Dialcaliper
Well-known member
I've been pondering designing an intake recently, and I'm wondering about intake runner length in relation to turbocharger spool. It seems like from a low rpm start that long runners that would produce higher intake velocities and resonance for more low end torque would also cause the turbo to spool faster?
But what happens to your throttle response when you shift and the engine stays above the usual spoolup RPM? Which design would allow the turbo to restore boost pressure faster, or does only the plenum size matter? I'm thinking of this also in the context of a dual runner intake (like the cyclone).
Could anyone who's using a cyclone manifold comment on whether the actuator works off pressure, vacuum or both? I guess the question being, when you shift and the BOV actuates, do the butterflies snap shut even above the threshold rpm until boost is restored?
I guess the real main question is, could you design a dual runner intake that is actuated solely off boost pressure, that wouldn't hurt throttle response after shifting? I'm thinking that you could design smaller short runners that are tuned right around the bottom of your turbo's spool rpm range, and once the manifold reaches near full boost, a wastegate actuator to open butterfly valves (I'd probably get 4 small throttle bodies to use, maybe from a motorcycle engine, and design an actuator that uses something like bicycle brake cables to open all four at the same time)
The problem in this case is that until manifold pressure is restored, you'd only have the short runners functioning.
Your short runners in this case would be sized pretty short for top end power, and the combined frequency would be somewhere in the mid-high range. I'm also thinking that the long runners could join the short runners closer to the butterflies instead of at the head to minimize the extra volume you have to backfill, and also allow slightly larger short runners.
Anyway, and opinions? One of the references I was looking at is this Penn state FormulaSAE design that's kind of interesting.
Penn
But what happens to your throttle response when you shift and the engine stays above the usual spoolup RPM? Which design would allow the turbo to restore boost pressure faster, or does only the plenum size matter? I'm thinking of this also in the context of a dual runner intake (like the cyclone).
Could anyone who's using a cyclone manifold comment on whether the actuator works off pressure, vacuum or both? I guess the question being, when you shift and the BOV actuates, do the butterflies snap shut even above the threshold rpm until boost is restored?
I guess the real main question is, could you design a dual runner intake that is actuated solely off boost pressure, that wouldn't hurt throttle response after shifting? I'm thinking that you could design smaller short runners that are tuned right around the bottom of your turbo's spool rpm range, and once the manifold reaches near full boost, a wastegate actuator to open butterfly valves (I'd probably get 4 small throttle bodies to use, maybe from a motorcycle engine, and design an actuator that uses something like bicycle brake cables to open all four at the same time)
The problem in this case is that until manifold pressure is restored, you'd only have the short runners functioning.
Your short runners in this case would be sized pretty short for top end power, and the combined frequency would be somewhere in the mid-high range. I'm also thinking that the long runners could join the short runners closer to the butterflies instead of at the head to minimize the extra volume you have to backfill, and also allow slightly larger short runners.
Anyway, and opinions? One of the references I was looking at is this Penn state FormulaSAE design that's kind of interesting.
Penn
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