I created this spreadsheet and I figured some of you could get some use out of it.

Change the values in the two tables at the top of the spreadsheet. These are the same two tables you will see in Tunercat; 1. % Change to Air/Fuel Ratio VS. Coolant Temp at WOT and 2. % Change to Air/Fuel VS. RPM at WOT. This makes it much easier and quicker to tune. Once you have the tables the way you want them, simply copy and paste the values from excel back into tunercat.

Air/Fuel Calc. Spreadsheet


Enjoy.

 

*** YEA DUDE that's the $HIT!!!!!!!! You da man, since no one else know's WTF your talking about LOL That's awesome dude that will definately help out.. You should post this in the COMPUTER/TUNING section...

thanks again

 

OK guess I'm an idiot, but how does this thing work?

 

If you adjust the tables in the spreadsheet, it will tell you the A/F ratio vs temp on the side. That way you can tweek the tables there first, get the A/F ratio you want, then copy them into TC. Much easier than doing it in your head or using the calculator on the computer. I wish someone would have thought of it earlier, it's so simple but so very helpful!

 

I agree, this is a great idea, and it's hard to believe no one thought of it sooner!

Thanks a lot! Edit: I see the graph now, cool.

However, I cannot get it to update the top tables when I directly edit the resulting AFR cells... it only works the other way around. Does it work for you when you pick an AFR? Will it change the % change cells when you do that?

 

There have been quite a few similar spreadsheets available before, so yes, it's definetely been done, but in my opinion, these formulas aren't very accurate in real life (proven on a dyno) and playing with them results in waste of dyno time.
Maybe someone here had better results?

 

Have you seen the idea posted on here of tuning the MAFS tables by disabling PE mode, and then getting the BLMs in the 14/15 cells to 128? This should make certain that the airflow is being measured correctly at WOT levels.

Then once PE mode is reenabled, the formula should have correct data input in order to calculate a reliable AFR. One person has verified this on a dyno. He was within .1 AFR I believe.

 

I have never dyno tuned my car so I can't give specific details on what has worked or hasn't worked. It is meant to be more of a generic tool than anything. If you are dyno tuning and need to richen/lean it out some, you can use the spreadsheet to figure out (roughly) how much to change the tables. From what you have you seen, are the approximate a/f ratios using the formula in TunerCat generally richer or leaner than the actual a/f ratios seen on a dyno/wideband?

I made it as a tool for my own tuning - just sharing it incase someone else might get some use out of it.

 

It doesn't work both ways. You have to change the tables, not the resulting a/f ratios.

 

I wrote myself a spreadsheet similiar to this one about 2 years ago...but this one is nicer. It displays the whole temp range all at once...for whatever that's worth.
And you're right, it isn't really a worthwhile thing to mess around with on a dyno at $100/hr. Ask me how I know.

I still use the ~10points of pe vs rpm to change a/f ratio by 1 point. Works well enough.

 

Well, IMHO the jury is still out on purposely allowing your car to run at around a 14.7:1 a/f ratio on purpose.
Although I just did this exact thing on my car last weekend so that I could experiment with this theory.