If you have a look at the power curves quoted by extractor manufacturer, you will see a power gain higher in the rev range but they don't
usually show results below about 2500-3000 rpm because there is a usually a loss in power.
Extractors have less back pressure and move the power band of the engine further up the rev range, which is good for people who
drive on the redline but not so good for people who drive around between 1500-3000rpm.
This is a very complex subject but do a google search on "exhaust back pressure" and you will get a lot of info.
As for the higher fuel use I am guessing that the extractors created a leaner fuel mixture and the computer compensated for this and increased the amount of fuel injected.
usually show results below about 2500-3000 rpm because there is a usually a loss in power.
Extractors have less back pressure and move the power band of the engine further up the rev range, which is good for people who
drive on the redline but not so good for people who drive around between 1500-3000rpm.
This is a very complex subject but do a google search on "exhaust back pressure" and you will get a lot of info.
As for the higher fuel use I am guessing that the extractors created a leaner fuel mixture and the computer compensated for this and increased the amount of fuel injected.
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