ninjaman

Hi all,
after the response to my topic on which is the strongest subaru for tunning or do I get an mitsubishi evo, I decided to look into it myself.
I have come up with a few questions which took me by surprise.
1) do subarus (any model) suffer from piston problems??
I have spoken to mechanics (owners of garages which specialise in subarus) that piston 3 is THE MAIN PROBLEM on subarus when they are tuned.....and it will need engine rebuild if not sorted out(£3000-5000)!!!!!

2) problem on mitsubishi is CLUTCH, also from well known mechanics dealing with evos.

If these are true (was in the old days but I only had a UK subaru on about 240-250bhp) then my choice would be the better mechanical/cost car, no prizes for which one it wil be

Do anyone here know anything about these (especially the piston 3 melting!!!) or more common problems on these cars..

This will definitely help me in choosing which one to get.
Regards
Ninjaman

Flat 4x4

With a name like Ninjaman won't you fear nothing ?

A short engine costs £2000-2500 from a Subaru dealer, fitted.
Yes, engines do melt

ninjaman

Thanks for the boost of knowledge from you
Engines melt?? I did not know that!!!??
Maybe you can explain why the piston 3 melts in a subaru???
Tell me how did I install and set-up HKS EVC4, FCON5, turbo timer etc with japanese manual and I am a management accountant, not in the business trade at all??? (I only brought HKS stuff and did not understand Japanese then but I can read some now) all running on 95RON and my subaru was sold even when it had 98,000miles on the clock????
My previous name on this board was karlo and people who know me from being on this board from 1997-2001 will remember me as being very helpful and honest (I hope)

So please take it easy on me please
I only want to know if this is true and can it be easily cured.
You people would not like me to get the wrong car for myself would you???

nom

Yup, pistons go (although not necessarily number 3), and no, no-one is sure why, so no-one knows how to fix it! Typically it appears to be a hole in the piston, so likely pre-ignition (probably because of det), but that isn't always the case! There are endless discussions on it with everyone coming from every angle (we haven't had one for a while - it'll probably be along shortly ) but tyipcally the discussions/stats don't seem to lead anywhere, unfortunately.
I believe last time the subject faded away, the suspicious culprit of choice was the oil pressure release valve (I think ) which has a notch in it that might catch... but that was just one of many ideas!

ninjaman

Thanks for the information nom.
I hope I have not started it again
I was wondering if the link (in the old days) cured this as you can stop the det from happening as you will see it on the tables etc????
It is just so that I can decide on what is best in the long run as I wil be heavily modifying the car I get. I just don't want any surprises which will cost me an arm and a leg !!!!!
And I want to be able to 'see' the problems way before any damage happens (gauges(Nito good prices please, if you are still in the business!!!)and possibly the Apexi stuff should tell me(anything else???).
Correct me if I am wrong but I assume that if everything is running correctly then I should have no problems??

The main thing to me is WHICH subaru model is the one to buy (sti verV or another model?
WILL need a 4 door model (family predicted in the near future!!)
And how can I tell if there is anything wrong with the car on the piston side???
Regards
Ninjaman

ustolemyname??stevieturbo

iTrader: (1)

Melting pistons...no one knows why?????
Pistns melt because of weak mixtures, and or detonation. Plain and simple really.
This can be due to bad fuel, bad fuelling, too much boost etc etc.
If a car is set up properly, then there is no real reason for any pistons to melt. Some people say that modifying the fuel rails to a parallel feed is a wise move, and will reduce the possibility of it happening, which is very possible.
Other causes can be attributed to faulty airflow meters, but these will also cause bad running too in most cases, so should be noticed before any damage is done, if you are clued in as to what is happening.
So, I dont agree that the engines melt. Some do, but they dont do it for no reason. Generally fuelling issues are the casue, and no3 just happens to be the first one to go. If you strip a blown engine chances are other pistons would also be showing signs of ill running.
No, when it comes to big ends failing...thats another story. It still wouldnt put me off a subaru. They are much easier to work on than Evos, and parts are also a lot cheaper.
I think clutches are a problem on any high power 4wd car, not really specific to an Evo.

nom

Well, regarding the 'no one knows why' and the 'if I have everything set up correctly then it should be OK', there are engines which have been set up very carefully & monitored heavily & still gone. Which was probably something failing quickly rather than slowly. But no-one knows what. So effectively, no-one knows why. But these are the excepton rather than the rule - it seems that as you say, if you get the car set up right (as in get rid of the standard ECU & do a proper map ) then the car won't give any problems.

darkblueturbo

ninjaman - the 3rd cylinder can be a problemwhen the engine is highly tuned (like over and above 300 horses) as it's closest to the Turbo in the boxer configuration. The heat can make it upto 100 degrees hotter than the other 3. It's also at the far end of the fuel rail so receives a (slightly) leaner mix.

An oil cooler, such as the one from rcdevelopments.com (no I'm not on comission from them), can help this become less of a problem by keeping the engine oil at lower temperatures (well obviously that's what it does)

darkblueturbo

on the clutch - I've knackered mine with about 220horses, so will be getting an AP Formula Organic one (rated up to 310ft lb).

MGJohn

Simple questions on this detonation-holed pistons thing.

How do standard (that is unmodified) well maintained Subarus shape up det/holed pistons-wise if near full performance is used frequently?

I get the impression, rightly or wrongly that it's mostly tweaked/chipped cars with higher than standard power outputs that are the ones much more prone to these problems.

If piston No.3 because of it's location near the turbo is prone to go first, surely the factory boys must be aware of this and make efforts to reduce or even avoid this problem . Or, is their attitude understandably one of "it only happens on modified cars so it's not a design or manufacture problem".

If that problem cylinder is prone to run lean because of fuel rail position again surely the factory boys will be aware of this and rectify with a factory redesign or modification. Ensuring a balanced fuel supply to each cylinder is essential in any highly tuned engine, not to mention a turbocharged one.

darkblueturbo

MGJohn - you're right I should have specified that the fuel rail and cylinder 3 problems only really occur when you start to modify the engine. Obivously a totally standard engine will be able to handle this as many of them do well over 100 000 miles.

TARManiAC

Top Gear November 2002 page 167:

Mr. Nick Palmers MY 99 had its piston no. 2 melting with only 49000
miles on it and full dealer story (they would know if it was modded).Is this a pattern for Subarus?

crusher

I thought the proximity theory ,no3 closer to turbo etc had been disproven..measured temps being marginally different,and in fact the problem had been isolated to the fuel rail design...I think Pavlo?? in Greece?? had been modifying said fuel rail run for a few years....the run is long and kinked and apparently measured pressures in the rail are lower...and so under high load/fuel demand situations the supply is found wanting...lean...bang!!!!

darkblueturbo

I'd suggest that this is not a trend for subaru's.

Haven't read the article, but I've read a lot of thread's on here. This would seem very much like an individual problem, modded or not, rather than a trend. Haven't heard of a great many problems like this.
All cars can have their problems, but this isn't a trend of the Impreza as far as I know.

I'm on my 3rd Impreza and the only problem I've experienced so far was piston slap, which was promptly fixed under warrenty.

nom

I don't think it is modded cars that go more frequently at all (stats were being collected a while back) - it did seem to be imports more than Euro-models, but the imports typically went 'with reason' (i.e. been driven hard) whereas the Euros seemed to go for no particular reason (this was just an impression possibly rather than true - many didn't post, they sent direct to Bob who was collating the info). One went 3 times () after complete engine replacement. Which, to me, points it in the ECU direction - this wasn't replaced. Imports can go quite easily because of the poor fuel we get here - even booster added to a dud batch isn't going to make the grade. So, badly set up ECUs - whether the oem one or 'home brew' could well do the job. Run a Euro on supermarket 95 - which could be as low as 91 - and even the ECU going full retard (which still means it's detting & possibly heading toward pre-ignition) may not be enough to stop the heat build-up to 'bang'. It only needs pre-ignition once to blow a hole.
I'd have thought that probably the safest set up is actually a well tuned (as in a degree or so back from det) ECU - so probably not the OEM set-up then - running with monitoring kit (especially knocklink, set to maximum sensitivity) and a keen eye on this, certainly after a new tank, even more so at an unknown garage, is the best way to prevent the problem.
But that's IMHO & really just common sense anyway. Running blind (only OEM gauges) seems a tad, well, like asking for it.

nom

Just spotted - fuel rail design - the measurement is taken from cylinder 3 so this should always be OK. Unless the cack oem fuel-pump is running at 100% anyway & just can't manage to keep the pressure there.
A big suspect, the cack-pump.

ustolemyname??stevieturbo

iTrader: (1)

Another point re No3 Piston. In my experience, the most common piston I have seen melt is actually No4. On any blown engines I have seen( about a dozen ), No3 would actually have been the least damaged from each engine I have stripped.
No3 is the most common big end failure I have seen but not the most common piston.