Boost issue - waste gate being opened too soon

[gazzy2000]

Hey, i noticed my BG (the one with the ST conv done) was initially boosting fine at 15PSI. I dont know or cant remember when it started.. but its only boosting now at 10PSI

I did do a lot of stuffing around with TPS and throttle body initially to reslove idling issues etc, I thought i had the TPS setting right etc (it is still idling ok, not that high when real cold though, but OK) The Engine is running sweet as otherwise

So i put a LED accross the Boost noid and run it into the cabin, and what i noticed is that the noid is being dutied by the ECU, (no codes either FYI) but the LED flashes as soon as i put my foot on throttle, i was of the understanding that the noid was normally dutied under load (or WHY) i.e. noid is normmally closed (no duty cycle) to let the boost build up to the preset amount then it gets dutied by the ECU to regulate the boost.

But the noid is being dutied at cruise i.e. very very light throttle, the only time it stops being dutied is when i take my foot off the accerlator.

So obviously the WG is opening to soon, I suspect this cud be the cause of the low boost?

- Does this mean the TPS is adjusted wrong??

- Is this s type of safe mode? (as mentioned there are no codes)

- DO TPS's affect the boost in this mannor and/or have anything to do with boost regulation?

- What else should i check.?

I may cable tie the waste gate shut and go for a quick burn to check all is good under boost and that it does go higher than 10 PSI.

When i had the car wide banded it was boosting 15psi no worries... i dont recall making any TPS changes after that. But i will check the voltages again.

I certainly dont suspect any vac leaks or boost leaks at this point + The Pill and noid is all plumbed correctly.

Your thoughts?

Gary

[Koom]

They quite likely run a preset amount of %DC to the solenoid to prevent boost spikes. If you leave the solenoid fully closed until you get right to your preset boost and then try to open it, it'll have a nice big fat spike before it manages to get the boost under control. This is quite likely what you are seeing. It all depends on how the boost control is configured in the factory ecu's.

[gazzy2000]

 Koom said:

They quite likely run a preset amount of %DC to the solenoid to prevent boost spikes. If you leave the solenoid fully closed until you get right to your preset boost and then try to open it, it'll have a nice big fat spike before it manages to get the boost under control. This is quite likely what you are seeing. It all depends on how the boost control is configured in the factory ecu's.

cool thanx, i got a good explaination from log1call, so i will post his recommendations + my findings once i have done a bit more.

[gazzy2000]

with wastegate disconnected it boosts fine.. (i didnt go over 15psi) so there is no boost leak or otherwise

reset the TPS did nothing (reset ecu of course)

LED wired on boost noid still showing the duty cycle of teh noid coming on far to soon IMO, so next i will replace the atmospheric pressure sensor, MAP sensor and finally the TPS.

[Stoffa]

I've got spares of all those sensors from a v5 if its any help

[Guest]

TBH - Ditch the factory boost you will enjoy the car more with an aftermkt system.

[gazzy2000]

 Stoffa said:

I've got spares of all those sensors from a v5 if its any help

sweet thanks, i will use the v5 bits off my bh, n i may hv to buy them off u if that turns out 2 b the prob

ta

[gazzy2000]

 Qwerty said:

TBH - Ditch the factory boost you will enjoy the car more with an aftermkt system.

thanks but I am not a fan fitting MBCs (or the like) to replace/bypass the factory systems, unless i can tune the ECU to suit

The car goes mint at 15PSI with the factory system and i feel at ease relying on the millions subaru spent on fine tunning the safety systems on their stock EFI & turbo systems... of course thats just me

example: what if your stock ECU goes into safe mode because of excessive det (for what ever reason), of which the ECU fail safe system would normally drop your boost to 10PSI to protect the engine from damage... and here you are forcing 15psi uncontrolled by the ECU through a bypassed MBC, perish the thought i say

[gazzy2000]

just mucked around at lunch time

disconnedted batt for half an hour, reconnected it and now the LED is flashing with no throttle lol, i can physically hear and feel the boost noid clicking when i look under the bonnet at idle

If i disconnect the MAP sensor it stops teh noid clicking (cycling)..... obviously it throws a CEL too.....

thats as far as i got at lunch

[gazzy2000]

well its fixed ;D

it was the boost solenoid, yay... a rock steady 15PSI now!

i havent checked the resistance of the old noid, i just fitted another noid and that fixed it, so what ever

Will fit the LED to the new noid and watch the characteristics of the duty cycle with a good noid

just happy to have it all back and running stock

cheers