Air Fuel Ratio
Jun 29, 2006 | 12:07 AM
#11
Staging Lane
Joined: Jun 2006
Posts: 53
Likes: 0
From: Tri Valley area, NorCal
Originally Posted by dewmanshu
not me. I am shooting, errr I was, I am retuning now, but I will ultimately shoot for 11.7.
What I wonder is, in the E85 motors, a higher AFR is more tolerable. Is there a formula to work out a safe but leaner scenario for running meth injection.
I would go to guess, at WOT, using what we know with our injector formulas we can get pretty close to a reasonable speculation of how much pump gas is going into each cylinder. Then with what ever jetting at whatever pressure for your meth, figure out the same. Obviously again, using a speculative formula sense you are just dumping meth down the TB, but figure out what the meth amount is. Then with those two numbers, whats you pump gas to meth ratio. I would be interested in that. Blah blah blah right? I bet with parish's single turbo setup he is able to squeeze a little more of leaner afr out of it versus less meth (alcohol).
So, with that said, could we change the afr ranges if we introduced alcohol injection?
What I wonder is, in the E85 motors, a higher AFR is more tolerable. Is there a formula to work out a safe but leaner scenario for running meth injection.
I would go to guess, at WOT, using what we know with our injector formulas we can get pretty close to a reasonable speculation of how much pump gas is going into each cylinder. Then with what ever jetting at whatever pressure for your meth, figure out the same. Obviously again, using a speculative formula sense you are just dumping meth down the TB, but figure out what the meth amount is. Then with those two numbers, whats you pump gas to meth ratio. I would be interested in that. Blah blah blah right? I bet with parish's single turbo setup he is able to squeeze a little more of leaner afr out of it versus less meth (alcohol).
So, with that said, could we change the afr ranges if we introduced alcohol injection?
The only readings I can get on my scanner are MAF, MAP, IAT, and voltages (Mv) for the four O2 sensor points. Oh wait, there are some percentage readings for the fuel banks (short and long term?) How do I convert that to A/F ratio?
Or am I totaly off on one this one?
Jun 29, 2006 | 12:18 AM
#12
Originally Posted by BlownChevy
As I too am learning as I go, here is one interesting fact that I picked up: 14.7:1 is considered perfect AFR due to the fact that it is as close to a 100% burn of the fuel as you can get.
What that theory does not leave room for is the situation that almost always occurs which is that in the limited time available for that combustion event to occur, not all gasoline molecules will be able to pair up with oxygen molecules for a complete burn. That is why running slighty richer will net more power than stoic. Less opportunity for the random oxygen molecules to hide out and avoid the flame.
Jun 29, 2006 | 01:26 AM
#13
Thread Starter
Joined: Mar 1986
Posts: 18,748
Likes: 7
From: Chatsworth, CA
Originally Posted by dc_justin
Yep. Theory states that 14.7lbs of oxygen is needed to burn 1lb of gasoline.
What that theory does not leave room for is the situation that almost always occurs which is that in the limited time available for that combustion event to occur, not all gasoline molecules will be able to pair up with oxygen molecules for a complete burn. That is why running slighty richer will net more power than stoic. Less opportunity for the random oxygen molecules to hide out and avoid the flame.
What that theory does not leave room for is the situation that almost always occurs which is that in the limited time available for that combustion event to occur, not all gasoline molecules will be able to pair up with oxygen molecules for a complete burn. That is why running slighty richer will net more power than stoic. Less opportunity for the random oxygen molecules to hide out and avoid the flame.
I have been running my truck at 12.2 since the we tuned for HP on the truck. Leaner will ALMOST always make more power than richer in a BOOSTED application. Yes 11.80-11.9 is safer, but 12.2 makes more power (on the Radix trucks) I can only speak for a Radix set up since that is what I have the most experiance with. I plan on starting from scratch with the new supercharger once it is installed......Reflash with the TechII and go from there.
Keep the tech coming, this is getting very interesting.
Jun 29, 2006 | 01:37 AM
#14
Originally Posted by BlownChevy
I have been running my truck at 12.2 since the we tuned for HP on the truck. Leaner will ALMOST always make more power than richer in a BOOSTED application. Yes 11.80-11.9 is safer, but 12.2 makes more power (on the Radix trucks) I can only speak for a Radix set up since that is what I have the most experiance with. I plan on starting from scratch with the new supercharger once it is installed......Reflash with the TechII and go from there.
Keep the tech coming, this is getting very interesting.
The reason leaner will ALWAYS (assuming octane isn't a variable) make more power is that the ~12.x fuel ratio is well beyond the best power point. The extra fuel is a necessity as it adds a cooling effect to the combustion process which helps keep the mixture from detonating. That cooling process reduces the peak cylinder pressure, which ultimately determines power.
If you could get away with running 13.7-14.0 booster without any detonation, I'd bet you'd see a bit more power than at 12.x.
Jun 29, 2006 | 04:06 AM
#16
It has been found experimentally that the ideal mixture, the one where these two elements are perfectly balanced is 14.7:1 by weight, i.e. 14.7grams of air and 1gram of fuel. Or 14.7lbs of air and 1lb of fuel. This is called 'stoichiometric', meaning in Greek measure of the elements.
here read this it may help i read it its long but you might learn something lol.
here read this it may help i read it its long but you might learn something lol.
Jun 29, 2006 | 04:50 AM
#17
Teching In
Joined: Nov 2003
Posts: 30
Likes: 0
From: united arab emirates
I am new in the truck tuning, but with 98 Camaro I set the WOT AFR to 12.2 at peak RPM and it was just perfect "performance".
we froget about timing!
burning is timing.
leaner or richer I believe it's different for each application.
we froget about timing!
burning is timing.
leaner or richer I believe it's different for each application.
Jun 29, 2006 | 09:29 AM
#18
Thread Starter
Joined: Mar 1986
Posts: 18,748
Likes: 7
From: Chatsworth, CA
Originally Posted by 2004Denali
Ok, since this is a learning thread can someone explain what Stoic is. I have heard it mentioned Alot but didn't want to be the idiot that asked.
In internal combustion engines, the air-fuel ratio refers to the proportion of air and fuel present during combustion. The chemically optimal point at which this happens is the stoichiometric ratio (sometimes referred to as stoich), where all the fuel and all the oxygen content in the air of the combustion chamber will perfectly balance each other out during combustion.
Jun 29, 2006 | 10:48 AM
#20
TECH Addict
Joined: Feb 2003
Posts: 2,864
Likes: 1
From: Geneseo, NY
So...what is the min A/F mixture that our engines can safely handle when out of PE mode ??.....I ask because it seems that you could command something like 15.1:1 instead of 14.7:1 to increase fuel mileage while in closed loop mode (kind of a DIY lean cruise mode - just set PE to come in earlier and adjust it to compensate for the leaner mixture), or - getting kind of off-topic here - you could log what MAP ranges you see while athighway RPM's and DECREASE the VE table at those points (therefor decreasing fuel delivery) to again act as a lean-cruise mode.