Massive engine judder when partial throttle lift off...Pls Help!

[Jameswwt]

Im hving this problem and been cracking my head to solve it. Ive changed to Turbosmart Race Port BOV but its still the same! When part throttle my engine will judder and the boost meter will go haywire....
When WOT ive no problem at all but when i lift off the throttle a little the problem comes immediately...
What should i do? Ive tried to stiffen my BOV spring but its still the same!
Ive tried switching off my Profec B II boost controller and the problem goes away immediately but my boost is only 1.3bar as when my B/C is on my boost is 1.6bar

Do i really a more stiffer spring as ive tried putting 2 springs on my bov but the problem still persist.

Ive tried the softest & medium spring tension but i will encounter premature opening on my bov.

When i go for the dual springs combination, the premature opening solved but the engine judder still occur whenever i lift off partial throttle during WOT.

Pls advise & how to solve this plm?

My setup :
GT3076R
GSC S2 cams
85.5mm Pistons

 

[TurboBob]

What engine control system? Stock, aftermarket? MAF or Speed Density?

How is the BOV connected? Recirc, or to atmo? Single vacuum line or dual?

When you back off the throttle and hold it at partial, does the surging continue, or just surge a couple times then smooth out?

How much boost are you running, and how much boost are you trying to hold when backing out of the throttle?

Oh, and what kind of car?

Bob

 

[Jameswwt]

Hi Bob,
im driving a 4G63T Evo 5 and im running a PFC standalone ecu with MAF sensor.
The BOV is connected singly direct to the intake manifold.
Yes, the surging doesnt stop whenever in high rev partial throttle and i gotta immediately WOT again than the surge stop.
Im boosting at 1.6bar with my GT3076R turbo with GSC S2 cams, 85.5mm pistons and stock intake manifold & TB.
Im using Turbosmart Race Port BOV the latest model.

Thanks

 

[TurboBob]

whats happening is that the turbo goes into surge, and the flutter is being picked up by the MAF making the car 'judder'. If you were running speed density it would still happen, but you would feel it less.

The trick to fixing this is to set up a way to shut off the boost controller when the TPS is less than WOT. I'm not very familiar with that boost controller, does it have a TPS threshold?

You will not be able to fix it by playing with the BOV in my opinion.

Bob

 

[Jameswwt]

whats happening is that the turbo goes into surge, and the flutter is being picked up by the MAF making the car 'judder'. If you were running speed density it would still happen, but you would feel it less.

The trick to fixing this is to set up a way to shut off the boost controller when the TPS is less than WOT. I'm not very familiar with that boost controller, does it have a TPS threshold?

You will not be able to fix it by playing with the BOV in my opinion.

Bob

OMG!!! What am i gonna do now???
Thanks for sharing Bob and would really appreciate if you could come out with an idea to solve my problem...

 

[TurboBob]

There are couple things you could do to make the greddy work (hacks), but switching to a boost controller that has a TPS input should solve it. (You said the symptom goes away if you shut the Greddy off).

 

[Jameswwt]

I hope my Greddy Profec B II B/C has the TPS input feature...Or mind to intro what electronic B/C that have the TPS input?

Thanks

 

[TurboBob]

I have personally used the MSD, BstC, Maft Pro, and ISAC.

Does the PFC have a boost control feature, or perhaps a VTEC output that could be used to enable the Greddy solenoid?

But there are many boost controllers on the market, so some digging may be required. Others may chime in here as well.

Bob

 

[Jameswwt]

Ok and Thanks Bob