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[whittlebeast]

The volume of air comes from the MAP x RPM / 100.  You compare that to the duty cycle.  You will end up with a distinct pattern in a scatter plot.  In anyone wants to post up a dm3 generic o2 data log off a fairly well tuned bike, I can show you guys.

Andy

[hrdtail78]

The volume of air comes from the MAP x RPM / 100. 
 

This is where you lose me.  Take away the /100, because we understand that is scale.  Any engine with MAP x RPM is always going to be the same number.  60 kpa x 2250 = 135000.  88 cuin to 145.  The number will be 135000. 

[whittlebeast]

That is true...  The part you are missing is that this has everything to do with the pattern of the scatter plot.  The units don't matter.

You really need to see it before you try to get your head around the math.  When it works for 200 hp / liter race motors every time, a 6000 rpm tractor motor should be a lay-up to tune.

Andy

[Steve Cole]

That is true...  The part you are missing is that this has everything to do with the pattern of the scatter plot.  The units don't matter.

You really need to see it before you try to get your head around the math.  When it works for 200 hp / liter race motors every time, a 6000 rpm tractor motor should be a lay-up to tune.

Andy

Math is math Andy and your math is really straight forward RPM*MAP/100 = airflow is simple enough and is what you have claimed. I've asked, as several others have asked and you still refuse to give us an answer.

How do you get airflow from RPM * MAP/100? Simple question Please give us a simple straight forward answer.

[mayor]

Maybe what me and everyone else is considering MAP to be is different than you (Andy).  MAP to me is manifold absolute pressure, which is not relative to a volume but rather more tied to available barometric pressure (if naturally aspirated).   If I used your formula as I understand it, a 96” bike and the same bike converted into a 103” would have the same values at 4,500 rpm if both were capable of achieving 100 kPa of MAP at that location?  How does that give a number that can determine whether the duty cycle number is correct? 

[whittlebeast]

Think of it this way,  If you double the RPM, the motor will process twice as much air.  Twice as much air means twice as many o2 molecules to mix with fuel.

If you are running 3000 RPM and 50 KPA you will get some numbers of molecules of 02 into the motor to mix with fuel.  If you then hold that 3000 RPM but go to full throttle, the intake will go to 100 KPA and twice as many molecules make it into the motor.

This is all +/- some due to VE but you get the idea.  Double the speed, double air.  Double density, and double air.

Now if you double the DC, you get close to double the fuel.  Sure, there is an offset due to opening time of the injector (or dead time, depending who you hang around) but all the units fall away and you wind up with a pattern.

Andy

[mayor]

Andy, you are missing the engine volume in that equation.  Yes as the rpm goes up the volume goes up, but the constant on the volume per fill needs to be recognized somehow.  Both a 96” and a 103” can have the same rpm range and MAP value, but the 103” has a larger base volume to start.  That doesn’t mean that a 103” will always out produce a 96”, but it does mean that it starts with a greater likelihood.  

[whittlebeast]

The engine displacement does not get in the way of the plots.  I have tuned 1000 HP twin turbo drag cars and 50 hp EU restricted Sportys this way.  They all wind up with a distinct pattern.

Try it on several motors you have tuned.

Andy

[Buckeye_Tuning]

Isn't this about using MV to determine WOT AFRs?

Take that other crap to a new thread.

[hrdtail78]

I agree this does deserve its own topic, but I don't if the mods here would let us start to many of these types of topics.

Take a 2012 103 engine.  Pick a 009 level cal.  Any stage 1 you want on the thing. Now install a 255 cam. Set up the VE's with Andy's math. Now remove the cam, and install a 260. Same displacement. Same injector size.  Completely different air requirements for different  RPM, and MAP.  Period.  The 255 doesn't have the duration to move the air at 5000 like the 260 does.

[mayor]

I agree this does deserve its own topic, but I don't if the mods here would let us start to many of these types of topics.

agreed, I think one thread loosely based on DIY tuning can be easily ignored....multiple becomes a different animal all together.

Take a 2012 103 engine.  Pick a 009 level cal.  Any stage 1 you want on the thing. Now install a 255 cam. Set up the VE's with Andy's math. Now remove the cam, and install a 260. Same displacement. Same injector size.  Completely different air requirements for different  RPM, and MAP.  Period.  The 255 doesn't have the duration to move the air at 5000 like the 260 does.

this was going to be my next example. 

[whittlebeast]

I agree this does deserve its own topic, but I don't if the mods here would let us start to many of these types of topics.

Take a 2012 103 engine.  Pick a 009 level cal.  Any stage 1 you want on the thing. Now install a 255 cam. Set up the VE's with Andy's math. Now remove the cam, and install a 260. Same displacement. Same injector size.  Completely different air requirements for different  RPM, and MAP.  Period.  The 255 doesn't have the duration to move the air at 5000 like the 260 does.

.... and the scatter plots will take a different pattern but if both motors are fully tuned, I bet the patterns will be distinct.  Blow the tune and the mistake will jump right out at you.

Andy

[mayor]

Isn't this about using MV to determine WOT AFRs? 

I don’t think it’s as simple as this being a separate discussion at this point.  I see his advanced thoughts on the tuning methods as relevant and still worth discussing on this thread, since he has stated that the narrow band sensor values would be too flaky to use in the manner that the OP has suggested and he offered an alternative method that he felt was better.  If he’s using only that one method and he insists that is creating a superior tune compared to using the OP’s idea of sensor voltage, then he should explain how that method is derived so that the rest of us understand where his thought process is. 

[mayor]

.... and the scatter plots will take a different pattern but if both motors are fully tuned, I bet the patterns will be distinct.  Blow the tune and the mistake will jump right out at you.

can you post up an example?  I don’t know about the rest of the fellows, but I’m not convinced yet based on your explanation of the math.  I also haven't seen a case yet at wide open where the sensor voltage was flaky, so maybe were aren't looking at the same things. 

[whittlebeast]

I don't have many examples of two similar motors.  You guys should have a zillion examples of very similar but different motors.

Most everything I get involved with involves motors nobody else would touch. 

Andy