Hi,
ive this nightmare which have hunted me for months as ive tried several ways to address it but only with disappointment.
The problem is my engine will judder vigorously and the boost meter will whacking up down vigorously too around 1 to 1.3bar when im on high speed and full boost & this happen when i let off the throttle a bit.

As we wont be full boosting all the way for few km's on the highway right.

Usually we will let the throttle off a little and let the vacuum drop a little only than wot again right.

When the boost meter whacking up down my engine will judder at the same time and when this happen ive to immediately WOT again and the judder goes away and my boost stay 1.6 bar stably. Holding boost greatly & stably when WOT without letting off the throttle until ive to lift off a little again.
This only happen when on high vacuum!

This is how i drive all the while. During my stock setup ive no such problem.

The problem only happen after i upgraded to Gsc S2 cams & GT3076R turbo.

What ive tried so far to address this problem :
0) Changed my Sard bov to Turbosmart race port
1) Added stiffer spring rate (dual spring now) to my current turbosmart 38mm WG
2) Changed to a bigger Aem Fpr
3) Added stiffer spring (dual spring now) to my turbosmart race port bov
But the problem still persist!!!

What happening??? My car runs fine beside this problem...

Some said this is cause by my bov as they said it does suit my application and i need a bigger bov such as greddy type r.

Please HELP!!!!

 

Could be that your bov is too tight and is just not oppening enough so on liftoff all/most of the pressure goes back to the turbo, try loosening the spring pressure and going back to just one spring in the bov. If you have a two step/launch control test while in idle to build some boost and then let off the throttle, that should give you an idea of how smooth or not your bov is operating.

Also check that your bov is installed correctly, the piston base should be facing the charge of the upper intercooler pipe, don´t know if your particular bov can be run in both push/pull, but it should be smoother when installed like oem.

Good luck,

Ricardo

 

Boost cut? Compressor surge? Both? Need more info. What ECU, OEM?

 

Hi Ricardo, ive the same plm while on single spring and that why i added another spring.
Actually, after i added another spring my response get better.

 

Im on PFC ecu and i dont think is boost cut...
Compressor surge maybe but im using ATP Gt3076r with surge housing...
How can i tell its a compressor surge?

Thanks

 

Can you try a stock diverter valve just for comparative purposes?

 

Hi Sparky, i dont hv the stock diverter valve and can i test by completely temporary close up the bov venting hole on the IC?

They said if the plm goes off than its my bov spring rate and i need further stiffer spring rate.

 

Naw, my guess is that the BOV spring may be in fact too stiff as you have it currently configured. The reason that I want you to try a stock DV is that it uses a much lower rate spring. If it were to still exhibit the same "surge" with the stock DV then we would know that your issue is NOT BOV related and you could look elsewhere for the cause of your problem.

 

Of course, DUH, I am not thinking I guess. You are being advised that it needs a stiffer spring and I am thinking that you need a softer spring. Well, we are at opposite ends of the causal spectrum aren't we.

 

I am not at all familiar with your type of ECU or your particular BOV's. Are the valves that you are using the recirculating or the VTA type? Is your ECU a speed density unit?

 

Im not very sure abt my Ecu as its a PFC standalone ecu and my bov is Turbosmart race port is a VTA type

 

if it only acts up when you let off the throttle its the bov. as stated by the others, it really sounds like its sprung far too stiff and isnt releasing properly. thats about the only thing that will cause off throttle compressor surge.

 

^^^agreed

 

Thanks N2oiroc but even b4 i change to turbosmart race port bov its happen on my sard r2d2 bov also...When im on stock turbo, there is no such plm...

Can i just temporary completely closed the bov vent hole and make a few high speed run and see if the plm still occur?

Can this method works to check whether i need a stiff bov spring?

 

Hi jameswwt, it could be that both bov you are trying are having opening/venting trouble because being set too stiff (too much spring force and preload). If you further restrict the venting of the bov it won´t get better.

Like other are suggesting, try with the softest spring with no additinal preload and see how that goes, if it works then you can start adjusting for a balance between responce and driveability.