batmanwrx

iTrader: (1)

after all the trouble iv had in the past trying to get my car to boost propper iv now developed a new problem

after reseting the ecu my car will overboost then drop down to 0.5 bar

stuff iv done in the past

replaced turbo

all new gaskets turbo exhuast ect

oil catch can

parrarell fuel lines

the car has got me stummped and dont no what to don next bar go down to the petol station with 5 euros and a jerry can and buy a box of matches lol

hope to here from yous soon,steve

Splitpin

It'd help us to help you if you included some of the pertinent info - in particular what type and model year of car, and any major mods. Some of what you're saying doesn't exactly make sense with itself in a context where we don't know the whole story.

When you say you've replaced the turbo, do you mean you've replaced a broken one with another of the same type? When you parallelised the fuel lines, did you stick with the OE regulator or did you replace it? If so, how did you equalise the fuel pressure (or did you remap round it)?

When you say the car "overboosts" after an ECU reset, exactly how much are we talking here? Again we need to know what sort of car we're talking about here in order to have at least an educated guess as to what's going on.

Splitpin

Further, if the car goes into limp-home boost control, it would appear that the ECU is still able to control the boost solenoid, which in turn is able to direct air to the actuator.

It sounds as though the first places to look are either the boost control pipework, MAP sensor, or the ECU itself, but these are very rough guesses at the mo. Help us by giving us a bit more to work with and we stand a better chance of pointing you in the right direction.

batmanwrx

iTrader: (1)

sorry for not giving enough info split pin im a bit of a novice

ill start from the beginen

i bought a 1992 wrx the engine went pop on the way home one weekend,my mate smashed his car 95/96wrx at the ring the same weekend so he sold me the engine then a friend (71/200) fitted it for me,i used my turbo from the original engine it seemed a little rough so when we fitted the engine it did not boost propper so we thought it was the turbo so got a turbo off fleebay fitted that still same problem so so turbo back off fitted a standard up pipe then replaced a few gasgets turbo exhuast and also the inlet manifold so when i had the manifold off i parraleled the fuel lines i use the standard fuel pressur regulator and still the same problem when built back up changed the boost solinoid (borrowed off scoobysmiff sp was working fine) checked all pipe work it never had a restrictor pill fitted but spoke with harvy and he asured me 92 wrx with 3 port boost solinod never had one fitted is that enough info or do you require any more ,steven

thanks for the help

Splitpin

Whoa, is there a shortage of full stops round your way or something?

There's a lot of confusion here, different turbos mixed with different engines, and, by implication ECUs and more here. So many opportunities for incompatibilities to be created. It sounds rather a lot like you've ended up with the wrong sort of turbo on your car, or the wrong sort of ECU for the engine/turbo. Let's run through some questions to try and nail things down:

1) Your car, prior to the engine failure. Is it a UK spec car, Japanese spec, or..? As you refer to it as a WRX we should assume that it's Japanese market car, but let's try and be sure here. The best thing would be to give us the Applied Model code, which you'll see on the ID plate on the offside (I think) front suspension turret.

2) Do you still have the original turbo from your car, the one that "did not boost proper" after you changed the engine? If so, can you tell us the numbers engraved or stamped onto the ID plate on the compressor cover?

3)The engine from your friend's car, is that UK/Japanese, etc?

4) The turbo that's in the car now, the one you got from Ebay. Can you tell us those ID numbers on the compressor cover?

5) What ECU is currently in your car? Your original one or...?

Grant74

iTrader: (10)

I would have thought check the maf, and definately any boost lines, as well as the piping to the intercooler

scoobysmiff

iTrader: (2)

The ECU is the original std one.

The turbo is a TD05 16g top entry Std fit, it was replaced with another TD05 std turbo and it made little difference, the original turbo from when he first brought it is currently fitted, the ebay one in the garage

The problem car is a Jap import and so was the car from which the replacement engine was sourced. They are/were both Phase 1 engines. When in the car before it crashed at the ring, it was running fine.

It has been paralled using the std FPR so will not need a reset of the ecu as it still see's the same values etc.

It doea have a decat and an induction kit, but before it blew up originally it was running ok on the same set up.

We have tried another boost solenoid (from my V4 Sti) and it was still the same, like Steve said, it has no restrictor pill fitted, it didn't have one to start with.

Both the manifold gaskets have been changed for new ones (Exhaust and inlet) so we are content we have no leaks from either of those.

Boost pipe work looks ok, no leaks could be seen, not sure on the MAF though, it may be the route cause of his initial problem as it's the same one that was fitted when the engine gave up.

What else do you think then gents?

batmanwrx

iTrader: (1)

cheers smudge where you staying you in the mess or you still got the house

Grant74

iTrader: (10)

Double and tripple check the vacum hoses, I had WBS (Weird boost syndrome!) and that was the cause, even though I checked many times.

For the price of 5mm vacum hose, replace it- its easy.

After that, if you have double checked the rest of the pipework for leaks, try and borrow a MAF thats then same- could well be that. You tried reading the ECU for codes? Jolly Green Monster has a guide on his site, or search here- may even be an archive technical thing on it.

batmanwrx

iTrader: (1)

done a ecu reset boosted fine for a while then went back to 0.5 bar there was also no faults indicated onece i done the reset

Grant74

iTrader: (10)

You checked it after it dropped the boost back I presume? The ECU must be detecting something.

batmanwrx

iTrader: (1)

thats what im thinking but no faults are showing up my boost issue has been on going for a while but still no joy

Splitpin

When you say at the top of the thread that the car "overboosts", what exactly do you mean? Boosting to the point of fuel cut, a couple of PSI over, somewhere in between, or...?

Given the extra info I can't disagree with Grant's advice above. However I would add to it a recommendation to check the pipework and connections to and around the MAP sensor and pressure source change solenoid (assuming there is one on your MY of car).

andyxros

the way i see things is there are 2 types of overboost

1, is were there is something wrong and like a blockage on a 3 port boostvalve, or an air leak to the wastgate actuator thus fuel cut will kick in say about 17.5psi and you need to wearing your seat belt

2, you have put some modifications on like full de cat, air filter etc thus changing the way the turbo charges so your boost valve duety cant keep up so the boost just gose up past its target preasure of say14.5 psi and so ecu just puts a little more to compensate and brings it back to say 10 psi then sorted for a split second so gose back up then back down and so on i.e you need a re map story end of (or a dawes devise)


an unmodified impreza will have no problems apart from air leaks to wastegate or blockage to boostvalve then fuel cut kicks in

put some mods on and thats it you need to change the way boost solinoid valve duety acts and thats it because you have changed the air fuel ratio with mods and they need mapping out or changing in other ways depending on the MY of car...

ecu is probabley sensing changes in air fuel mixture and keeping b.v open so all air opens watesgate so psi wil be limp home but they may be nothing wrong with the acutal maf, etc there just doing there job its the mods thats wrong till ecu knows its right by other means i.e re map, chip,piggy back etc

batmanwrx

iTrader: (1)

the overboost is not really the issue i think that was just a one off the car had been lying for a few months while i was back in the uk but still only boosting to 0.5 bar there is not much left to try im totally on my ars* with this one grrrr

batmanwrx

iTrader: (1)

bttt

Splitpin

I can't add any more to what's already been said. Really need to have hands on the car, and, ideally, a Select Monitor plugged into the ECU. This should give you (or an experienced mechanic) the ability to see exactly what sensor inputs the ECU is seeing at the moment it decides to pull boost - and from that it should be possible to determine exactly why it's happening.

Sounds like the time to call on a Subaru specialist.

batmanwrx

iTrader: (1)

i would have done that a long time ago my friend but im out in germany and its not like i can just nick down the local lol thats why i appreciate all your imput so much,steven

Grant74

iTrader: (10)

Bit random, but on the old MR2's we used to get a problem with certain downpipes catching on the wategate, so it either stuck open, or wouldnt open. generally produced much more random results, but didnt start after you changed the downpipe did it?

And no faults are showing even after it cuts boost to 0.5bar?

I feel your pain being away- I live in jersey and sometimes I may as well be on the moon when trying to sort things!

batmanwrx

iTrader: (1)

cheers grant im thinking about trying to get it back to the uk now im so pi**ed with it

batmanwrx

iTrader: (1)

update

right this is how it is now,the car will boost totaly fine after a ecu reset but after a short while the car struggles to boost over 0.5,if i drive the car hard it will go above 0.5 bar but only if i push it hard above 5 and half to 6000 rpm this is not right,after the reset the dump valve sounds loud but after a while it just goes quite but again louder if i push it hard.

ami right in thinking its not in lim[p home mode if it goes above above 0.5 bar when im pushing it

i dont like to drive the car to hard so i just thought it was in limp home mode because i dont like to hammer it