Exhaust Length Matching
22nd February 2004
A intake pipe length table was found from Bill Sherwood's car section website under "Engines" then "Intro" next to "Exhaust". A restoration of the graph in the new Excel format looks like: -
The exhaust side of the story is much easier to explain when compared to the previous intake, because this exhaust does not have VVT difference.
Toyota 4A-G 20v AFM exhaust closes at 250 degrees. This is the only criteria or specifications required for using the chart.
The chart is for the use of 4-1 extractors and the values can be taken off for use immediately.
If a 4-2-1 system is required then slight modification of the chart's results are required. They are very simple.
Assuming the optimisation for 4,000 rpm is required and the value from the chart is 8.42 feet which is equal to 2.57 meters.
Divide the number by half and that will be the primary (for a 4 into 2 into 1, it's the 4 part, therefore all 4 cylinder's immediate exhaust port).
As for the 2 part, then divide the number by half again.
In this case the 4-2-1 has 1.29 meters primary and 0.64 meter secondary.
Finally, again the exhaust diameter? as this is associated with port frequency related to port length. So what is the port diameter used / based on the assumption to use the chart correctly?
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