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logging AFR


ccgoodwrench

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I have been thinking about logging my AFR through HPTuners [non pro] with the EGR 5 volt position singal, I know our trucks don't have a EGR valve, but looking at the engine section under general tab you can enable the EGR and under the airflow tab the table is filled in with numbers.[it's like GM was going to put the EGR valve in and then decide not too]. so i think the wiring is their at the PCM, Anybody else have any thought's on this, i think this might work

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I have been thinking about logging my AFR through HPTuners [non pro] with the EGR 5 volt position singal, I know our trucks don't have a EGR valve, but looking at the engine section under general tab you can enable the EGR and under the airflow tab the table is filled in with numbers.[it's like GM was going to put the EGR valve in and then decide not too]. so i think the wiring is their at the PCM, Anybody else have any thought's on this, i think this might work

 

With EFI people use the EGR circuit to log Fuel Pressure, so it is possible to log AFR trough the EGR circuit. It might have to take some creativity and a custom PID to get proper results.

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  • 2 weeks later...
Try this connecting wideband via A/C or EGR for no pro HP Tuner its for a Vett but should help.

Thanks that helped, But i still can not figure out the pid stuff, One of these days I will get it figure out. Or maybe my PCM dosen't acept the input of the wide band.

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Thanks that helped, But i still can not figure out the pid stuff, One of these days I will get it figure out. Or maybe my PCM dosen't acept the input of the wide band.

 

I just got mine to work great through the ac/switch. Where are you having problems? Did you program your analoge out 2? I'll walk you through it if you want.

Edited by dozer (see edit history)
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I just got mine to work great through the ac/switch. Where are you having problems? Did you program your analoge out 2? I'll walk you through it if you want.

I'm not really sure where the prolbem is, I followed the steps in that link you supplied, I think I'm getting close I get a reading of 0.04 volts in my scanner under PLX wide band hook up to pin 55 of the PCM. If you could walk me through it step by step i would appreciate it

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I'm not really sure where the prolbem is, I followed the steps in that link you supplied, I think I'm getting close I get a reading of 0.04 volts in my scanner under PLX wide band hook up to pin 55 of the PCM. If you could walk me through it step by step i would appreciate it

 

I tried pin 55 and could only get 0.04 also. Im begining to belive pin 55 is not the egr pin location on our trucks. So i went with the ac/switch. Also make sure your wideband is putting out 0v-5v i checked mine with my ohm meter and it read 2.5v or so at idle and higher with engine off and gauge on.

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I have about 2.35V coming out of the PLX, what color is the ac wire and how did you tap into it

 

The plug is located right off a line coming off the ac pump down on the bottom of the motor. Kinda looks like a fuel pressure sending unit. Unplug the the plug it has 3 wires and tap into the red wire red wire with black stripe. I soldered the connection with a quick connect. When logging unplug ac/switch and connect signal wire. When done diconnect wire and plug ac/switch back in. If you leave it pluged in during logging it will throw off the 0v-5v signal.

 

ACswitch.jpg

Edited by dozer (see edit history)
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The plug is located right off a line coming off the ac pump down on the bottom of the motor. Kinda looks like a fuel pressure sending unit. Unplug the the plug it has 3 wires and tap into the red wire red wire with black stripe. I soldered the connection with a quick connect. When logging unplug ac/switch and connect signal wire. When done diconnect wire and plug ac/switch back in. If you leave it pluged in during logging it will throw off the 0v-5v signal.

 

ACswitch.jpg

so i will only half to change my pid, and did you ever wire a switch in the cab to switch for AC to AFR, i'm guessing to wire the switch in series to completely disconccet it from the AC singal. I think that PIN 55 will work, I think their is some kind of formula that has to be changed.

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No i just unplug the quick connect for now, maybe next weekend I will add a switch. I could never get a reading from the egr even with 2.5v going to it. I have not read anywhere that PIN 55 is egr on our trucks for sure.

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I did mine like this.

 

Name: Wideband

 

Abbrv: AFR

 

 

Sensor: Air Fuel Ratio

 

Units: :1

 

Under Function i put: ([PID.7101]/.625)+10

 

 

So, basically ([PID.7101]/.625)+10 is a mathematical formula. PID.7101 is the number HP tuner has assigned to the AC pressure switch. Every sensor HP Tuner scans has a PID of it's own. So what you are doing is telling HP Tuner that you want to moniter PID 7101. If you do not add the rest of the formula /.625)+10 your newly named PID would only read the volts it's receiving from the sensor. When you complete the formula, you are telling HP Tuner that you want to take PID.7101 (which can read 0v-5v) and whatever it is reading at that time, divide it by .625, then add 10 to that number. That will give you your AFR. For example, If I was putting out 2.5v this is how the formula would work:

a) First, 2.5 divided by .625 That equals 4.

b) Take the 4 and add 10 to it. That makes your AFR 14:1

 

However, this is the formula that I use for my gauge, which has a range of 10 to 18. This is where I come up with .625 If your range is different, then you will have to do this step:

a) Figure out the numerical range of your gauge (mine is 8, which I got by taking 18 minus 10=8)

b) Then take 5 (which is the range of the sensor...0v-5v) and divide it by the number just calculated. (for me it would be 5 divided by 8 = .625)

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haven't had much time to play with the truck, do i add the pid 7101 under the table display, user defined configuration, I figured out that my gauge range is 10-20 so i used ([PID.7101]/.5)+10 cause i tried to hook it up under the AC pressure switch wire R/B stripe, and it was disconnected from the sender, and I still can't get it to work :banghead: I keep on getting unsupported parameters when I try and log, I need one of those books that is (HPTunning for dummys) Oh I appreciate your patice with helping me out, thanks man

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