Best Twin Turbo Setup For Stage II

[CMac455]

I was wondering what a good twin turbo setup would be for around 1400rwhp. I was thinking 6766's, but I can't decide on the correct hotside to run. As far as primary sizes go, I am thinking of 1 7/8". As far as turbos go, I was thinking either 2.5" tubing to a .81 A/R T3 or 3" tubing to .81/.96 A/R T4's. Red line would be around 9k RPM. I'm driving it on the street, so it would be nice to have something that spooled somewhere in the neighborhood of 4500-5000 RPM.

What do you guys think?

 

[Dusty Bradford]

Those 6766's would work great. I put a set of 6765's on a Stage 2 a while back. ATR headers to .96 T4 housings and it would build boost so fast I was suprised.

 

[CMac455]

Do you remember what size tubing you ran to the turbos and the rpm it spooled at?

 

[CMac455]

Anymore suggestions?

 

[Dusty Bradford]

It was ATR twin turbo headers. I'm not sure of their specs. I'd guess 1 7/8 primaries into a 2 1/2 tubing to the turbo. I could hit the 4400 rpm 2 step chip while on the foot brake. Spooling was no issue at all.

 

[Dusty Bradford]

Here's a pic of the headers.

This is the only one I have that will upload. You can't tell much about the headers. They may be a 3 inch collector made to fit a T4 flange. I have a better pic of the headers but it won't upload.

 

[Dusty Bradford]

They look kind of like the headers in this link.


http://www.turbobuicks.com/forums/parts-sale/98009-new-stage-2-153-block-twin-turbo.html

 

[CMac455]

Thanks, Dusty. I called Precision up and the tech there told me that I shouldn't go for anything bigger than a 6266 with a .82 A/R T3 turbo. He said it would be too lazy. If I had full boost by 5k, then I would be happy. Optimally I would like to have full boost by 4500 RPM.

From what you mentioned, you ran two 6765s with .96 A/R T4s and they spooled by 4400? If that's the case then the 6766s should be a great fit. I'm going to run journal bearing turbos, by the way.

 

[Dusty Bradford]

1400 rwhp will need alot of turbo IMO. If Precision thinks you can make that much power with 6266's then you can use them. I thought it would take more than twin 62's to make that much power.

You won't need full boost by 5000 rpm. No way to hook something with this much power that early. 1400rwhp will be well over 35psi. You will have to ramp the boost in over a period of time. I'm not sure how much power this car made but it was enough to run 139mph in the 1/8 at over 3600#

 

[CMac455]

I've called them and got anywhere from 7675's with a .81 T4 to 6262 with .82 T3 housings. It's like shooting in the dark to decide.

I understand what you mean about the boost. I suppose if I were to keep it at 900rwhp, or 15psi, then I would like to hit that by 5k. Not necessarily all 35psi. I don't want to run into exhaust backpressure issues, however. How does 6766s with .81 A/R T4's sound? If I can get those to spool decently then I may just go with that. I would also like to try to build headers like you showed in your picture. The turbo seems like it would spool better bolted to the collector instead of 2.5" piping running to it.

 

[turbobuick]

Subscribed.

If someone is handing out advice on how to make 1400 r(rear)whp with a Buick V6 I'm listening that's for sure!!!!

Now if you are talking F(flywheel)WHP then I would say a pair of billet wheel 67's with T4 .85 housings and 1.75" primaries. That is a total guess for me with S2 heads and twins but would be where I would start.

 

[fxdxlr8]

I have a set of the headers pictured in the link.
Let me know if you are interested if you decide to go that way.

 

[FastDiesel]

I have a set of the headers pictured in the link.
Let me know if you are interested if you decide to go that way.View attachment 158518

how much for them headers or do you want to trade for something else

 

[Dusty Bradford]

He doesn't have a Buick engine. It's a Ford based engine similar in bore and stroke to a V6 Buick which is why he's here looking for advice.

 

[CMac455]

He doesn't have a Buick engine. It's a Ford based engine similar in bore and stroke to a V6 Buick which is why he's here looking for advice.

That's close to being true. I didn't want to say it because I wanted to get as much help as I could. Truth be told I'm going to the SVO V6 which is a completely aftermarket based engine that is similar to the Stage II engine. It's a 3.400 stroke and a 4.130 bore with 360cfm heads.

Basically anything that the Stage II motor does the SVO will want the same.

 

[Dusty Bradford]

You won't run into a situation where people don't want to help because it's a Ford motor. The issue is there are probably less than 5 people on this board who have even made close to 1400rwhp with a V6 and less than that who used twins to do it with. Only 2 full body cars have ran 7.90's which is still less than 1400 rwhp and they both used a single Precision HP4788. The most powerful twin turbo car would be Duttweiler and he uses twin 42/76's but he's got to be over 1400rwhp.

I'd say 1 7/8 or 2" primaries feeding a 3" collector mated to .8??? T4 flanged 6766's will get you where you need to be.

 

[turbofabricator]

Or be really wild and run quad billet small turbos. Just copy my set up on both sides. Now THAT would be different.

I agree that 1 7/8 will work. I really don't think that 1 7/8" would hold you back. 2" might cause spooling issues. The diesel guys make serious power with near stock manifolds. The LSX guys run over 200 mph on ported cast iron Chevy truck manifolds. Not alot of power to be had in exotic header designs.

 

[JayC]

To put it into perspective for you, we had Borg Warner 75s on the BWR car and only made a little over 1300 at the wheels. We had more left and probably could have gotten it to 1400 but that was with 75s. I dont think you're going to get there with 62 anything.

 

[bison]

That would be tough on 62's. Might be doable but they would be huffing. It's not easy to build an engine that will make 900whp@15psi then make 1400whp with the same cam and torque converter. You have to sacrifice something. Typically a 90* v engine that would make that much power is going to need a lot of rpm and boost to get it done. The cam required would make it a turd below 6000rpm. You would probably be building something that has a power band from 7000 to 8000rpm. Maybe more to hit 1400whp. Having it spool by 5000 doesn't matter since it won't have crap for cylinder pressure down that low. It's easier to build a larger displacement engine with more cylinders then you can have a more useful powerband

 

[Alky V6]

I'm running a pretty wild cam to most of you, and I recall entering a 6.90 1/8 mile index class last year, just to play around. By the end of me attempting to slow the car enough for the class, I had lowered the boost down to 8 psi and still couldn't slow the car down enough to run in the class. 8 psi with a single 91mm and 224 cid. At that boost level, the shift points were, IIRC, in the mid to high 6,000s, where normally I shift it at 7200-7800 rpm.
So you see, a large cam and large turbo on a small engine does not necessarily mean a complete dog in the midrange.