I have a 93 truck with a 8625 ECM. I have gotten my truck to run decent with the wrong injector flow rate with the $E6 and $0D mask using the wrong injector flow rate. However, when I try to set the correct flow rate of 110 lbs/hr in both the E6 Mask and 0D I then have to make my VE tables muh more rich. So rich that I quickly max out the table at 99.6. I do not understand why I would need to add fuel for a higher BPC as I would expect to need less.

I have gotten the vehicle to run decent with 61 lbs/hr in closed loop, but would like to start open loop tuning and would like my AFR tables to be closer. I have confirmed that the hex values are changing in the bin at the specified location. I thought at this point in tuning that I would finally be able to figure out step 1. Please advise.

 

The injector flowate is not a BPC like the older TBI ECMs. It is in grams/sec per injector. Higher gram/sec injector flowrate = shorter pulsewidth because a larger injector delivers a greater mass of fuel per second. The raw hex value in the cal is (grams/sec injector flowrate x 819.2).

 

So is there any recommended strategy for changing this with larger flow rates? I really would like to get my open loop afrs closer to the commanded afrs, as well as not having the o2 swings be so drastic.

 

Yes, upping the injector flow rate in the BIN will lean it out.

Are you sure your 110lbs/hr is accurate? I wouldn't think your VE should be over 100 with an accurate flow rate specified.

Where did you find the Commanded AFR in $0D? I did not see it when I looked.

 

Well im running 454 injectors at 20psi so it should be close. Any time I emter a value of greater than 100 in the ve table after I save the bin those values end uo being 99.6. I am referring to the tables for afr vs pe vs rpm. I also believe there is an open loop afr table in $0d but would need to confirm that when i am at my tuning pc.

 

There are two main parameters for the AFR in the $0D for normal operation. The first is the stoich AFR for the fuel in use, which is a constant used in closed loop. The next is the open loop AFR table, which is only used when in open loop and no PE. There is an option to use it in closed loop as well, but I wouldnt recommend it as you can end up commanding something other than stoich, which will be fought by the closed loop fueling.

There are also other things such as choke and initial enrichment as well, but those only really come in on startup.

 

Care to elaborate on the choke/initial enrichment? My truck would not start last night in the cold because it was flooding out during cranking.

I have more details in my post:
https://www.thirdgen.org/forums/diy-...ortec-tbi.html

Thanks.

 

The only thing that I needed to change for start-up was crank bpw vs temp. I reduced this by multiplying the table value X*(old injector flow/new injector flow)=new table value. With mine that was the only adjustment needed, but you may need to dial it in as needed.

Note: Injector flow is not entirely accurate when you take into account changing injector offset. We really want to know how much fuel we have added for a given BPW duration with both these parameters, but this worked well for me.

 

I was able to solve my issues by using the same injector offset as RBob here: https://www.thirdgen.org/forums/di...or-offset.html. This did give me enough fuel in demanding areas with the VE table, however at Idle I was rich and hitting the minimum Sync BPW allowed. I tried decreasing this value and even at .20 bpw it was still rich. Looking at my duty cycle though I was only at 20% during high demand times.

I then decreased my fuel pressure to 15 psi from 20 and adjusted the injector flow and offset and she seems to be really happy. I think that I am pretty darn close to having my fueling 100% on point now.

 

Link doesn't work.

I'd like to look at the offset and maybe that would help me out. Seems logical that if I need to remove a fair amount of fuel at idle/low rpm and add at a higher rpm the offset could be coming in to play.

And I will modify that table and see if she's better at cold temps too. Thanks.