rssshen vette

I need the advice from those who have an Accel DFI system. I am trying for the first time to tune my 85 Vette. I've made a lot mods to my car with the last mod being an Accel Gen 7 DFI Thruster. There are several dyno performance shop in the Hampton Roads, Va area. Each one I've talked to said they don't have Accel program or they haven't done any tuning with accel programs. So I started on my own. I have no experience in tuning so I need as much help as I can get. CF member 93VettePilot sent me his tune to start as a base and I've made some changes up until this point. It would be a great help if someone that has knowledge of tuning this system could take a look at my progress and advise me of. I have driven the car, but it not running as it should. I've been working on the startup and idle and I think I've gotten that under control. It's the drive ability I need to get a handle on.

Accel programs will not load up on photobucket. So I'm not able to attach it in my post. I would send by email to view. Thank in advance!

oldalaskaman

scan and tune section would be a better place to post this

rssshen vette

Posted there too... I got no response so I'm trying the tech/performance section.

DVNCI

Not familiar with the Accel product but for the most part all the systems are essentially the same.

I assume you are running a MAF? If so, you need to get the MAF calibration right first. You should see several MAF tables referencing "airflow" or maybe "frequency" or something like that.

Those tables simply tell the computer that for a given MAF voltage/frequency there is a given airflow. With mods that changes. I would hold the car at a steady speed AND RPM for an extended period - is it adding or subtracting fuel? You can make a global across the board change and probably be in good shape on the MAF tables.

That will get you 75% of the way there for drivability, but to get it truly dead nuts you'll need to adjust the MAP tables, they will probably be listed as VE or Volumetric Efficiency. To get these in shape, disconnect the MAF and the car should now run in speed density mode (at least I think the Accel should do that - the GM's do). Hold the car at 1K RPM, adjust VE across the board for the 1K RPM. Now hold at 1.5K RPM and adjust for that specific RPM. Then do 2K, 2.5K, and 3K. After 3K it's less important to adjust VE.

For a GREAT book on this see "Engine Management Advanced Tuning" by Greg Banish. He does a nice job of making it all understandable.

383vett

The Accel gen 7 is a speed density engine management system and shouldn't need a maf. It is a pretty complicated system. I have a buddy that has flown to Texas and somewhere else to take the hands on training course given by Accel. He is still fine tuning his Callaway TT.

rssshen vette

Accel DFI does not use a MAF. It's a speed density system. So far I've figured out the easy stuff like how to adjust the fuel start, fuel afterstart, and Idling. I've made a few changes in the VE table but I'm not sure if I'm headed in the right direction. It's a pain in the @$$ not knowing. RUKWRK and 383VETTE Thanks for your response.
RUKWRK I see you spend some time at the track in Bowling Green? I'm retiring from the military and moving back to Clarksville, Tn this April. I plan on getting back out to the the track a few times this year.

DVNCI

Yep, I live in BG, was actually gonna mention if you happen to be in Clarksville anytime soon bring the car by and I could take a look.

Since it sounds like you only have to worry about VE, just start with 1K, 1.5K, 2K, 2.5K, and 3K

So for each RPM, try to drive around a bit and hold the RPM steady as much as you can. With a scanner (or maybe it's built into Accel not sure) you should be able to log how far off you are from stoichiometric.

rssshen vette

Thanks for the info. I'll look you up when I return to Clarksville. I'm really looking forward to getting back to BG. I haven't had my Vette on the track for 2 years.

93VettePilot

The timing tables and VE tables are the most important. The start tables are pretty advanced stuff that usually can be left alone. Do you have the wideband on yours? If so the Calmap software has a feature to tune VE cells at the push of a button. Also you can use the wideband corrections to bring the AFR back to the desired. Another table that helps driveability is fuel injector timing tables. Adjust these tables at idle to get the lowest Map and it means that the engine is basically running better so the IAC closes to maintain RPM. Watch your map to determine what the best timing is too.