Rule of thumb for PE vs RPM against AFR
07-18-2007, 08:53 PM
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Rule of thumb for PE vs RPM against AFR I'll keep this short as the details aren't really pertinent in my opinion. What's the rule of thumb for PE vs RPM against AFR? This is for my LT1. I'm not stupid, I have fooled with LT1 Edit before but was kinda wondering in most cases what % would equal about 1 AFR point either way. As of now, last time I was on a wideband, I was seeing a flat 13.5:1 AFR at WOT. Until I could get on the wideband again, I was hoping to bump my PE % up and theoretically achieve 12.5:1.
07-18-2007, 09:09 PM
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I think it works like this...
WB_AFR/PE_Commanded_AFR=%Error
If you're commanding 10:1 and seeing 9:1, that's .9 or 90% meaning you're 10% rich. So, you would need to remove 10% from PE fueling.
If you're commanding 12:1 and seeing 13.5:1, that's 1.125 or 112.5% meaning you're 12.5% lean. So, you would need to increase PE fueling 12.5%.
I believe you would need to do the equation for each cell to get it straightened out.
WB_AFR/PE_Commanded_AFR=%Error
If you're commanding 10:1 and seeing 9:1, that's .9 or 90% meaning you're 10% rich. So, you would need to remove 10% from PE fueling.
If you're commanding 12:1 and seeing 13.5:1, that's 1.125 or 112.5% meaning you're 12.5% lean. So, you would need to increase PE fueling 12.5%.
I believe you would need to do the equation for each cell to get it straightened out.
07-18-2007, 10:41 PM
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Originally Posted by SSpdDmon
I think it works like this...
WB_AFR/PE_Commanded_AFR=%Error
If you're commanding 10:1 and seeing 9:1, that's .9 or 90% meaning you're 10% rich. So, you would need to remove 10% from PE fueling.
If you're commanding 12:1 and seeing 13.5:1, that's 1.125 or 112.5% meaning you're 12.5% lean. So, you would need to increase PE fueling 12.5%.
I believe you would need to do the equation for each cell to get it straightened out.
WB_AFR/PE_Commanded_AFR=%Error
If you're commanding 10:1 and seeing 9:1, that's .9 or 90% meaning you're 10% rich. So, you would need to remove 10% from PE fueling.
If you're commanding 12:1 and seeing 13.5:1, that's 1.125 or 112.5% meaning you're 12.5% lean. So, you would need to increase PE fueling 12.5%.
I believe you would need to do the equation for each cell to get it straightened out.
I follow you mostly. Equation is no problem but I think the problem might be my interface. I use LT1 Edit and for power enrichment I have two tables. One for PE vs coolant temp which I basically flatlined cuz car should be relatively the same temp when I am about to go WOT anyway. Second is PE vs RPM. That table uses % of fuel rather than AFR. Am I totally off base here????? Only time I see a "commanded AFR" is in open loop (on my interface).
07-19-2007, 08:30 AM
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You mean it uses EQ? In other words, you have a number like 1.2 in your PE vs. RPM table? If it's EQ, the way you get AFR is STOICH/EQ=AFR. Using my number above, 14.7/1.2=12.25, or a commanded AFR of 12.25:1. If you have any values in the PE vs. ECT table, you will have to factor them in. Usually, most people work off of the PE vs. RPM table though...
07-19-2007, 11:15 AM
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I'm getting no where quick. Forget the PE vs temp. I've got that took care of. I wanna know strictly PE vs RPM. My tables show "% change at 400 rpm" and then "% change at 800 rpm" and "% change at 1200 rpm" so on and so forth. I've got 13.5:1 AFR at WOT. I want to know theoretically how to calculate what % change I need to input to achieve a 12.5:1 AFR.
07-19-2007, 12:18 PM
#7
Download this Excel file. http://www.mediafire.com/?2czngzxdfyt
Then copy the data from your % temp table and % rpm table into the spread sheet. It will show you what your commanded A/F is. Then adjust the #s in the % rpm table until you get a 1.0 richer commanded A/F if that is what you want. Then copy those numbers back into your cal file. It works with the data in Tunercat. I've never seen what LT1Edit data looks like, but it should be the same. Commanded A/F will not always equal your actual, but for just richening it up 1 point, this method should work.
Then copy the data from your % temp table and % rpm table into the spread sheet. It will show you what your commanded A/F is. Then adjust the #s in the % rpm table until you get a 1.0 richer commanded A/F if that is what you want. Then copy those numbers back into your cal file. It works with the data in Tunercat. I've never seen what LT1Edit data looks like, but it should be the same. Commanded A/F will not always equal your actual, but for just richening it up 1 point, this method should work.
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07-19-2007, 01:09 PM
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That looks pretty neat. Thanks for that link. I'll play with it. Although I don't understand why it shows all the data for coolant temp and nothing for RPM. Looks like it should be the other way around. (Mine's based all around RPM anyway.) Regardless, I'll tinker with it.
07-19-2007, 01:13 PM
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Well didn't take long for me figure it out. 
One more quick question, how will injector constant affect the PE tables? Or will it? Reason I ask is I was using a lower constant when I achieved the 13.5:1 and bumped it up for street driving.
One more quick question, how will injector constant affect the PE tables? Or will it? Reason I ask is I was using a lower constant when I achieved the 13.5:1 and bumped it up for street driving.
07-19-2007, 01:22 PM
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Originally Posted by 2xLS1
The spread sheet is populated with stock temp table data. You normally don't edit that table at all. You enter your RPM table data into it (copy and paste from your cal to the spread sheet) and it calculates the commanded A/F for you. You should only change injector constant if you change injector size.
