well ive been tuning on my new 350 in my 95 truck since thanksgiving and i finally got an lm-1 wideband. i know i need to set it up in open loop and get my ve table right to my commanded afr. but i wanted to hook it up with what i had to see how far off my tune was. it was pretty bad i think. i set up my lm-1 for a 14.13 lambda since we have 10% ethanol fuel here. i also have commanded afr at 14.13 in the bin. it seemed to cruise at around 13.4 afr average so i guess my o2 wing points are a little high. i can get to that stuff later. when i did a wide open throttle pull from a stop it immediately went to 10.5afr so i must have to much ae. it then jumped up to 11.5 and steadily leaned out to 13.5 at 5000rpm. the pe afr is commanded to 12.5 so i need more fuel up high but my ve tables are at 98% already in the 90 and 100 kpa between 3500 and 6400 rpm. that is what i need to adjust right? soo does this mean the only whay to get it richer at high rpm is to increase fuel pressure? right now im at 19lbs with 65 lb injectors. should i just increase it before i go any farther? thanks

 

yes up the fuel pressure and verify the results. that will allow more room on VE tables < 99.

Did you set the BPC correctly?

you may want to monitor the DC% as well to make sure the injectors are not maxed out. dont be surprized if you need a lot more FP. I would play conservative on the RPMs until you confirm A/F WOT under 13.0/1. when at WOT what are the MAP readings? should be <100.

OK i see now 2.00 TBI so should have MAP under 100 at WOT.

 

well i have a 16197427 ecm with $0D mask so there is no bpc. its just the injector flowrate, which i have set to 85.42lbs/hr. (calculated from 65lb at 11psi to 85.42lb at 19psi) im still not sure if gm referenced the lbs/hr at 11 or 12psi. but for calculations i used 11 which is nominal of the 9-13psi stated in my haynes book. im not sure how much horsepower my engine is capable if but maybe i should just up my fuel pressure to 25lbs. that should support 330hp. which should be safe. what do you think? thanks.

 

The only things to be aware of is the cranking pulsewidth and AE. Those will need to be tweaked as the fuel pressure is increased. Usually you decrease them proportionally to the increase in flowrate. Also, if you make the pressure too high, the pulsewidth will get short enough that the PCM will enter async at all times at idle.

 

Not if you have the sync fuel at idle bit checked it won't. I am idling with .6-.8 msec showing.

 

True... So long as its over 400 usecs, itll still pulse the injectors. I think once its below 400 usecs, the PCM automatically clears out the pulsetime. I remember seeing something like that, so its probably not a bad idea to avoid dipping below 800 usecs if possible. Ive noticed that theres some non-linearity below that with my injectors.

 

ok so i will increase my pressure. maybe my engine is going to make more power than i thought. i wasnt expecting to have to have my pressure that high. thanks.