Lean Cruise AFR

[Blue71]

I was looking at some stock $OD bins ( Open Loop AFR Vs Coolant Temp Vs Vacuum ) tables, seen some that had AFR as high as 16.9:1

I know all engines are different, some can run leaner then others.
Whats the best way to tune for this without burning a hole in a piston.

[94Blazer383]

Originally Posted by Blue71

I was looking at some stock $OD bins ( Open Loop AFR Vs Coolant Temp Vs Vacuum ) tables, seen some that had AFR as high as 16.9:1

I know all engines are different, some can run leaner then others.
Whats the best way to tune for this without burning a hole in a piston.

I tried to tune Lean Cruise a few months back and never really got the results I was wanting. I was using my LM1 and emulating watching the AFR while driving I have been thinnking about giving it another shot since gas has gone up, but I never drive my truck anymore.

[93ChevyTBI]

Originally Posted by 94Blazer383

I tried to tune Lean Cruise a few months back and never really got the results I was wanting. I was using my LM1 and emulating watching the AFR while driving I have been thinnking about giving it another shot since gas has gone up, but I never drive my truck anymore.

Once you get this down without blowing the blazer up, then I'll come by for a retune.

I'll be by around 7:00m tonight to try the PCM. Cool?

[93V8S10]

Lean Cruise seems to work well with my PCM. Here's my simplistic take on it.

To start with I set the entire table to 14.1 (10% E). Then from previous experiments I know that my engine wasn't happy with anything leaner that 16.0 and I knew that I didn't want any thing leaner than 14.1 at high load or cold temps. So I set everything from 30VACkpa to 56*C to 15.0 and called it good.

Haven't noticed any problems so far. Seems that the PCM cuts fuel after a couple seconds of idling or steady state driving and responds instantly to increased TPS demands.

[Blue71]

Have Lean Cruise up and running, been keeping a close eye
on the WB and for Knock counts, datalogged most of the day.
Had to do a few tweaks here and there, so far I've Been able to
cruise 70 MPH between 50 to 60Kpa at 15.5:1, motor doesn't seem to even know its running lean, no knocks no sputters no nothing.

Going to run this for a few days and see how it goes, I might be able to run a little leaner.

[oldred95]

Apparently I have a vacuum leak and mine until its completely heated up and the leak seals off likes to run around 16:1 at cruising speed and idles upwards of 17:1 and it hasn't caused any problems. Before I got the wideband it was running as lean as 19 and 20:1 at light throttle. I've never had any knock counts from it as long as I use a reasonable amount of spark advance. I realize running it that lean isn't good but I didn't know it was actually that bad and it hasn't hurt it any. Once its in tune though I'll try to target 15.5 or 16:1 to maintain some power while at cruise.

[93ChevyTBI]

Wow!! you guys are doing a good job getting that Lean Cruise going. Just for the sake of argument, how many mpg can you pick up going from 14.7 to 16.0 AFR?? I'm guessing 2 mpg max...which I think is great. Can you get more or is 2 stretching it a bit?

[90C350]

Just wondering if you guys know how to set up lean cruise settings with the 7747 ecm. I can always use a little more MPG.

[94Blazer383]

Originally Posted by 90C350

Just wondering if you guys know how to set up lean cruise settings with the 7747 ecm. I can always use a little more MPG.

I dont know if you have that capability or not? You could always convert to a 7427.

[94Blazer383]

Originally Posted by Blue71

Have Lean Cruise up and running, been keeping a close eye
on the WB and for Knock counts, datalogged most of the day.
Had to do a few tweaks here and there, so far I've Been able to
cruise 70 MPH between 50 to 60Kpa at 15.5:1, motor doesn't seem to even know its running lean, no knocks no sputters no nothing.

Going to run this for a few days and see how it goes, I might be able to run a little leaner.

Sounds like you are ready for a Hydrogen booster.

So what do you have enabled, just lean cruise? What about the temp table at 48C7? Do you have it maxed out?

[Blue71]

Originally Posted by 94Blazer383

Sounds like you are ready for a Hydrogen booster.

Soon, still waiting on a few parts.

Originally Posted by 94Blazer383

So what do you have enabled, just lean cruise? What about the temp table at 48C7? Do you have it maxed out?

L48C7 set to 151.25

[94Blazer383]

Yup thats maxed out.

Sweet...I think I will give it another shot.

[Tbi-MAX]

Originally Posted by Blue71

Soon, still waiting on a few parts.




L48C7 set to 151.25

hey Blue, i just borrowed your table. im not going to run it untill my new WB02 gets here. but at part throttle/cruise im around 12-13.... so i really would like to lean it out to 15.5!

the amazing thing is im getting 12mpg regardless weather im on hwy or city... in OL. and im rich all over still, but getting better.

i always wanted to know how to enable hwy mode on the 7427 pcm... and yes, mine was disable by default. lol

now with my stock 350 i got 22mpg.. wonder what lean cruise would have done in big blue?

[94Blazer383]

Originally Posted by Blue71

Have Lean Cruise up and running, been keeping a close eye
on the WB and for Knock counts, datalogged most of the day.
Had to do a few tweaks here and there, so far I've Been able to
cruise 70 MPH between 50 to 60Kpa at 15.5:1, motor doesn't seem to even know its running lean, no knocks no sputters no nothing.

Going to run this for a few days and see how it goes, I might be able to run a little leaner.

Any results?

I played around with mine yesterday after I got home from the lake. I enabled lean cruise and drove up the street watching the laptop, I was seeing 15.5 on the desired AFR, but I didn't have the wide band installed to confirm it. I will try it today when I get home from work, I have burnt the piss out of my arms and hands trying to install the WB on on hot truck. Anyway, the truck ran fine like you said, no knocks.

I recently started over with a fresh .bin from my truck BJLF. For some reason the truck would not go into closed loop, no lean cruise enabled, my desired AFR stayed around 12.8 and would not budge. I ended up going back to the .bin I had been using and everything was fine. I checked everything I knew would keep it out of closed loop and could not find anything, closed loop temp settings etc...Its weird, swap chips out and its fine. When I get time I will compare the bins in TunerPro.

[Blue71]

Originally Posted by 94Blazer383

Any results?

Just fill up the tank I'll see if MPG is any better, shouldn't take to
long to find out, I average 150 to 200 miles a day.

[94Blazer383]

Originally Posted by Blue71

Just fill up the tank I'll see if MPG is any better, shouldn't take to
long to find out, I average 150 to 200 miles a day.

Yup, I filled up the boat and my truck at the same time last Wed....it hurt.

[94Blazer383]

Originally Posted by 94Blazer383

I recently started over with a fresh .bin from my truck BJLF. For some reason the truck would not go into closed loop, no lean cruise enabled, my desired AFR stayed around 12.8 and would not budge. I ended up going back to the .bin I had been using and everything was fine. I checked everything I knew would keep it out of closed loop and could not find anything, closed loop temp settings etc...Its weird, swap chips out and its fine. When I get time I will compare the bins in TunerPro.

Man I feel stupid, 12.8 sounds a lot like my battery voltage doesn't it? I forgot to mod my .bin to show desired AFR instead of battery volts... I wasted a lot of fuel trying to figure that out last night.

[93ChevyTBI]

Originally Posted by 94Blazer383

Man I feel stupid, 12.8 sounds a lot like my battery voltage doesn't it? I forgot to mod my .bin to show desired AFR instead of battery volts... I wasted a lot of fuel trying to figure that out last night.

[Blue71]

Originally Posted by 94Blazer383

Man I feel stupid, 12.8 sounds a lot like my battery voltage doesn't it? I forgot to mod my .bin to show desired AFR instead of battery volts... I wasted a lot of fuel trying to figure that out last night.

Ya, been there done that, I've started over any a times.

Originally Posted by 93ChevyTBI

I'd be nice to the man that tune my truck, hate to have him forget
something on the next tune.

[93ChevyTBI]

Originally Posted by Blue71

I'd be nice to the man that tune my truck, hate to have him forget
something on the next tune.

He wouldn't forget something...that would be too obvious. He'd take the opposite route...program something to happen where I'd have to drive home 45 miles home on the interstate doing 10 miles per hour or so. He'd make me think I blew it up or something when all he did was lower the rev limiter or something like that.