Quote:
Originally Posted by jamesm
Whenever i change the port ratios i just change all 3 tables at once. I've found that always running the minimum amount of port ratio necessary for a given setup will allow for significant gains in terms of knock suppression on pump gas.
I essentially monitor Direct Injection Time Final and/or DI requested volume (the latter of which is only available in an unreleased RaceRom beta, so not much use to most folks). I'll then gradually bring down the PI ratio until i'm ~10-20% under what i consider to be a safe limit (1ml or 6.5ms depending on the param that i have access to).
I used this technique on an NA tune last night and was able to make considerable horsepower up top in the most knock-proned area of the curve. With stock port ratios knock up there was an issue @ ~15-17whp over stock (can't remember the actual timing or AFR values, i'd have to look), and by the time i brought down the port ratio and added a couple other tricks we were at 29whp over stock with no knock in sight.
something to consider trying if you're fighting knock above 6500rpm or so. On an NA car you'll never get close to any limitation, even with 0% port ratio across the board.
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Might be a stupid question, but how do you figure the amount of ignition advance you can add safely besides the absence of knock detected? Or do you have to add advance incrementally until knock or the lack of power increase is detected then pull back timing?