How the PCM controls fuel
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Post Fiend
Joined: Feb 2006
Posts: 11,892
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From: Middle Tennessee
How the PCM controls fuel
I have been trying to get to the bottom of how our PCMs control the fuel supply to our engines. I know it controls RPMs by adjusting the fuel supply but am not sure how it does this. I would think pulse timing and duration maybe along with HPOP pressure to the injector. Now I've heard it does this based on accelerator position and I think it was the MAP sensor.
While snooping around I came across this at smokin diesel
I know it is about a cummins but our trucks have this too right. Does this apply to our rigs as well? Wonder if I need to try to get my IAT sender back into my system for a more accurate reading instead of zip tied next to it? I don't generally like to play with something until I know how it works. I could definately see some very poor performance result if this is how the PCM controls things and something is out of whack. Could explain some really bad fuel economy too.
While snooping around I came across this at smokin diesel
I know it is about a cummins but our trucks have this too right. Does this apply to our rigs as well? Wonder if I need to try to get my IAT sender back into my system for a more accurate reading instead of zip tied next to it? I don't generally like to play with something until I know how it works. I could definately see some very poor performance result if this is how the PCM controls things and something is out of whack. Could explain some really bad fuel economy too.
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Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
Originally Posted by mech2161
The iat being under the hood would see higher temps than in the tube. This would lean the fuel not richen it.
Posting Guru
Joined: Oct 2004
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From: Morgantown WV
If your running a Quikk filter there will not be that much difference. If you still have a stock air box drawing from the front the sensor would see higher temps and lean the fuel. This may lower power but not reduce mileage. Yes is helps fuel control along with coolant temp and oil temp, tps and map.
Last edited by mech2161; Mar 28, 2006 at 11:12 AM.
Lead Driver
Joined: Oct 2004
Posts: 7,413
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From: Columbia, MO
Just a suggestion, but have you called one of the tuners, like Jody Tipton, to pick their brain? I'd be willing to be that Jody could fill your head with a lot of knowledge. There's a bunch of different sensors that can contribute to the fuel control. There's the AIT sensor you mentioned, but there's also another one in the y-pipe. You've got the throttle position sensor, IPR, MAP, CPS, oil temp, coolant temp, etc... But, I don't know for sure which ones will change the fuel delivery.
