open loop maf tuning
 

I'm redoing a tune for my buddy's truck. It's a 99 4.8 whipple charged on 8lbs, Walbro 255, and 42 pound injectors. The truck still has a 1bar map sensor. So, since a speed density tune is out of the question. The proper way to tune it with the 1 bar map seems to be with the maf.

I have put the truck in MAF ONLY mode by disabling dynamic airflow at 1rpm and re enabling it at 2rpm. The problem is on my MAF error config, in my scanner, I am getting big afr swings per cell.

For example, In the cell 3000hz, I will be getting the average count close to 0, but the min and max will be -20 and +20 respectively. It goes very rich on decel and lean on acceleration.

Does, anyone have any suggestions to what the problem might be? I have dfco, cot, and ltfts turned off. I am also forcing open loop via the scanner. I've used my config on other trucks and never seen swings like this, so that rules out the config being wrong.

Also, does this sound like an injector problem to you? I haven't check the injector settings yet, because I haven't got a chance to look at the P/N on the injectors. I have adjusted the injector flow rate.

This is a 99 truck with the vaccum fuel pressure regulator. Should injector flow rate be flatlined? Ive tried it both ways.

Sorry for the novel.

I dont know if you just typed it wrong but to disable the VE table you would actually set disable at 2 and re-enable at 1

Just checked the tune and I had it correct. The disable was set to 2rpm and the enable at 1. Sorry I wrote it backwards.

Rich on decel might be throttle cracker. Lean on acell sound like transient fueling. Does it just spike lean for a few frames?

Im pretty sure it drives lean and doesn't just spike. Im going to check throttle cracker specs. Would a log help?

Throttle cracker and transient fueling were stock. Do they need to be adjusted for a stock cam?

Can you post the tune / scan and config?

Problem with the injectors themselves? No. Problem with the injector data in the tune for the injectors which are being used? Very possible.

I also included a stock tune file. This is a working tune so don't pay attention to the timing table or the ve table yet. It looks as if the injector data was changed from stock. I'm redoing it. Someone else originally did this tune.:popcorn2:

Your IFR should be the same across the board. I would start by making sure all the injector data is correct