Any suggestions on removing fuel at idle ?

Do I jsut got into the VE tables and start slashing values in the 400-1200 rpm range ? Someone also mentioned raising the injector rating to lower the pulse width?

THoughts?

THanks
Jon

 

Remember that if you change the injector constant, it affects all rpm's...not just idle. Is the car rich everywhere?
If you're just trying to take some fuel out at idle, then take 5% out of the VE tables at idle rpm/map and watch the blm's. See what affect it has.

 

Why remove fuel at idle? If your running a big cam (lots of overlap) I would just run an open loop idle, in my 94 PCM it will let me run open loop to 1200 RPM which is about right, and thats what I did.

Then I just ran it on the dyno to get my baseline to see how close my setup was (gutted MAF caused problems), and it was fairly close to what my open loop tables said.

 

Only problem with trying to go open loop on a DA3 is that it doesn't have an open loop AFRx10 table like a mass air car would have....and I have no idea how to do it at all for the DA3.
The only open loop tables that it has are:
Open Loop % Change To Fuel/Air Ratio Vs. Coolant Temp and
Open Loop % Change To Fuel/Air Ratio Vs. MAP

and values are input in the same manner they are for PE in a mass air car.
I don't know if the values for these tables would still be based off of the VE tables or what.

Anyone know how to do a open loop for a 93?
I'd love to know!

 

If you want to run open loop all the time then go in to ECM constants and max out "Min Coolant Temp for Closed Loop" and Min Coolant Temp for Closed Loop, Cold MAT".

Although I havent tried it yet I "think" the VE tables work for our cars even in open loop so you may want to try adjustments there first.

If you want to try just running open loop at idle then do this:

1. Pull up "TPS threshold Vs. RPM for Power Enrich mode"
2. Take all the values under 1200 rpm and set them to 0.0

Now the car will run in PE mode at idle or anytime TPS = 0% and RPM < 1200. Since the ECM doesnt try to adjust the A/F ratio in PE mode you can use now the PE table to adjust fuel at idle. This is called "PE Idle" by some.

That said I tried it back when I was having problems and it gave me a weird surging problem at low RPM's (although I think my ECM is fubared so you may have better luck).

I feel your pain though, I went though all kinds of crap to get my car to run right and all I have is a stock motor with longtubes! I got so tired of my car running aweful in closed loop I went to open loop 24/7 and I've been happy ever since

Good Luck!

 

Hey Jason,
How did you tune your car in open loop?
Did you do it all on dyno w/ a wideband or just by driving it quite a bit?
Here's a dumb question....what exactly do the O2's and blm's do in an open loop program? Can you still use them in the same fashion you would a closed loop program?

 

Well shucks.

For open loop WIDEBAND all the way, no ifs about that one. I ran open loop, and just verified my AFR table against what the wideband said, and they were very close (I had 110% MAF fields due to gutted MAF, and thankfully that was about right).

 

Yeah...but like I said, the DA3 computer doesn't have that AFR open loop table. That would make things quite a bit easier.
homer voice/ "stupid 93 computer!"
Hopefully it still uses the VE tables to get it's pulsewidth for the injectors and then uses the other 2 open loop tables to further modify the pulsewidth.

Hey Dr. Mudge....I'd like to see your open loop file, if you wouldn't mind. I still should be able to learn something about open loop...and probably programming in general.

Thanks!

 

Dan:

Hate to say this but I havent really done any real tuning since going to open loop. The only thing I've changed is I increased the injector constant slightly (24.1 to 25.2) to lean it out a little because I was getting mid 900mv readings from the O2's all the time. I also added a bit to the PE tables to make sure it stayed pretty rich at WOT. With those changes I get high 800mv readings at part throttle/idle and mid-low 900's at WOT.

As I mentioned the car is basically stock except for bolt-on's so I suspect the factory programing is pretty close. Thats why I can get away without a real tune. I'm still getting 20-22mpg in mixed driving so it cant be that far off If I were running a cam or anything more radical I would need a dyno tune for sure. A DIY wideband O2 is on my Christmas list so I'll get this thing dialed in correctly pretty soon

In open loop the ECM basically ignores the O2's and BLM's. It just runs off its tables and ignores everything else. You can still read the O2's but the BLM's stay locked at 128.

IMO open loop is good because the ECM does exactly what you tell it and nothing more. But at the same time its also bad because it cant compenstate if something isnt right. For that reason alone I dont really recommend anyone run open loop unless its just for troubleshooing purposes. Too easy to run lean and burn something up...

If you ever find out if the VE tables work in open loop on a 93 let me know! I've been meaning to try it myself but I'm lazy and swapping chips is a PITA.