How to achieve fast spool up of turbo

[S4turbo]

All the tuner books I've read that consert NA engines say you move the torque/HP curve towards higher rpm if you shorten the runners orport them too much. I think the main reason is that in order to pack the cylinders with at much air as possible, you need a long, narrow header in order to get high air velocity into the cylinder at low rpm. The air will then continue to fill the cylinder even when the piston has started to move upvards. With high rpm the long, narrow header will be an obstruction, but less so on a turbo charged engine.

This is why they use dual channel headers (is that what its called), where the air takes the long route at low rpm and a longer route at higher rpm.

Hm, maybe such an intake would help on a turbo engine as well? I guess all the high powered Audi V8 engines uses this type of header?

J

trying to think logical
I would say on a TURBO CAR

shorter intake= less volume to pump for the turboto reach target pressure= more air earlier in the cylinder= more exhaust earlier= faster turbo spining with less volume to pump to reach target pressure= more air in the cylinder= more exhaust= etc ...
For me it look like earlier spool up or what?

My 2 cent's thinking. might be wrong. This is only for turbo car.

[maRS2]

Your right for NA engine but i think it does not work for turbo engine look at all rally race car subaru, evo, audi S1 they all have as short as possible route from turbo to intake.

[S4turbo]

One good example of long headers is the IMSA header. So it is not easy to know what is right or wrong. Well, 730 HP doesn't seem very wrong, but I would expect a race engine to be optimized towards high rpm use. So they are willing to sacrefice low end spool up, as the engine never runs in that area. Thus short headers?

Hard to know really.

J

Your right for NA engine but i think it does not work for turbo engine look at all rally race car subaru, evo, audi S1 they all have as short as possible route from turbo to intake.

[maRS2]

IMSA is track and no problem about lag as you know evry turn and know braking and accelerating point's and that's why I gave you example of rally car that need as less lag as possible as it's instictive drive and also they have the intake restriction that don't allow them to have high rpm HP

[maRS2]

Froma what I can see here the imsa car also had short intake
p://www.audistory.24max.de/old1/eimsa.htm

[maRS2]

http://www.audistory.24max.de/old1/eimsa.htm

[CR500Dom]

So why is most of the people say that those reverse inlet make the engine more responsive and give less turbo lag?

Dont confuse runner length with Intake volume

The reverse inlet manifold could have longer runners for better low end torque and faster port velocities, but with a smaller overall intake volume that gives better response everywhere with less lag

You want the smallest possible intake ports and Intake volume, with the longest Primary runner length (For better VE) that will still give you enough flow to make your Top end Target HP

HTH
Dom

[maRS2]

when you say primary runner do you mean the 5 tube going from cylinder to manifold plenum?

[CR500Dom]

when you say primary runner do you mean the 5 tube going from cylinder to manifold plenum?

Yes

[maRS2]

Ok thanks CR500Dom all clear now

[audiman]

Mudcrabs indeed. WTF??

Quick spool up.... Mmmm.... how about buying some sort of anti lag device? Although these generally make cars run at gigher EGTs and can shorten the life span of a turbo/engine. Tubular manifolds dont always give better spool up. But IME, on my car, compared to Doug's with similar setups (CR/Turbo etc etc) the tubular manifold was slightly better for spool up.