mart360

I have noticed over a period of time that there have been a number of "big end failure " threads posted , the replys usually centre round oil change methods and service intervals......

Well this post is the complete opposite, im not looking for any of the above, i would like some topical feedback on what people really think.

To get a car into production the manufacturer ( subaru ) has to follow certain regulatory guidlines and procedures that govern the manufacturing of motor vehicles, they have to ensure that parts meet specifications both there own and due to legislation certain legal requirements... one of the key things the manufacturers look for is piece part durability and fitness for purpose... now this is where it gets interesting... the parts that 1st tier suppliers send to subaru must all meet subarus requirements... one of which covers life and warranty issues... basically the part must give 3 years service without fail....

now i know we have issues with engine drability,and the question is.. is there a weakness in the engines.... well ..who knows???

subaru arnt admitting it are they??

As any engineer will tell you there wil always be two sides to a problem, both must be investigated to find the true fault...

i would like to explore the other side of the engine issue but dont want any of the you should do this.. well what do you expect replys....i get them all day at work!!!

it works like this...

subaru ...rugged cars rally winners stonking performance...

however where did subaru make its start?? farm vehicles!! and are they treated lovingly and given services on the dot top notch fluids etc... be honest ..probably not... but they still run and they still perform why... based on what we see here they should fall over...

is it that by cosseting the car, giving it all the best fluids and unique methods for servicing we are causing the problems..

lets face it when the scoob is on a flat out rally run, does mr solberg say to his guys at the end of the stage,, "hang on ive got to let the engine cool, so as not to damage my engine and turbo"???

do his mechanics have prefilled filters ready to swap... ?? from what ive seen time is of the essence!!

look at the AK 47 machine gun,,, it has generous tolerances and yet it can be dropped in sand/ mud/ water shaken out and it will fire without fail... compare it to our equivalent and it jams at the mere sight of a grain of sand...

did subaru get it right when they specified mineral oil for there engines is the piston slap part of the manufacturing tolerances..

will they run on and on with missed services oil changes etc..

its a forum people

post away

mart

Simon C

My car never gets serviced on time nor has it ever. I've known this car since it was 6 months old ( ex demo and its the hother halfs old car). It does however get serviced within 1k of its service interval and so far has never missed a beat.

Just my 2p worth.
Simon

BOB.T

It's not scientific but...

My dad drives "sensibly" and regulary services the car, it's a 1.6 zetec, it burnt oil for fun, it dropped a valve, within a year it dropped another, it's now had the engine replaced.

My bro drives "sensibly" and regualry services the car, it's a 1.6 zetec, it burns oil for fun and I think it's starting to drop a valve!

I drive like a nutter, service the car as and when summat drops off, my engine is fine and doesn't use oil!

As for SRT, I see what your saying but those cars only do one event, 200o kms? and then have a full rebuild, you'd do well to knack one in that time!!

T5NYW

iTrader: (4)

There aren't many 2.0Ltr 250bhp(average) engines out there but the Scoob has as good a reliability compared with most performance cars of say 150-200bhp

As any Engineer will tell you, "They don't go wrong untill something Breaks"

I and many I know, do intermediate services, 5kmiles/6months with Fully Synthetic oil but it is as likely, to have a componant failure as someone who does it every 2 years

I am happy to save Stress(Mine) as I have done more than asked of me happy to drive it to Germany and back without worrying It's my pride and joy, so treat it well but not for it's looks

IMHO

The WRC engine has 2 things in common with your Scoob

1) Uses Petrol
2) The Crank position

simularity probably ends there, LOL


Tony

fivepint

IMHO most manufactuers get it wrong, just do a search on the net for BMW & Nicasil (sp), its a fact of life that some cars will fail, just some manufactuers are better at cover ups than others...

I think the high number of failure posts just indicates the succes of the car, when the nuber of failures is compared to the number of sales I reckon the Subaru would be on a par with most others,

just my 2ps worth

The Marrawda

so what is the best oil to be used on your motor,subaru that is, and i have 2 say i will service my baby every 4000 miles, is that over the top or what.

dead_neurons

i think if you check the JD Power survey Subaru do come out pretty well compared to most others.

/2ob

dead_neurons

try here

CNN Article

Leslie

Subaru engines do have narrow big end bearings because of the short length of the engine. This means that the bearing pressures are higher in units per square inch or whatever you like. naturally the big ends are more likely to fail with harsh usage than other makes of engine with wider bearings.

An awful lot depends on how the car is driven. If you treat it with mechanical "sympathy" and it is serviced regularly and properly, then it's chances are going to be that much better. I dont mean not to use the performance, but just to be wise how you do it. If you redline it on every gearchange and don't bother to change the oil etc. then it is obviously more likely to fail. If you have allowed the engine to detonate then the bearings will be severely hammered. The real killer for any engine is very high RPM with little pressure in the combustion chambers to act as a cushion. Normally supercharged or turbocharged engines don't suffer from that too badly but the dump valve can lose most of that pressure on the over run. The bearing forces involved in trying to stop the rod and piston going through the top of the cylinder head at high RPM are far greater than the forces produced by power from the firing stroke. There is a great deal of difference to the effect on the rod and big end bolts by forces in tension rather than pressure. Distortion of the big end eye can also cause bearing failure.

John Bank's engine produces immense power on a motor with standard internals and has been reliable so far, I suspect even to his own surprise. He has tuned his engine carefully to avoid detonation, and to run on a good fuel mixture. It would be interesting to know if he uses very high RPM to achieve the power.

Les

johnfelstead

Sorry Les, but that is nonsense. All engines run on vacumn when off the throttle, usually around 0.7BAR negative presure. Dump valves etc are the other side of the throttle buterfly, which is shut.

Subaru engines are very reliable if you leave them alone and dont modify them, considering the number of mods people do without checking the effects, it's amazing more dont fail.

MGJohn

With the basic concept of a smallish (2 litre) engine giving much more power than most equivalent 2 litres, it's a very true fact that "you don't get owt for nowt". All other things being equal, a highly stressed 2 litre giving say 300 bhp will expire much sooner than say a much less stressed 5 litre producing a leisurely 300 bhp.

My unmodified Rover Tomcat 2 litre T16 Turbo engine develops a fairly leisurely (around) 200 bhp (RR graph read out shows 208 but, how accurate are all RRs?). Andy Nicholls' basically same but modified Rover engine in his now famous MG Maestro develops well over 400bhp .... but, he has to maintain or even rebuild it at certain frequent intervals....."Owt for nowt".

MGJohn

BTW, that JD Power survey thinggy .... concentrates on fairly new cars ... three years old or thereabouts. Not a true test of reliability IMHO. Assess those same cars after say seven or eight hard use years and it may just be a different story. Now that's a survey I'd pay attention to. Just my 2pees worth ...

greasemonkey

Er, yes, they do.

For starters, the drivers won't normally kill their engines immediately after a stage, they'll leave them idling to keep the fluids circulating and the fans spinning. Then there's invariably a road section, and a queue to book in at the Service "in" control to allow everything to cool before the engine gets stopped.

Secondly, one (well, more than one actually) of the selectable dash display screens in the Impreza WRC shows the exhaust gas temp. Drivers are advised not to switch the engine off until this has dropped below 500C - precisely because of the risk of the oil boiling in the turbo!

Moot point as under normal circumstances the oil wouldn't be changed during a rally. If the filter has been changed, by definition something's gone wrong, and as time is indeed of the essence, niceties like pre-filling filters may come second to avoiding road penalties. Still, as that engine isn't expected to last more than a few hundred kilometres before being rebuilt, it's something they live with.

Road car engines are expected to do hundreds of thousands of kilometres, and as time is not of the same essence when servicing them, there is no good reason not to take sensible measures to avoid risk to the engine.

I can't speak for Prodrive, but at least one leading privateer team routinely pre-fills the filter and dry-cranks the engine of all the cars that go through their shop - whether roadcars, Group N, Group A, or WRC.

If you're going to make analogies between rally teams and road cars Mart, it might help if they were correct!


[Edited by greasemonkey - 9/18/2003 8:25:04 PM]

pugoetru

well i drive my car hard all the time subaru ford peugeot whatever and as yet i have never kiled an engine they get serviced when i feel like it which isn't that often!

although i have to admit i was more carefull with the subaru due to reading all the dead engine threads.
they do seam to die with no or little warning so i dont care anymore if it dies it dies
but it still got driven hard and will when its back!

Leslie

Jonfelstead.

The statement you quoted from my post is absolutely true. I stand by it from a great deal of personal and practical experience and also the comments from many other engine builders and tuners.

Of course under normal circumstances engines have a vacuumn in the inlet manifold on the overrun. However, supercharged and turbocharged engines have another factor which you have not allowed for. I am sure you do not need me to tell you that when you take your foot off the throttle even though the turbo has no significant drive from the exhaust it still has a huge amount of inertia since it is spinning at many thousands of rpm. It will still be producing a large amount of boost from the compressor. This pressure in the case of a turbo these days is released by the dump valve. The throttle valve does not shut completely and without a dump valve pressure will find its way into the cylinders and cushion the piston assemblies as I described. A supercharged engine will experience the same effect. This is why I mentioned this and in the early days of supercharging racing engines the builders were surprised at the reliability they achieved in comparison to normally aspirated engines. When I built my first turbocharged race engine dump valves were not available and the first time I approached Paddock Bend with it and took my foot off the car felt as though it was still accelerating because the pressure was being forced past the closed throttle slides! I was lucky to escape the infamous fence on the exit of the bend. I then was forced to invent a dump valve so that I could drive the car. To avoid more criticism, it was the first British made turbocharged car in racing which will explain the lack of available parts and it was a learning experience of course. However, 265 BHP from a 1298 cc engine made my 1200lb AUW car go unforgettably well.

I did not say that the Subaru engine was particularly unreliable. I did however give a likely reason for big end failure. The point I was making, and I think it was clear enough, was that if you treat your engine with care it will last, but if you mistreat it and don't take care of it, then you can expect it to fail eventually. Pretty basic stuff really! Maybe if you read my comments about John Bank's engine you might retract your criticism of my post on that account.

I think you jumped to a conclusion from my post perhap's and it was a rather harsh comment from you, although I do realise that I did not fully explain the point about combustion chamber pressures. I hope this one will make things clearer.

Les

Rotten spelling again!







[Edited by Leslie - 9/21/2003 10:03:02 AM]