Modify stock FPR?

[decathect]

I know that in the Honda world this has been done...

I know most of you will suggest that I get an aftermarket one. However, for my own purposes, and for the sake of argument, I am wondering if it would be possible to maybe drill a small relief hole in the inner piston of the FPR to relieve the excess pressure from a walbro 255? Right now I think my pump is overrunning my stock FPR and the pressure is too high.

Would this at all be possible? Has this been done before? VFAQ out there about it? (ha, I looked but didn't find one).

THanks!

 

[decathect]

the 2nd relay is for the standard fuel pump rewire. I'm doing both this low/high voltage thing in conjunction with the fuel pump rewire to make sure I get consistant, good voltage that isn't hampered by stock wires.

 

[steve]

Then it would typically go in front of the "speed" relay and it's output would connect where you have the battery going into the otehr relay. That way the other relay only works when the pump is on.

 

[decathect]

SPDT = Single pole double throw.

Or, I could just have the voltage source for 85 come from something that is only powered when the car is on.

Either way would work fine though.

 

[350war]

Why not run your 12v thru your pressure switch. The switch itself works like a spst relay. Sorry my paint skills are not the best.

 

[jeffo]

I doubt that the contacts of the switch could handle the current of a bigger pump, they are made to switch light loads. With the resistor in parallel, the current might not be too bad, but I wouldn't try it.

 

[decathect]

right, i agree with jeffo, i'm not entirely sure how many amps that switch could handle. Plus, if you look at my way, if the the switch fails, the pump gets full power by default, rather than the lower voltage. That way my engine won't blow up because its running too lean at full boost.

 

[the_mork]

Replying so I stay posted.

I considered trying this on my car at one point but I never got the ambition to do the project. I have a bit of an advantage in that I'm already running an evo8 ecu so all I would need is to figure out the wiring and let the computer do the switching for me.

If you get somewhere with this (or even not) then I might revisit this project when I get the car out in spring.

 

[decathect]

Absolutely, I'll keep this thread updated. I won't be trying it for another week or two though.

I will also be monitoring A/F's in conjunction with this with my wideband, to make sure I'm not cutting too much fuel when boost hits.

 

[350war]

I see if the power to the coil was lost it would give full voltage. Thats good thinking now I understand why you would want 2 relays. I also like the idea of running a potentiometer. If the switch was wired in the way I drew it the system would not be redundant if the switch failed.

 

[Ceddy]

I also like the idea of running a potentiometer.

You have full pump current running thru the potentiometer.

A 30 Amp potentiometer is going to be big and very expensive.

Remember all components need to be rated above maximum current flow.
You don't want overloaded electrical components anywhere near your fuel system.

 

[350war]

Ceddy you are right about the expensive part. Check this out IML Rotary Dimmers: Rotary 12 volt DC Dimmers - Rotary 24 volt DC Dimmers - ILDIM and ILVPC Dimmers from SailorSams.com Dimmers. Look at the ILVPC variable power dimmers.

 

[decathect]

that symbol is for a rheostat, that's what i'll be using. Hopefully I can find one that isn't prohibitively expensive. Otherwise I'll just have to use a resistor, and figure out what size to use.