Rb20det Plenum

[B0oStEr]

I'm planning to build either an RB25 or 30 using the R32 RB25DE head.

If I bolt my RB20DET plenum to the RB25DE runners at what power level will it become restrictive enough for it to be worth changing to an aftermarket manifold?

[r33_racer]

I think normally 400+ before you need to change it. But then again i dont know if that particular manifold is suited for a 3 litre engine... But im pretty sure the general rule of thumb is a minimum of 1.5-2 times engine capacity for plenum capacity.

[Turbine]

It's probably not a matter of it being restrictive, but more a question of if it will distribute the air evenly to all cylinders.

<_<

Use the standard RB20 plenum but modify it internally for that effect.

Turbine

[TTT]

Sydney Kid has said many times that the standard RB20det plenum and runners are good for about 450 engine HP.

he has also said MANY times that the standard equipment DOES disribute the air MORE evenly to each cylinder in comparison to many Aftermarket items.

when you use the RB25de head, us the bottom half of the RB25de runners and use the RB20det upper runners and plenum.

Cheers