Need help, Rising rate or just a mean looking regulator?

[Guest Looking for apt in Alb Ny]

Hey guys. I bought this fuel regulator that is suppose to be a rising rate but looks more like an imitation. I received it today.Nowhere on the box or instructions does it explain the boost adjustment just psi. I got it for 90 bucks on eBay. What are your thoughts Junk? try it? useful but not the real Rising rate. Either the guy didn't know it wasn't a rising rate or I got took advantage of ? I will give him an email unless I still made a good deal.

On the box it says it has a better response time than stock fuel regulators up to 7 times better. Seems like its worth holding on to. It is well built made in Italy by FSE called power boost valve.here is the eBay link. any help to my question is most appreciated thanks Juan @ JSK 73 Turbo

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=42604&item=2415489037

[DatsunBoy77]

http://www.fuelsystem.co.uk/pbv.htm

 

Sorry for the big pic

 

Ryan

[Guest Looking for apt in Alb Ny]

do I need a one way valve when its under boost? it has a vacuum port. I hooked it up to my vacuum port on the engine and blew through the intake side while adjusting it. works very well. I would think that the boost would raise fuel pressure pushing on the internal diaphragm but so would the spring when its not under vacuum? I'm confused how this works. Is this a rising rate? Will my pressure rise as boost is applied? Thanks Datsun boy for the help

Juan

[SleeperZ]

I hate to pee in your wheaties, but why do you want to install a RRFPR? What fuel pump are you using? These RRFPRs are hard enough to tune -- even when you know what it's specifications are, they cannot be tuned very well (you run rich at lower RPMs).

 

I'm just curious - I've run 250rwhp with stock injectors and FPR, with just a pump upgrade. Why do you want to sacrifice driveability to get a tiny bit more on the top end?

[Guest Looking for apt in Alb Ny]

I am just asking a question. I obviously dont know anything about regulators other than that they control fuel pressure. I was always lead to believe that a rising rate increases fuel pressure with boost which sounds like a good idea to me. I wasnt aware that a rising rate was not worth looking into. Thanks Juan

the question still remains open to anyone is this a rising rate? it doesnt mean I want to use it just identify. Can I use this with no problems?

[SleeperZ]

I am just asking a question. I obviously dont know anything about regulators other than that they control fuel pressure. I was always lead to believe that a rising rate increases fuel pressure with boost which sounds like a good idea to me. I wasnt aware that a rising rate was not worth looking into. Thanks Juan

 

No problem. I cannot personally testify to RRFPRs being hard to tune - maybe someone with real-world experience can chime in.

 

Increasing fuel pressure with boost may seem like a good idea, but it really only works well with a speed-density EFI system, like on Hondas. The Honda systems cannot recognize when the manifold pressure rises over atmospheric (they have a 1 bar MAP sensor) - they fire the injectors like the motor is at open throttle, according to the rpm of the motor, regardless of how much boost there is - so rising rate is good here. For a Nissan system where the air is directly measured and fueled instead of inferred by a MAP sensor, a RRFPR will raise the fuel pressure the same amount whether at 3000 rpm or 6000 rpm. If you are smart, you will optimize the fuel pressure for maximum boost at 6000 rpm and that leaves the engine running PIG RICH at 3000 rpm.

 

At any rate, what I am saying is a RRFPR is an effective band-aid for a turbo'd Honda, where it is an inferior tuning device for an EFI that is designed to run boost.

[DatsunBoy77]

Hey Juan,

I believe that it is a RRFPR that is why it has the the vacuum line on it. A FPR doesnt require vacuum pressure, unlike a RRFPR.

 

-Ryan

[Guest Looking for apt in Alb Ny]

A rising rate gradually rises with boost.It doesn't just dump all the fuel at any boost level It can be adjusted. I have heard that with every increase of 1 pound of boost the fuel pressure should increase 6-8 psi. if you have 12psi at 3000 rmps then that's 12psi ? The power level is there. It just has to stay rich as rpm level increase. I would think this to work with any engine system and be necessary as mention in Corkey Bells' Maximum Boost. I appreciate the help Nathan. the only way to see how this works out is to install it and tell you the results. Nathan Datsunboy thanks Juan

Oh Datsunboy,I think a pressure regulator requires a vacuum line so it knows when its at idle just like the stock FPR on Z's

Im sure this is not a rising rate. There is no adjustment for boost.

[SleeperZ]

Hey Juan' date='

I believe that it is a RRFPR that is why it has the the vacuum line on it. A FPR doesnt require vacuum pressure, unlike a RRFPR.

 

-Ryan[/quote']

 

All good pressure regulators for EFI will have a vacuum port. It is necessary for most EFI systems to maintain a constant fuel pressure relative to manifold pressure. This requires the pressure regulator be referenced to manifold vacuum (or pressure) via the vacuum line. A RRFPR will increase fuel pressure relative to manifold pressure, ie: your base pressure will be greater, so you will get more fuel flow for the same pulse width at boost than you will under a cruising condition.

[z-ya]

I'm using the same regulator. It's a Malpassi rising rate type. It's a nice unit. I've been using mine for over threes years without problems. You got a good prive too, I paid twice that. It is adjustable. Take the small nut off the top, and you will see there is a set screw with a lock nut. Put a scredriver in the set screw, and loosten the locknut. Then you can adjust the pressure using the screwdriver. Remember to tighten up the lock nut after adjusting it.

 

As fas a tuning, I've had no problems. I agree that I probably don't need a rising rate FPR, but it's works fine for me. Of course I am running a programmable ECU.

 

Sleeperz, why do you think a RRFPR will run rich at idle? If you set the idle fuel pressure according to spec, it will idle like a stocker. The only time the RRFPR behaves differently than a non-RRFPR is under positive manifold pressure.

 

Pete

[Guest Looking for apt in Alb Ny]

thats what i was looking for ! someone who could tell me its a rising rate. ! thanks buddy

[SleeperZ]

Sleeperz' date=' why do you think a RRFPR will run rich at idle? If you set the idle fuel pressure according to spec, it will idle like a stocker. The only time the RRFPR behaves differently than a non-RRFPR is under positive manifold pressure.

 

Pete[/quote']

 

I didn't say it would run rich at idle. I say it will run rich at full boost at 3000 rpm if you set it to run right at 6000 rpm. The reason speed-density systems run them is to get the needed fuel above atmospheric pressure - airflow is unknown because they use a MAP sensor.

 

On a Nissan EFI, airflow is KNOWN. It will deliver the fuel for the measured air. RRFPR will raise fuel pressure the same amount at 3000 or 6000, it doesn't care. So people install these because they run lean at high rpms (the injectors are maxxed), and the RRFPR will compensate. But it raises your fuel pressure at rpms where the injectors are not at full duty cycle, so the increased fuel pressure will cause it to run rich.

 

Does that make any sense? I've given this quite a bit of thought, and I think I am accurately describing the EFI and the RRFPR's behavior.

[Guest Looking for apt in Alb Ny]

you make sense a zspeed all i wanted to know was if it was a rising rate. im aware and appreciate your time explaining this. Thanks Juan

[Afshin]

Hi, my understanding is that the RRFPR will raise fuel pressure in accordance with manifold pressure (ie boost) only, so if there is low boost at 3000rpm it will mimimally affect fuel pressure/delivery, however if at 3000 rpm you are running high boost then it will richen the mixture significantly. The ECU will vary the pulse width according to air flow or mass or pressure depending on your set up. Either way the RRFPR will not add the same amount of extra fuel at 3000 rpm vs 6000 at low or high boost since the ecu will still change the injector pulse width.

The net result is that it will increase fuel delivery by the same percentage under boost only. So for example at 6 psi it would increase fuel delivery by 10% over your ecu program for 3000 or 6000rpm accordingly. At 0 psi there would be no effect and at 12 psi there would be a 20% increase from baseline ecu programing for any rpm (these numbers are made up as an example only)

I hope this helps

[SleeperZ]

Hi' date=' my understanding is that the RRFPR will raise fuel pressure in accordance with manifold pressure (ie boost) only, so if there is low boost at 3000rpm it will mimimally affect fuel pressure/delivery, however if at 3000 rpm you are running high boost then it will richen the mixture significantly. The ECU will vary the pulse width according to air flow or mass or pressure depending on your set up. Either way the RRFPR will not add the same amount of extra fuel at 3000 rpm vs 6000 at low or high boost since the ecu will still change the injector pulse width.

The net result is that it will increase fuel delivery by the same percentage under boost only. So for example at 6 psi it would increase fuel delivery by 10% over your ecu program for 3000 or 6000rpm accordingly. At 0 psi there would be no effect and at 12 psi there would be a 20% increase from baseline ecu programing for any rpm (these numbers are made up as an example only)

I hope this helps[/quote']

 

Yes I think I understand, but my point remains. IMHO, the only reason this device is used (in a measured-air system) is the car is running lean on the top end because the injectors are maxxed out wide open. To repair the mixture at that operating point with a RRFPR will result in the car running too rich at lower RPMs at the same boost level. A boost controller will keep a constant boost level across the rpm band.

 

A RRFPR is a band-aid at best for maxxed out injectors. There is no other reason to run one, unless you have no intercooler and you want to run 10:1 mixtures across the RPM band to combat detonation. That results in poor power production. The proper way to fuel a boosted engine is with an intercooler and a regular FPR referenced to manifold pressure, adequate injectors and either a factory ECU setup or a tunable aftermarket system.

 

Last post on this, I promise.

[Afshin]

I do agree with you Nathan, you are clearly correct in saying that it results in a rich mixture under boost at low RPM if it is set up to to account for lean conditions at high RPM. I had used a RRFPR for 2 years a decade and 3 turbo Z's ago and is now in my garage and not used in my current set up (hint).

My point was only to clarify to everyone that it only increased fuel mixture as a percentage and not fixed amount and under high boost condition (not that you ever claimed otherwise). The reason for bringing this point up is that in the end it does not affect driveability in any noticeable way unless you rely on it exessively by grossly increasing fuel pressure. In my experience the RRFPR can serve as a effective band aid, but certainly not as the solution of choice .

[DAW]

A rising rate FPR is not exclusive to a turbo'd engine. The stock FPR basically has an idle pressure, and every other engine load pressure, i.e., maximum manifold vacuum, vs some value other than maximum. The most practical application is to use a higher capacity fuel pump than stock but use this pressure judiciously depending on engine load (and demand for enrichenning). At idle, it provides the same pressure as stock (or more if needed; or less if needed (like when using larger injectors)). As throttle opening increases (and vacuum falls) the rising rate FPR provides a proportionate match in fuel supply, with wot (no significant vacuum = atm pressure) receiving the calibrated pressure sought. Turbos are just calibrated with endpoints continuing on into the positive (atm + boost) pressure range.

 

The value of the rising rate FPR is that you can protect your engine from detonation death if you don't have the $1,000-$2500 or so to do it right. The issue is not if it is better than an aftermarket stand-alone engine management $y$tem, but rather is it better than stock at performance and protecting the engine when compression ratio or boost are raised.

 

The rising rate is more of a hydraulically-based enrichment device vs the computer-modulated ECU and therefore is more crude, but the CPU can increase injector dwell to stay open at max engine load and if there is not enough pressure or injector orfice there; it will be too lean. The load-tailored pressure is a means of covering for a non-tuneable ECU or injectors that should be larger. The ECU can be tricked into thinking it needs a shorter injector pulse if things get too rich or too lean.

 

For the money, it's a reasonable approach but if you can afford an SDS then don't bother with the rising rate. I don't think I understood a post (above)...what is a low-rpm/high boost situation and how long does it last? DAW

[DAW]

addendum...shorter injector pulse if to rich; longer if too lean. DAW

[SleeperZ]

For the money, it's a reasonable approach but if you can afford an SDS then don't bother with the rising rate. I don't think I understood a post (above)...what is a low-rpm/high boost situation and how long does it last? DAW

 

I think I'm the one who coined that. I'm operating under a few assumptions here: Turbo motor, ECU that measures airflow directly, and a lean condition under maximum boost/maximum RPM. I'm also assuming the lean condition is a result of maximum injector duty cycle reached (which may not be the case - the airflow meter may also be saturated.)

 

Under that condition, a RRFPR is installed to correct the lean condition at maximum RPM/maximum boost. Since your fuel pressure will be boosted higher according to manifold pressure only, and not RPM, at lower rpms and maximum boost, you will be too rich. From my own experience, and most street turbo setups, maximum boost setpoint is reached by 3000 or so RPM. Redline is 6000-6500. Result - you will be slower from being too rich just to save your motor at the topend (not that saving your motor is a BAD thing...) And it will last the whole time you are trying to go fast once you hit boost.

 

My recommendation - turn down the boost slightly until you can tune the car properly with bigger injectors.

[DAW]

Nathan, I think what I'm saying is that if the airflow sensing and injector duty-cycle are maxing out, then more fuel pressure may be a fix. Since the ECU is using airflow, temp, and rpm as parameters, if you first beef up the baseline fuel support based on engine load accross the board; and then fine tune the rest using the ECU regulation available (i.e., airflow and rpm parameters for full boost wot over 3,000 rpm); it seems a better solution than a stock FPR and stock fuel pump with the ECU pegged all the time at its full capability to try to meet the demand.

 

I see how an Adjustable FPR could create a rich low speed condition after the pressure has been set high for max load, but that is why Rising Rate FPRs make some sense, because variable pressure corresponds to variable engine loads...with fine tuning done by the ECU. You don't want regulator set to a pressure that the ECU won't be supplementing in some way to add needed richness. For example, use of the rising rate FPR might mean that the air flow meter be tuned so that a "weaker" signal is sent to the ECU, cutting down injector duty-cycle if pressure + injector time = too much fuel. Overall, there's no "free lunch" here, it's just the concept that for a given duty-cycle and injector orfice, the cheapest way to enrichment is to increase the pressure, creating more net fuel sprayed, and the way to avoid over-richenning at low speed is to have a regulator that can link pressure values to engine load (manifold pressure). With bigger injectors installed it still protects against over-rich low speeds if it is set properly, and if the ECU function is retained as the ultimate mixture fine tuning device (it might take fooling it into thinking there's less airflow than there actually is, to compensate for contributions of big injectors and/or higher fuel pressures).DAW