Fred

This topic is made to share my experience with my scooby.

Just before beginnig I just want to say I'm not a mechanics and english is not my first language... so if there's errors correct them but don't shout at me!. Thanks.
Also some informations are not sure at 100%, so be careful...

This first thread is just done to make a try to put a pic. If it's ok the complete story follows...

[img]

Fred

let's try again I want the pic appears directly here

Fred

That ok, no space needed at the end, let's go...


Hi all

For those who are interesting just have a look at this "little" motor problem…

Subjet : impreza turbo 110000 Kms, model std European car MY94, standard boost=0,8b (11,42PSI)
Car life : Standard from 0 to 50000 kms (31250 miles),
From 50000kms : Boost 1,1b (15,7 PSI)
From 90000kms (56250 miles) : Boost 1,35b (19,28 PSI)

All boost pressure are intended in 3th gear.
The highest pressure is achieved of course in 5th gear : 1,45b (20,7 PSI)

- This car was drove very hard. Doesn't mean I don't take care of it (I pay a lot attention for warm up and cooling down turbo) but when I drove it was not for doing fuel economy…

Few months ago I was driving softly, strangly the car has some difficulties to accelerate, it's like if ignition was missing on one cylinder or something strange the motor. Suddenly I start to saw smoke in the mirror… ouch!… turbo broken I think myself. Lot of smoke in low revs…seems to disapear when reving up. At idle the car was "not so bad".
I heard nothing special, no noise, no shake,First strange signs were few kms before.
I drove carrefully to home (about 5 kms). Check the oil : lost 1 liter till start to smoke. Well done, seems to have big problem…
As the turbo was always thought as the problem we start to remove the intercooler : a lot of oil was inside…so we remove also the turbo but nothing wrong in it . Very acceptable play, nothing broken…
So start to remove spark plugs and, ouh!!!, the rear left was completely oiled.
If fact if there's a problem inside the motor you can also have oil between turbo and intercooler because of a suction pipe.

Ok. Know what to do and hope not for too much bad things inside…

After demounting the motor, we found :





yep, it's not the rings who broke first, but the piston has broken between 2 rings.
This type of brakeage looks like that it's the end of life of the material. The piston is tired…
It's not a overheating.

Difficult to examine other pistons. Probably the opposite hot piston is not far to the end. But visually nothing is wrong



At least the piston color is good and got a good brown color. Mixture not too poor, not too rich…


Fortunately the cylinder not suffered from that. Just very little "traces" on the broken side. Just to be polished (maybe "honed" is the good english word ?) and that's done for the motor-block.

One another important thing is as you can notice the oil spray piston cooler are in the cylinder. That helps running at high boost .
Be careful : It was discovered that impreza since beginning of 95 have no spray. There's only the inclinated stand and the hole!. Since the smallest turbo there's nothing (even the inclinated stand is not done).
Note that 5 door cars never had spray, even the MY94.

Note also that the standard head gasket is very strong. I never had problem with despite high pressure.

As a conclusion we can say that the impreza is however a very strong car. If you run a standard car I think you can easily reach 200 000 Kms (125000 miles) and without big problem I think.

Now there's a lot of labour still to do, the more difficult is to come!!!

MorayMackenzie

Thanks Fred,

That was a most interesting read!

Moray

GavinP

Fred,

That is a very good read !

Did you increase the fuelling when raising the boost or change the ignition settings ?

The "Training WRX" book says that the standard fuel system starts having problems above 1.2bar. It also states that the standard pistons are the weak link with early non-STI cars. Would you agree with this ?

Are you going to put forged pistons in your car ?

Thanks

Gavin

Fred

Thanks guys

First I must say that this car was modified by a man here in switzerland who start many years ago rallying with a legacy and now with a impreza (unfortunately he just crashed the car 2 months ago). He developped himself all his upgrade.
I took the opportunity to thanks him because he helps me a lot, especially now...

Gavin : As this guy do that, I cannot go deep in details (and I understand that a guy who develop himself something will no give all the "secrets" of his labour even to a customer) but of course fuel was increased and ignition was modified. The standard chip was replaced by a reprogrammed one.

I don't know wich kind of "problems" your book speak about. But in my case the car was always running well, whatever the conditions, the season...etc. I believe they means that over 1,2b the standard fuel injectors are too small to make the appropriate debit needed(if programmed)for this ratio ??? (note : I was running with the standard injectors)
It also depend on what they called the weakness of a piston : pistons are designed to run with a standard car. As I said before I think that a standard motor will makes you easily reach high mileage. So even if the piston broke first in my case, regarding to the mileage and the power, I don't think that's a "big"weakness.
I think the gearbox is a weakness because here some guys have problem even with non-modified cars...

Difficult to judge about pistons : early cars have piston oil sprayer. Late cars have no sprayer but hardened piston... Maybe in the first case pistons are better to hold high temp and in the second case pistons are better for a "longer" life ???

pat

Fred,

Judging from the damage to your piston (ring land failure) I'de say it was cased by too much pressure, (perhaps knocking also). You mention that you'de had 1.45 bar boost out of this car; that's almost 22 PSI, quite serious boost for the European spec car!

If you wish to continue running this level of boost, pop a set of forged pistons in there.... STi ones are OK, Cosworth and JE very good, all of them much better than the original part. In any case, I would suggest that you replace all four at the same time, even if the other 3 look OK (they've had a hard life....)

Still, to get 110k km out of a european spec car running this much boost before failure is very impressive!

Cheers,

Pat.

GavinP

Fred,

I was making the same point as Pat - it looks like too much boost although the mileage travelled is interesting.

A company in Australia called MRT co-wrote a book on the WRX called "Training WRX" - see

Fred

Pat :
anyway logicaly this high pressure severely reduce the life-time of the parts so that's right that the piston broke due to this boost, this is a consequence...

About knocking, I've read here that STI cars in england got a lot of problem ?, I never read in details the story but why the knock sensor on these cars do not detecting the problem ?
(it is too late when it's detected ?, and when a car is knocking do you feel it physicaly ?)

That's right if in the case I'll continu like that it's a opportunity for forged piston (and many others modifications), but I own this car for 4 years so it's time to re-put the car in standard, change everything who had hard life as you said and look forward.

You know it's very hard to change something you like but I'm saying to myself that if I listen to me I will always got this car in ten years, so... I must do the step. Even if I got many years of fantastic pleasure with this car (make the lights on highway because Honda nsx or Alpine V6 turbo slow down you...)

Thanks for the informations for the forged pistons qualities. Do you know where best quality/price for forged pistons could be find ? (graham goode got a very good website)

Gavin : be careful, MY94 and MY(95-96) are not the same (in the motor level I mean).
Some MY95 and all 96 do not have piston oil sprayer : this makes all the difference!. If your car is a 4 doors MY94, I think it's ok.
17PSI is ok for MY94, 17PSI is too much MY95 cars(difficult to say but it seems that spray cooler disapeared around April 95).
Read here, there's some interesting details :

GavinP

Fred,

I think my car is a strange case - 94 WRX Automatic 4-door with 220ps.

I would suspect that it does not have the oil spray as it is fairly down-tuned. The same engine appears in 5-door models also.

With pistons, there are apparently two options - buy STI pistons or purchase blanks and get them machined to the height required.

One site you may want to look at is

firefox

Howdy

Just for the record...

NEVER use TDI!!!

There are loads of places to get pistons for the scoob... direct replacement.. over size... blank... "taller"... all different types...fit new rods too.

J.

MorayMackenzie

But Firefox, TDI are always so surley and arrogant over the phone, they must be experts who simply don't have time to talk to timewasting idiot customers how can you not recommend them to everyone?

Moray

GavinP

Oops..I have re-read my previous post and it looks as if I am recommending TDI - I have no experience of dealing with them - the URL was just to show some of the options available.

Some more appropriate URL's would be:

Fred

thanks for the answer moray,

The term "distributor" was only a problem in my technical english vocabulary

Just for the information, as noticed pat above for detonation, I made a error I think to run with a defect coil. As it took time to found the problem I made kms with some "bang" in the cylinder due to ignition cut off/on.

I suppose it surely decrease the piston lifetime (as the 4 coils were changed at the same time, I don't know if it was a defect one on the broken piston)

So for all who have 4 coils direct ignition : when you got high mileage, moreover on a boosted car, don't hesitate to replace all the coils if one goes on the end(I know it's expensive, but it worth...)

Anders

Fred sharing your pain

Fred

Thanks for the support anders

But you know for me it's like in the real life : someone who worked hard during his all damn life will have some parts to be changed one day...

Just a question on your 22B : how is your ignition ? (do you have 4 coils like me or a distributor?)

MorayMackenzie

Fred,

I think the 22b, as with all STIs of version 3 onwards, has a twin coil transistor ignition system rather than direct ignition (a coil over each plug). There are no mechanical parts in the transistor ignition, so no distributor.

Moray

jwhitton

What is the bore wear after 110000kms?

I assume you are not going to use new pistons in a bore with this many miles?


jon

firefox

Hi..

Cant stop long... tea is ready..

You have several choices with bore/cylinders/pistons:

either risk fitting new pistons/rings into the old bores and hope you dont get blow-by/leakage

Fit new liners and standard pistons/rings

Or have it bored and fit over-sized pistons

Either way.. the bores will need rehoning for the new rings and pistons

Cheers,

J.

Fred

Yep!

Bore not measured at the moment.
But original honage still very visual and looks like a brand new one...

Probably gonna hone the cylinder with the piston problem, and will see if others needs
a "touch"
Anyway will put original pistons and rings...

Thanks for your previous (and futur) comments !

Anders

I am having my bores addressed over sized pistons have arrived. I am off to take some photos today

firefox

Anders...

You still copying me ?

I thought you were in more advanced stages than that ?

Mine is back together.... fitting it Tuesday... waiting for some stuff to arrive..

J.

ps - I told you I should have done it.. lol

adam99rs

Great post Fred lease keep us informed. This thread was forwarded to me by one of the members (forget who) today, with the quote"1.1 bar oost on stcok internal? Say your prayers". This refers to the fact that Iam now running 1.1 bar on my internally stock US 2.5RS. As you guys know, our cars here have the 2.5 iter, SOHC motor (I think your Legacy's have it too), and run 9.7:1 compresion. As I have always been envious f the superiro cars yougusy get in Europe, I turbocharged mine about a year ago, and have driven 26k so far, without a hiccup. My latest mods were fitting the Apex S-AFC, the Apex ITC (to control timing at given RPM points), and fitting a fuel pump from a 97 Sura Twin Turbo. My car is now running consistently low 12 second 1/4 miles, as measured on the Gtech, at trap speeds of 112-114mph. Again, this is all on a stock motor, and using the factory fuel injectors (330cc), which are surely maxed out now.

Firefox - do you still have those spare injectors? If so, hw much do you want for them?

Anders - been out of the loop recently (hovering on impreza-rs.com), but I am intruiged by your car (for obvious reasons!) - is it undergoing a full rebuild? Are the rmors that you and firefox are entering the car in this years Monte Carlo rally true?!!? (joke)

Anders

Nicky Grist does intend to play with my cat in Catalunya

Car should be back on its feet end of this month, for a gentle running in

Then engine is out and will be dynoed on a bench.

Steel internals, uprated parts, larger intercooler, otimised fuel rail, oil catch and water injection.

Basically over engieered to stop this happening again.

Still not sure which engine management system to use.