impreza wont rev properly and dump valve sound different
23 August 2019, 08:20 AM
#1
impreza wont rev properly and dump valve sound different
so my 2007 hawk sti hasnt moved for 2 weeks, i started her up yesterday to move around on my drive and gave her a 3 hour clean then locked her up,i have an appointment @ unity subaru in leicester this morning to have a key coded so i drove out of my street onto the main road and tried to accelerate.............
in 1st gear it wouldnt go past 4k
in 2nd gear it wouldnt go past 3k
in 3rd and 4th gear it wouldnt go past 3k
when the car hit those rpm's it was spluttering really badly
there are no warning lights and oil pressure is good.
the dump valve seems quieter almost muffled (forge dump valve)
in 2nd gear i tried to floor it and was met with a sound like a trumpet...............
any ideas?
when i last used her the car ran perfectly
in 1st gear it wouldnt go past 4k
in 2nd gear it wouldnt go past 3k
in 3rd and 4th gear it wouldnt go past 3k
when the car hit those rpm's it was spluttering really badly
there are no warning lights and oil pressure is good.
the dump valve seems quieter almost muffled (forge dump valve)
in 2nd gear i tried to floor it and was met with a sound like a trumpet...............
any ideas?
when i last used her the car ran perfectly
23 August 2019, 09:39 AM
#12
The dump valve looks fine to me, the bit of light you can see in the pic is supposed to be like that. The piston seals downwards towards the silicone pipe on the left, so if you could see it open through those holes and the piston having moved upwards towards the right then I'd have concerns, but it looks closed to me.
Sure it'll be a simple boost pipe having come off.
Sure it'll be a simple boost pipe having come off.
23 August 2019, 09:56 AM
#13
The dump valve looks fine to me, the bit of light you can see in the pic is supposed to be like that. The piston seals downwards towards the silicone pipe on the left, so if you could see it open through those holes and the piston having moved upwards towards the right then I'd have concerns, but it looks closed to me.
Sure it'll be a simple boost pipe having come off.
Sure it'll be a simple boost pipe having come off.
ive just started her up and it will rev freely whilst stationary,i can see the dump valve opening and closing but there is no whoosh sound. i only revved her to 5k as dont want to upset the neighbours
23 August 2019, 10:07 AM
#15
Is the first picture in that lot, the shot of your dump valve taken when reving the car up under boost? Looks like it's opened up.
You normally won't hear the dump valve when the car is static reving and not under load.
Boost pipes seem to look in place. What about either end of the FMIC?
You normally won't hear the dump valve when the car is static reving and not under load.
Boost pipes seem to look in place. What about either end of the FMIC?
23 August 2019, 10:14 AM
#17
In which case I'd say you need a new dump valve spring mate. The dump valve is opening even on tickover vacuum pressure by the looks of things which isn't normal and will cause the car to run crap.
You can take these apart to change the springs, so it's worth removing it to see what it looks like inside.
You can take these apart to change the springs, so it's worth removing it to see what it looks like inside.
23 August 2019, 10:16 AM
#18
In which case I'd say you need a new dump valve spring mate. The dump valve is opening even on tickover vacuum pressure by the looks of things which isn't normal and will cause the car to run crap.
You can take these apart to change the springs, so it's worth removing it to see what it looks like inside.
You can take these apart to change the springs, so it's worth removing it to see what it looks like inside.
23 August 2019, 10:34 AM
#21
Cool. For the £2 cost or whatever they are it would be worth getting a dump valve blanking plug on order too and something to block the vac pipe with. Then you can 100% be sure it's the dump valve if it makes boost and drives fine without it fitted.
23 August 2019, 10:49 AM
#23
Depends what size silicone hose that is from your FMIC setup as it may not be standard. I believe the standard recirc pipe blanking plug is either 34mm or 25mm, think 34mm for newage and 25mm for classic from memory. Best off to just take your dump valve off and measure the flange size to be sure. It's only 1 clip.
23 August 2019, 10:53 AM
#24
Depends what size silicone hose that is from your FMIC setup as it may not be standard. I believe the standard recirc pipe blanking plug is either 34mm or 25mm, think 34mm for newage and 25mm for classic from memory. Best off to just take your dump valve off and measure the flange size to be sure. It's only 1 clip.
take off dump valve and bung the pipe up and the small pipe from the top of the dump valve needs blocking up aswell and then go for a drive and hit some boost
take dump valve apart and replace spring with same colour spring from forge motorsport, should anything else need replacing? should i de-grease the entire thing aswell whilst its apart?
23 August 2019, 10:58 AM
#25
Yep, that'll do it. Nothing else required hopefully.
Don't worry if it's a little odd on idle to start with as the ECU sometimes complains with tiny changes like blanking a dump valve until it learns again, but that won't stop it making boost. You should see it make boost and drive perfectly normally without the dump valve. Will even sound better!
Don't worry if it's a little odd on idle to start with as the ECU sometimes complains with tiny changes like blanking a dump valve until it learns again, but that won't stop it making boost. You should see it make boost and drive perfectly normally without the dump valve. Will even sound better!
23 August 2019, 11:00 AM
#26
Yep, that'll do it. Nothing else required hopefully.
Don't worry if it's a little odd on idle to start with as the ECU sometimes complains with tiny changes like blanking a dump valve until it learns again, but that won't stop it making boost. You should see it make boost and drive perfectly normally without the dump valve. Will even sound better!
Don't worry if it's a little odd on idle to start with as the ECU sometimes complains with tiny changes like blanking a dump valve until it learns again, but that won't stop it making boost. You should see it make boost and drive perfectly normally without the dump valve. Will even sound better!
23 August 2019, 11:08 AM
#29
No, makes such a small difference to the fuel readings it's not worth a remap and won't harm your car at all. Depending on what turbo you have it could wear the turbo out faster by not running a dump valve, but quite honestly I wouldn't let it bother you at all.
23 August 2019, 11:10 AM
#30
No, makes such a small difference to the fuel readings it's not worth a remap and won't harm your car at all. Depending on what turbo you have it could wear the turbo out faster by not running a dump valve, but quite honestly I wouldn't let it bother you at all.