What is the smallest pulse width an injector can due I have a base pulse width of 68 and the blms are still rich in the idle zones to the tune of 117 or so I have a 305 with heads exhaust and an open element with a raised injector pod on the tbi. I am using orange/black injectors from a 350 at 13.5 psi according to the gauge. I currently have the blm in the 400 rpm 30 map at 5. that does not seem right especially when the surrounding cells are in the 20s.

Please help??
Thanks to all John

 

The minimum async pulse width on the L03 was 686.65 usec (with the 55 lb injectors). It enters aysnc mode at 839.25 usec. I don't know why GM used those numbers and I've never had a car run in that region (that I'm aware of), but it might give you some insight ...I assume your 61 lb injectors would have very similar limitations to the 55 lbers.

Why is your base pulse width so low? It should be 135 on a 350. I had 90 lb injectors on a stock L03 and it ran fine with a base pulse with of 81.

 

The BPWC at 13.5 PSI with 61 lb/hr injectors on a 350 gives a BPWC of 111 (I'd round to 110)

 

So what's the stock fuel pressure for the 135 BPWC? Around 9 psi?

 

And that is the 64 thousand dollar question. The service pressure for TBI's is 9 to 13 psi. I really wish I knew what pressure Rochester rates the injectors at. I usually use 11 or sometimes 11.5 psi, as it is the median.

RBob.

 

The ORG/BLK injectors take about 600 usec to open & close with a dribble of fuel (please don't quote that number as exact, it is a ball park figure from memory).

For the base pulse width of 68. Is that your BPC value? Or is it the PW value from the patched ALDL stream? If from the ALDL stream that is about 1.04 msec PW. Then add in the bias (397 usec?) for 1.4 msec PW.

Have you disabled CCP and EGR while tuning?

RBob.

 

to clear up i have a 305 using 61 pound injectors the bpc is 68 and still shows rich
I have done the calculations for a 305 with 13 psi the bpc should be 110 could i have a leaky injector??? how can i check?/?

 

To check for leaky injectors jumper the fuel pump on, engine off. Check for dripping. If there is dripping most of the time it is the injector O-rings leaking.

RBob.