U only have to worry about partial throttle surge below the wastegate spring crack pressure...setting on the EBC. Now if u have pre-loaded the wg spring to achieve a higher boost...you have to watch out for partial throttle surge as the ebc is helpless under the wg crack pressure.

In the worst case (all 2 common!) of a high (>10psi ) WG spring rate and partial throttle surge at say, <10 psi....u have a problem.

The solution is a hybrid solution using a secondary 1/2" to 3/4" solenoid valve. You need to pipe the solenoid valve in its own recirc loop. Drive it via a parameter based aux. that will allow u to open the valve when the boost,rpm and tps are in the surge range. Thus easing u past the 'bump' of throttle surge and allowing smooth spool up to the higher boost levels with no harm/wear to your turbo.

 

I'm using a Tial QR and a quick spooling turbo. Another member turned me onto the TPS WGDC correction table. It works really well for eliminating surge.

Question for Tial: I'm using a "3PSI" spring on the QR, I have boost leak tested my system past 60 PSI. What is the advantage to a stiffer spring?

 

yes i ran new 1/4" id reinforced line from intake mani to the qr at high boost it vents fine but at low boost 1-5lbs it flutters instead of venting 5-10 it flutters then vents and over 10 it vents proper.

 

it's to keep the valve shut at idle if you are on a draw thru system, if you are blow thru MAF, SD, or MAP there is no advantage to using the stiffer spring

 

thinking you might need to drop a spring pressure

 

Don't u mean spring rate TialSport.

 

Thankyou! The car has been runnining SD for a while now. I really don't think many people realize this. It took awhile for it to sink into my head.

 

I recently upgraded to a GTX30 turbo setup from STM and using the stock crushed BOV drivability was fine. When I upgraded to a Tial QR and slightly larger cold side IC piping I noticed that the part throttle 15-20 psi area was fluttering and bucking when trying to dial in my suspension on back roads. Granted I could go lighter throttle with slight flutter or WOT for perfect acceleration but sometimes you need to balance a corner exit at 15-20 psi especially in the rain.

Looks like an 11 psi spring was ordered with my Tial QR so I'm going to compare an 8 psi and 10 psi spring to see how they fair. My idle at vacuum is about -8.5 psi so aybe the 8 psi is slightly too soft. Possibly I can also reduce the intake advance and exhaust retard mivec on my Evo X but would rather keep those settings there for quick spool. At WOT I'm right at the surge line for spool at 3800 rpm but other than that this turbo is killer for a street/track double duty setup. Looks like 600 crank HP at 28 psi pump gas and 650+ on E85 at 34 psi will be quite doable.

 

that was some good info...

 

I got this with the 9psi spring. It drives like stock on my Evo5 with the only difference being if I come off the pedal slowly at mid throttle levels, I get compressor surge, or flutter, whatever you want to call it. That is a non-issue to me since I just let off the throttle quickly so that it goes to vacuum and vents like it should.

 

Any updates for this ? I got a qrj bov with the same problem on my Evo IX . I got this problem https://streamable.com/ugcnx

 

The QRJ flutters in the stock turbo. The lighter spring they offer helps, but it still does it.

 

I, too, get this surge flutter with my Synapse DV and FP 71HTA turbo with antisurge cover. Not much we can do.

 

If I need to spend 2k euros to stop the flutter from the bov I 'll better change tial bov

 

FWIW, I found the stock slightly crushed BOV to work well on a smallish turbo like a Red. I made an adapter to mount the stock bov on a tial flange I went to a lighter spring in my Tial QR and I still preferred the stock bov for less then 530whp. Over that level or approx 30psi on the red the stock bov started to leak.

The stock bov drove really well and worked excellent for a fast spooling turbo.

I would avoid compressor surge or flutter if possible.