ram tubes, worth getting??

[QikStarlie]

yeh its a bad comparison i know. it definitely effected the peak with the shorter runners, or at least dropped the midrange. ignore the power & torque figures. different boost level and dynos as you say. looking at the curve on torque graph, in the 2nd picture. the first peak is where it comes on boost. then levels then jumps up again. boost was very stable in those runs also. 1st dyno with standard inlet. the torque peaks basicly when it comes on full boost, holds for awhile then tapers off.


the manifold i ended up with was longer than the "short" runner one. but still alot shorter than factory.

[KinLoud]

This is a thought exercise to help understand how intake length might affect power/torque in a turbo engine...


The pulse that travels up and down the intake runner at the speed of sound.

The speed of sound (almost totally) depends on the temperature (with minor changes due to humidity and pressure).

NA engine - intake air temp is fairly constant as the revs rise (ignoring pod filter sucking hot air etc.
So the tuning effect of intake length is constant as the revs change.

Turbo engine - intake air temp will be approx atmospheric (same as NA) at idle and up to boost threshold.

As boost rises the intake air temp will rise due to adiabatic heating (due to increase in pressure) and due to compressor inefficiency.

As the intake air temp increases the pulse will travel faster up and down the intake - giving the same effect as a shorter runner in NA engine.

POSSIBLE RESULT

Short intake runners plus increased speed of sound (speed of pulse up and down intake) might raise the tuned rpm above the max rpm of the engine.
This could
- remove the 'boost' effect of intake tuning and/or
- shorten the effective length of the intake so that the 5th pulse reflection becomes the dominant effect (as per QikStarlie's post) and/or
- make my brain hurt from thinking hard after 11pm

ALSO
Just remembered some investigation/experiments I did on the standard and modified 3sge intakes I used on my old racecar engine.
Look here viewtopic.php?t=57312&highlight=intake
And here http://www.allpar.com/history/memories/bob-scott.html

Ken