I'm trying to switch to E85 and initially was severly maxing out my injectors (83 lb/hr going to 143% dc at 6000rpm). I picked up a set of FMS 1600cc injectors knowing they would be overkill but trying to make them work. I've been able to get them down to pulsewidth of 1.4ms at idle with afr at 8.31 (stoich for e85 is 9.78) or lambda = 0.85. This is with base fuel pressure of 45psi. Any lower pulsewidth and the engine stumbles...maybe they're not eving moving fuel past that point.

My question is how much can I lower the fuel pressure on these injectors and still have decent spray pattern, fuel atomisation, etc...

Is 25psi base pressure too low?

 

Is this with your Megasquirt?

Have you considered raising your idle speed?

 

This is the motor in my Chevelle...I'm using EFILive now, stock GM pcm. I raised the idle speed from 700 to 850 which helped. I'd like to keep it there if possible since it's a street car.

 

I've been down to 34psi with those injectors but, I was idling at 950rpm. I wouldn't go much lower than that. Have you tried adjusting your idle timing to see if it helped? Also verify you are getting full voltage to the injector which will improve it's response time.

 

Just tried that tonight...it took a while to figure out what was causing the spark at idle to go from 19 det to 40 deg which was causing quite a bit of surging. Got that figured out and have the timing static at idle at 28 deg (is this too high? the motor is a basically stock Chevy 6.0L with a mild reverse split cam) . After that I adjusted the VE a little and was able to get it to lean out a bit to between .906-.951 lambda (this is with base fuel pressure at ~32 psi).

I'll have to check the voltage at the injector, thanks for the suggestion. Ever heard of anyone running a dc/dc converter to run the injectors at a higher voltage (16 or 24v maybe)? Would this be a bad idea?

 

I dont think injectors see more than 0.5volts if i remember correctly

 

You still need to shoot for gas O2 readings..

 

Is this assuming I'm looking at a wideband gas readout?

The numbers I posted are converted from the lambda reading using 9.78:1 as stoich for E85. Lambda doens't matter what fuel is being used.

 

Gotcha, just making sure.

 

i have ran a set of 150 frpp injectors on my mod set up and drove on the street for a bit with the old dfi, i had a clean 850 idle, but the cam overlap usually can mess with fueling at idle to i think.