Defined Autoworks Header Install!

[NoDOHC]

Here are a few waveforms with open headers.

The time scale is listed on the bottom, the pressure scale is 3 psi/division.

This is what the exhaust pressure looks like at Idle (1000 rpm due to e-fan):


Revving from 3000 - 5000 rpm, WOT:


Revving from 5000 - 6000 rpm, 40% Throttle


Revving from 7000 - 9000 rpm, 50% Throttle:


Bouncing off the rev limiter (10000 rpm):


No wonder rotaries are loud! A piston engine exhaust output looks much more like a sine wave, this looks like a triangle wave (more high frequency components). The blowdown (pressure remaining in the chamber when the port opens) is ridiculous. This is probably due to the early exhaust port opening (75 degrees BBDC).

It is easy to see the dip in the pressure that is caused by the header scavenging. This dip moves relative to the wave due to the wave frequency changing and the header length not changing.

By looking at this data, it appears that the headers would produce optimal tuning about 7,000 rpm (we want a minimum pressure on the exhaust port as it closes - negative pressure is not indicated my my transducers).