trying to get these things to even idle in my car!! i have the OBDI conversion so im running tuner cats. the equation i found online was the square root of my current fuel pressure which is 65lbs divided by the tested fuel pressure of the injector which is 43.5 multiplied by the size of injectors im running which is 80lbs. i plugged this number in and the car runs pig rich. the car goes tuesday to finish the tune and i want to beable to drive the car on the trailor and off it and onto the dyno. can anyone help?

 

Did you turn the minimum pulse width (in ECM Constants) down from the stock settings of 1.4mS?

 

Calculations never worked for me, just keep increasing the the injector size setting until it runs good, this will lean it out.

 

Did you get 1.222 X 80 #/Hr = 97.8 #/Hr?

 

we ended up increasing the number 5 at a time till the car would idle. its idleing high right now but i can get it on the trailor like this and then pull it on the dyno for the tuner to mess with it but the number i originaly had was like 119 wish was waaayyy to big and that was using the formula. i didnt change my injector ppulsewidth, didnt think i had too. the car had 50# injectors in it originaly... the setting for that was 19.99

 

If you came up with 119 using the formula, you didn't use it correctly. The number should have been 97.8. Appears you simply divided the new pressure by the old pressure, and forgot to take the square root of the result.

(65 / 43.5)^0.5 X 80 = (1.494)^0.5 X 80 = 1.222 X 80 = 97.8 #/HR

 

Injuneer is talking about the "Minimum Pulse Width", this is the absolute minimum the PCM will pulse the injectors regardless of what it says it is pulsing, used for things like idleing and decel.

With the stock number which is around 1.4 the large injectors flow way too much fuel at idle and decel, and if your in closed loop the PCM trys to keep pulling fuel but it cant, though the injector pulse setting in Datamaster for example will show it's under 1.0 but it's really not, and makes for really nasty adverse effects when tryihg to tune around this.

Do everyone a favor right now and move your "minimum pulswidth" to around 1.0 or even 1.1 before the tuner takes over, or make sure he does it with you there to watch. If the car doesnt run after changing this then play with the Injector Size again cause tuning needs to be done with this set to 1.0 or slightly above.

This has been proven to be a problem time and time again, you have to do it with those injectors, the displayed pulse width is exactly that, just displayed, not actual.

 

I could have sworn that was me!

 

Thank god we're all on the same team... hahah. Sorry man