[Mk2] [Turbo] Compressor surge/wastegate chatter/whatever you want to call it..

[mr2nut123]

Once and for all want to settle this arguement (only experienced engine tuners reply please)

Does this kill your turbo? I have read so many varying posts across the net, some say it kills your engine, some say turbo, and yet some say it doesn't do any harm at all (providing it's a well made Turbo with full steel internals built for high power).

Say if you had a turbo capable of around 500bhp and didn't run it's full potential (low boost, around 400bhp) would this be fine with an external wastegate with screamer setup?

[Chris]

Do you mean running without a BOV? Myself and Andy F do not run BOV's and large turbo's with external wastegates and screamers.

[Steve Horrocks]

I keen getting temped to run mine without a BOV as I love the noise!
It should be ok to run without, it'll put a little extra stress on the turbine blades and add a little lag (no real issue on a 500bhp turbo!) as that is what they were developed to combat, but other than that........

think i might go get another pipe made up now without BOV in it so I can swap & change! LOL

[AndyBrad]

My understanding was that ceramic turbos should be used with BOV to protect the blades. Any thing else is personal choice.

I don't believe they reduce the lag either as your asking the turbo to refill all the intercooler pipework, whereas with no BOV on a quick gear change the intercooler pipework remains pressurised and is instantly avaliable when the throttle is opened again.

[nailmonkey]

My undersating was that ceramic turbos should be used with BOV to protect the blades. Any thing else is personal choice.

I don't believe they reduce the lag either as your asking the turbo to refill all the intercooler pipework, whereas with no BOV on a quick gear change the intercooler pipework remains pressurised and is instantly avaliable when the throttle is opened again.

They definitely do reduce lag.

When you lift off with no BOV and the throttle snaps shut, the air goes the wrong way through the compressor wheel causing the characteristic noise. This also has the effect of stopping or slowing the rotation of the turbo, hence the term 'compressor stall'. This means that when you reapply the throttle, the turbo has to spin up again which creates a noticible amount of lag.

When you lift of with a BOV, the excess pressure is bled out of the system and whilst the turbo then has to re-pressurise the system it's almost instant as the turbo is still spinning.

Nik

[AndyBrad]

They definitely do reduce lag.

I never noticed any difference on my impreza and was actually advised aganst using on by the guy who mapped it as so many off them leak at high boost.

[jimGTS]

i have run no bov on my apexi turbo and i can tell you it DOES reduce leg between changes!

BUT you have to be running through the gears pretty dam quick. it has caught me off guard a few times when i was running no bov. boost was instant!
if you change gear at an average speed when just going for blast in the twisties or whatever, theres prob no difference betwene bov and no bov.
but say down the straight, and quick enough changes, you definatly do reduce lag. well from my limited experience anyway with the setup im running.
id bet it was running no bov for quite a while.

i now run a greddy type R to be on the safe side. i have the spring set pretty tight tho.

[cantfindausername]

So no bov reduces lag.... interesting. Will have to give this a try. Lucky I have some 3" stainless spare and a bucket load of silicone to match

[jimGTS]

if you got a strong turbo its werth a try.

perhaps its just the addictive noise, and not the lag difference i noticed, lol.

[cantfindausername]

GT35R should take it - Especially while its only at 1.25 bar

[jimGTS]

ive got a greddy blanking plate, as well as the bov, so i can choose what i fancy running at the time, lol...
maybe just make a small plate that can be bolted over bov hole!

thatll save you swapping out ic piping!

[cantfindausername]

Mine is an HKS SSQV, I couldn't get it off when I tried. Its only clamps to get it off.

I'm just wondering if disconnecting the feed pipe to it would keep it shut. I'm not really sure on the workings of them.

[jimGTS]

yeh im not 100%...
tho i would have thought that the pipe is there to provide pressure on the valve to stay shut when on boost. as that pipe goes to a manifold pressure source doesnt it.
running no pipe, im not sure what would happen.

[cantfindausername]

I can't remember. Gonna have to look around now. Thought they had some design to make sure they didn't leak, like they were pressured shut, then vacuumed open.

[cantfindausername]

love google... http://www.hksusa.com/products/more.asp?id=792

[cantfindausername]

Having read that it seems I was right. The boost holds the valve shut.

So, disconnecting the vacuum would indeed disable the BoV. As such, I'm wondering if an electronic solenoid valve could be used to interupt the vacuum feed so you sould in effect, switch the BoV on and off from the cabin

[jimGTS]

thats what i thoguht to, boost holds valve shut, but with no pressure source to keep it shut or open it up, how would it react on boost and in vaacum.


i would have though that boost would slowly open the valve up, as it hasnt got an oppoiste force keeping it shut.
so you could leak on boost.

[cantfindausername]

Nah I think thats the whole point of the design. The higher the boost, the tighter the seal.

A normal bov pushes open, so boost can overcome the spring and you get a leak. The SSQV is pushed closed by the boost, and pulled open by the vacuum. So if you have no vacuum feed to it, it will never open.

[jimGTS]

Nah I think thats the whole point of the design. The higher the boost, the tighter the seal.

A normal bov pushes open, so boost can overcome the spring and you get a leak. The SSQV is pushed closed by the boost, and pulled open by the vacuum. So if you have no vacuum feed to it, it will never open.

arh ok, i guess opposite to how my greddy work then.

[cantfindausername]

There are probaly a few that follow the same principle out there, but it would definately seem like the "cleverer" design