Trumpet Runner Length Vs Torque Curve

[slow_r31]

as per topic does anyone have any information (calculations or rules of thumb would be great) for trumpet/runner length in a individual runner/tb setup on a naturally aspired motor

thanks

james

[NA_R33]

Also the radius or curves of the trumpets effects it aswell. Ive got it all in a notebook at home, dont know if there is any specific calculations as every engine varies but there are rules of thumbs, just cant remember them off hand.. Best way to do it is to make up some sliding trumpets and vary the lengths whil its on the dyno...

[rob82]

Tuned length runners - ahhh. Just serch helmholtz resonance - this is the thoery behind timing the intake pulses to the opening of the valve. Very cool. Mercedes did alot of testing back in the early eighties and actually created a motor over 100% volumetric efficiency.

[BigDatto]

General rule of thumb:

Short trumpet, good for power (like tuned length header)

Long trumpet, good for torque (like interference header)

Those in the pr0n industry would disagree...

I tried a bunch of different bellmouths on twin webers on a high comp L series motor some time ago. The overall spread of power & torque didn't really differ that much, just moved up or down the RPM range.

that's been my real world experience anyways.

Have fun.