I finally got my tuning eguipment and chip burner! Now I have by bpc set and timing set in the chip. Runs better but I still have a lean pop on tip accell. I havent go a laptop yet to datalog but what would cause this. Do I need to set up my ve table a bit?? Or would it have more to do with timing? its just of idle or when im in a high gear going slow and want to accellerate a little. Its a 350/8.5 compression/461 heads comp xe256cam/ 18psi fuel pressure/headers/full 3"eshaust/ and 461 heads with Air-gap manifold. Ultimate tbi mods as well. Any help on this until I can datalog would be greatly appreciated.

 

This is an AE issue. On tip-in, you need more fuel to cover for fuel settling out on the manifold walls, coming out of suspention, extra air coming into the manifold on throttle opening, and just more for acceleration. That airgap manifold really complicates things as well. The AE requirements are all over the place with a manifold like that. The wall temperature varies alot and the internal volume demands alot of extra fuel when the manifold plenum is cold. I have alot of experience with those, and the AE corrections require one to take the manifold temperature into account as well as the engine temp and IAT for manifold filling, which means more complicated control algorithms. They make the AE operation transparent, but theyre time consuming to calibrate.

Overall, cold the airgaps need LOTS of fuel, but not very much when its hot. Might almost be better off getting a stock q-jet manifold. Wont flow as much, but itll make life easier as you wont be constantly chasing lean and rich tip-in issues. On top of this, the smaller manifold will have better velocity, which will avoid potential issues at low speeds. Also, the more constant the manifold temp is, the easier itll be to tune.

 

In a stock $8D setup, the intake manifold temperature sensor is somewhat insulated from the intake air, thus the sensor temperature is somewhat controlled by the intake manifold itself. And of course there are a few tables dealing with AE vs. manifold temp.

Does the TBI stuff have anything similiar? If the air gap manifold design does have these more radical temperature swings and varying AE requirements based on the metal temp, then perhaps a sensor to measure manifold temp may be of use.

 

My 7747 ecm does not have any application for a Iat sensor. I think that the newer ecm do and I may convert to one in the near future. But I really think that I will be going with the EBL setup and work things out from there!! I have gotten rid of the lean spike almost in just 10chips. But it is still there if I really hit it hard from 1/4 to 3/4 or more throttle. Oh well. Time to spend more $ I guess LOL

 

what i did with the 7747 was to start lean then add TPS-AE until rich(gurgle) then back off on TPS-AE. from there play with the TPS filter coefficient to see if that helps. If you provide most of the AE TPS in a short duration(all at once) and it helps, you may need to add more AE TPS to account for the lack of duration you took out. Also the PE can be brought in sooner to add enrichment right after the AE times out. I think mine times outand at 50% TPS it blends nicely. At 70%TPSPE there is a noticable(WB) gap in log.

you may see differing results on a warm intake verses a hot intake. I have access to a temp meter so to speak and i may check my manifold tepms over a 20 minute drive. seems my cool OL operation(155 F) AE is better than when I have a fully warmed heat soaked intake(200F). I hooked up IAT but after 30 days I found out new IAT sensor was defective. the new one in box awaiting install.

 

Thats great info, thanks again Ronny!!! I will try that out in my next couple chips and see what happens. I think that will work with the pe in sooner because right now it seems pretty good and then has a short lag. Thanks for helping out a newb!!