stevieg89

bit of a weird one this. classic shape with import EJ20 engine

the car was overboosting so after a bit of thinking i thought that the boost control was faulty so connected the turbo nipple straight to the wastegate and the overboost went away . got a boost gauge on the manifold and adjusted the wastegate until it overboosted again then turned the turbo back down and its now its boosting at 9psi without overboost (TD05 AFAIK) replaced the boost solenoid today with a known working one and it has started overboosting again just as it was before. what can the problem be. check engine light hasn't come on either. it was dynoed yesterday at 304bhp without boost control connected. can post up dyno printout later this evening

Splitpin

Your failure to provide us with any useful information makes it difficult to provide you with specific advice.

Assuming you're in the UK, and without knowing what model of car you're talking about, the cause of overboost in this weather could be nothing more than the combination of freezing conditions and an ECU without any means of compensating the boost solenoid duty according to intake air temperature.

mr flipsone

iTrader: (1)

bit vague open ended question......

but primarily as stated cold dense air charge causes overboosting.especailly in winter or early in morning

stevieg89

its a 96 P reg impreza turbo

heres the dyno printouts from yesterday




thats interesting about the intake temps. its my mates car and i suggested for him to get an aftermarket boost control unit as i think that the stock control unit isnt working correctly. anything to check would be great. he hasnt had it on the road properly as its been in his garage for an engine rebuild and hes been running it in since the new year. hopefully the overboost will go when the weather gets warmer. if its any use it has an aftermarket air filter on it

Splitpin

That's nice of you, suggesting he spend his money counteracting something that may simply be down to freak weather.

Our ability to advise you is still more than compromised by your failure to tell us exactly what sort of magnitude of overboost we are talking about here. Are we talking 1psi over target, or 10?

Go outside, see if it's cold. You've created a problem for yourself in that you've told him your suspicion about "something being wrong" with the stock boost control unit.

You could check to see whether the boost control pipework is contaminated with oil, and put the ECU into test mode and make sure the solenoid switches cleanly and consistently, but beyond that, your best option for now is probably to sit back and wait until the weather warms up and then take a view - depending on how bad this overboost is.

Hopefully, provided tinkering in the meantime hasn't taken the wastegate preload outside the ECU's compensation zone.

The rookie

iTrader: (1)

You say you adjusted boost without connecting actuator direct to compressor feed, you shouldn't be able to make that big a change with the stock part, is he running a non stnd actuator? If so therein probably lies the main problem, the boost control is programmed for a known actuator pre-load and progression, change it and you wreck it.

Simon