DigitalFusion

Hey all,

I am kinda confused (yeah, whats new?). The hondata site says to use a 1:1 ratio FPR for the boost option. They say:

Now according to Vortechs site, the lowest rate they sell is a 3:1, and the AEM one is kinda spendy. Does Vortech make a 1:1 but its just not listed? I dont get it. What RRR's are u guys running? (those of u on hondata anywoo)

TurboInteg95

actually you can just use the stock regulator that is on your fuel rail. If you have an aftermarket fuel setup go look in a summit magazine or something for an FPR, my friend bought a nice one for like $90. I think it was a paxton or aeromotive or something, i dont remember.

Xerxes

i don't know about integras, but the stock regulator on a 99-00 civic si DOES NOT increase fuel pressure above 0' vacuum.

-Xerxes

DigitalFusion

if it helps, I have a B16A3. The Del Sol VTEC motor

dustin

Ahh it HAS TO!!! that's how they work man! I'll bet you actual money it does...


Take the regulator apart and look inside... it doesn't know the difference between boost pressure and spring pressure So unless you've tapped the pressure source for the FPR off something with a check valve in it (like the civic si cruise control line?) then it definately raises fuel press. in boost

DigitalFusion

ok, so i DONT need a RRR? I only plan on less than 300 WHP and less than 10 PSI

dustin

I'd still get an aftermarket regulator.

Note that we are NOT talking about a Rising Rate Regulator. Those are regulators that raise pressure at a rate higher than 1:1.

Factory regulators, and all std. fuel pressure regulators, are 1:1. This is to compensate for vacuum (or boost) in the manifold working against fuel pressure in the rail to maintain fuel delivery based solely on injector pulsewith (else in high vacuum, much more fuel would be delivered at the same pulsewidth than at 0 vacuum, since the motor is trying to "suck" the fuel out of the injectors)

Dustin

TurboSedan

For standalone setups where the regualtor will not see extreme fuel pressures, the AEM is a great unit though it is expensive. I use it and have not had a problem with it.

Sonny

It doesn't, Dustin. I tested several of them with my own car, in car fuel pressure gauge, in car boost gauge. Boost kept going up, fuel pressure was constant.

I had 3 of them. 2 of them did not rise under boost. 1 of them did. The 1 that did rise under boost was STOCK. The ones that did NOT rise under boost had B&M chop tops on them, so they may have had enough preload on the spring to max it out early.

Additionally, I was at DSR when Doug tuned Modacar's JRSC type R there. I watched him check the static fuel pressure at idle. 50 psi. I watched the fuel pressure gauge during the dyno pull. It was ALWAYS 50 psi.

Draw your own conclusions.

Sonny

Sonny

I just wanted to add that my conclusion was to use the AEM FPR.

Even though I found a stock regulator that did rise under boost, it wasn't 1:1. It was more like 1:1 up to 3 psi, then 0.7:1 up to 9 psi. Besides, after you install a high output pump, you won't be able to get the idle pressure back down without drilling holes in the stock one.

I kept my rising OEM fpr only because I was running the stock fuel pump and that pump was maxed out with the 450cc injectors, 50 psi of fuel pressure under boost, injector duty cycle around 70-80%, and a JRSC @ 8psi.

Sonny

dustin

The FPR is just a hole with a metal plate over it, and a spring pushes the plate down over the hole. On the spring side, is a port for vacuum. The compression force in the spring maintains static fuel pressure.

If we were to clamp the disc over the hole and effectively plug it up, fuel pressure at the rail would rise to the highest level attainable by the pump in the system at the current flow rate of the injectors. Likewise, if we were to completely remove the disc, fuel pressure would be zero at the rail. To maintain fuel delivery vacuum, the FPR is responsible for lowering fuel pressure in response to manifold vacuum. That is, if manifold vacuum increases X units (lower pressure), the FPR must drop rail pressure X units to maintain the pressure differential between the m anifold and rail. To accomplish this, vacuum relieves some of the spring force and allows more fuel to flow. In much the same way under boost, additional force will be added to that of the FPR spring, and less fuel will be allowed to flow through the regulator. This will (attempt to) increase fuel pressure at the rail.

All honda FPRs are practically identical, the only significant difference being the strength of the spring (that determines static fuel pressure, i.e. the ITR spring is stronger because its fuel pressure spec is higher).

Understand, though, that the fuel system has no sort of "Active feedback" mechanism like, for example, a turbo wastegate. The system will only /attempt/ to add or remove fuel pressure. No system actually measures fuel pressure at the rail and reacts. This is where our disagreement lies. To put it another way, in boost your injectors are probably at a resonably high duty cycle. Thus, fuel is being injected into the cylinders and this is significantly going to affect rail pressure.

Let me try to explain even further. To your factory FPR, the injectors are 4 precisely controlled "leaks" in the fuel system. If I were to drill a 1/2" hole in my fuel rail, no matter how hard my 1:1 OE FPR tried, I would still have zero fuel pressure. The FPR /is/ adding fuel pressure in boost, but the fact that the injectors are flowing a ton of fuel significantly detracts from this.

Fine, you may say. But how come when the car is idling if I pull the vacuum line off and pinch it I see fuel pressure raise about 10psi? This is because at idle, the duty cycle of the injectors is so low that it barely affects fuel pressure at all.

I run 50psi atmospheric fuel pressure on my GSR. With the vacuum hose on at idle, I see 40psi. On the dyno, as the car went through vacuum, fuel pressure peaked at 50psi at 0 vacuum/boost. At full boost (7psi), fuel pressure was at 50psi. My Aeromotive 1:1 regulator WAS adding fuel pressure in boost, but the flow rate of the injectors was effectivey /canceling/ the added fuel pressure out.

It is entirely possible for the regulator to /add/ pressure in boost, and it depends entirely on the fuel demands of your motor and the flow rate of your fuel pump at pressure.

Dustin

Sonny

I understand the basics of how the FPR operates, but thanks for posting the info.

I am merely stating my observations from tests of several different FPR's.

Stock FPR #1, B&M chop top:
Idle = 34 psi
Static = 44 psi
9 psi of boost = 44psi

Stock FPR #2, NOS chop top:
Idle = 34 psi
Static = 44 psi
9 psi of boost = 44 psi

Stock FPR #3, no chop top:
Idle = 34 psi
Static = 44 psi
9 psi of boost = 51 psi (not quite 1:1, but close)

AEM FPR
Idle = 34 psi
Static = 44 psi
9 psi of boost = 53 psi (exactly 1:1)

The gauges don't lie. The first two FPR's clearly indicate that pressure was not rising under boost.

The FPR's job is basically to maintain a constant pressure differential between the manifold pressure and the amount of pressure behind the injector. At 20" of vacuum, you essentially have -10 psi of pressure in the manifold...or 10psi of vacuum sucking on the injector tip. With 34 psi behind it plus the 10 psi pulling on it, your overall fuel pressure is 44psi. At atmospheric pressure (0psi/0"), there is no "suck" on the injector tip, but you have 44 psi behind the injector, so your overall pressure is still 44psi. At 9 psi of boost, you have 9 psi pushing against the injector, but you have 53 psi behind it (in the case of the AEM FPR) and again, your overall pressure is 44psi.

I realize that you probably know this already, but I'm stating it for general info. This is the reason I do not burn maps for people who don't have a 1:1 regulator like the AEM, SX, etc.

Sonny

Aeka GSR

hrm, ive got a stock fpr with a stock fuel pump running 440 injectors at 8 psi with a hondata on my GSR. Will i be fine?

GruvyTune

Dustin is correct on this one.
I just tuned a guy's GSR recently and he had an inline and stock rail and regulator. Tuned to 11psi without any problems. Static fuel pressure stuck at 50psi but that was ok with the hondata and 450cc DSM injex

Sonny

I didn't mean to imply that Dustin was incorrect...I don't think there is any form of correct/incorrect in this case. It's just that you either have a regulator that rises or you don't.

That's all fine and dandy as long as you take that into account when you are tuning your car or someone else's car, but that piece of info is very important if you are doing tune swaps with other people. If you've got a regulator that rises 1:1 under boost and you've tuned it for 15 psi and you give it to someone who has a regulator that does not rise, that could spell big trouble.

All of the maps that I have are for regulators that rise 1:1 under boost. I think from a tuning standpoint, it's the cleanest way to go or otherwise you have to consider another variable when tuning.

Sonny

dustin

I've been wrong before....

.... I forget when it was though..


ahaha j/k. I dunno man