RRFPR as FMU

[Guest joeyfeets]

I just bought this "boost-referenced" fuel regulator that ups the fuel pressure based on boost (via vac line from intake mani).

 

I was going to replace my stock FPR w/ this aftermarket one but found out that its range is 36-45psi. The FSM states stock specs on a z31 is 33psi @ idle & 44psi @ WOT. Im probably going to return it & get some real engine management, instead of pushing the envelope on my stock fuel system. The below thread helped w/ that decision...

 

http://forums.hybridz.org/showthread.php?t=90040&highlight=fmu

 

I just had a weird idea about this product though. What if I used it as an FMU? It has a boost/fuel ratio of 1:1. Although most FMU's are either adjustable or on a preset ratio (12:1,10:1.8:1,etc), could this be used as an FMU (just on a waay lower ratio)?

 

I know this "boost-reference" regulator I bought is not intended to be used as an FMU. It is still basically a rising rate regulator (based on boost as opposed to preset ratio). Since as far as I'm concerned, a rising rate regulator is the same as an FMU. And this boost-reference regulator is essentially the same as a rising rate regulator. So I should be able to use the boost-reference regulator as an FMU???

 

1) RRFPR == FMU

2) boost reference FPR == RRFPR

3) So.... boost reference FPR == FMU???

 

l just replace the FMU in pic w/ the aftermarket regulator & that'll be the setup. It was only $50 so its a cheap experiment but once I use it, I cant return it. Wanted to get some feedback on this before making decision to test it or return it....

[evildky]

you said the stock rating is for 33psi at idle and 43psi wot how many lbs of boost is that? and what is the psi @0 manifold pressure?

what are your power and boost goals? what are you trying to acomplish?

 

I had one of those on my car for a while it worked fine and made tuning a bit easier, I had to upgrade to a larger unit when I upgraded my fuel system

[Guest joeyfeets]

you said the stock rating is for 33psi at idle and 43psi wot how many lbs of boost is that? and what is the psi @0 manifold pressure?

what are your power and boost goals? what are you trying to acomplish?

 

whoa... ok, well my ultimate goal is to replace the entire fuel system w/ prob DSM injectors, walbro pump, z32 filter & some type of fuel/spark management. Thats probably far into the future, for right now I got this cheap regulator & just want to use it. It might help supplement some high boost lean spots I have.

 

As far as the measurements, I'll have to check that out. The nissan service manual states that at 0 vacuum the fuel pressure should be 36psi & once the "accelerator is depressed it should jump to approx 43psi". I would have to test it myself to see what psi is reached at a certain boost level.

 

Just wanted to see if the theory behind using the extra riser reg as an FMU would work....

[Guest bastaad525]

"Rising Rate" implies an FPR that increases fuel pressure at greater than a 1:1 rate relative to boost pressure.

 

"FMU" is just a fancy term that companies like B.E.G.I. came up with to call their RRFPR.

 

In the case of that Adjustable FPR (NOT an RRFPR) that you bought, when they say the range is from 36-45 psi, that is most likely 36-45 psi static at idle with vacuum reference disconnected. It shouldn't have a 'maximum' pressure, as far as how high it will get on boost. In other words, if you set it to 45psi, and run 15psi of boost, then at WOT it will provide 60 psi of fuel pressure.

 

the maximum 45 psi that it lets you adjust to is not that big of an increase over stock either way though, however, I read somewhere that someone running one of these just removed the locknut and that allowed them to adjust up to like 50 psi (again, at idle with no vacuum reference connected).

 

And no, there would be no point in trying to run this 'as an FMU', since it only increases fuel 1:1, it wouldn't function any differently than a stock FPR. That's not to say it's useless. Installing it would still provide some adjustability to your fuel pressure and fuel curve as a whole. It doesn't sound like it will allow a lot of increase, but should be enough to support a bit more power.

 

Nothing wrong with trying to 'push the envelope with your stock fuel system'. A few of us here do it. I run a 'true' RRFPR, with an adjustable rate of gain (the one made by B.E.G.I.). It runs in line with my stock FPR, but doesn't have any effect on fuel pressure until about 3-5psi of boost, at which point it increases pressure at an adjustable ratio. I have it set to provide 70psi of pressure at WOT, and with that I greatly increased the flow of my stock 270cc injectors, enough to support over 230 rwhp and running pretty rich, whereas before they were running lean at about 200 rwhp. I could up the pressure even more to support more power (one member on here has been running 100psi thru stock NON TURBO injectors on a turbo motor for two years now), but at the time I tuned I was more concerned with keeping boost down in the interest of longer turbo life.

[Guest joeyfeets]

And no, there would be no point in trying to run this 'as an FMU', since it only increases fuel 1:1, it wouldn't function any differently than a stock FPR. That's not to say it's useless.

 

thank you, i've been trying to figure this out forever. Too many people were telling me a riser & a stock regulator shouldnt work together. Im still gonna return it & get something more useful, but I eventually might get a riser reg. anyone have an opinion about this MSA one?

 

http://www.zcarparts.com/store/merchant.mvc?Screen=PROD&Product_Code=11-3074&Category_Code=PFFC14

 

[Guest bastaad525]

that one that MSA sells is actually the B.E.G.I. one, that's the same one I'm running right now. Though, I ordered mine straight from B.E.G.I. Funny thing is, it cost me more to get it straight from B.E.G.I., most retailers carry it for a little bit cheaper, I think like $30, but at the time, EVERYONE was sold out and on back order on the thing so I just got it from them. And yeah, I love it, BUT, I would say that, though it works and works well, it's not exactly the perfect solution for when you need more fuel. It doesn't allow any fine tuning of different areas of the fuel curve... it basically only allows you to adjust the fuel curve as a whole, richer or leaner. The undesirable result being that, in order to get the high rpm/full boost air-fuel ratio to a safe level, I have to put up with a super rich mid range (3000-4000rpm).

 

This isn't the fault of the RRFPR, as anyone who's dynoed a bone stock 280zxt will tell you, it likes to run really rich like that. I love the RRFPR because it was super simple to install and tune (it has only two adjustments, and only one that you actually need to worry about). Though I could have achieved much the same result by simply going with larger injectors and tweaking the AFM spring, and honestly, I could have done that cheaper, since I've seen sets of 370cc injectors go for as little as $60. And by 'much the same result', that means, the same drawbacks as well .

 

You may want to do a search for posts specifically by me, about the RRFPR, I posted a lot of info and questions some time ago right around the time I bought it, about how it works and a possible solution for better tuning that I worked out with one of the engineers over at B.E.G.I. (for which he already sent me the parts, but unfortunately I still haven't been able to test since I haven't gotten my wideband O2 sensor yet). There are some other good threads with discussions between me and Cygnusx1, who also has this same RRFPR.

 

Whoever was telling you an RRFPR and your stock FPR wouldn't work together doesnt' know what they're talking about. There are SOME types of RRFPR out there that are meant to completely replace the stock FPR, but most of the ones I've seen (like the B.E.G.I. one) are meant to work WITH the stock FPR, usually inline with it and after it in the fuel return line.

[mc]

They[begi] show up on EBAY selling pretty cheap [used units]....I'd like to get the BEGI 2035 for my remote turbo 3.0 1988 200sxSE...The 2035 RRFPR has even more ajustability.