I plead ignorance on the subject so let me ask the folks who have tinkered with wastegate spring stiffness. If you use a really stiff wastegate spring, like 1.4 bar, does that effect your off-throttle drivability while under partial boost?

This is the only drivability issue I face: when I'm accelerating at half or 3/4 throttle and then let off the throttle a little, my car often bucks. It may very well be the BOV, but I have a very forgiving diverter valve on the car (Forge RS with adjustment to full soft).

If I went with a 1 bar spring (all I would have to do is take out the small .4 spring inside the Tial wastegate), what drivability changes would I notice?

 

Wategate spring presure should have no effect at all on part throttle drivability.

I am running "big blue, small blue" in my Tial WG right now (around 27 psi MINIMUM boost pressure) and have no bucking problems on a lift from part throttle. I am using the AEM EMS converted to speed density though.

What intake pipe are you using? If the inlet from the BOV is too close to the MAF sensor, or (even worse) is angle toward the MAF rather than towards the turbo it can cause a "studder" in the MAF readings on part throttle lift which can cause a bucking in the engine. Making the BOV spring pressure a bit higher can help in this situation because less of the air is dumped from the upper IC pipe into the intake pipe, so there is less chance of reversion in the MAF sensor.

Have you logged the MAF readings when doing some part throttle lifts? I bet you will see some funky readings if you do!

Keith

 

You may need to plumb a 2nd BV/DV, at or near the intercooler outlet tank and either set it at the same pressure as the one closest to the TB plate or balance it to open a lb. or two after the original one. I don't know if that is physically possible or not and still have the 2nd valve be recirculating. Does your compressor cover have anti-surge porting?

Has your car had this drivability issue ever since you went to your current setup? Since I assume you are experiencing this surging at low boost conditions, the WG shouldn't be venting anyway and if you were to go to a weaker spring the WG would open even earlier, at lower boost levels..... killing spoolup.

 

Bringing this one back from the dead..... I have read that turbo lag can be decreased by running a higher pressure spring in the wastegate. I currently have a 1 bar (14psi) spring in my 38mm Tial; would I realize any benefits by running a higher pressure spring ~21psi? I am using a Hallman MBC to increase the boost from the 14psi to my daily 28psi.

 

It definitely won't hurt

But I wouldn't think you'd see a noticeable improvement unless your mbc is leaking by prematurely. I've read a few articles in turbo mag that state a stiffer spring will help response, but all that says IMO is the boost controller being used in the article isn't doing it's job properly.

I've got the same spring and wastegate as you, and the same boost controller. Just for kicks it might be worth buying the extra spring and playing around a bit. Maybe I'll do that next weekend.... Still gotta put some springs/retainers in and an adjustble fpr this weekend.

 

I may try it and see what I notice, the spool isn't bad on the setup right now, but I figured the extra spring pressure in the wastegate probably can't hurt either. I'll report back on my findings