rising rate fuel pressure regulator question...

arvcube · Post by **arvcube** » Tue Sep 06, 2005 3:10 pm

im putting together my fuel system and came across a decently under-priced new adj/boost sensitive rising rate fpr (begi style). is it possible to use this with megasquirt and plumb it directly to the fuel rail llike a regular adjustable fpr? i understand that rrfpr's are usually used in conjunction with the stock fpr's....thanks in advance...

wildman · Post by **wildman** » Tue Sep 06, 2005 3:35 pm

sure you can use it, it gets plumbed into the fuel line after the stock unit..

you would want to have it in place before tuning,, as it will definetly effect the table in the boost areas.

arvcube · Post by **arvcube** » Tue Sep 06, 2005 3:58 pm

wildman wrote:sure you can use it, it gets plumbed into the fuel line after the stock unit..

you would want to have it in place before tuning,, as it will definetly effect the table in the boost areas.

what i meant was, can this rrfpr be used in place of the stock unit? i have a fuel rail that has no provision for a stock style fpr...can i use this rrfpr as you would an external adjustable fpr or does it have to be used with a stock fpr?

efahl · Post by **efahl** » Tue Sep 06, 2005 7:51 pm

Is it really a rising-rate regulator, or is it just a MAP referenced one? The latter is much preferred as you have a fixed req-fuel calculation, the rrfpr gives what will appear to be funky numbers when you are tuning (there have been loads of threads on this over the years; should also be some commentary in the manual).

Eric

arvcube · Post by **arvcube** » Tue Sep 06, 2005 9:34 pm

efahl wrote:Is it really a rising-rate regulator, or is it just a MAP referenced one? The latter is much preferred as you have a fixed req-fuel calculation, the rrfpr gives what will appear to be funky numbers when you are tuning (there have been loads of threads on this over the years; should also be some commentary in the manual).

Eric

the unit is the fuel pressure regulator offered by EIP...
per description..
"This FPR is made from billet aluminum and cnc machined. It is fully adjustable and boost sensitive. Fuel adjustment is possible for base as well as the rate at which fuel pressure increases proportionally to boost input. Adjustable from 1:1 all the way to 12:1 rate of rise. This adjustability means flexibility for various applications. Includes a new high quality stainless steel mounting bracket. "

need to know if this will work or if i have to rid of this and get another fpr...thanks for the response...

efahl · Post by **efahl** » Wed Sep 07, 2005 6:43 am

Sure sounds like the description of an rrfpr to me. And it also sounds like you can adjust it to have a 1:1 rise, which basically disables the "rr" part and just makes it a MAP referenced regulator. In any case, it should work just fine, so use it since you already have it; a non-linear rrfpr is pretty much transparent to tune around, and the only problem it would present would be a "too flat" VE table compared to an identical engine with true MAP referenced fuel pressure. Oh, assuming of course that you don't get the fuel pressure too high (90-100+ psi) and lock up the injectors... (This usually only happens when people try to run small injectors at high pressures to get enough flow.)

Eric

arvcube · Post by **arvcube** » Wed Sep 07, 2005 7:27 am

thanks for the reassurance eric...my target hp is around 260-270 so i will be using 44lb injectors. figured that the 36's would be maxed out at that hp and i want to run a lower fuel pressure to achieve my hp goal

Minami Kotaro · Post by **Minami Kotaro** » Wed Sep 07, 2005 7:30 am

Your VE table will indeed look funky, and you will indeed need to keep a close eye on your fuel pressure.

I kind of wish I had a regular 1:1 boost-referenced regulator instead of hte rising rate I have, but if the price is cheap enough go for it.

efahl · Post by **efahl** » Wed Sep 07, 2005 8:07 am

Ok, it's the top one here?

http://www.eiptuning.com/eip/fuelpressu ... ators.html

If you can get it for a good price, go for it. Just set it and forget it. (1:1, of course.)

Eric

arvcube · Post by **arvcube** » Wed Sep 07, 2005 9:35 am

that's the one....coo......ronco action set it and forget it!

andereck · Post by **andereck** » Wed Sep 14, 2005 8:57 pm

I know this is an old thread, but I just saw it. The "regulator" mentioned may be misnamed by the distributor. It appears to be a bleed adjustable "FMU". It would be active really only under boost and plumbed into the return line after the stock regulator. Boost applied to the diaphragm will pinch off the return line resulting in higher system pressure. You can see the adjustable bleed attached to the boost reference port. This lets you dial in a leak to adjust the amount of fuel pressure increase....to a point. The problem is that under vacuum you have a leak of course and the disproportionate area would mess up your vacuum reference under part throttle. Most of these units are designed to do nothing under vacuum and rely on the stock regulator for control, hence the adjustment stud that is there to keep its influence out of the picture under vacuum.

efahl · Post by **efahl** » Thu Sep 15, 2005 7:20 am

Mark,

Arg, that sounds like a real hack and something to stay far away from... Thanks for the info.

Eric

arvcube · Post by **arvcube** » Tue Sep 20, 2005 3:38 pm

andereck wrote:I know this is an old thread, but I just saw it. The "regulator" mentioned may be misnamed by the distributor. It appears to be a bleed adjustable "FMU". It would be active really only under boost and plumbed into the return line after the stock regulator. Boost applied to the diaphragm will pinch off the return line resulting in higher system pressure. You can see the adjustable bleed attached to the boost reference port. This lets you dial in a leak to adjust the amount of fuel pressure increase....to a point. The problem is that under vacuum you have a leak of course and the disproportionate area would mess up your vacuum reference under part throttle. Most of these units are designed to do nothing under vacuum and rely on the stock regulator for control, hence the adjustment stud that is there to keep its influence out of the picture under vacuum.

so basically what you're trying to say is i can't use this regulator, correct? if so, i guess i will have to get rid of it and buy one that i can use...

andereck · Post by **andereck** » Tue Sep 20, 2005 4:44 pm

Basically, no, it would not be a great choice. Assuming you have a MS and the appropriate sized injectors a standard vacuum referenced regulator is sufficient. Most have equal area on both sides of the diaphragm to give you a 1:1 pressure increase under boost. You use the MS to feed the engine more fuel via the map signal. FMU's are used when a forced induction kit is installed on a vehicle and the factory injectors are used. Without the substantial increase in fuel pressure the kit would not be able to deliver the power it was engineered for. They are fairly common with blower kits, and while indeed a "hack" they provide for acceptable performance for some applications.

TurboDave · Post by **TurboDave** » Wed Nov 16, 2005 6:38 pm

Again - old post, but i just found it!

This Fuel pressure regulator in the link below looks to be a TRUE rising-rate unit (the SFMU, not the FMU). I'll be purchasing one of these shortly.

http://www.vortechsuperchargers.com/pro ... l_fmu.html

Quote:

Q: Is it necessary to use a stock or another regulator with the SFMU?

A: For almost all applications only the SFMU would be used. Using the restrictive stock regulator with the SFMU with a high flow rate pump would cause the rail pressure at idle to be too high and cause a rich condition. Because the SFMU has so many adjustment features most requirements can be met with it alone.