Sameer

Nathan,
How does the larger pipe from the WG help with reducing boost? Am I missing something here?

strudel

The one I have non there now is a curved pipe approx. 1 1/4" i.d. Open pipe no baffling.

Sameer

Mine from Fabspeed

WERK-I

The problem isn't in the WG or the WG exhaust pipe. The GHL headers have somewhat restrictive tubing going from the headers to the Wastegate flange. It twists...it turns...and it has a somewhat small diameter.

If B&B or GHL is lurking, I'd be happy to have my car as a guinea pig for a Tial WG(already have) mounted on their headers where the WG is located closer to the turbocharger flange and exhausts out the left rear valence cutout. The new muffler would exit out the valence cutout on the right side.
I know...I'm dreamin'.
Dave
'85 Factory Slantnose 930

Kevin

Dave, you are right about the WG exhaust pipe. The diameter should be opened up and it could be shortend a good 8" or so.. With everyone installing Tial's, it makes sense to redesign the circuit.

nathanUK '81 930 G50

Sameer, Strudel seems to be overboosting. The wastegate dumps unneeded exhaust gases from going to the turbo which would make it spin even faster and therefore for it to produce even more boost to the intake assy.
If the turbo does not need this exhaust it is bled off via the wastegate, having a restriction in the wastegate will not help overboost. Looking at the stock setup that I have, I could see that the muffler on the wastegate would be more of a restriction than the wastegate itself.

Having a larger pipe for the wastegate will help reduce overboost. Stephen has mentioned that the GHL wastegate pipe is of too small a diameter, the ones he got for me of a larger diameter than when they first made/designed their product. This is probably due to the K27HFS being such a good turbo.
With my stock K26 and stock headers I blanked off the small hose going from the IC to the wastegate so my wastegate never opened, I still only made .75bar, time for upgrades...

Using the GHL headers and a K27HFS with the stock wastegate I had would probably have been fatal. I seem to remember that someone on this board learnt the hardway as they already had fitted a 1bar spring before they upgraded something. They overboosted and damaged their engine.
I have requested a .5bar spring from Stephen with my Tial as I have a EBC.
It will be interesting to see what boost I get without using the EBC.

Correct me if I am wrong guys or missed something.

I have a question now while we are on this subject.
By fitting a K27HFS is it the case that I will not have anymore exhaust flowing out of my main muffler as more exhaust is going to go through the wastegate ? or will it not not make much difference as I have increased the power output of the engine.

Took so long to write this, someone beat me to it about the GHL's...

nathanUK '81 930 G50

Dave, Strudel says he has stock headers.

WERK-I

nathan,
Thanks for the clarification. When my stock wastegate failed, it went to 1.4 bar on a K27-7006/B&B system.
Strudel, you might want to check out the wastegate valve/valve guide and the diaphram. If the valve guide becomes worn, the clearance, if excessive, will cause the wastegate to open late, if at all. check the valve seat and valve for corrosion as well. The diaphram gets hard due to age and the environment it works in. this will cause unpredictable WG action.

Hope this helps.

Dave
'85 Factory Slantnose 930

Sameer

Thanks for clearing it up for me guys, now I understand better.

strudel

I'll have my mechanic look at the seat & diaphram. I'm looking for a stock .7 bar spring if anyone has one for sale. I may try running the car without the w/g exhaust tip and see if that has any bearing. The car will be down for a week. I'm having Wevo modify my trans brace to use their transmission mounts.

strudel

I had another mechanic look at the spring that was in the w/g and he said it was a stock spring. Other than the boost gauge not reading right, is there anything else that would cause over boost?
Harold

Kevin

You need to get a good gauge installed to find out where you are at.. You have verified the spring, now install a gauge..

strudel

I installed a stock spring and it hit 1.4 bar.
I swapped out to another gauge and got the same reading.
I had the motor running and ran 15 psi - 20 psi through the control inlet and the wastegate didn't open. This is with the stock spring.
This is a stock waste gate. So this seems like the next thing to replace. Any recommedations on what I should get?
The motor is an Andial twin plug w/gruppe B cams, Andial fuel enrichment & intercooler, stock heat exchangers & DP muffler.
Thanks,
Harold
'79 930/DP935

nathanUK '81 930 G50

Everyone uses the Tial. I got mine from Stephen of Imagine Auto a few weeks ago. Looks awesome. He will fix you up.

mailto:PorschePhD@ImagineAuto.com

WERK-I

Is the line coming off the top of the wastegate vented to the atmosphere with the test you just conducted?

Dave
'85 Factory Slantnose 930