Yukonf3
New member
Had a chance to make some runs today with my F3 stock exhaust connected to a digital manometer.
I can tell you unequivocally that the stocker flows really well....up to about 5,500 rpm. Idling - 0 psi, rev at 3k - 0 psi, cruising at 4k in 3rd - 0.2 psi. In fact even at WOT, psi is under 1 until about 5K . Then it starts to choke quite quickly, building to 3.5-3.7 psi near redline.
For street, anything under 2 psi is quite good. So, there is room for improvement on the system.
I then removed the stock secondary muffler and ran the tests again, Interestingly, max psi was 2.2 so it appears the cat flows quite well. So, is the secondary muffler the bottleneck??
I'm going to make a cat delete and run the test again for definitive comparison.
Some conclusions, the stock exhaust flows very well from idle through to 5,500 rpm with negligible restriction. Making an exhaust change after the collector, like a cat delete or two bros slip on is NOT going to effect power in the mid range either plus or minus, from an exhaust flow point of view (pulse timing is another matter). So removing the cat, then adding a baffle to increase back pressure for mid range is not likely going to matter much. What you might be doing is disrupting some poorly timed back pulses, but that's for another post, another time.
There is power to be gained from 5,500 to redline by reducing the overall restriction, assuming the ECU will compensate. (I'm going to run some wideband tests later as well to see how each exhaust config affects the a/f ratio (or not).
More tests to come...
cheers,
I can tell you unequivocally that the stocker flows really well....up to about 5,500 rpm. Idling - 0 psi, rev at 3k - 0 psi, cruising at 4k in 3rd - 0.2 psi. In fact even at WOT, psi is under 1 until about 5K . Then it starts to choke quite quickly, building to 3.5-3.7 psi near redline.
For street, anything under 2 psi is quite good. So, there is room for improvement on the system.
I then removed the stock secondary muffler and ran the tests again, Interestingly, max psi was 2.2 so it appears the cat flows quite well. So, is the secondary muffler the bottleneck??
I'm going to make a cat delete and run the test again for definitive comparison.
Some conclusions, the stock exhaust flows very well from idle through to 5,500 rpm with negligible restriction. Making an exhaust change after the collector, like a cat delete or two bros slip on is NOT going to effect power in the mid range either plus or minus, from an exhaust flow point of view (pulse timing is another matter). So removing the cat, then adding a baffle to increase back pressure for mid range is not likely going to matter much. What you might be doing is disrupting some poorly timed back pulses, but that's for another post, another time.
There is power to be gained from 5,500 to redline by reducing the overall restriction, assuming the ECU will compensate. (I'm going to run some wideband tests later as well to see how each exhaust config affects the a/f ratio (or not).
More tests to come...
cheers,
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