boost questions

aderiley · Post by **aderiley** » Sat Jan 07, 2006 8:02 pm

could do with some help, i have a 94 uk legacy 2lt turbo ej20 engine i have just changed the factory dump valve for wide body 32mm vent to air, it sais to add washers to up vent pressure i now have 3 washers and getiing a fluttering sound with the whoosh, it is the dump valve or do i have to many washers and wastgate is chirping? also hw high can i ajust my adjustable boost to running 12psi at the moment, when does the fuel cut of come in? how can i up it? and car is allegedly chipped would the chip be likely to up cut off pressure ? lots of questions hope someone out here can help . ade

free5ty1e · Post by **free5ty1e** » Sun Jan 08, 2006 5:05 pm

No idea on what your alleged chip would or would not do.

As far as the BOV flutter you're hearing, that's usually compressor surge. Meaning your BOV is alternately blowing off pressure and then closing before releasing it all, forcing any remaining pressure back towards the compressor (since the throttle plate is closed), which in turn raises the pressure in the pipes again, which in turn causes the BOV to blow off some pressure, repeating the whole cycle.

Not good for turbos. That flutter is essentially trying to reverse the direction in which your turbocharger is spinning.

Adjust the BOV to vent more freely (softer?), so that when it opens it vents all pressure in the pipes, and when it closes there is no pressure remaining to surge back and attempt to reverse the turbo's rotation.

Of course, this problem is much worse at significant boost levels. If you're getting a flutter at less than 1 psi, there may not be anything you can do about it. My HKS has no adjustments and works great, but there is a small amount of flutter at trans-atmospheric pressure levels.

Fuel cut occurs when the pressure sensor sees 13+ PSI for more than ~3 seconds or so. Look up vrg3's FCD, works like gangbusters, no more fuel cut. Without an intercooler on a stock VF11 turbo, however, I wouldn't recommend any more than 13 psi anyway. With an intercooler, perhaps 15 psi. (all this is based on my experience with the US/Can EJ22T, no idea of any specifics for your particular engine)

aderiley · Post by **aderiley** » Mon Jan 09, 2006 9:57 am

thanks will take out some of the packing washers, car has water cooled intercooler so will look at raising to 15psi

aderiley · Post by **aderiley** » Mon Jan 09, 2006 7:04 pm

have removed all packing washers but still getting fluttering sound. car was running 12psi boost on standard bov with no flutter sound

free5ty1e · Post by **free5ty1e** » Tue Jan 10, 2006 3:34 pm

Hmm... what kind of BOV is that with the washers anyway? Maybe we should get some more info on it.

Did the flutter change at all with less washers? Or did it sound about the same?

555BCTurbo · Post by **555BCTurbo** » Tue Jan 10, 2006 6:41 pm

free5ty1e wrote:
Fuel cut occurs when the pressure sensor sees 13+ PSI for more than ~3 seconds or so. Look up vrg3's FCD, works like gangbusters, no more fuel cut. Without an intercooler on a stock VF11 turbo, however, I wouldn't recommend any more than 13 psi anyway. With an intercooler, perhaps 15 psi. (all this is based on my experience with the US/Can EJ22T, no idea of any specifics for your particular engine)

His car is the UK Spec one which is the DOHC EJ20G, AWIC, VF8 Turbo. iirc...their fuel cut is set a lot higher than ours.

My advice would be to put your stock diverter valve back on, because if you keep surging your turbo it ain't gonna last long at all!!

aderiley · Post by **aderiley** » Tue Jan 10, 2006 7:27 pm

bov doesnt have makers mark on it, new from ebay looks like a turbo XS 32mm not the usual 25mm it will open at 5psi when i close the throttle doesnt seem so bad now at higher presures. have an fcd on oder so will be raising the boost to 15psi at weekend

free5ty1e · Post by **free5ty1e** » Wed Jan 11, 2006 3:00 pm

Did you say your BOV will open at 5psi? This is not how BOVs operate... they will hold pressure as long as there is not too much of a differential between the pipe pressure and the intake manifold pressure. When the throttle plate closes, the manifold goes to vaccuum, pulling the BOV open due to the difference.

Does this valve have a fitting for a manifold reference, by chance...?

My GReddy Type S, as I recall, operated funny too until I hooked up the intake manifold to one of it's nipples as a reference. If you're not providing this reference, the diaphragm (what a funny word) inside won't be fully separated from it's seal when it's supposed to blow off pressure, and it won't matter where you have it set.

Got a photo?

By the way - is Nick correct on your engine specs? VF8 and an AWIC? Nice...

aderiley · Post by **aderiley** » Wed Jan 11, 2006 7:35 pm

only one nipple as per standard bov, comes with adaptor to run as recirculating or vent to atmo, its full uk spec about 280bhp at present, i have digi camera but dont think i can post pics on this forum? the old std bov would vent as soon as throttle was closed as well

free5ty1e · Post by **free5ty1e** » Wed Jan 11, 2006 8:43 pm

Umm... obviously this nipple is connected to your intake manifold... right?

Other than that - I got nothin'

aderiley · Post by **aderiley** » Sun Jan 15, 2006 5:13 pm

ok upped boost to 14psi, looking down into the bov the piston seems very slow to return shut, do you think i need to add some of the packing washers supplied (to increse spring pressure) ?

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

boost questions

boost questions