What size turbo with atr headers

[434nova]

What is the biggest size turbo am I able to fit on atr headers and fit under the stock hood and without interfering with anything. I was wondering if a 88 mm will fit. I am looking at running a 4788 turbo with the t4 flange. How does this setup fit. Thanks

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[forcefed3.8's]

How fast do you want to go? An 88 will fit, but will have alot of lag. Picking a turbo isn't about what is the biggest that will fit.

 

[434nova]

Im looking to go 8.90s or better. I looked at some 76mm turbos but it looks like I will be max out around a 8.90 or so. What do you recommend on a turbo ?

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[forcefed3.8's]

The turbo (7675 billet wheel) I have has gone 8.4's. I am far from maxxing it out. I have gone just as fast with a smaller turbine and a 76 compressor that was a mismatch of wheels.

 

[434nova]

How much stall are you running with that turbo ? Does it spool up quick ? I am building a 276 stage 2 headed motor

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[rag231]

Are your ATR headers 3 or 4 bolt, for the record?

 

[434nova]

4 bolt

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[norbs]

The 76-75 is a hybrid the standard garrett gt42-76 has a 81mm exhaust so it should flow even more if your looking for more HP? It spools Just OK but its not fast spooling to me.

 

[forcefed3.8's]

I am running a PTC 18 blade, it stalls 3800 at 0 boost with the wastegate open. It spools great. I am going to try a 20 blade to see if I can run enough rpm to make it couple. Spool up and converter stall will depend on compression and cam selection.

 

[norbs]

He will be using stage 2 heads, they do not have the velocity, my spool times are about 3x as slow as yours with a looser converter 20 blade. It also depends on the base compression ratio.

 

[750H.P.V6]

The spool up will be dependent on base compression ratio, camshaft profile, displacement, convertor stall speed, turbo size and turbine housing A/R and tuning variables. Rob's combo is well sorted. A smaller turbo will be much more responsive (AKA: fun to drive) than a larger turbo.

Neal

 

[434nova]

I understand on the spool up variables. Here is where im heading 276 ci ,stage 2 heads , 4000 - 4500 stall , 9.0 compression , 76 - 88 mm turbo , cam in the high 220s low 230s , ar in the 1.10 or less. How does that sound. I am still learning on these turbo buicks , some parts I havent gotten yet ( turbo , cam , stall ) I would like to run high 8s but a low 9 is fine. I am also looking to run around 30 to 35 #s of boost to get there if possible.

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[turbobitt]

I understand on the spool up variables. Here is where im heading 276 ci ,stage 2 heads , 4000 - 4500 stall , 9.0 compression , 76 - 88 mm turbo , cam in the high 220s low 230s , ar in the 1.10 or less. How does that sound. I am still learning on these turbo buicks , some parts I havent gotten yet ( turbo , cam , stall ) I would like to run high 8s but a low 9 is fine. I am also looking to run around 30 to 35 #s of boost to get there if possible.

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Going to be difficult to get 4000 RPM stall with stage 2 heads......
AG.

 

[434nova]

What would you say is going to be the range of stall with say a 76mm turbo with a .96 ar. I have fully ported champion gn1 heads on my 235 ci engine. Wouldnt the cc of the runner be the determing factor of rpm range ? My champions work great on my motor with a te45a turbo , that is a 66mm size turbo and I have a 3200 stall. What would you say is the cc of the runner on the stage 2 heads to a gn1.

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[forcefed3.8's]

I would use your GN1's on the stage 2. If they are 8 bolt, they can be converted. I am running regular GN1's not R's into the range you want.

 

[norbs]

What would you say is going to be the range of stall with say a 76mm turbo with a .96 ar. I have fully ported champion gn1 heads on my 235 ci engine. Wouldnt the cc of the runner be the determing factor of rpm range ? My champions work great on my motor with a te45a turbo , that is a 66mm size turbo and I have a 3200 stall. What would you say is the cc of the runner on the stage 2 heads to a gn1.

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The optimal flow rpm range on the a S2 alum head is 7500 rpm with 276 ci.

I would use your GN1's on the stage 2. If they are 8 bolt, they can be converted. I am running regular GN1's not R's into the range you want.

He bought a set of stage II heads, the ports will drawf the GN1 heads, hence the rpm potential is now shifted to 5000+ to 8000 RPM + He will need the biggest turbine wheel/ AR possible or it won;t be efficient. He will require a 19-20 blade PTC and the proper cam to make it work. ....

 

[434nova]

How would a 4.11 gear work with a 28 inch tall tire with my combo ? I have a choice between 4.11 or 3.50 but since im gonna need to rev this motor would the 4.11 be better. This with a turbo 400 trans.

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[turbobitt]

How would a 4.11 gear work with a 28 inch tall tire with my combo ? I have a choice between 4.11 or 3.50 but since im gonna need to rev this motor would the 4.11 be better. This with a turbo 400 trans.

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3.50's with 28 inch tall tire.
AG.

 

[Mike E]

I understand on the spool up variables. Here is where im heading 276 ci ,stage 2 heads , 4000 - 4500 stall , 9.0 compression , 76 - 88 mm turbo , cam in the high 220s low 230s , ar in the 1.10 or less. How does that sound. I am still learning on these turbo buicks , some parts I havent gotten yet ( turbo , cam , stall ) I would like to run high 8s but a low 9 is fine. I am also looking to run around 30 to 35 #s of boost to get there if possible.

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My opinion. If you choose the turbo and camshaft correctly the stage 2 heads won't be as big of a detriment as most think. If you only want to run high 8's you can get there with as little as a 6768. With the right cam it will spool great and still make good power. Your cam choice in the high 220's/low 230's could be right but there is so much more to it than duration numbers.

 

[Mike E]

Turbobitt is right on with 3.50 gears and a 28" tire. With the right turbo and cam, you won't need to spin it to the moon and it will be much more fun.

I would put my 277" 67mm combo against any for quick spooling and fun factor. And I bet my Ta heads flow almost as much as the typical stage 2 head.