EFI Anyone?

[RallySnake]

TexasDoc,

I tried your suggestion to change to a richer A/F ratio. It was at 13.5 with the new firmware. I dropped it to lower values and ended up at 13 to 1. I played with the idle speed too. It is much better now, but still hunts a little. The important thing is, it doesn't stall anymore! I just re-read your post and I will try the fuel table adjustment next.

Thanks!
RS

[Texasdoc]

If you ran it already with the new afr target, you probably don't need to edit the fuel table. Look at the learn table at the idle cells - how much adjustment is it making?

Boring EFI stuff to follow. Ignore it if you like. Maybe it will help somebody in the future. Took me forever to learn how the EFI system worked.

There is a table (don't remember it's name - let's call it the limits table) that limits how much the system will adjust the learn table to reach the desired AFR. Let's say this limit table is set at 5% in the idle area. Your system will start with the fuel table, read the O2 sensor, then compare that to the AFR table. If the measured AFR is lean, it will add fuel to the learn table. If it is rich, it will subtract fuel - it can even be negative in the learn table. The system always mathematically adds the fuel table to the learn table. If the learn table hits the maximum change listed in the limits table, it won't adjust it any further.

So if your fuel table is at 5, your learn table is at 1 and your limits table is at 25%, the system will increase the learn table to 1.25 in an effort to make it richer.

So, in your case, you adjusted your desired AFR then ran it. You didn't adjust the fuel table so the system likely increased the fuel by increasing the learn table. So unless your learn table is being limited by the limits table, you are okay. Got it?

If it still hunts, play with the afr a bit. Go to 12.5 - see what happens. Try adjusting the timing in the 9 cells of the idle - 9 cell grid - 3x3. Find the one cell that your car mostly idles in. Make the cells with a lower rpm (three on the left) one degree higher than your idle timing and the three on the right 1 degree lower. Try 2 degrees on either side. The faster timing helps the motor speed back up to the desired rpm, the lower timing helps to slow it back down. Find what your motor likes.

[Gaz64]

Originally Posted by Texasdoc

If you ran it already with the new afr target, you probably don't need to edit the fuel table. Look at the learn table at the idle cells - how much adjustment is it making?

Boring EFI stuff to follow. Ignore it if you like. Maybe it will help somebody in the future. Took me forever to learn how the EFI system worked.

There is a table (don't remember it's name - let's call it the limits table) that limits how much the system will adjust the learn table to reach the desired AFR. Let's say this limit table is set at 5% in the idle area. Your system will start with the fuel table, read the O2 sensor, then compare that to the AFR table. If the measured AFR is lean, it will add fuel to the learn table. If it is rich, it will subtract fuel - it can even be negative in the learn table. The system always mathematically adds the fuel table to the learn table. If the learn table hits the maximum change listed in the limits table, it won't adjust it any further.

So if your fuel table is at 5, your learn table is at 1 and your limits table is at 25%, the system will increase the learn table to 1.25 in an effort to make it richer.

So, in your case, you adjusted your desired AFR then ran it. You didn't adjust the fuel table so the system likely increased the fuel by increasing the learn table. So unless your learn table is being limited by the limits table, you are okay. Got it?

If it still hunts, play with the afr a bit. Go to 12.5 - see what happens. Try adjusting the timing in the 9 cells of the idle - 9 cell grid - 3x3. Find the one cell that your car mostly idles in. Make the cells with a lower rpm (three on the left) one degree higher than your idle timing and the three on the right 1 degree lower. Try 2 degrees on either side. The faster timing helps the motor speed back up to the desired rpm, the lower timing helps to slow it back down. Find what your motor likes.

I love reading from others that truly understand what they are talking about.

I use timing in the same manner to control idle speed on one of mine with a carb.

Gary

[fastd]

As a follow up, I just got my Sniper EFI system back from a professional installation; only put about 30 miles on the car but added about 35 hp (also went from 2.5" to 3" exhaust). I didn't have the carb dialed in all the way prior to switch - the engine was recently rebuilt and was still tuning the carb but decided to go with EFI instead.

Man, throttle response and more even power with not flat/rich spots...really please with it so far.

[RallySnake]

I have been making a lot of changes to my system after running the Targa California rally. During the 4 day event, my engine ran progressively worse. I tried everything I could think of with the EFI tuning and got it running OK at low speed. But any major power request was rewarded with spits and barks out the exhausts. While testing the car at home, the system got so bad I had to limp home.

After getting very frustrated and removing all the changes I had made, I finally started looking at my EDIS ignition system. I had a spare EDIS-8 module and switched it out. All the problems were solved! The EDIS module and system has been running great in my car for 4 years. Evidently, the hot weather during the rally and it's proximity to the upper radiator hose pushed it too far. I have protected the new unit with a couple of layers of heat protection and hope this never happens again.

There were also some issues with the throttle cable sticking. I decided to try to improve the leverage by making a small bracket that moved the throttle stud about 3/8" farther above the primary butterfly shaft. I also had to give the accelerator pedal about 1/2" more travel, too. Wow, this really made a difference! The engine is so much more controllable now. I don't think I will bother with the progressive link again.