optimum inlet length - cammed / itb gti6

[jammapic]

OK, so backtrack a tad...

I talked about using staggered trumpets to move harmonics in the torque curve, and make for a smoother power band and more area under the curve.

But, they say the proof of the pudding is in the eating, so here it is.



Here, you can see two dyno plots overlaid. The one which makes peak power at slightly higher RPM is with the shorter trumpets, and the one with power at lower RPM are the longer trumpets.

You can see the shape of the curves are identical, but higher and lower RPM peak power. This is normal for longer and shorter trumpets. This is the key here.

When we have two of the trumpets long, and two short, we effectly find a "middle ground" in the curves. This is helpful as we fill the troughs with power, but we do also lose our peaks - hence the peak power is marginally lower.

What's important though, is area under the curve. Clearly, the more the better, and by filling the troughs we make the car smoother and more drivable.

Below is the outcome of the staggered trumpets:



We actually did find a little more power with some more ignition advance and leaning the mixture out a touch, but the shape of the graph remained largely the same.