gif.

Cheers,

Alex


[This message has been edited by AlexM (edited 11 July 2001).]

Any car that has egt rising quickly in a short space of time is in trouble probably with fueling, trouble with the gas analyser on the rolling road is that it is measuring what was happening some seconds earlier than real time. On the rollers at Easter my car shows 6-7% over but I know it was at more than 90% injector duty from 5800 rpm upwards. Oil temps in the 130's are again not normal and come from the high egt and lean mixture which heats the oil in the turbo and increases the block temperature as well. A good oil such as Castrol RS is proably what saved the day, a lesser quality oil would probably have resulted in big end failure. As Nito says this indicates the importance of using the right oil and paying attention to the engine ie not running at high revs and high load for too long.

The oil pump generates the pressure, the pressure relief valve controls how much, the system (including the filter) then determines the flow rate, to cavitate the pump must spin too fast into too high a system.

I have not been inundated with information disappointingly, maybe its not such a big problem, hardly I think ...

Disregarding the detting issues which will certainly cause oil film breakdown etc and bearing failure if severe enough for long enough the main points that are emerging so far are ...

Oil quality and oil change procedure, certainly if not done correctly then
wear particles will sit in the bearing and attach themselves, with time and
normal use these will not be a problem. Oil quality is an obvious (or it
seems to be) issue but how many people actually ensure that their servicer
puts in the "right" oil, until this thread almost no-one I suspect.

Certainly engine abuse by holding at high revs under load is not good sense,
this could induce oil film breakdown and cause bearing pick up. If this then
spins the shell in the con rod the oil feed hole will be blanked off, no oil
is almost instant failure. Bearing spin is caused when the big end bolts
stretch a bit allowing the bearing to "loosen", if pickup occurs it will
then turn. By stretch we are talking very small amounts here, certainly
100ths of a millimeter.

Temperature can be increased in differing ways, lean running with no det, persistant det, carburised oil, increased coolant temps will heat the oil, high boost on a small turbo (charge temp increase) would all contribute to increased temperatures which could lead to oil breakdown.

Whilst all the individual points are valid its a combination of several that causes the problem.

The most common circumstances are, just serviced (up to 700 miles before)
just had high revs heavy load for a period, slowed to negotiate a roundabout or something similar and the bearing is gone.

It seems to affect standard and modified cars alike including UK versions. Early cars don't seem to suffer any less.

BTW re the P1 thread, that car would have still been tight at 2000 miles, running on NUL (95) is really asking for trouble especially as the quality can vary imensely. Its quite probable that det caused the issue but, at 2000 miles it would have been serviced only 1000 mile earlier so it fits the general pattern even without considering the NUL effect. With the four mentioned we could have maybe six in total as a guesstimate.

I must say that this is by far the most interesting thread I have seen on scoobynet and wonder whether it may be worth SDB creating an 'Engine Failures' area on the BBS to ease collation of data. We all have a vested interest in trying to find out what exactly causes this and how to try and prevent it.

Someone earlier mentioned without giving details that some 'leading brands' of oil don't give as much protection as you would expect - does anyone have anything to back this up and if so please say. Apart from using race oils what should we use. So far I have been using whatever the dealer puts in at the normal intervals and castrol magnatec 10W40 half way between the normal 7500 intervals but without changing the filter. I generally don't drive my car hard but my 12 or so mile commute is a lot of slow stop start and the oil probably gets pretty manky. I would be interested in what people think of Magnatec and the other non race synthetic oils out there - costco for example sell chevron fully synthetic 5W40 for about a tenner a can. Is this sort of stuff sufficient when changed frequently?

A set of gauges sounds like a good investment too - what are the essential ones - oil press, oil temp, boost - is EGT worth having? Likewise knocklink and lambda link.

The common theme also seems to be engine braking (or possibly more correctly, breaking http://bbs.scoobynet.co.uk/smile.gif ) under high loads. Is it likely that the damage was already done while running at high revs or is it the slowing down itself that kills the bearings - can slowing down gently after a high speed run help reduce the strain?

I personally would be interested in knowing what the max speed people have had out of their scoob without suffering engine damage is and what sort of car this was in (uk/STI modded etc). Don't bother to say where this was attained though temperatures might be interesting if out of the ordinary.

My STI V 4 door 145(ind) not sustained for long (itg filter, magnex centre, SS Backbox). After reading all this it may not do this again http://bbs.scoobynet.co.uk/frown.gif


Cheers,

Eric.

Bob,

So two main factors - a susceptibility to oil film break down which surely implies that the bearing is overloaded at high engine load/speed, compounded by the possibility that the bearing shells are spun when the bearing picks up due to problems with the rod bolts. I'm still not clear how servicing procedures could have a significant impact (assuming normal good practice is followed).

It is a bit disappointing that more data hasn't been provided by those unlucky enough to have suffered. Luckily with my weedy TD04 there isn't much point exceeding 6.5k rpm anyway http://bbs.scoobynet.co.uk/smile.gif.

Cheers,

Alex

I may be wrong, but I thought using "race" type oils (and most other "race" type fluids) was a VERY big no no for road cars.

Why? well they are supposed to last a few hundred miles max, and are often used in engines that will be rebuilt regularly, so are only asked to provide enough lubrication to prevent a failure, whilst minimising the loss of power due to the fluids.

Not the same as 4000 miles of stop/start/thrash road driving!

Or has something changed in the last few years?

robski

I demand that I may or may not have seen an indicated 170mph for a short time on one occasion. STI 3 RA VLimited with a little tuning work.

lap after lap of bedford, with an indicated 145 on 1km long straight, accelerating hard from about 50.

Jap import 22B, approaching 7500rpm at that speed. Redline oil, not changed before or after track day.

Indicated 152mph in an unmodified MY98 for approx 30 miles... I definately won't be doing that again!.

Cheers,

Alex

Sustained high speed cruise last year, returning from Amsterdam to Calais, typically 100-130mph where traffic permitted with a max speed of 148.1 on one very clear straight stretch (all indicated by GPS so presumably fairly accurate). No engine problems so far.

Bob, this was before the VF22 was fitted, and the car was running on its original map which had conservative ignition timings at the top. By 145 there was very little further acceleration, so I backed off rather than running for ages on wide open throttle.

The car was fully loaded though (five-up plus bags in the back) which seemed to help the directional stability and also helped with the whip-round when the Belgian police pulled us over and demanded cash. =( Still, glad they didn't nick us in France, I've since heard that I might have ended up in the cells if they'd caught me doing that sort of speed there.

-= mike =-

I must admit that I did 140-160mph in my sti5 for approx 1.5 hrs filled up then did another high speed stretch.

This was from the South of France right up to Dunkirk - and the temparatures that day were fairly hot - we made good progress though!!

Interestingly the VF22 turbo failed soon after that trip - on changing the turbo (which had been on about a month the oil apparently was not changed!)- oil was Silkolene 5w40w. (interestingly this invalidates the warranty on my VF22 Hybrid for running such thin oil - think they were after at least 15w50w at Turbo Dynamics to safeguard the turbo)

I think I may have got away lightly.

This thread rules!

Regarding the oil...to begin with...I've just installed an oil preassure gauge in my car.

I'm running Motul Competition 300 (something) 15-50 fully synth.

Oil preassure seems to run quite high-ish, up towards 100 psi - just a smidge over 7 bar (max on the autometer gauge), and it idles at 50 psi.

Somehow I think this is a wee bit excessive...I'm thinking oil change, and go for a 10-40 one, or is it safe to run the 15--50?

As per Sweden, AFAIK there hasn't been a single case of no3 bigend going tits-up, the Impreza has only been around for 2-3 years, but *all* of them gets a fair bit of stick.

Most of them seem to be run at 95ron even though there's 98 available... http://bbs.scoobynet.co.uk/rolleyes.gif I'm on a mission to spread knowledge. http://bbs.scoobynet.co.uk/wink.gif

I think it's a bit strange that engines seem to let go left and right down there, we haven't had a single one yet (apart from a few Superchipped tossers).

Cheers

/Jerry

Indicated 250kph sustained for 3 minutes once on MY00 Euro UK spec Turbo with mods exhaust, induction, Electronic boost controller running 1.2 bar but above 160kph turned it down to 1.0 bar. Outside temperature was about 25 deg Celsius. I use Castrol RS 10/60 oil and change it with filter every 4000km, roughly 2800miles. Been changing oil and filter like this since new.

After this thread I won't be doing that speed again. Probably nothing over 5500 revs in top.

WREXY.

[This message has been edited by WREXY (edited 12 July 2001).]

This is something I wrote regarding oil a few months ago but nobody seemed to be that interested at the time, times change.

Andrew,

very informative. Is Castrol RS 10/60 becoming unavailable then?

WREXY.

Thanks WREXY.

The major high street car parts stores used to stock Castrol RS 10W-60 but a few months ago replaced it on their shelves with a 0W-40 version. The most suitable oil I see in these stores now is Mobil 1 Motorsport 15W-50. Some people on this BBS still use RS 10W-60 but I don't know where they are getting it from.

As Robski says it is well worth noting that race oils are not designed for road use, as mentioned above they are specifically designed to be changed after a low number of miles. So while it may seem as though you have a better oil .... most oil manufacturers do a race oil, best to avoid.

Magnatec, IMHO not really up to it but a good oil in the right application. Vauxhaul boys tended to use it in the Cav and Calibra turbos to minimise turbo oil seal leakage ... I used to say it was only better cos it carburised (I could have been wrong though)

Jerry, most cars idle at 2 bar and max at 6 bar, least most of the ones I've seen do, that oil sounds pretty good if you are getting those figs (assuming your guage is accurate). Idle pressure is no problem, 7 bar should be ok as well. Is that after a thrash or during normal driving ?

Andrew, worth the read.

Hello Bob!

It reads 100 psi on regular (brisk) driving when warmed up, a blast will make it go down towards 90 psi.

http://bbs.scoobynet.co.uk/smile.gif

Thanx mate, I'll keep with the Motul oil (though silly expensive, but said to be a really good one) then!

/J

Suggested oil change intervals here are 5000km, or about 3000miles (correct me if the math is kaput).

I personally follow WREXY's line - changing more regularly, between 3 and 4000kms (in fact all of my friends change oil at this rate, I believe).

While we run B4s, I have noticed that one of our buddies with a Prova ECU has a very intrusive limiter (cuts aggressively at 7250 in lower gears =safer?) than our OE units which will go to 7500rpm without blinking.

Apologies for the lack of tech input.

Adam,

I think NDT means don't overrev when changing down, i.e. don't go from 3rd to 2nd at 70mph!

Your corky bell book 'maximum boost' explains all about the phasing of inertial and power loads http://bbs.scoobynet.co.uk/smile.gif

Cheers,

Alex

Adam,

Not entirely relevant I know, but from what I recall, it may actually be illegal to coast the car (e.g. clutch disengaged for longer than necessary, such as declutching and rolling down a hill ). If not actually illegal, I am sure the practice is frowned at in the highway code. I believe the rationale behind this is that you do not have as much control over the vehicle in this situation as you really should have.

Mind you, it's less likely to wear the gears out than driving along with your hand on the shifter... http://bbs.scoobynet.co.uk/wink.gif

None of which alters the fact that you will shortly have a much sexier intercooler than I have at the moment, dag nammit. http://bbs.scoobynet.co.uk/smile.gif

Moray