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

hi there
dose it make a difference if i use larger injectors say from a 2.0L in my 1.3L engine that is running throttel bodies??? standered injectors from a 1.4 are in at the momment at 38psi fuel pressure. But the duty cycle is maxing out at 116% WICH I WOULD SAY IS TO HIGH, and i can feel it because the car dies at to end of rev range 6000/6500. Have tried some larger injectors out of a 2.0L but the car would not rev at all. Had it on a rolling road for 5hrs yesterday to try and get it to run better with different injectors but wasn't any good at all. The man that was doing the tunning is use to omex ecu's so was ok with tunning as he did it for me a couple of mounths ago, but went and did a rally after tunning and found the problem at top end.
Has anyone got any clues as what i can do??
cheers
Rich

Increasing the fuel pressure with your current injectors should proportionally increase the flow through the injectors as well as having a positive affect on atomization.

Do you have an adjustable fuel pressure regulator?

HI THERE
Thanks for getting back to me about pressure problems. Got my self a adjustable regulator yesterday. Going have ago at fiiting it at the weekend. At the moment the pressure on the stander reg is at 38psi been told by my tunning bloke to put it up to around 45/48 psi and then reduse the ve map by 5%. The reason is that the duty cycle at the momment is far to high at around 116%. Going to put pressure up to try bring it down a bit to around 85%. If you have any more tips or ideas that would be realy good.
cheers
Rich
Running a 1300cc vauxhall engine on throttel bodies at 40mm in diamater.

I think I would start with the adjustable regulator set at 38psi and get it running and go for a test drive. I would then drop your required fuel setting by 5% to 10% at which time you will be running lean. I would then increase your fuel pressure until your AFR at idle is back to where it was. I would guess this would be around 40psi or so. Then I would tune your VE table in the upper RPM range with the new required fuel value and fuel pressure. Tuning the VE table in the upper end should be a pretty small adjustment if any.

I think at 45psi your required fuel will be closer to 15% lower. I like making several small adjustments rather than one big adjustment.

I am no expert here so feel free to ignore my advice and seek a more informed opinion.

Make sure to save your current MegaSquirt config so you can fall back to your present settings if you have trouble.