I recently went to the dyno. I have a hybrid s5 turbo. THe boost would rise with the rpms. Peak boost was at redline. The boost graph was a steady slope to redline. What could this be?

 

Was it overboosting or just would take till redline to make what the wastage is set at?

 

overboosting. WHat ever internal actuator BNR uses was hooked up directly and it was seeing 19 psi.

 

More than likely the waste gate is insufficient with hold boost at the desired pressure. It's a common problem that has plagued all factory turbos. I recently built a car with a stock upgraded turbo that wouldn't for the life of it hold steady boost.

So what I did, put a external waste gate on the factory manifold. Lol.
You can try porting the stock waste gate holes in an effort to help.

 

Did you buy this turbo new from BNR? Has anyone adjusted the wastegate arm tension at all?

 

I had the same issue with my S5 based BNR Stage 4 hybrid turbo.

Went with ported wastegates and clipped "P" trim wheel- still boost creep

Open air vented the stock wastegates- better but still boost creep.

Adapted 60mm external wastegate with wastegate passages ported out to max casting allows- still some boost creep.

Ported out the manifold and exhaust housing runners to eliminate the velocity stacks and make flow favor the wastegate instead of the turbo- fixed boost creep.

Instead of all this work, I would advise putting a restriction in the exhaust as far back as possible to limit flow and so eliminate boost creep.

Japanese tuners put a "gasket" of thick metal with an undersized hole in it at the joint right before the mufflers.

Now that you fixed boost creep, start saving for a full single turbo kit if you absolutely need more power.

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/most-modified-stock-turbo-how-stop-boost-creep-221849/page2/

This old thread of mine-

 

Originally it was a hybrid some other company made. Then i had sent it to BNR and i spent a good bit for them to rebuild it to their standards which include using a new exhaust housing from a stocker. YEs it is a P-trim exhaust wheel one.

I was under the impression boost creep happened right after peak torque right as the turbo spooled up then would loose psi at red line... Mine was the opposite. HAd like 8 psi at 5k rpms.(really?) and from 5k to 8,200 it sloped up to 16-19 psi.

 

Boost creep will happen always when wastegate can´t divert enough mass flow. For the amount of money which probably went into modifying stocker, you would be better with full T04E 60 trim on tubular manifold with huge room to grow.
Hybrids are just too big compromise IMO. Never ending battle with boost creep by modifications which compromise spool up and consequently denying purpose of small hotside...

 

Here was my fix for a car I built to eliminate boost creep. I agree though after the time and money could've went with a nice aftermarket setup.

 

You may need to adjust the tension in the wastegate arm. Even then if that is not a factor here, you would probably be better off just having a high flow cat welded in.

 

Wastegate armbis fully extended. And I have a full 3" Turbo back.

 

Waste gate is too small dude, even if you port it.

IF you port it too much, you'll lose manifold pessure because the wasgate will crack open just from exhaust pressure. You're reaching the limitations of the stock turbo.

I'm happy with my boost spikes (its tuned for it :P)

 

I've done the same thing in the past, rock solid boost control then...

 

Works flawless now!!!

 

just with a single runner?

 

On a s4 manifold its open outlet. On a s5 however you have to either run 2into1 or put your pipe in the center of the divider so the sides are split for the wg runner.

 

about what.............. it helps if you include what your curious about