MicroSquirt.com read only forum (Jan.15,2018)

it megatune you do the calculation for the required fuel.
does everything take its calculations from this ?
as i cant find the exact size of my injectors...its pretty hard

It's pretty important. The relevance of your injector pulse widths and VE map value depend on the correct required fuel. You can use injector test mode to measure the actual delivery of your injectors into a graduated cylinder. This will give you the best information from which to start your tuning.

Or you could guess, to get things running, and tweak from there. I wouldn't expect your injectors to be rated much more than 12 lb/hr.

Req fuel is a single value that directly affects all fuel calculations within MS. If you increase the req fuel value by 8% for example, the amount of fuel injected under all operating conditions will be 8% more. Same if you decrease it.

If you are starting from scratch with a new install, and have no base map to start with, and don't know your injector size, then as you tune you may notice all the values in the VE table are rather low or rather high. If this happens, in Megatune you can rescale the VE table and rescale the req fuel so that the numbers in the VE table are more reasonable. To do this, open up the VE table, click on Tools, VE Specific, Reset ReqFuel. Enter your new required fuel value and tick the box for the "Reset ReqFuel in Constants?" prompt. Then Megatune will automatically set the new reqfuel value in the Injection Control page and rescale your VE table so that the overall fuel delivery remains the same.

So at the end of the day, it is not so important that the req fuel value is theoretically correct, but moreso that the numbers in the VE table aren't ridiculously high (approaching 255) or ridiculously low (where you lose resolution of the pulsewidth). If the req fuel is set to achieve a usable range of values in the VE table, then that is good enough. As usual there is more to it than just that, but thats the basics as I see it.

Ian.

Thanks again Ian
i am having the injectors cleaned and tested...i should have done this in the first place.

regards gary