rennmax

I did a search but couldn't find any reason why you wouldn't leave the resonance flap open all the time.

Or would you lose torque if the flap was open under 5000rpm?
Thanks.

DaveK

I suspect that if this was beneficial, Porsche would have done it.

springer3

The theory is that the inlet pipes act like organ pipes, and have regions of lower and higher pressure in standing waves. The location of the high pressure and low pressure areas change with frequency (engine speed). Any combustion engine is an air pump in one form or another. In a piston engine, it takes energy to pull the air in, and energy to compress it. The goal, of course, is to have a high pressure point right at the location if the intake valve. Two beneficial things happen: 1) you get more air into the cylinder, so in this case you make more power in the lower RPM band, and; 2) the engine does less work pulling in the intake charge, and therefore fuel economy improves slightly.

On the practical side, any engine change means your DME map will be off because the engine is not configured as designed. Driveability and emissions could suffer. It would be an interesting experiment, but I doubt it would be a successful one.

NineMeister

With a standard or RS engine, the ideal resonance flap opening speed occurs at approximately 5600rpm, i.e. about half way between peak torque at 5000rpm and peak power at 6100rpm. The opening speed represents the intersection point on the graph of the flap closed torque curve and the flap open torque curve, effectively giving the engine the best overall torque performance. By inference, if you leave the flap permanently open you will lose torque below 5600rpm, if you leave it closed you will lose power above 5600rpm.

Unfortunately I do not have a complete flap closed/flap open run to show you, but here is an example of a full flap closed graph against the next run with the flap opened at 5600rpm. The engine is a modified 964 engine on cams & Motec, so although the power is more than you will get with a standard 964 engine, the result for the standard engine would follow an identical trend. I hope this helps.