ehall

Is there any good reason to go larger than a 38, on a 2.5 ltr 951? If so, I don't know what it is. You can't make cherry pie with apples. If spool up is the issue, you're better off going to larger displacement. Spool up can only be manipulated to a finite extent.

Duke

Not sure I follow you here Pete, without a WG you will always boost much, much over 2 bar regardles of turbo.

True that the turbine and compressor needs to be matched to the intended boost pressure, but without a WG you will always overboost.

gt37vgt

I've seen people run successfully with out wasgates by running big hotside A/R's and a dual port blow off and solinioid set at boost pressure . I might try it on my VGT set up. The car works just fine but there is still the risk at over speeding the turbine to 150k rpm .
and I still think its crazy to go smaller than factory waste gate

seattle951

I have been trying to confirm that the factory wastegate size is larger than 38mm. Can you point to a reference?

Duke

Crazy aussie!
For a 1/4 mile car perhaps but not for a street or race track car.
Hmm VGT setup sounds interesting though..

Duke

IIRC it's 45 mm. I have a few laying around in the garage. Can post some photos with measurements tomorrow if you want.

seattle951

The size is measured by the size of the valve, correct?

TurboTommy

seattle951;
I have also been confronted with wastegate decisions in the past and have done some research:
The stock wastegate is 38mm. (yes, it's the size of the valve)
Wastegate size has no effect on spool-up.
Contrary to what was said, here, a "tighter" hotside does not need a larger wastegate; it's the other way around.
A larger wastegate does not reduce back pressure; or more accurately, it does not give you a more favourable back pressure : boost pressure ratio.
A larger wastegate is only needed if you have boost creep.
I don't know of anyone actually "needing" larger than 38mm, even on a 3.0L.
If stock wastwgate plumbing is used (ie; wastegate valve opening into pipe), the valve size is less important than the size of the pipe which it is opening into.

gt37vgt

well you are more likly to get "creep" if you get a chepo ebay 60mm gate with 61mm can . but we could then descus wich way the gate opens .
and i have back up the earlier statement that smaller hot side bigger wastgate as the 951 is in factory trim you can't get the CFM through the hotside so it needs to get out especially if you have a big **** compressor

TurboTommy

gt37vgt;
I'm having a hard time deciphering through your english and sentence structure, but basically:

????????????????????????????

seattle951

This was the final conclusion I came too after reading the posts on this board, referencing a few engineering books and calling trusted vendors. Unless there is a boost creep problem, there is no advantage to a larger wastegate. The only caveat is that the larger units are usually made with more heat resistant materials for heavy duty track driving. Since my car rarely sees the track except for the occasional DE day, the 38 mm Teal is a great match.

Thanks to everyone who added to this discussion through this tread.

Also, thank you for the PMs. It was interesting to learn that others are having the same issues with the same make/model of aftermarket wastegate that I have currently on my car (about to be replaced).

kasturbo

What issues are you having with your current unit? Is it a Lindsey?

Rogue_Ant

Care to explain that?


-Rogue

Keithr726

+1 with synapse. The ability to custom tune it is a HUGE plus. I think I might have been the first or one of the first 951s to use it. Its been a year and 3k and it has worked flawlessly.

Accuboost with single attachment to synapse port = perfect for me. It also has the ability to be used WITHOUT a mbc.

333pg333

Crazy Aussie, oh you don't know the half of it. Seen 'Wolf Creek'??? They modelled this guy of gt37vgt...