Power Commander Question

[donpearsall]

I turbo-ed my ZX-10r and replaced the existing 330cc injectors with 600cc injectors. I know I will not need the full capacity of the new injectors but decided to try them. The question is how much to tell the Power Commander to decrease flow. I still have yet to start the bike after working on it, but wanted to set the Power Commander before trying to start it rather than risk flooding it. Is it simply a matter of a straight-line reduction? Like decrease the flow 45% across the board? I don't know if injectors work on a linear basis.
Thanks
Don

[hotrod]

Their rate flow rate at constant pressure is linear. If you increase the size of the injectors by x percent they will flow x percent more fuel than the injectors they replaced "at the same fuel pressure".

Fuel flow changes at the square root of the fuel rail pressure change so if you also modify the fuel pressure you will have to make that correction too.

For the same injector pulse width your new 600cc injectors will flow 1.81x the fuel that the old injectors did, once you get engine rpm up a bit.
There is a slight chance that this will not hold at low rpm due to changes in dead time for the injectors.

Once you make the initial correction at idle the new larger injectors will be using very short pulse widths. It takes a finite amount of time for an injector to open once it sees an injection pulse, so if that pulse width at idle is short compared to that dead time for them to respond, they may not have time to fully open up, and you will have to either increase the pulse width at idle or if your injection system has the means make adjustments for the dead time of the newer injectors. That lag in injector opening is called different things by different engine management systems but look through your docs for the Power Commander and see if they mention such a setting.

You might have to go to an injector company like RC engineering to find out the dead time for the new and old injectors if you cannot find it published on the web.

Larry

[RansomT]

I don't think you will be able to pull enough fuel out at idle/low rpm with a Powercommander (most PCs will only go -50%).  What type of Fuel pressure regulator do you have installed? 

[donpearsall]

Thanks for the replies everyone. RansonT, I have installed a Magnafuel rising rate FPR, almost identical to the one that I have on my RCC turbo kit for my Hayabusa.
Don

[RansomT]

Thanks for the replies everyone. RansonT, I have installed a Magnafuel rising rate FPR, almost identical to the one that I have on my RCC turbo kit for my Hayabusa.
Don

If you are referencing vacuum/boost, then you might get it close enough to idle "o.k."

[Jonny Hotnuts]

Should be able to lean the entire map out by decreasing the fuel pressure a bit. Clearly getting the bike on a dyno and having a map done will be paramount.

~JH