What the feck is wrong now. Sometimes this car does my head in!

On the way home at WOT in 5th the boost went to about 18-19 psi, usually 16. Then it rocked between about 10psi and 18-19psi in a harmonic fashoin. It was like the boost solenoid was half cut or something and had really slow reactions! Anyway I cheked the pipes for breakages etc and put some brake fluid in the tube to the solenoid. Didn't really have a chance to retest it. So, if this doesn't fix it what is it? Oh, and i checked the ecu error codes, no problems reported. Also, another piece of news, dp recently replaced under warranty (catted) and its a ppp.

Cheers

Paul.

Can't help with your problem Paul, but my MY98 (PEphase 1 ECU) has a similar problem. Used to give 15 psi max, but suddenly started to give up to 20 psi, but also loads more boost early in the rev range, ie will give 17 psi in 2nd gear at 3500rpm. Occasionally overboost cuts in. This happened once before 4 a couple of months, then suddenly it went back to normal.

Graham

take it you mean brake cleaner not brake fluid.

sounds like the boost solenoid kicking in.john banks tried different restrictors on my car and the solenoid ossilated the boost as you described.I think his car did this after fitting his d/p which is why he got the MBC and disconnected the solenoid.

sorry yes cleaner lol. Its never done it before though and i haven't had anything done except the dp, which i wouldn't have thought would make a difference. Anyway, i took it for a blast up the road and it looked ok again. I don't understand though. It was like the solenoid was slow, realising that it was at v high boost and quickly choking it. Too much so to 10 psi and then suddenly thinking nah let it go....and so on. Maybe it was just dirty?

Next time the weathers a bit cooler you'll notice the same thing again I guess - a few decat'ed my99/00 PPP'ed cars do the same.

Change restrictor size or fit a needle or Dawes (leaving solenoid in place, if you want) valve.

Richard

but mines still got the cat? For now anyway ;)

Hi There,

Since your are talking about boost faults could you tell me what standard boost a 1999 STiV5 should be running?? I am seeing 18psi Oh and on another gauge 1.3 Bar????? the latter must be wrong otherwise the engine should cut ???? I THINK...

Also I am selling a 1993 WRX which aslo had boost trouble... I used to show 0.8 Bar but drive flat sometimes going back to 0.5 safe mode. The odd thing is that it never showed up on the ECU log??? To try and cure the problem I have changed -
Plugs, Ignition Coils, MAP sensor, and rubber pipework. Any ideas ??? help!!

THANKS

Sorry Paul - can't read :)

I'd try cleaning the solenoid as well as the pipework if it does it again - and check your oil level, it's common for this to occur if overfilled.

Richard

Not sure this is relevent but.....

I changed my downpipe to a 3.5 inch stainless custom made racing one and found I had massive overboost. I changed it back tonight to the original with cat and if you are interested will let you know the results tomorrow.

l8r

cheers everyone + foz. It hasn't happened since. Funny that i always get little quirks on long drives??

Foz, i can't answer your original question but you might want to try a seperate post in drivetrain. I don't know what the boost on a sti 5 generally is? You could try controlling any overboost with a boost controller or maybe even a dawes? Are you monitoring other things such as fuel and knock? including the wrx?

I am booked in anyway at ss for a new downpipe so hopefully i won't overboost that often. Once I have my afr i intend to disconnect the boost solenoid anyway and use the dawes.

Also, i am sick of annoying rattles that i think are down to heat shields. I have even had my dp replaced under warranty due to this and yet I still have some kind of vibration? Hopefully ss can sort it for me cos i am sick to death with taking it to the dealers with the same faults only to have them come back again. Sorry about changing the content of the thread but i just wanted to get that off my chest.

still don't know what caused my original symptom. It wasn't overboost. It just went higher than normal and then rocked between 10psi and 18-19psi. This was wot at 70 mph, felt really jerky inside the car. I am not particularly worried about it but curious as to what the boost solenoid was trying to do exactly?

anyway let us know what happens foz.

regards
Paul.

Hi Paul,

Just to let you know... the standard DP was no better ...still got 18psi....very confusing....

Foz,

Do the sti's have a restrictor in place between the turbo output nipple and the wastegate and if so has it been tampered with?

Cheers

Paul.

Thanks, Paul...

It does have a restrictor.....not sure what the diameter is or is meant to be???

??

My issue still appears to be happening although not that often. If it overshoots sometimes it undershoots and then settles. Otrhers it just peaks and settles.

So how do i clean the solenoid then as I am not convinced that my brake cleaner hasn't evaporated by the time it reaches the solenoid.

Cheers

P.S. Wheres the chepest place to buy some turbo tube?? Or a Kit. I just need about 20 cm of tubing, u know the stuff for gauges.

[Edited by paulwadams_my99 - 2/19/2002 10:43:10 AM]

Hi Paul,

Connect do a reset ....i.e. Connect the green and black connectors with the ignition ON but do not start the engine. Then the solenoids should all kick in...On then OFF repeatidy. Whilst this is happening squirt brake cleaner into the boost control valve. Listen for a change in noise whiach means the cleaner is reaching the valve. Then ...you should have a cleaner valve.

Julian

cheers foz, hows ur motor going these days sorted out ur probs?

Umm - thats not strictly true. If you join both sets of connectors you reset the ecu. If you just join one of the colours, then you'll either put the electrics into test-mode (definitely) or display ecu error codes (I think) depending on whether you connect green or black. Trouble, can't remember which is which - is search still down, lol?!

Richard

dowser are u sure??? Because whenever i have connected both connectors you can hear all kinds of relays going etc, it sounds like it is in test mode. Does it not do both?

I am pretty sure the black ones do the codes. So do you think i only need to connect the green ones?

[Edited by paulwadams_my99 - 2/20/2002 9:31:17 AM]

I can't remember which colour plug does which. If you connect both I know it works but you reset your ECU as well.

The 10-18 PSI phenomena is the closed loop boost control system trying hard and failing when because less boost goes to the wastegate diaphragm - ie wildly underdamped. A downpipe can do this, but things would have to be fluctuating a bit already for it to do this I reckon. There could be a split hose between the T-piece and the intake after the MAF sensor. The restrictor could be gunked up. Basically anything that would make the wastegate diaphragm see less of the boost - so boost overshoots target.

Paul - Yep! Just switch on the ignition and everything will go 'mad-cow', cycling each of the underbonnet electricals in turn.

Remove solenoid bracket and hoses, turn it upside down with a rag underneath, turn on ignition, spray cleaner (I use wd-40, then electrical cleaner). Just keep your hands away from the fans :)

Richard

Hi all,

Apparently 18psi seems standard for an STiV or STI4. At the very least it is not unusual.

By the way, I said to connect both connectors to be sure. There would be no harm in doing the ECU reset at the same time. Like I said all the key valves cycle.

If you are worried about boost ... I have taken the precaution of ordering and will install a Knock Link... just to keep an eye on things.

l8r all

Julian

John,

hmmm, i have played withy the tubes when i temporarily fitted the dawes. I can't see any splits though. Can u get that restrictir out or do you have to replace the whole pipe? I think i might soak that whole tube in brake cleaner, perhaps i have got some crap in there?

had the dp done, ahh it sounds much better and pulls nice too and I am not talking about the local biggleswade talent! Cos you wouldn't want to as you are probably related ;)

Hi Paul,

Did you notice anymore overboost with the new DP??

Also ...for the restrictor.....You can pull that section of pipe off then keep it straight and hold up to a light. The hole diameter is big enough so that you should see clearly through it and the circumference should have a sharp profile. Any crap in the pipe or restrictor should be obvious.

As John... has mentioned before, if you want to limit boost you could try a larger restrictor BUT I would do this using another pipe as an interchangeable replacement. I am considering doing this myself if the knock link I am installing shows any serious 'det' other then transitional.

L8r

Julian

Julian,

hi again! I haven't got overboost but it looks to have increased peak at times to about 17psi so thats probably 18 realistically. Not had fuel cut though but it still sometimes overshoots and then drops and then steadies agian. Other times, which i prefer, it peaks and then settles without dropping below the desired boost so i still think that somethings a little odd. I'll have a look at the weekend.

Its no different with the dp except sounds and fells better, no overboost and no further problems. I don't have any cats now but i have the prodrive backbox which does the job brilliantly. Its noisy if you want it but still quite quiet in car. Its perfect for what i want!

You can get the restrictor out with a bit of squeezing outside the tube, but be careful not to cut the tube with the pliers - maybe protect the sharp ends with a cloth. You can straighten the tube and look through it at a light to make sure the restrictor is fairly clear.

k cheers John, i'll have a look at the weekend.

:) Paul

ok thought id sorted it. When i cjecked my tubes there was indeed a crack where it connects to tthe t piece so hacksawed it off and it was ok, 50 miles liater and its still doing the same, I checked the restrictor looks ok? Tomorrow i am gonna take the lot apart.

can i separate the tube from the solenod end? it looks pretty fixed solid?

Pull harder (but still gently).

Just found a cool fix for over boost on my motor. Quick visit to halfords to pick up MIG welding tips. Pre-drilled in 0.6 and 0.8mm orrifices. I switched my current to the 0.8 and get peak 15psi and setlled 14.7 psi boost.

WHAT is more important only ever green leds on my knock link!!!

Before with 17. ~18 psi I was getting red flashes on the knock linl but could not hear them ...BE careful standard guys!!

l8r all,

Julian

Sorry all .... my typing lets me down again... to add to that last message..a paragraph which helps explain what I am barking on about to less inexperienced....

Just found a cool fix for over boost on my motor. Quick visit to halfords to pick up MIG welding tips. Pre-drilled in 0.6 and 0.8mm orifices. I used this to replace the standard bleed back orifice between turbo and wastegate. I switched my current to the 0.8 and get peak 15psi and settled 14.7 psi boost.

1000 apologies ...lol :)