Safe AFR for DI Motor w/ Boost
Jul 20, 2014 | 06:29 PM
#31
With port injection, a good portion of the fuel doesn't even have any positive contribution to the actual combustion. When you richen it up to 11.5 AFR on gasoline, basically all of the fuel added between 12.5 and 11.5 is for knock prevention. During the compression stroke, that additional fuel is vaporizing, absorbing heat from the compressing air and metal surfaces in the cylinder. It also serves to slow the combustion down to make sure your peak cylinder pressure occurs at a certain crank angle to maximize torque on the power stroke.
When the fuel is direct injected, it doesn't need to be injected in surplus to absorb heat. All it needs to do is do its job in combustion and that's it. So a lot less fuel is needed. Like Area57 said, the optimal range to shoot for is high 12s AFR. 12.8, plus or minus 0.3.
When the fuel is direct injected, it doesn't need to be injected in surplus to absorb heat. All it needs to do is do its job in combustion and that's it. So a lot less fuel is needed. Like Area57 said, the optimal range to shoot for is high 12s AFR. 12.8, plus or minus 0.3.
Fuel Trim Info - Ross-Tech Wiki
O2 sensors as a tool
E85 max power ratio questions
FUELS DATA
Air
Just to make sure this is perfectly clear, these values hold regardless of the amount of boost or lack thereof. However, something critical to keep in mind is when the injection begins with respect to crank angle. Since it is not a diesel and doesn't use compression ignition exclusively, fuel must first be allowed to disperse in the cylinder prior to firing the spark plug. So, the injection event must precede ignition for this to occur. With that said, its obvious at this point that you have fuel in a hot, increasing compression environment. What does this mean? There still exists the potential for preignition! Hence why the genius above states that he started seeing knock on his DI truck as he was leaning it out. Unless gas engines someday utilize compression ignition, the potential for preignition will continue to exist. Therefore, additional enrichment for the purpose of knock prevention will still be necessary.
Always make sure you get someone knowledgeable to work on your vehicle's tune, or if you're doing it yourself, make sure you read about it A LOT. A good foundation knowledge is crucial to getting things to work properly. A great example of this is about 6 months ago when supercharged680 (a member on this site that I built a truck for and shipped overseas) came to me about issues he was having with his truck not running quite right about a month after it got there....torque bucking at cruise, down on power, etc. He sends me the tune and it turned out that our fabulous thread contributor ayousef here had raped the **** out of it. It wasn't even the same tune, but some hack job that was thrown together I surmise in an attempt to prove to his friend that he knows something. I had supercharged680 put the original tune back in and the truck suddenly ran fine! It would seem that ayousef made quite a fool out of himself trying to tackle a complicated task with such elementary knowledge on the subject. I would advise everyone to take everything this clown says with a ******* block of salt.
Jul 20, 2014 | 06:34 PM
#32
TECH Resident
Joined: Aug 2008
Posts: 927
Likes: 0
From: Dubai
You made a fool of yourself, bro. I got rid of your dumb *** because I get tired of explaining things to idiots who think they are right regardless of the information presented to them. You can lead an ignoramus to knowledge, but you can't make him think.
Furthermore, no ad hominem has occurred at all here. Might want to work on your knowledge of logical fallacies. Here's a quick lesson for you...this is called the genetic fallacy:
You are wrong and ******* retarded because you think magical evil genies possess your friends.
While that most certainly is a genetic fallacy, lets be real here: how in the **** is anybody supposed to take you seriously when you're so prone to believing things that would get you put in a psych ward? For anybody reading...yes indeed, that is what this clown believes.
I will have a discussion about the science behind engines, but I will NOT debate with someone who simply debates for sport.
Furthermore, no ad hominem has occurred at all here. Might want to work on your knowledge of logical fallacies. Here's a quick lesson for you...this is called the genetic fallacy:
You are wrong and ******* retarded because you think magical evil genies possess your friends.
While that most certainly is a genetic fallacy, lets be real here: how in the **** is anybody supposed to take you seriously when you're so prone to believing things that would get you put in a psych ward? For anybody reading...yes indeed, that is what this clown believes.
I will have a discussion about the science behind engines, but I will NOT debate with someone who simply debates for sport.
Also, incase you don't understand what an ad hominem attack is, calling me an idiot, a fool, a clown and ******* retarded instead of adding any useful information to the discussion is as classic as is gets of you.
but im not the one getting butthurt here, you are claiming to know **** about direct injection engines without even having tried or tuned a FI direct injection engine nor owned one, you cant run as FI direct injection engine at 12.8:1 AFR but what do you know ive seen your shitty tune on Ahmad's truck, don't make me show the world how it looks like Mr. tuner engineer.
Jul 20, 2014 | 06:37 PM
#33
TECH Resident
Joined: Aug 2008
Posts: 927
Likes: 0
From: Dubai
For anybody concerned about the validity of my statement, here are 5 sources for the information:
Fuel Trim Info - Ross-Tech Wiki
O2 sensors as a tool
E85 max power ratio questions
FUELS DATA
Air
Just to make sure this is perfectly clear, these values hold regardless of the amount of boost or lack thereof. However, something critical to keep in mind is when the injection begins with respect to crank angle. Since it is not a diesel and doesn't use compression ignition exclusively, fuel must first be allowed to disperse in the cylinder prior to firing the spark plug. So, the injection event must precede ignition for this to occur. With that said, its obvious at this point that you have fuel in a hot, increasing compression environment. What does this mean? There still exists the potential for preignition! Hence why the genius above states that he started seeing knock on his DI truck as he was leaning it out. Unless gas engines someday utilize compression ignition, the potential for preignition will continue to exist. Therefore, additional enrichment for the purpose of knock prevention will still be necessary.
Always make sure you get someone knowledgeable to work on your vehicle's tune, or if you're doing it yourself, make sure you read about it A LOT. A good foundation knowledge is crucial to getting things to work properly. A great example of this is about 6 months ago when supercharged680 (a member on this site that I built a truck for and shipped overseas) came to me about issues he was having with his truck not running quite right about a month after it got there....torque bucking at cruise, down on power, etc. He sends me the tune and it turned out that our fabulous thread contributor ayousef here had raped the **** out of it. It wasn't even the same tune, but some hack job that was thrown together I surmise in an attempt to prove to his friend that he knows something. I had supercharged680 put the original tune back in and the truck suddenly ran fine! It would seem that ayousef made quite a fool out of himself trying to tackle a complicated task with such elementary knowledge on the subject. I would advise everyone to take everything this clown says with a ******* block of salt.
Fuel Trim Info - Ross-Tech Wiki
O2 sensors as a tool
E85 max power ratio questions
FUELS DATA
Air
Just to make sure this is perfectly clear, these values hold regardless of the amount of boost or lack thereof. However, something critical to keep in mind is when the injection begins with respect to crank angle. Since it is not a diesel and doesn't use compression ignition exclusively, fuel must first be allowed to disperse in the cylinder prior to firing the spark plug. So, the injection event must precede ignition for this to occur. With that said, its obvious at this point that you have fuel in a hot, increasing compression environment. What does this mean? There still exists the potential for preignition! Hence why the genius above states that he started seeing knock on his DI truck as he was leaning it out. Unless gas engines someday utilize compression ignition, the potential for preignition will continue to exist. Therefore, additional enrichment for the purpose of knock prevention will still be necessary.
Always make sure you get someone knowledgeable to work on your vehicle's tune, or if you're doing it yourself, make sure you read about it A LOT. A good foundation knowledge is crucial to getting things to work properly. A great example of this is about 6 months ago when supercharged680 (a member on this site that I built a truck for and shipped overseas) came to me about issues he was having with his truck not running quite right about a month after it got there....torque bucking at cruise, down on power, etc. He sends me the tune and it turned out that our fabulous thread contributor ayousef here had raped the **** out of it. It wasn't even the same tune, but some hack job that was thrown together I surmise in an attempt to prove to his friend that he knows something. I had supercharged680 put the original tune back in and the truck suddenly ran fine! It would seem that ayousef made quite a fool out of himself trying to tackle a complicated task with such elementary knowledge on the subject. I would advise everyone to take everything this clown says with a ******* block of salt.
Jul 20, 2014 | 06:44 PM
#34
Whose tune ran correctly? The enrichment in my tune was handled by the methanol injection....if you didn't know, there was a lot of it. Making the numbers look ideal in the tune doesn't make it work correctly. When you decreased the VE values to add in fuel through the power enrichment, the PE might have suddenly looked fancy....but you just pulled about 25% line pressure from the transmission. And you never changed shift pressures in the trans. So not only did your hack job run like ****, you set your friend up for a burned up transmission. Good job, **** stick.
Jul 20, 2014 | 06:46 PM
#35
Again, with the debating for sport. You get proved wrong over and over and try to perpetuate this by bringing up more bullshit for us to call you out on. Why don't you try actually spending time learning about this stuff instead of being a **** sucker who just likes to argue?
Jul 20, 2014 | 06:55 PM
#36
but im not the one getting butthurt here, you are claiming to know **** about direct injection engines without even having tried or tuned a FI direct injection engine nor owned one, you cant run as FI direct injection engine at 12.8:1 AFR but what do you know ive seen your shitty tune on Ahmad's truck, don't make me show the world how it looks like Mr. tuner engineer.
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