ec

Hi, I'm a new Impreza owner.

What opens the waste gate in a Subaru turbo setup? Is it purely passive through gas pressure or are there electronics in it?

TIA,
Eddie.

dowser

Electronics - a boost control solenoid bleeds air away from wastegate actuator. Controlled by the ECU in OE application.

Richard

ec

Thanks. It must be possible to keep it open then - I'm thinking of motorway cruising where the engine is around 3,000 RMP and it tends to surge when the turbo spins up. It might be better to drive and give improved long distance consumption if the waste gate was open and turbo essentially disabled via a switch.

Eddie.

greasemonkey

If the engine literally is surging if you so much as twitch your right foot when cruising, it may be that the boost control solenoid has oil in it (common problem after cars have just been bought/serviced, as it's caused by slight overfilling). This can be corrected by flushing it through with brake cleaner or a similar solvent. It may simply be that your right foot needs to learn a little moderation however.

If the car is working as it should, your plan is likely to cause more problems than it solves. Attempting to override the ECU's control of the boost solenoid electrically (presumably via a relay) would likely cause a check engine light, and maybe even put the car into limp-home mode. Even if you got it working without throwing errors, you would likely find the car was a b*tch to drive with the wastegate held fully open, and you wouldn't even save that much fuel, as the ECU would still be putting too much fuel in.

TBH if you've just bought the car and your first instinct is to improve the fuel economy, you should probably sell it and buy something a little more practical. Imprezas use fuel, and this is something you should have been aware of prior to driving the car out of the showroom.

However, it is fair to say that the standard ECU's (and the one in the 2000 model year cars in particular) run rich, and you can make real improvements in fuel consumption as well as improve the throttle response and output by having it remapped. If you're desperate to change things, this would be the way to go.

[Edited by greasemonkey - 1/19/2004 11:00:39 AM]

dowser

Not so easy - wg actuator operates around .7 bar, so this would be the minimum boost available if you were to put a switch into the solenoid's signal line. And fitting the switch may also throw a CEL.

Richard

ec

Thanks all. I think the potential to lower the level at which it opens is useful but messing with it in this way is unwise as either the ECU will detect that it is open circuit and go into error mode (like the Yamaha Exup valve) or make untrue assumptions about its state which could be big trouble, so it's best left alone.