D-Jet Fuel Pressure Regulator, How high should it go? Options

[GregAmy]

What should be the maximum capability of the stock D-Jet pressure regulator? Mine only goes to 36.

If that's normal, is there another similar-format regulator that can go up to around 45psi?

Background: Microsquirt project. Was hoping to use the stock regulator, but now need something that I can easily mount in the same location, if possible. Injectors I'm using are rated at 43.5psi.

Discuss!

[GregAmy]

Since we're going deeper into the design...

And, by the way, before we get too deep into this I wanted to recognize the assistance I've received from EricP, @Montreal914 . He has his own build going on but we've been swapping info back and forth. Thanks, Eric!

My design basis an over-riding "prime directive": use as many stock components as reasonably possible, and try to design it such that anyone can install it. I also have a design cost of <$1500 in parts. Unless someone wants to take this design and sell it as a kit for the community (and if you do, please contact me), I plan to do a full write-up of parts build lists, sources, design, and instructions.

Toward this, my goal is to use the "stock" fuel pump and pressure regulator, if at all possible.

I got the pump I'm using from Chris Foley at Tangerine; it is a 2-port replacement for the factory 3-port. He thinks it's the Bosch 69133. I've yet to find any specs on that pump but I havne't looked hard; I was working under the impression that the limiting factor here was the regulator. Maybe that was a flawed ASSumption.

More later; time to go to work to pay for all this. - GA


EDIT: Current plan is to tune the engine to 35psi, with "255" as the flow number for the injectors.

[JamesM]

Since we're going deeper into the design...


My design basis an over-riding "prime directive": use as many stock components as reasonably possible, and try to design it such that anyone can install it. I also have a design cost of <$1500 in parts. Unless someone wants to take this design and sell it as a kit for the community (and if you do, please contact me), I plan to do a full write-up of parts build lists, sources, design, and instructions.

Toward this, my goal is to use the "stock" fuel pump and pressure regulator, if at all possible.

Totally possible but you may be better off just running d-jet, l-jet, or possibly vanagon injectors, with load resistors at the stock pressures in that case. Pretty much every d-jet component except for the throttle position sensor can be re-used in a Megasquirt build (including the stock wiring harness if you are crafty enough) but having run one like that for ~15 years I can tell you it has its short comings. My first d-jet to MS conversion i think my total parts cost including the MS ECU components (I soldered it myself) was roughly around $150 bucks, but the necessary labor was beyond what i would recommend to anyone.

I got the pump I'm using from Chris Foley at Tangerine; it is a 2-port replacement for the factory 3-port. He thinks it's the Bosch 69133. I've yet to find any specs on that pump but I havne't looked hard; I was working under the impression that the limiting factor here was the regulator. Maybe that was a flawed ASSumption.

More later; time to go to work to pay for all this. - GA

Not sure about the Bosch 69133 but the factory 2 ports are also supposed to have a built in over-pressure circuit. Hard to say what might be limiting your total pressure but that MSD FPR that is rated 36-42 PSI has the Bosch d-jet part number on it. So I would think that if everything were healthy you should at least be getting close to 40 if not more. I have first hand seen one that was set ~50psi.

That being said if all you can get is 36 you could just leave it there, those injectors may be fine running at that and while it is helpful to know the exact response and flow numbers at a given pressure it isnt mandatory as you build your own fuel map anyways. Given thats the top end of your fuel system output and the bottom end of acceptable pressure on the injectors though I think Jeffs point as to a safety margin may be something to be considered.

Compromises like this are why i have moved more and more away from using a lot of the d-jet bits over the years. I can elaborate on the details a lot more if you like but that only matters if you are interested in changing your goals slightly. I get your current goals, I used to share them, and they are totally doable, just realize they involve compromises and one of those being running as optimally and reliably as it could, though no more so than running a d-jet system. You just wind up inheriting its short comings.