Air/fuel ratios

[Need2Speed86]

Im currently reading a book on advanced engine tuning and have been browsing some various forums on e85 tuning.

I have however gotten a bit confused, and I dont know if its fact that the lambda for e85 is much lower that gasoline. Anyways for the sake of this discussion we will talk on gasoline.

If I understand correctly lamda or stoich for gas is 14.7

So in theory an A/F ratio of say 12.6 would be rich and 15.1 would be lean?

However it seems that every forum I browse says the exact opposite where 12.6 would be lean.

Can someone clarify?

 

[cobra916]

stoich for gas is 14.64.. stoich for e85 is 9.76.. rich is lower numbers and lean is higher numers.. so 10 is rich and 14 is lean..

 

[01yellercobra]

It's not quite that cut and dry. Different throttle openings and different engine set ups require different A/F ratios. Yes, stoic for gasoline is 14.64. But that A/F will only be seen at idle and part throttle or light loads. Once you go WOT the A/F requirements change. For a N/A motor at WOT 12.6 might actually be on the rich side. Some people go for 13:1 or 13.5:1. Now if the motor is boosted (supercharger or turbo) then that same 12.6 is lean. For a boosted engine you want to be in the 11.5-12 area. Personally for a boosted vehicle I shoot for 11.5.

 

[Need2Speed86]

so then my understanding that anything under the stoich for gas is richening the A/F ratio is correct. Makes sense.

 

[harvboi05]

i find it easier to explain afr's with closed loop and open loop.

closed loop (using the o2s) your ecm will be trying to hit your target AFR which is usually 14.7. open loop (WOT not using the o2s) the ecm will be running off the maf, and the AFR will be whatever you calibrate it to.

the lower the number the richer the AFR, the higher the number the leaner the AFR. its not really cut and dry lean rich, it can be more and less too.

 

[mastwolf]

Do your self a HUGE Favor, Start tuning via Lambda.

That way, the only thing that ever will change...is the amount of fuel needed to get to your target lambda. When I started I would use the lambda*14.64 to get an idea but you can get used to dealing with lambda.

As long as your going for like lets say .82 (aka 12.0 in the NON e-10 fuel, 14.64 stoich) you could tune e-85, e-10, race fuel all day long, because the only thing that is changing is the amount of fuel it takes to reach lambda 1.0


Chris

 

[Need2Speed86]

As long as your going for like lets say .82 (aka 12.0 in the NON e-10 fuel, 14.64 stoich) you could tune e-85, e-10, race fuel all day long, because the only thing that is changing is the amount of fuel it takes to reach lambda 1.0


Chris

Not quite sure I follow this?

 

[01yellercobra]

Not quite sure I follow this?

Lambda is another way of talking about A/F. But with lamdba 1.00=14.64. So 1.00 would be your stoic reading. A lower lambda number is a richer A/F. So .82 lambda is richer then 1.00. And 1.10 is leaner then 1.00. To convert lambda over to what most consider a normal reading is a simple formula. lmbda
X stoic = A/F. So 1.00x14.64=14.64, or stoic. .82x14.64=12.0. If you do any tuning with PRP type software all the fuel tables are in lambda.

 

[Need2Speed86]

Lambda is another way of talking about A/F. But with lamdba 1.00=14.64. So 1.00 would be your stoic reading. A lower lambda number is a richer A/F. So .82 lambda is richer then 1.00. And 1.10 is leaner then 1.00. To convert lambda over to what most consider a normal reading is a simple formula. lmbda
X stoic = A/F. So 1.00x14.64=14.64, or stoic. .82x14.64=12.0. If you do any tuning with PRP type software all the fuel tables are in lambda.

thanks this was explained a bit better.

 

[01yellercobra]

thanks this was explained a bit better.

Good. I kept rereading it and wasn't sure if it was clear enough.

Misspelling brought to you by tapatalk

 

[Need2Speed86]

So out of curiosity what are the more popular tuning programs for Ford? Currently in the process of reading a book on tuning.

 

[01yellercobra]

I've been using SCT for about 5 years now. It's pretty popular around here. I know a tuner that has both SCT and Diablosport and he used SCT more often. But then I think it comes down to what you know and are comfortable with.

 

[HAwkeye4040]

Im currently reading a book on advanced engine tuning and have been browsing some various forums on e85 tuning.

The book in question, where could I find a copy?

 

[Need2Speed86]

The book is called engine management advanced tuning by greg banish. Ive really contemplated taking his class but its 550 dollars. Ive also briefly started a book on airflow theory but havent made it but a few pages in.

http://www.sctflash.com/products.php?PID=43&VID=

Is this all I would need or do I need the flasher to load my custom tune programs onto the CPU itself. Possible data logging software as well. Wish I had access to a dyno to learn all this

 

[01yellercobra]

You need a hand held or a chip and chip burner to load the tune onto. You download the Livelink software from SCT's site. You don't need a dyno to learn all of this. It was about 4 years before I finally put my car on a dyno. And that was because I couldn't get a good straight run in to dial in the WOT.

 

[HAwkeye4040]

The book is called engine management advanced tuning by greg banish. Ive really contemplated taking his class but its 550 dollars. Ive also briefly started a book on airflow theory but havent made it but a few pages in.

Thank you, kind sir. I was able to find this and another about engine intake and other systems on Amazon.

 

[gmcconn1]

I have taken Greg's class and highly recommend it if you are going to try your hand at tuning. Books are good but you will go further faster in a classroom type enviornment where you and others are asking questions.

 

[jayman33]

As soon as I get done with some training and my master's I'll be diving in the tuning realm. It really interests me, don't know exactly how complicated it is after you break the barrier and understand the basics.