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Tuning AFRs on the dyno according to EFI101

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  • Tuning AFRs on the dyno according to EFI101

    Autoworkz and I recently attended an EFI101.com class in Orlando. The class is a basic introduction into how efi works and how to go about tuning standalone ecus. The tuning method they describe requires a good dyno and does not in any way rely on reaching knock/detonation to find optimal timing or afrs. While much of it was review I did learn a bit about tuning AFRs on the dyno. I just want to see what you guys think.

    The basic idea behind their afr tuning method is that your engine will make peak power within a certain window of afrs. That is to say you could make peak power anywhere from an afr of 12.5 to 11.5 at 10psi of boost. Any afr richer or leaner than that window will produce a dramatic loss in power. When I say dramatic loss in power I would consider this to be something near 10hp or more but this will vary depending on the engine and the load. So now we know we need to stay within this window of afrs. The next question is where do we want to be within this window. The efi101 class teaches that you should aim for the richest mixture within the window. The reasoning behind this is that while you might gain a very small amount of power (1hp) by running in the leaner area of the afr window, you will lose the advantage of the thermal management the extra fuel provides when running in the richer part of the window. Basically your sacrificing the relatively insignificant gain of 1hp or so for a richer mixture that will keep your engine safer and help it last longer. Makes sense to me.

    Now as far as finding this optimal afr you’re going to need a good load holding dyno. The afr tuning process should basically consist of you monitoring power output as you change the afrs. You should be able to see the power fall off as you go past the rich end of the afr window. Bring the afrs back to just before the power fall off and you should be good to go.

    This brings up an interesting note. I’m sure most of you have heard someone respond to a dyno graph saying “ lean it out and you should get more power.” Based on what I’ve just gone over I feel a statement like that is very inaccurate. Unless you are very familiar with the specific engine in question there is no way to say exactly what leaning out the afrs could do. A leaner afr could gain 1hp, gain 10hp, lose 20hp, or melt the engine. I looked at some dyno graphs the efi101 instructor had at the class and some of the afrs were as rich as 10.4:1. That means that a mixture of 10.4:1 was still optimal for that particular engine at that particular load. You can’t just assume 12.5:1 is the best afr for power and aim for that.

    Now so far this afr tuning method has been aimed at optimizing for power and safety. Of course there are also times when you want to optimize for fuel economy. Fortunately, the fact that ecus have fuel maps and timing maps allows us to tune for both power or economy in the same tune depending on the area of the map we are tuning. When it comes to tuning the afrs for the low load areas of the fuel map we can aim for the leaner side of the afr window. In fact, the instructor said he sometimes leans out the mixture until the engine starts to misfire and then richens it up a bit. The reason we can do this is because the engine is producing a very small amount of power at these low loads (

  • #2
    All of what you said sounds dead on to what I have read in my book "How to tune and modify engine management systems. I put some qouts out of the book.

    "The best-power ratio for gasoine 12.2:1 or .83 lambda."

    "All rour-cycle gasoline engines require mixtures that fall between lean and rich best torque, in the 11.5 to 13.3 gasoline range."

    "However, and engine calibrated on a dynamometer of almost any kind will almost definetely run suboptimally rich on the street and track."

    "Mean best torque should fall in the 12.4:1 range at the highest power settings, but boosted engines may require more fuel cooling to fight knock and meltdown."

    "Bob Norwood points out that super-duty engines always make the most power as you lean them out right before they burn down."

    "But peak torque makes the most cylinder pressure, and it requeres slightly rucher mixtures than peak power."

    "You can take it to the bank that a poston engine will make peak power at somewhere between 11.8 and 13.0 afr."

    "Peak EGT typically occures at about 75 degrees fahrenheit lean of best power, and temperature falls off from there in both the lean and rich directions."

    These are just a few quots from this book. I could go ON AND ON but you get the point. A lot of what you just said matches up to what the book says.

    I would recomend this book to anyone who wants to learn. Book is by Jeff Hartman, Motorbooks workshop.
    Attached Files
    85 Z31 6.0 LSX turbo 766whp/792wtq
    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

    Comment


    • #3
      Now on top of that, Now you have to take ALL OF THE INFORMATION(And there is A LOT of info to remember) you have learned over the years and try to pull it from your memory banks while you are paying the premium per hour on a dyno and trying to get as much accomplished in a quick amount of time. BUT WAIT dont go TOO FAST or you blow the engine up. :shock: :shock: :shock:

      There is so much to remember just on the fuel requirments and the spark requirement that just that alone can seem overwhelming. Good luck to anyone who is willing to take this on.
      85 Z31 6.0 LSX turbo 766whp/792wtq
      04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

      Comment


      • #4
        The only thing I dont like about some of those quotes is that they suggest an afr of X is what you should aim for in your tune. I feel like this is a bit general because each engine is going to like a different afr. The aim of the efi101 afr method is to create a tune on any engine without having any preconceived ideas of what the afrs should be. I think it's important for people to realize that while an afr of X might create peak power on one engine it could also melt another engine. The dyno is the best way to get a realiable and powerful tune.

        I have to disagree partially with the quote about running richer on the street then on the dyno. This depends entirely on how the dyno is setup and how it's used. A typical inertia dyno can't accurately simulate load but a good loading dyno should have no problem. I see no reason why a car would run any different on the street compared to on a dyno if the dyno was setup correctly.

        Comment


        • #5
          Very good information, I appreciate you sharing with us. I believe this aptly named "window effect" is also true of timing as well.

          Both of my dyno-run VG engines had a dramatic falloff in power below 11.0AFR, and would keep gaining power as you leaned it out all the way to 12.0 (I didn't bother going any leaner than that for the same safety reasons). Thus, I never saw a need to run down into the 10's as is so popular with engines like the 4G63. As you know, VASTLY different AFR's are necessary at different RPM and load. This is why I can't understand why so many fuel maps I see are set to something like 12.0 at all boost levels above 3000rpm, and only timing is changes ad load/rpm increases.

          However, I also had a dramatic falloff in power once you went below somewhere around 13BTDC of total timing advance under heavy load. I tried it with the entire map retarded (distributor clocked fully counterclockwise) and the power output curve (during a WOT pull in 4th) looked almost the same, but was just missing about 200hp over the entire graph... From memory, at 10BTDC and 18PSI it made something stupid like 210rwhp. I'll have to see next time I am there if I can get the run files.

          Additionally, more timing won't make much more power once you are in the window. About 1-2hp per degree is typical. my 7.8:1 engine consumed timing like nobodies business and didn't knock, so it seemed OK to get the extra 10hp by running up as high as 30 degrees under full load. Now I run a lot less timing, make only a little less power, and have a much safer tune driving a much more expensive engine.

          Comments/ideas?

          Comment


          • #6
            Stinky wrote: The only thing I dont like about some of those quotes is that they suggest an afr of X is what you should aim for in your tune. I feel like this is a bit general because each engine is going to like a different afr. The aim of the efi101 afr method is to create a tune on any engine without having any preconceived ideas of what the afrs should be. I think it's important for people to realize that while an afr of X might create peak power on one engine it could also melt another engine. The dyno is the best way to get a realiable and powerful tune.

            I have to disagree partially with the quote about running richer on the street then on the dyno. This depends entirely on how the dyno is setup and how it's used. A typical inertia dyno can't accurately simulate load but a good loading dyno should have no problem. I see no reason why a car would run any different on the street compared to on a dyno if the dyno was setup correctly.
            Yeah I see what you are saying. He does also say in the book though to do what you mentioned. Running on the dyno finding the peak power and backing off a little from there.

            Yes. the car should run EXACTLY the sam as on the dyno but like you said, the key ingrediant IS the dyno being set up correctly. If you manage to find a dyno that can simulate real world conditions exactly I can pretty much gaurentee that you are going to pay through the nose for dyno time, which like I mentioned puts that much more pressure on you to get it done quickly with out blowing it up.

            Either way it is a good book, I'm sure if you read it you would agree with a lot of stuff said in it. But like anything there are going to be parts not everyone agrees with. Its give and take.
            85 Z31 6.0 LSX turbo 766whp/792wtq
            04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

            Comment


            • #7
              I have to double check but I think I've read that book.

              As far as adjusting timing they basically said to watch until you reach peak torque. There should be a point at which the torque peaks and additional timing gains no power or loses power. At that point you can either leave it or back it off a degree or so if you feel you want the extra margin of safety. Apparently if you start detonating at some point the power will fall off and you will know to back off on the timing. The only thing I'd be worried about is that on an engine where one particular piston tends to detonate easier then the rest this way of tuning could allow for problems. The engine could be detonating while still gaining power with additional timing.

              Satan, you're right about the dyno time. A good dyno isnt going to be cheap. On the other hand the quality of the tune and the time it takes you to tune on a good dyno vs. a cheap dyno could make the extra money worth it.

              Jason, approximetely how much power difference did you notice between 11.0 afr vs 12.0 afr?

              Comment


              • #8
                He goes pretty in depth about ignition timing as well talking about flame front speeds and How different AFR effect that(not that that is ignition but...) He does mention that with a run of the mill stand alone that you do have to tune for the leanest of the cylinders wich is usually two more so than the others. BUT, if you run a higher end EFI system you can tune each cylinder individually.

                As far as the ingniton topics he discusses however, he talks about best for ecconomy and best for drivability and best for power and so on. He goes into great detail of why the timing "should be" what he says with certain applications. OK ok i'll stop pumping up his book, hell I'm not even paid for it.

                I guess my point is this. You can pay to get your info from a school(stinky maybe you got this class for free, I dont know) OR you can go find the info yourself for a fraction of the cost in most cases. What does this have to do with the topic at hand? Nothing, so I'll shut up now :shock:
                Attached Files
                85 Z31 6.0 LSX turbo 766whp/792wtq
                04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                Comment


                • #9
                  Good info, thanks. I need to get a copy of that book apparently.

                  Stinky- just curious about the idea you stated about having a cylinder that wants to detonate easier than another. Generally speaking, what would cause that? (this could easily apply to NA engines with a cylinder that wants to run leaner or richer than the others)

                  Here is my thought: Nearly any engine is going to have one or 2 cylinders that want to behave a bit differently than the rest when it comes to AFR and timing. Shouldn't the tune be tailored (however it can be) to keep those cylinders inside a safe operating range?

                  Ive dealt with this on a couple NA engines with trying to find the best and safest timing while keeping power at a maximum. The "off" cylinder(s) was always my concern.
                  Just stand back and throw money.
                  Performance costs money.
                  Reliable performance costs more.

                  Comment


                  • #10
                    OR-Zman wrote: Good info, thanks. I need to get a copy of that book apparently.

                    Stinky- just curious about the idea you stated about having a cylinder that wants to detonate easier than another. Generally speaking, what would cause that? (this could easily apply to NA engines with a cylinder that wants to run leaner or richer than the others)

                    Here is my thought: Nearly any engine is going to have one or 2 cylinders that want to behave a bit differently than the rest when it comes to AFR and timing. Shouldn't the tune be tailored (however it can be) to keep those cylinders inside a safe operating range?

                    Ive dealt with this on a couple NA engines with trying to find the best and safest timing while keeping power at a maximum. The "off" cylinder(s) was always my concern.
                    This is why you always have to tune for the leanest cylinders. NO engine is 100% perfect when it comes to balancing VE of each cylinder. There for one or more cylinders will always run leaner. This is why GOOD tuning is so damn expensive. It means an EGT probe for each port along with a wide band sensor for each port. Along with the system that can actually tune each cylinder. Expensive as shit. So what do you do if you cant afford that? Tune for the leanest.
                    85 Z31 6.0 LSX turbo 766whp/792wtq
                    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                    Comment


                    • #11
                      Here is an article on the innovate site about running TOO rich. If you care to read it. Its not THAT good :roll:

                      http://www.innovatemotorsports.com/resources/rich.php
                      85 Z31 6.0 LSX turbo 766whp/792wtq
                      04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                      Comment


                      • #12
                        Thanks Satan. That pretty much confirms what I instinctively have known to date.

                        I need to start reading the Innovative forum more.
                        Just stand back and throw money.
                        Performance costs money.
                        Reliable performance costs more.

                        Comment


                        • #13
                          Satan wrote:
                          Stinky wrote:
                          The only thing I dont like about some of those quotes is that they suggest an afr of X is what you should aim for in your tune. I feel like this is a bit general because each engine is going to like a different afr. The aim of the efi101 afr method is to create a tune on any engine without having any preconceived ideas of what the afrs should be. I think it's important for people to realize that while an afr of X might create peak power on one engine it could also melt another engine. The dyno is the best way to get a realiable and powerful tune.

                          I have to disagree partially with the quote about running richer on the street then on the dyno. This depends entirely on how the dyno is setup and how it's used. A typical inertia dyno can't accurately simulate load but a good loading dyno should have no problem. I see no reason why a car would run any different on the street compared to on a dyno if the dyno was setup correctly.


                          Yeah I see what you are saying. He does also say in the book though to do what you mentioned. Running on the dyno finding the peak power and backing off a little from there.

                          Yes. the car should run EXACTLY the sam as on the dyno but like you said, the key ingrediant IS the dyno being set up correctly. If you manage to find a dyno that can simulate real world conditions exactly I can pretty much gaurentee that you are going to pay through the nose for dyno time, which like I mentioned puts that much more pressure on you to get it done quickly with out blowing it up.

                          Either way it is a good book, I'm sure if you read it you would agree with a lot of stuff said in it. But like anything there are going to be parts not everyone agrees with. Its give and take.
                          I have read that book, i took it back to the library last week, but i believe it said the reason your dyno tune may be rich is because of the fact that no dyno can simulate actual running conditions. They can put a fan in front of the car, but that doesnt simulate whats happening on the road with cold air being forced into the engine bay at high speeds. I think the book said that the heat sink affects means more fuel may be required on the dyno for cooling Satan can you look in the book to see the reason they give.

                          OR-Zman wrote: Good info, thanks. I need to get a copy of that book apparently.

                          Stinky- just curious about the idea you stated about having a cylinder that wants to detonate easier than another. Generally speaking, what would cause that? (this could easily apply to NA engines with a cylinder that wants to run leaner or richer than the others)

                          Here is my thought: Nearly any engine is going to have one or 2 cylinders that want to behave a bit differently than the rest when it comes to AFR and timing. Shouldn't the tune be tailored (however it can be) to keep those cylinders inside a safe operating range?

                          Ive dealt with this on a couple NA engines with trying to find the best and safest timing while keeping power at a maximum. The "off" cylinder(s) was always my concern.
                          I believe this is due to the fact that a plenum cant distribute the air perfectly to each cylinder in the same quantities and temperature. Also it is unlickely that 6 injectors at the same duty cycle will spray exactly the same amount of fuel. I assume balancing/matching injectors helps this, but even still they have a certain % differential.

                          Just my thoughts.

                          Stinky, one of the quotes in this book is "any tuner will tell you an engine made max power before it blew up" refering to leaning out the mixture.
                          You disagree?

                          Comment


                          • #14
                            I believe that leaning the mixture out will get you a little more power. The method of tuning I wrote about is aimed at creating a good tune without taking the engine to the edge and risking problems. Obviously each engine and situation is different but I think most people would give up a few hp to run on the richer and safer side of things.

                            Comment


                            • #15
                              i totally agree with you, i know when i come to tuning my Mega squirt i will be keeping it on the rich side, cause i cant afford the consequences.
                              But that being said there are race teams that rebuild the motor after every race, be it drag, or circuit racing and they run right on the limilts. But then again these cars are tuned by experts that are paid big bucks to get the best tune.

                              That book that Satan refers to is definately worth a read,

                              .. Ahh the complex world of engine management.

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