Guys,

I was driving back to work after a chinese lunch, when thought crossed my mind. Maybe is was the soy sauce or the egg rolls, but here it is.

We all shoot for BLMs of 128, which essentually means the computer is making no corrects to the AFR, which is 14.7.

OK here is the thought. The throttle response etc all improves when the computer for a lack of better terms is taken out of the loop, in the sense of not making corrections. Suppose that we are at 128 BLMs and have a perfect AFR of 14.7. How do we know that is the best AFR for making power? Maybe the car would make 30hp, or even more with a richer AFR?

Looking at it from a standpoint of WOT, different setups like different AFRs. A turbo might like a richer AFR of 11.5-.8 where a NA engine wants 12.8.

The point I am trying to bring about is how and what makes us think that AFR of 14.7 or 128 BLMs is best.

Also I would like to say that I understand that is where best gas milage will begin, since 100% of the fuel is supposedly being burned etc, and that a leaner mixture would yeild even better gas milage results, but the point I am trying to make, is why 128? Maybe a richer mixture of 120 would yield more powerful results and snappier driving?

Just a crazy thought that I would like to hear what you guys opinions are.....

Thanks.

 

No body ever really said 128/14.7 is the "perfect" mixture for
driving or power. its the most engine safe while being safe to the environment and cats.
Actually like Grumpy always says "give the engine what it wants"
not what you want.
The only problemm is that you may tune for 120 but the ecm is going to make corrections for 14.7, so you could do a few things .
Limit blm to a max 120 or so,tune to 120 and then lock BLM's all together, or do what I have been doing is disable closed loop and then tune from WB. Or if you had a way to cut 02 voltage feedback down 7%,then the ecm would think its 14.7 @ 128 but essentially it would be at your desired 120.

 

7730 8D
I have found this to be true.

I've set my comanded AFR to 14.0 and tuned to 128 which gives me a WBO2 of 14.2 to 14.3 and this seems to be best for my combo with the big Cam, however I had to set my Idle AFR to 13.8 with the WBO2 for a good Idle with the Closed throttle timming @ idle of 23deg.

I have the HMF set to 15.0 ,15.5 ,16.5 @ 60, 50 ,40KPA
This seems to give me a WBO2 AFR of 16.3 in High mode Fueling.
I tryed 17.0 but it seems to get a little rough under light throttle.

As Grumpy has said I gave the Engine what it likes.

It seems to run very well at 14.2 AFR all over.

Also I've found that 11.7 AFR @ WOT is best for my combo, thats with the water alky injection.

BTW my car passed the Emissions on the rollers with room to spare running at this richer AFR.

 

toggling over 14.7 is more to keep the converter happy. For idle and cruise its fine. Then tune for WOT to whatever the engine seems to want.

Or you could go open loop.....


BW

 

I think it was probably the Moo Goo Gai Pan, or maybe the Chow Kow Meow...

Even the older .bins seem to have target AFR adjustments. Am I being too simplistic, or wouldn't that be easiest? (At least to test.)

 

Saturn beat me to it, but the only reason to run 14.7:1 is because you have a cat. Thats the AFR it does it's magic at. Also, the actualy cycling rich/lean for an average of 14.7:1 is also specifically done to help the converter do it's job

 

Sorta like I said in the first reply?

 

If you are thin skinned and have no sense of humor do not continue.
Do not ignore this warning! ! !!!

While driving back from, doing some piddy thing, I wondered what was going on at EFI-TUNING.com.
Other then bashing me, seems like not much.
I guess this is still the site with the valid tech info..
LOL

Like the others that quoted Grumpy, give the engine what it wants.

For the others that mentioned setting the commanded AFRs at other then 14.7 you might try changing the O2 rich, and lean cross over voltages. But, I'm just guessing, LOL.

And going open loop gets you complete freedon to run whatever you want. Remembering the when ever you change the AFR in closed loop you're still just toggling across that AFR, and just averaging that AFR.

Off road use, yada yada.
Sticks and stones..................

 

Is there a way to do that other than at idle?
I asked TC and they gave me the idle r/l threshhold table,but only for idle.

 

On the 31T code it reads as only a rich and lean, not rpm specific, and changing them on it resulted in a change in the WB, with a commanded AFR change. A couple guys running the 42 code said the same thing. For the time to try a chip or two would be worth a try to verify if it works that way on the 6E/31

 

1) As I understand it, we only shoot for 128 because that's in the middle of a range that the ECM can self tune from, so we don't lose tune so easily and so there is a smooth transition from one learning block to another. Whether you've got 120 or 136, you've still got an AFR of 14.7 if that's what you've commanded. That's the whole point of BLMs AFAIK.

2) In SD systems, without changing your cruise AFR, you can set the "best AFR for power" (AE mode) so I'd assume that MAF systems will let you do the same, given that one system is as good as the other .

3) Again, there is no equation between AFR of 14.7 and BLM of 128 unless you command it.

4) You aren't richer at 120 than at 128. EG for SD's, if your BLM is 120, it's just that the ECM has to multiply your VE's by 120/128 to get your commanded AFR.

Now, I wouldn't quote Grumpy, because everyone knows he doesn't know what he's talking about, but someone said that if you set "the commanded AFRs at other then 14.7 you might try changing the O2 rich, and lean cross over voltages." That's a very helpful comment, because the NB O2S are rich/lean at 14.7 and if you change your rich/lean boundary to some other point, you're going to have to let the ECM know how to tell where this AFR point is at in terms of O2S voltages. This also doesn't sound very good to me, because once you get any distance in AFR away from 14.7, a NB sensor voltage is notoriously insensitive to AFR change and you could be leaned out super quick and not know it.

That's the other reason (besides the stoich fact of life and looking after the cat) that I can see for the 14.7 standard commanded AFR.

John.

PS. Please humour Grumpy and stick to the facts so it doesn't ruin this useful thread you've started in a flame war. If I'm wrong, I'll learn something. If you're wrong, you may too.

 

Guys,

Nice replies, even with the pokes.

The reason I started the thread was to let others that might not have seen the benifit from maybe not being at 128 BLMs. The newer people all think that 128 is ideal.

I understand exactly what is happening when your at 120 BLM.

I think a lot of people fail to see the benefit that might come about from exploring other AFRs for cuise than 128 or 14.7.

It seems that people are content with getting 128 then moving onto WOT tuning. And never looking back. For that I thought it would be a good idea to bring up the subject.

Thanks for the replies.

I'm sure a few people are going hmmmmm, never thought about that before.

 

Grumpy has covered this topic in the past.

14.7 is what the cat needs to live. Doesnt mean anything as far as optimizing the fuel curve the motor actually wants.

 

I have no cat, I live in Michigan, we don't need them. Since Leaner is meaner... that means that I can get even more power out of my combo at all throttle positions? Will it effect WOT stuff at all or is that only the AE stuff?

Ohh yeah!

hmmmmmm......

 

Only up until a point.

Tuning is about giving a car what it wants. That means in order to find out what it likes, you have to experiment.

I've run idle mixtures from 15:1 to 13:1.
Light cruise mixtures of 16.5 to 12.5.
And WOT from 13:1 to 11.5:1.
Currently it seems real happy at 14.2 at idle, 13.8 cruise, and 11.8 WOT. The 13.8 cruise isn't the best MPG AFR but it's real easy on the engine.
Under light loads, the leaner mixtures are slower burning so you need to add some timing, to account for that.

 

See folks, this is what it's like in BruceWorld. The GN is Real Happy and he's still Grumpy .

John *ducks for cover*