"vacuum gauge" to balance stacks?

[fkemmerer]

Len,

It your car is running better in Alpha-N mode, then by all means use it. Alpha-N has somewhat less adaptability to changes in barometric pressure and air temperature than a speed density setup would. The other tricky part of tuning with Alpha-N has to do will the large throttle blade area of most stack EFI setups. In many cases, the throttle bodies will reach maximum air flow at only part open settings below 3,000 RPM. This means that your pulse widths will reach their max values at TPS openings of 70-80% in the lower RPM ranges.

What is your camshaft like?

- Fred

[kobrabytes]

Cam 248/252 at 50 and 112 degree lobe separation.

[fkemmerer]

Your CAM is pretty close to what I have in my 482 FE (mine is 242/248 @0.050, 112 degree LSA, Lift is .645/.635in). My setup uses speed density mode and idles nicely at about 800 RPM. I was also at the 60% load point in my map at 800 ROM idle. I did use the timming trim feature to help get a smooth idle and my TWM intake has an IAC installed. Do you remember what your VE table setting was at idle in speed-density mode? Mine is at 26. Also, what is your motor's displacement again?

- Fred

[kobrabytes]

VE at idle was 35.

No IAC on mine...

I'm at 527 CI.

[fkemmerer]

Originally Posted by kobrabytes

VE at idle was 35.

No IAC on mine...

I'm at 527 CI.

Well, I guess if its not broke don't fix it! If you are getting good drivability from Alpha-N mode, leave it alone. If you decide to try speed-density mode again you might try lowering your VE values at idle until you get a reasonably close match between target and actual AFR. I've got mine idling at a target AFR of 14.5 and I'm using a maximum of two degrees of timing trim. With these settings, I am getting a pretty smooth idle at around 800 RPM. It is a good idea to balance your stacks with a gauge (your orignal purpose for this thread). I did this and my idle quality improved quite a bit. Be sure to follow the proceedure that TWM recommends when you do this. It involves unhooking parts of the linkage and adjusting other areas of the linkage to get things right. I think that their website has a .pdf that you can download that explains how to do this. Good luck with the rest of your tune and let me know if you would like any help with that.

- Fred

[kobrabytes]

THanks Fred!

len