Turbo Question

[434nova]

Lets say i a have a combination that makes 30#s of boost at 700 hp and 5500 rpm with the turbo being all in and the turbo flows 75#s a min and i switch to a turbo that flows 90#s a min, at the same 30 #s and 5500 rpm will the car make more power or not? Or will i have to run more boost to get more hp and rev it more to more hp from the combination?

 

[forcefed3.8's]

It will make about the same. You might pick up slightly if you were running it out of its range.

 

[Jerryl]

This is a great question of a very complex model, due to all the variables involved.

If the turbo is not the limitation of the system, an excessively large turbo will slow the car down because it will spool slower.

 

[V6sleeper]

In that bracket of power from 70#s min to 75#s min I would opt for a 6266 to take full advantage of spool up, anything more then 75#s a min id jump right over a 64mm and move up to a 67mm.

 

[Nigel]

This is a great question of a very complex model, due to all the variables involved.

If the turbo is not the limitation of the system, an excessively large turbo will slow the car down because it will spool slower.

Complex definitely describes it. I would love to have an engine dyno to set up a buick V6 on and test a bunch of different combinations. I don't think I will ever have that kind of coin.
I am guessing that the biggest change in peak power would come from a turbine that runs at a lower exhaust back pressure so long as the compressor can keep. But as you say, it will spool slower. The game changer would be a turbo that can spool adequately, but that would be able to run at a lower exhaust back pressure than the boost pressure(fantasy as of right now maybe for a practical application). You could then get an undiluted cylinder charge and the turbine would give a net gain in pumping power instead of having pumping losses, truly making the most of the lost exhaust energy. Would also open up new possibilities for cam shaft optimization.

 

[Mr.Spool]

Lets say i a have a combination that makes 30#s of boost at 700 hp and 5500 rpm with the turbo being all in and the turbo flows 75#s a min and i switch to a turbo that flows 90#s a min, at the same 30 #s and 5500 rpm will the car make more power or not? Or will i have to run more boost to get more hp and rev it more to more hp from the combination?

It will be moving the same amount of air at 30psi and 5500 rpm but the 90lb/min turbo will usually take longer to hit 30psi.this is the reason why turbo buicks must leave on power right away and not leave off idle and why the combo must be matched to get the most out of it.