Deceleration Shudder While Still On Boost

[M E S O G L E A]

If I'm driving while boosting and decide to reduce throttle slightly (while staying on boost), the car will shudder or chatter. To avoid this, I must fully release throttle then reapply at a lower level.

My reasoning for this issue:

I have a HKS SSQV, HKS 2530 Kai and Nismo super copper mix single. Any reduction of the throttle while boosting increases vacuum causing the post-compressor intake charge to be vented to the atmosphere. The unsprung friction plate transfers all of that angry compression braking to the drive train causing the car to shudder the same way the SSQV sounds, like a the sphincter of the universe gobble. I know you all dont like the SSQV because its all ricer but the wife loves it and its the thing to do here in Japan.

Anyone else heard of this before?

Edited December 20, 2008 by M E S O G L E A

[Adriano]

I doubt its the clutch really adding to the issue, you already know its the BOV.

[M E S O G L E A]

OK, so you are saying to reinstall the OEM BOV.

[M E S O G L E A]

What causes this, the dual stage valve system in the SSQV?

If I reinstall an OEM GTST/GTR BOV, what about the bleed hole on the flange? I was thinking of trying the Dodge BOV mod but it seems like it will act the same as an SSQV.

Anyone else have similar issues using the SSQV?

[R31Nismoid]

What about the bleed hole?

Leave it. Its there to serve a purpose

[M E S O G L E A]

So I leave the bleed hole an let boost escape? I am running a PFC that is tuned for the atmo SSQV.

I have a friend that has an SSQV and his doesnt act like mine and does not have the solid clutch plate.

Why does everyone hate the SSQV and other aftermarket BOV's?

[R31Nismoid]

Because you don't need them, the offer no performance gain. If anything, a hinderance

[M E S O G L E A]

You are saying I don't need to worry about the pressure loss out of the bleed orifice, doesn't that cause a rich condition?

[R31Nismoid]

The GTR BOV's only leak low rpm/idle

Therefore, it does not matter

[M E S O G L E A]

Well, I installed the OEM BOV and it idles like crap.

I tried the Dodge mod and still idles like crap.

I cover the outlet with my hand and it idles fine

I put the SSQV on and it idles fine.

What makes you so sure its the SSQV and not the solid clutch?

[R31Nismoid]

I never said anything about the clutch, you just asked about BOV's so i told you

[M E S O G L E A]

Well thanks.

I try the OEM one at a later date, need to order the GTR BOV and some suspension bolts today.

If it's tuned for atmo and revert to recirc, will it need to be tuned again?

[M E S O G L E A]

I apologize for being stubborn.

I installed a new OEM GTR BOV today. The car no longer shudders like the gobbling SSQV. It does, however, cut-out "softly" if I release the throttle partially on boost and the idle is not perfectly happy. I attribute this to a small recirc leak because I used some ill fitting plumbing coupler until I get the proper hose.

Have you any idea how ridiculously hard it is to find automotive hose in Japan? Auto part stores might have a small section for performance with no universal hoses and an isle or 3 dedicated to air freshers, mirrors and useless Hello Kitty accessories.

[gotRICE?]

Im sure next time you will take the gurus advice before you fire at them then

These guys know what they are on about, so when you ask a question, you get a reply, 9.9 times out of 10 it will be correct.