Accel Gen VII tuning
I've been "playing" with the Accel Gen VII on my 427 small block chevy for most of 2 years now. I had the earlier version on a 502 in my 67 Vette and was VERY unhappy with it - but the Gen VII is actually very tunable and I think "easier" than "we" make it out to be. Really -- this is little different than tuning a carb and curving a distributor. The motor parameters are put in - knowing your cam and head facts are critical here... and the Gen VII will build a VE table for you... which you can then fine tune. I frankly had the most trouble building a proper A:F table! You talk to one guy and he tells you idle should be around 14.7:1 -- so you try to tune this ala a "new" car (which run these very lean AF's) and find the thing just won't run ----- so like most tuning --- you resort to what the motor wants. My 427 - Canfield headed - Comp Cams 288 wants a really FAT idle AF... and then I adjust the VE to read (taking the O2 sensor off line) the programed AF... The Accel Gen VII with a wide band O2 sensor also has an "auto calc" button.... so I have a buddy drive -- and I tune various areas using the auto calc and then smooth the areas around these cells. When I see very little O2 "input" - i.e., when the O2 is adding or subtracting less than about 2 or 3% then this is "good"....
Tuning the "curve" is also pretty straight forward -- starting at 18 degrees intial -- you can then add timing up to your total timing baselines... My car runs best at idle with 20 degrees (900 RPM - low vacuum signal) - rising very quickly to total 36.... during the drive and tune session -- I work on the high vacuum light throttle cells -- going lean as much as 15:1 and 45 degrees timing... not much different than a distributor with vacuum advance....
Trust me -- I've tried real hard to make tuning this thing hard -- and finally after all this time -- have realized I made it overly complicated -- and changed too many parameters too soon.... when it really comes down to AF (jetting) and timing (curving the distributor) - the rest of the stuff is selectable for fans - AC - idle air control (I plug the air port on the TB and set the idle so that the IAC motor is doing basically nothing at idle).... and then you just have to remember that for every "CHANGE" you have to reset the TPS (throttle position sensor) as this piece works on voltage readings for a linear throttle response. When you raise or lower the set screws on the linkage - you've changed the voltage reading at the TPS... and the computer has to be told to reset... THOSE are the learning curve issues that take time to get --- and ALSO remembering to SAVE the program to a file! Keeping your "old" one so if you mess it up - you just reload and start over....
I AGREE WITH ACCEL TECH SUPPORT --- SAYING THEY SUCK IS A MAJOR UNDERSTATEMENT... they're non-existant. You buy ACCEL -- you're on your own! But there's plenty of people out there that can help. All in all -- it's fun tuning this way.
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