I have a weird lean condition when I let off the throttle in my truck and start to decelerate. I'm running speed density in open loop and dfco is turned off for tuning purposes. The only way I can keep it from surging with the throttle closed is to jack up the ve numbers in the low map area below 25kpa to add a bunch of fuel to get it back to 14.7afr. Everything else with my tune has worked fine for two years now but I know that something isn't right with low map area being set to 120% ve when 30kpa and up is normal. Anybody got any ideas? Could be in the tune or mechanical? I have went over everything in the tune a hundred times and can't find anything unusual.

 

Sounds like a transient fueling (dynamics) problem to me, do you use HP Tuners or EFI Live, post up your tune when you get a chance... It sounds like you need to increase the 20-40kpa column(efilive)/row(hptuners) on the Impact factor and Evaporative time tables.

 

I'm using EfiLive. I'm not sure how to load a tune on here but here's a shot.

 

BTW does this tune go with the truck in your sig? The reason i ask is your VE table is really high and IMO the reason for that is your injectors are not setup for 60lb and your engine size is also wrong... Both of those are well overstating your VE table, which is probably causing some of your fueling issues...


Besides that i made the changes to your transient fueling tables.

 

your tune is set up for a 5.3L. Check out B104. Your cylinder volume is only 666 cc. The correct cylinder volume for a 6.0L is 746cc's

 

I'm seriously baffled you didn't blow that thing up with it expecting a cylinder volume of only 666 cc's. I'm assuming you just swapped in a 6.0 and forgot to retune for it?? Once you correct that cylinder volume I think you'll be set.

 

Honestly I just noticed the cylinder volume last night and I did miss that. The funny thing is that the 6.0L has been in for over a year and running high boost with no problems on that setting. I think your right on the ve being over stated because of the cylinder size being wrong but it has never caused any issues. The settings I have in for the 60's are what I have seen everyone using for the motrons which flow 72lbs at our fuel pressure. I'm going to change the cylinder size and retune to see if that gets rid of the decel problem.

I couldn't find the tables you listed above. Do you have the numbers for them?

 

B0104 sorry

 

I found that one. I was looking for the other ones you listed "Impact factor and Evaporative time". Thanks

 

That was black GMC.

I wouldnt worry about all that.

Your issue is the wrong engine size. I predict it will solve your problem.