Why wastegate a stock turbo, or 38R...

Big Bore · Nov 16, 2011

unless it's in a compound setup? A stock injectored motor can't make enough boost to even come near needing a wastegate, and for most trucks running a 38R they have either stock injectors, or stage I-II's, which isn't going to make enough boost to matter.

Just wondering if I'm missing something. OBS trucks didn't have a WG, and I know for a fact those turbos will take 32psi all day long every day. Van turbos don't have a WG. I have the WG tightened shut on my 38R with 175/30% injectors and never see over 30 psi.

Now I see Lott running compounds with a 38r using the factory WG.

JoeDaddy · Nov 16, 2011

Subscribed... I been thinking about closing mine mechanicaly.

skew12 · Nov 16, 2011

Subscribed.

superduty4x4 · Nov 16, 2011

The OBS trucks have a 1.15 A/R exhaust housing, compared to a 0.84 A/R housing on an SD turbo. Since the stock turbo is out of its MAP at around 25psi, and a truck with just a chip can easily make that, having the gate makes sense to help keep the turbo from overspooling, in theory anyway.

lincolnlocker · Nov 16, 2011

My wg is also turned tight on my 38r and the red line taken off and i hit 38-40psi

David N · Nov 16, 2011

Ok, so I have the red line taken off of my 38R and it makes 40 psi now... before it only made around 30 psi. But what are you guys talking about mechanically closing? Sorry if its a stupid question.

JAP · Nov 16, 2011

JoeDaddy said:
Subscribed... I been thinking about closing mine mechanicaly.

I messed around with my waste gate a lot. Everything from having it wired shut, to having a direct drive pressure reference to the actuator.

Best setup I've found is tightened down about 8 turns and have a direct boost reference.

mattman347 · Nov 16, 2011

If your line is taken off it will mechanically stay closed by the spring pressure. 40 PSI is at the top of the boost pressure for the 38R, you guys may want to look into a 1.15 housing for more efficient flow and less drive pressure. I have some in stock if you are interested!!

JAP · Nov 16, 2011

David N said:
Ok, so I have the red line taken off of my 38R and it makes 40 psi now... before it only made around 30 psi. But what are you guys talking about mechanically closing? Sorry if its a stupid question.

Wiring or welding shut. I definitely wouldn't. You should get a drive pressure gauge. It would really open your eyes to what the wastegate is doing.

Big Bore · Nov 16, 2011

lincolnlocker said:
My wg is also turned tight on my 38r and the red line taken off and i hit 38-40psi

This is something I've been wondering about, I'm making about 10psi boost less than you on 175/30% from Swamps.

Would nozzles make that much difference? I did notice some soot around the preturbo egt probe clamp awhile back and meant to check that. Sounds like I need to look around for some leaks.

JAP · Nov 16, 2011

The nozzles definitely play a role. Tuning could be the difference as well.

Big Bore · Nov 16, 2011

JAP said:
The nozzles definitely play a role. Tuning could be the difference as well.

I've had over 10 sets of tunes from 3 different tuners and the tunes I have right now make the most boost, I've had tunes that were max PW (over 4ms if you can believe it) and while data logging when I had the dual Termies on the truck I had all the ICP being commanded, 3200psi I believe. I have DI up pipes, Spearco IC with Banks tubes, BDP billet intakes and a Tymar. Uppies, exhaust housing and down pipe are all ceramic coated. I've always had between 25 and 30psi and thought it was low. 38r has ported compressor housing and high flow outlet. I've had a boost fooler on it, and it was the same then also. In fact boost was a little lower.

I'm starting to think I've got a high pressure leak somewhere. Being at high altitude shouldn't cost me 10psi.

JAP · Nov 16, 2011

Build a tester. I didn't think about the elevation. Why wouldn't you think elevation would cause it?

Hotrodtractor · Nov 16, 2011

Back pressure is why I would add a wastegate to those chargers, not boost pressure.

JAP · Nov 16, 2011

Hotrodtractor said:
Back pressure is why I would add a wastegate to those chargers, not boost pressure.

:whs:

Gearhead · Nov 16, 2011

for ever 2 lbs of drive pressure you drop and boost stays the same, it's like gaining a pound of boost.

CSIPSD · Nov 16, 2011

Hotrodtractor said:
Back pressure is why I would add a wastegate to those chargers, not boost pressure.

Exactly... Drive pressure is what kills the stock turbo, even the 38r...

At 25psi the stock turbo with the wastegate disconnected will see 50-52psi back pressure. That is A LOT of side loading on a turbo.

JoeDaddy · Nov 16, 2011

Hotrodtractor said:
Back pressure is why I would add a wastegate to those chargers, not boost pressure.

add?????

Arisley · Nov 16, 2011

Big Bore said:
I'm starting to think I've got a high pressure leak somewhere. Being at high altitude shouldn't cost me 10psi.

Frank, you are not at high altitude. High altitude is 5 to 6 thousand feet. You are at extreme altitude. It is a wonder you can even get enough oxygen to bust off a motor up there.

I really want to come up and visit though, you have some awesome views.

dietoremain · Nov 16, 2011

CSIPSD said:
Exactly... Drive pressure is what kills the stock turbo, even the 38r...

At 25psi the stock turbo with the wastegate disconnected will see 50-52psi back pressure. That is A LOT of side loading on a turbo.

Exactly.. that is why they dont live long being boosted above that very often...

38r is much better but still needs to be careful, the stock set up lacks... its all about a T4 setup!