How far could a pt67/76 dbb get me?

[evil666]

Does anyone know how far I can get with a pt67/76 dbb turbo with a precision .63 AR. I was thinking of upgrading to a 71 dbb with a billet wheel. At the same boost (28 psi) that I am running will I see a big gain or will I only see big gain if I run the 71 at really high boost, lets say like 35psi. I was also thinking of changing my precision .63ar to an .82ar, but don't know if its worth it. My car down low feels pretty crazy cause the turbo spools up very fast, but on the street it is hard to get traction sometime. This is why I would like to get a .82 ar, so it could reduce a bit of the power down low but maybe give me some more top end power. I want to hear from you guys if its worth it, or if I am better off going just up grading to a bigger turbo?

Thanks ahead of time,
Marco

 

[BEATAV8]

I think you would see best results by switching to a larger or more efficient turbine wheel.
I have the same old 6776 ball bearing turbo with a .63A/R turbine housing and just bought a new 6766CEA with a .85 turbine housing to replace it. Looking to capitalize on lower back pressure.

IMO the old 6776 is great 10 sec turbo but if you want to go 9's it's gonna be harder on the engine than a more modern turbo would be.

 

[Mr.Spool]

Does anyone know how far I can get with a pt67/76 dbb turbo with a precision .63 AR

140 mph /9 sec pass on a turbobuick.

 

[Mr.Spool]

I was also thinking of changing my precision .63ar to an .82ar, but don't know if its worth it

its something that you must try to get on your combo to get a real answer,i can tell you that the .63 ar will get the car into the 9's if all else is there.

 

[Mr.Spool]

I was thinking of upgrading to a 71 dbb with a billet wheel.

I have seen these cars slow down with bigger turbos,not enough air into the motor soon enough.remember the if you make the turbine and compressor and ex housing bigger there needs to be enough ex gas to get things moving,its a balance a lot of owners miss with these cars.

 

[bison]

If it's a cast T04z with a large compressor cover and a clipped P trim (t04 76 trim) it will support 9 sec power. With iron heads it would be over 30psi to be all in.


BPE2013@hotmail.com

 

[turbodaniel]

If you decide to go with a 71.. I am selling my 71 billet ,ball bearing that Precision just freshened up

 

[evil666]

140 mph /9 sec pass on a turbobuick.

Did you run 9 sec pass at 140 mph? WOW to you or who ever you know that ran that quick on that turbo. Would you know the combo of the car and at how much boost?
Thanks,
Marco

 

[Mr.Spool]

Would you know the combo of the car and at how much boost

all of it the boost number varied between the iron head and the aluminum.too many guys switch before maxing out the turbo,dont let the boost number intimidate you

 

[Mr.Spool]

taking weight out of the car will really help as well.

 

[evil666]

its something that you must try to get on your combo to get a real answer,i can tell you that the .63 ar will get the car into the 9's if all else is there.

What do you mean exactly by if all else is there. Do you mean combination and boost?
Look at my set up in my sig and my 1/4 mile runs. The car is not that far from the nines and this is with a flaring tranny on my second to 3rd shift and a convertor that I am not to sure is doing it's job well. Everybody that looks at my FAST XFI files tells me something is up with the convertor. The convertor works great off take off , and I know with more boost off the line I could go get some more ET. The thing that I find weird is that I only get a 200 rpm drop from 1st to second (5450 to 5250 letting the transmission shift on its own). So I know if I figure out these issues and with some more boost off the line, 9.90@134 or 135 , I should be there. I just sent my Fast XFI files to Dusty to look at so I could get his opion on the convertor. But to get 140 mph with this turbo, what should I change in my set? Maybe if I go to a bigger front mount intercooler instead of a stock location, roller cam set up and more boost.
Thank again,
Marco

 

[evil666]

all of it the boost number varied between the iron head and the aluminum.too many guys switch before maxing out the turbo,dont let the boost number intimidate you

Up to how much boost is this turbo going to keep on giving me more power. Also don't want to go to crazy on boost, don't feel like picking up engine parts off the track.

 

[evil666]

taking weight out of the car will really help as well.

I think that is pretty much the weight out of my car, wont be taking off any other parts. I like everything to be there, like my a/c for example.

 

[evil666]

If it's a cast T04z with a large compressor cover and a clipped P trim (t04 76 trim) it will support 9 sec power. With iron heads it would be over 30psi to be all in.


BPE2013@hotmail.com

I don't know Bison, is this info stamped anywhere on the turbo?
Thanks,
Marco

 

[evil666]

Is it true that with a billet wheel turbo, you have to run a lot more boost to make it be worth your while?

 

[BEATAV8]

My old 6776 has gone 133mph, 3850lb running 27psi. After that I ran it at 30psi for a while on the street and sure, it was pulling harder. But unfortunately after a while it pushed out a cometic gasket. No detonation, just lotsa cylinder pressure and lotsa pulls. I wish I was logging backpressure but I wasn't. I imagine it was well over 50psi exhaust pressure with 30psi boost.

After that I quit worrying about maxing out my old turbo.....

The newer turbos offer lower restriction turbines and still get you the transient response you need. As long as it spools up nicely, go ahead and run a turbo that can support quite a bit more than you need and don't worry about "maxing it out". The 6466CEA is a good example. Capable of 900HP but hardly anybody uses all of that. But the turbo still has a reputation for wicked fast spool up even with a .85 A/R turbine housing.

 

[Mr.Spool]

Also don't want to go to crazy on boost

then you have hit your personal risk limit and there is nothing wrong with that.

 

[Mr.Spool]

I think that is pretty much the weight out of my car, wont be taking off any other parts. I like everything to be there, like my a/c for example

nothing wrong with that just understand this is the easiest way to make the car faster.

 

[we4Mateo]

I think you would see best results by switching to a larger or more efficient turbine wheel.
I have the same old 6776 ball bearing turbo with a .63A/R turbine housing and just bought a new 6766CEA with a .85 turbine housing to replace it. Looking to capitalize on lower back pressure.

IMO the old 6776 is great 10 sec turbo but if you want to go 9's it's gonna be harder on the engine than a more modern turbo would be.

Doesn't mph determine how hard you're being on parts? I would think an engine running at 140mph with turbo A @ 28psi would be just as hard as turbo B running 35psi at the same mph. As long as it's knock free, cylinder pressure should be the same.

 

[BEATAV8]

Doesn't mph determine how hard you're being on parts? I would think an engine running at 140mph with turbo A @ 28psi would be just as hard as turbo B running 35psi at the same mph. As long as it's knock free, cylinder pressure should be the same.

I think whichever turbo runs less backpressure will be easier on the engine. There will be less internal EGR during any period of valve overlap, and lower backpressure will free the engine up pull higher and make more power with less boost. Turbo "A" with lower boost and back pressure should provide better volumetric efficiency and better pumping efficiency.

Focusing on cylinder pressure.... Peak cylinder pressure is the result (primarily) of boost, temperature, timing, fuel quantity. The combo with less boost and better pumping efficiency should have lower peak cylinder pressure. That cylinder will be putting less effort into pumping the gasses than the one running with turbo B.