What size turbo with atr headers

[434nova]

I am gonna have dan at dls spec my cam. I am going to have my heads flowed so I know exactly what I am working with. I have a friend that had a stage 2 motor from dutwieller. It dynoed 720 at the flywheel. The motor never went higher than 6200 and it went 9.67 @ 142. This was back in 92. He also used a 66 mm turbo on his combo. Car had a small solid roller in the high 220s on a 114 lobe sep and a 580 lift cam. Car really surprised alot of people back then. I feel with todays technology on turbos, cams , etc i should be able to achieve my goals. My friend also had a stage 2 that put down 1200 rwhp with twin 72 mm turbos. That car went 8.40s with major boost leaks and issues. In fact he also a member here but has posted lately his name is Sarge on the board maybe some of you know him.

Posted from the TurboBuick.Com mobile app

 

[turbobitt]

My opinion. If you only want to run high 8's you can get there with as little as a 6768.

I don't completely agree with this. The stage 2 heads will want some RPM and I think the turbine will limit the performance in a high RPM application. Although the turbo may get it there is some applications, I don't think this is one of them.

Allan G.

 

[norbs]

The heads require the massive exhaust flow from either turbine size or turbine wheel diameter. I increased the tubine size and it had a huge effect on HP with very slight change in LAG...

 

[434nova]

When you say turbine size u mean ar size ? So you put a bigger ar and made more power? Was it at the same rpm or higher? Thanks

Posted from the TurboBuick.Com mobile app

 

[Mike E]

I don't completely agree with this. The stage 2 heads will want some RPM and I think the turbine will limit the performance in a high RPM application. Although the turbo may get it there is some applications, I don't think this is one of them.

Allan G.

If we had a set of champion/ ta heads that flowed 300+cfm and a set of stage 2 that flowed the same, same size valves, same shortblock, same camshaft etc. the only difference being port volume, why would the stage head need more rpm? I understand the stage will have less port velocity, but is that going to make a 1000-2000 rpm difference? I'm not an expert by any means, but I don't see why? I think you can overcome low rpm port velocity/torque with low rpm boost.

I agree the turbine will limit potential, but its a trade off for a setup that spools like mad. But even a 68mm turbine can go high 8's. The rest of the combo has to be there, but that is the case with anything in the 8 second zone.

Yes, he could go the typical route and overturbo the motor and run high 8's with a lazy 60'. But it will be slower to spool and cary all these "stage 2" traits that people seem to complain of so much. I haven't tried a small turbo, on a larger stage 2 headed motor, but If I had time I would try it myself based on what my motor acts like now. Just trying to think outside the box.

 

[turbobitt]

If we had a set of champion/ ta heads that flowed 300+cfm and a set of stage 2 that flowed the same, same size valves, same shortblock, same camshaft etc. the only difference being port volume, why would the stage head need more rpm? I understand the stage will have less port velocity, but is that going to make a 1000-2000 rpm difference? I'm not an expert by any means, but I don't see why? I think you can overcome low rpm port velocity/torque with low rpm boost.

I agree the turbine will limit potential, but its a trade off for a setup that spools like mad. But even a 68mm turbine can go high 8's. The rest of the combo has to be there, but that is the case with anything in the 8 second zone.

Yes, he could go the typical route and overturbo the motor and run high 8's with a lazy 60'. But it will be slower to spool and cary all these "stage 2" traits that people seem to complain of so much. I haven't tried a small turbo, on a larger stage 2 headed motor, but If I had time I would try it myself based on what my motor acts like now. Just trying to think outside the box.

The port volume kills the low end response. Regardless of whatever cam I tried the motor wouldn't come alive until 5000+ RPM. If a 67mm turbo is your best recommendation for this guy to run in the 8's than go for it.
AG.

 

[Mike E]

I don't think it's the best, but it may not be as bad as everyone thinks. It has it's trade offs. I thought it wouldn't have worked on my motor well, but I'm pleasantly surprised. I'll gather more data on mine as I get more runs this year.

 

[turbobitt]

Keep in mind the OP wants to go "8.90's or better". I think 8.90's with a stage 2, stage 2 headed car is a modest goal at any typical Regal/GN weight and will be easily achievable. Now with that being said, I think the turbo selection would be better based on whatever stretch goal you may have or at least have sufficient margin to cover the goal.
AG.

 

[Mike E]

I would like to run high 8s but a low 9 is fine.

I'm recommending based on this.

 

[J-B Racing]

I have the 4788 and I am extemely happy with it. But I run Mike's Headers and the Spooling is FAST..

 

[bison]

I would never rec a turbo with a turbine anything smaller than a 75mm exducer for over 900hp. You are choke flowing the potential of everything else and running a lot of ex pressure that will hurt cylinder filling dramatically at high rpm. Could a 68mm turbine flow 100lbs/min. Maybe. Will it lop off a crap load of power in an engine that has enough head and valvetrain to rev to 7500. Absolutely. You'd be choke flowing a 270ci to 6300rpm. There's no point in that. You're using a lot of cylinder pressure to move the car and reducing the engines efficiency out the back big time. It will have tremendous pumping loss on the ex stroke and the ex closing event better be spot on or it's going to be off in power quite a bit. It's like trying to run 9.50 on a 65mm turbine. It probably could be done but limiting your potential by using that small turbine will change the entire combo and you will be pigeon holed by ex pressure . There are ways to drop some back pressure but doing so isn't necessary in non restricted racing.

 

[434nova]

Hey bison what size turbo and ar would you recommend for my combo ? I always hear a turbo size but really no mention on ar size. Thanks

Posted from the TurboBuick.Com mobile app

 

[norbs]

When you say turbine size u mean ar size ? So you put a bigger ar and made more power? Was it at the same rpm or higher? Thanks

Posted from the TurboBuick.Com mobile app

I Really dont have any true HP numbers I am only going by fuel numbers on the transbrake, and more fuel/lbs means more hp to me with no other changes. I had 21 psi backpressure at 10 lbs boost, now I think its close to 12-13 lbs backpressure at that boost. The spool time is only marginally slower than before maybe 1 second more from idle to 15 psi.

 

[norbs]

If we had a set of champion/ ta heads that flowed 300+cfm and a set of stage 2 that flowed the same, same size valves, same shortblock, same camshaft etc. the only difference being port volume, why would the stage head need more rpm? I understand the stage will have less port velocity, but is that going to make a 1000-2000 rpm difference? I'm not an expert by any means, but I don't see why? I think you can overcome low rpm port velocity/torque with low rpm boost.

I agree the turbine will limit potential, but its a trade off for a setup that spools like mad. But even a 68mm turbine can go high 8's. The rest of the combo has to be there, but that is the case with anything in the 8 second zone.

Yes, he could go the typical route and overturbo the motor and run high 8's with a lazy 60'. But it will be slower to spool and cary all these "stage 2" traits that people seem to complain of so much. I haven't tried a small turbo, on a larger stage 2 headed motor, but If I had time I would try it myself based on what my motor acts like now. Just trying to think outside the box.

The port velocity can make a huge difference, where the TQ comes in to effect. My motor is a complete dog at 4500 RPM, the fuel numbers show about 200 HP... as an exmaple..

 

[turbobitt]

Hey bison what size turbo and ar would you recommend for my combo ? I always hear a turbo size but really no mention on ar size. Thanks

Posted from the TurboBuick.Com mobile app

The A/R is kind of like a fine tuning thing. The turbine needs to be sized correctly and the A/R selected according.
AG.

 

[bison]

Hey bison what size turbo and ar would you recommend for my combo ? I always hear a turbo size but really no mention on ar size. Thanks

Posted from the TurboBuick.Com mobile app

Id use an s400sx 82mm BW or equivalent BW based unit. Lmk if you are interested. You'd be using an a/r in the 1.1 range

 

[turbobitt]

Id use an s400sx 82mm BW or equivalent BW based unit. Lmk if you are interested. You'd be using an a/r in the 1.1 range

I'm sure this could be made with the 80/87 turbine or the smaller 75/83 turbine. Both with 1.10 a/r and T4 flange. This would more than cover the goal and leave a good amount of room for more potential.
AG

 

[bison]

I'm sure this could be made with the 80/87 turbine or the smaller 75/83 turbine. Both with 1.10 a/r and T4 flange. This would more than cover the goal and leave a good amount of room for more potential.
AG

Yes. I agree 100% with those. The 75/83 will may be a better choice for a v6 engine if "only" looking for high 8's. Even the cast 80mm BW stuff is brutal and should be considered.

 

[434nova]

Bison I am pmd you on that turbo.

Posted from the TurboBuick.Com mobile app

 

[bison]

Replied