FOZ STiV5

Hi all,

I have been having various debates with specialists regarding how tough an WRX/STI engine is with varying answers. The is especially so when compared with an EVO 4, 5, 6.

So what are you thoughts provided the engine is looked after???

submannz

The Subaru engines are less stressed than the EVO engines. There are some many variations of the STI's from the factory that it is hard to say.

I have had work done on my motor and the engine has been thrashed over heated etc(just starting to leak a little oil around the seals) and 200,000km later still going strong. This car is raced on a track and gravel and grass.

Down at the drag strip. I have seen more EVO's crap themselves than Subaru's. If a Subaru dies it is normally a gearbox failure.

Dan


[Edited by submannz - 2/18/2002 9:17:59 PM]

FOZ STiV5

Cheers Dan,

Thats interesting ... I know my Brother had a company Uk Impreza turbo... and we used to practice standing starts in it.... torture I know ..but hey ..a company car.

Anyway .. it never grumbled ... but the gearbox did sound rough after 60K.

I have an STiV now .... and I am unsure just how much punishment I can give it. To be honest...I will look after this one.....my WRX did get thrashed though..

l8R

Sieze

Tuff till the big end overheats and wrecks the crank conrods and turbo.

Neil F

I once read an article in a rally magazine where a guy chose an Evo over a Subaru for his competition car due to the Subaru's "weak" gearbox.
There was a photo with the story and some accompanying text showing all the block casings and crankshafts that he had left over after all the engine failures...

Neil.

Adam M

if it means anything, STi engineers refer to the subaru engine as glass.

The sti shortblock only differs from the wrx or uk in that it has forged pistons which are lighter so it puts less stress on the con rods enabling it to rev to 8000rpm.

The engine is by no means strong.

I would also have to disagree entirely with submannz, the evo engines in this coutry seem to sit happily all day long at 1.4 to 1.5 bar producing massive power with zero internal mods. The more cautious have put in arp rod bolts but that is about it.

It is possible he thinks the engine is more stressed because it runs 8.8 compression rather than 8.0 of the subaru engine, but this just improves its thermal efficiency and its off bost response. It should mean it is less happy with higher boost but this doesnt seem to be the case.

In short I know of hundreds of scooby engine failures but proportionally very few evos. but then, I could be mixing in the wrong circles.

EvilBevel

Think I have to agree with Adam here.

You only have to look at GrpN. rallying ...

FOZ STiV5

So given a choice which motor would you go for??

STiV or EVO 4 maybe 5?????

Neil F

Adam.

I thought there were more differences than just the pistons?
I'm sure the brochure that I have for the STi5 (I think) says that it has a forged crank and different con-rods? It definately says that the engine is blueprinted as well.
Incidentally there are also differences in the heads regarding sodium exhaust valves and higher spring rates etc (to allow the 8000rpm limit).

Neil.

[Edited by Neil F - 2/20/2002 1:06:24 PM]

FOZ STiV5

HI Neil,

I agree with everything you said and the followers are solid to deal with the 8000 rpm.BUT!!! the blue printing???? some people recon there are different levels.... the later engines well?? some questions raised!!

The pistons are tougher... but the engine as a whole does not like high revs.... watch the tensioners ... and change it with every cambelt.

The biggest issue I recon is the dropping of the closed deck block on later STi's. This is something that people with busted engines incorporate on an STi rebuild....i.e same everything with a stroked bottom end....

If anyone knows anything else, please let me know.

l8r

Julian

submannz

Yes I have to agree with a previous post hear, then problems is not the crank shafts but the con rod bolts give up the ghost. I had this on my first engine. I then had a group A bottom end put in the car, which runs massive conrod bolts.

The later WRX's use twin baulk rings in the gearbox so can handle slightly faster gear changes, plus the gears are very slightly stronger.

Dan

[Edited by submannz - 2/20/2002 7:44:46 PM]

NDT

The weak point on the Subaru boxer (STi or not) appears to be big ends.
Worse on the STi, as it revs higher (and big end load is influenced far more by engine speed than anything else.)
I think they are just fundamentally too small, due to the boxer layout, which forces you to use narrower bearing areas.

Is the EVO a cast iron block? that might also help.....

Nick

Adam M

Neil and Julian,

I did say i was referring to the short block. The heads are entirely different, high temp sodium cooled valves, solid lifters, under bucket shims etc.

Dont know about this blueprinting lark.

I do know the rods are not forged, I think all the cranks are. They are the same. except the phase 2 has the thrust bearing in a different location.

I would also agree that the big ends do seem to be a problem, but if you have a long look at the conditions in which all the big ends seem to fail, I dont think high engine speed is much of an issue. High vehicle speed yes. Have to check with Bob on that one, as he is the one who collated all the info.

to my knowledge the evo block is also alloy, and in standard form it certainly has greater strength than the subaru. Once internal mods have been done though, there is no reason to believe this has to be remain the case,as uprated impreza engines seem to be every bit as strong, infact, some of the monsters seem to be able to produce significantly more bhp and lbft than any of the evos I have seen.

How long they last is difficult to say, but without question there is no shortage of stronger parts available for them.

FOZ STiV5

Thanks, for the info Adam....
I intend to look after this one anyway....

Fitting a knock sensor in about 20mins to help keep track of any transitional knock.