My 83 chevy truck with TBI conversion from 89 truck runs like s**t! I have the abilty to burn my own chip and have burned many over the last 2 days. I keep getting the same results! The motor "pops" back up thru the intake upon hard accel and wont pull (no power) I have mover the AE tables way up and no change? If I hit the throttle hard to the floor the truck bogs and then as the rpms increae it gets a sudden burst of power then it just fades away??? If I install bigblock injectors what will I need to change as far as the BPW settins go? My stock setting is 135 now with the stock 350 injectors. HELP!.....

 

What is the formula for sizing the injectors? I seen it on this site somewhere... I can't believe that this stock system wont feed my almost stock 350, only mods done is a cam and aluminum intake and the cam is "idle to 5000" pretty mild. I'm guessing HP at 250 to 275. It almost has to be a fuel delivery issue or and injector problem?? Last time I checked my fuel pressure it was 13 psi and thats with a Carter P5001 external pump. Could the pressure be "going away" under load?

 

Injector sizing is here: http://www.rceng.com/technical.aspx

Also calc's the HP goal.

Quote:The motor "pops" back up thru the intake upon hard accel and wont pull (no power) I have mover the AE tables way up and no change?

sounds like a lean condition. Do you have a fuel pressure gauge? If so I would attach on for sure. First test is oen the TB plates engine in neutral and check if pressure drops. I dont recommend but some will duct tape a FP gauge temp to window orlet it sit inside of window with window cracked. have a passanger monitor. A GM Delco TPI pump is preferred. Not a TBI pump.

Can you datalog the duty cycle? I believe Tunerpro RT will allow that. If not there is a patch somewhere here that explains how to add.

Hot does the engine react to a slow accelleration to WOT locking in 2nd gear rather than a hard stab? That way you stay out of AE but end up in PE.

I would suggest increasing fuel pressure to 18-20 and then recalc your BPC. That will add significant fuel.

 

I GOT IT!!! Turns out to not be fuel at all!!! The timing module in the dist. is the problem. I decided to change it based on another message board explaining something about the 3 digit number on the module. I should have a "369" module but I had a "399" I dont know the diffrence but it runs strong and pulls hard now. Got some minor tweeking now but i'm happy!

 

i was just about to say it sounds like not enough timing.

 

If you want to know the why's and how's of the differences in the ignition modules, back up to the sticky's, Tuning Guide Book, Chapter 5, '8746/'8063/'7747 section:

Spark Latency in the Ignition Module

You can also correct/tune the latency table for which ever ignition module you have.

On another note being a little subtle is always helpful. This site is for 3rd gen f-body's, and not being over-bearing about a vehicle that isn't goes a long way. Thanks.

RBob.

 

I'm sorry for posting my truck questions here. I was refered to this site because of the EFI knowledge. I'll keep my truck questions on the other boards and refer here for some great info, Thanks for all the help.