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Old 03-19-2023, 09:15 PM   #449 (permalink)
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Location: Oklahoma
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WJ - '03 Jeep Grand Cherokee Laredo
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90 day: 14.59 mpg (US)

ZJ - '94 Jeep Grand Cherokee Laredo
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Originally Posted by t vago View Post
Eh... I'm not sure that will work.

The problem is, that at the interface between the fuel injector nozzle and the intake manifold, there is a varying pressure differential. Most cars handled this by varying the fuel pressure with a modulated fuel pressure regulator operated by intake manifold vacuum so as to maintain a more-or-less constant pressure differential.

Chrysler fuel systems were different in that they forced fuel pressure to be constant (either 49 or 58 psig) and used manifold vacuum to figure out the differential and therefore the amount of adjustment needed to deliver the precise amount of fuel.

I'm thinking that if you do install your fuel pressure sensor to the fuel rail port of your Jeep, you will find it will have a fuel pressure that will vary a little bit due to absolute fuel consumption (ie, engine loading), but you'll still have to compensate somehow for the pressure differential between the fuel system and the intake manifold vacuum. Such a differential will cause anywhere between 3% to 9% variation between the rated flow rate of the fuel injectors.

You can still pursue it, and I'll help as much as I can.

Good to hear! It is of course still a work in progress, so do let me know if you run into any problems with it.

For instance, I just discovered a nasty little bug related to the refactoring I did to the Chrysler fuel injection correction. Yay... The bugfix should be committed to the git repo presently.
Ah that makes sense! I didnít consider the varying pressure in the manifold relative to the rail.
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