Hi, can someone tell me if a aftermarket fpr has a vacuum port on it, does that mean it a rising fpr. I have one with a vacuum port on it. How can you tell if it is a rising one. Thanks Tony

 

I'm not sure how you can tell if it's a rising FPR, but the OEM (and I think almost all fixed pressure) FPRs have vacuum ports.

Edit: I'm just trying to say that I don't think the vacuum fitting would be a distinguishing feature.

 

There are very few that just lower rail pressure under vacuum, so the chances that it's a rising rate are very high. You can always check the part number/vendor's website though to verify.

 

Its one of the jdm universal fuel pressure regulator from ebay an thay don't return any emails. The regulator looks real nice but there no marking on it to id who makes it.

 

Oh yeah, they don't really have a whole lot of info on them. I would bet it is a rising rate, an easy way to tell would be to put a gauge on it, run fuel through it (just jumper the fuel pump test connector, or similar), and then use a mityvac or similar to apply boost to the nipple and verify that pressure rises.

 

Easy way if you have a pressure guage.

Connect a vac line to it and blow into the vac line to create pressure. If it goes above the static rate you have a rising rate FPR.

So say it's static of 38psi. Under vac it may be 30-35psi. So blow in it. If it pegs at 38 then it's not. If it goes to 39+ then it is(assuming you can create 1+psi of pressure blowing).

 

If you can't get the 1 psi by blowing, you can always use a basketball--stick one end of the vacuum tube over the FPR fitting, and the other over the big end of a b-ball inflation needle. Poke the needle in the basketball, and you've got 7 - 10 psi.

Basketballs make great tools. I understand you can also play sports with them.

 

Can you explain static rate what it means im not sure what it is. Thanks

 

Static pressure is what it's set at without vacuum or boost, you'll see it change from this rate when you either apply vacuum or boost to the nipple.

 

Incorrect. A FPR that works in boost (like the stock TII one) does not not mean it's rising-rate. Normal FPR's increase fuel pressure linearly with manifold pressure whether in boost or vaccum. Rising-rate FPR's increase the rate the fuel pressure increases when in boost.

All FPR's have a vacuum port whether they're rising rate or not. They have to be referenced to manifold pressure or they don't work.

 

So NZConvertible how can i tell if it a rising one. it not installed yet. i hate to put the car back togeter an it not be a rising one. What well happen if it's not a rising fpr and it's on the car . Thanks Tony

 

if its not a rising rate fpr then whatever you set the fuel pressure at it will always be that fuel pressure regardless of what the manifold pressure is...if it is rising rate then as manifold pressure increases then net fuel pressure increases at some power of the manifold pressure...personally i hate rising rate fpr's beacuse they just add more variables when trying to tune the engine.

not sure if you understand why the vacumm line is there but ill explain regardless.

the fuel injector is exposed two different pressures at any given time...manifold pressure on the injector outlet and fuel pressure on the injector inlet. because you are trying to flow fuel into the manifold, the greater the manifold pressure the more it pushes back on the fuel...so in example. if you have true static fuel pressure i.e the fuel line pressure remains the same then as your manifold pressure increases your net fuel pressure decreases. lets say your fuel line pressure is 50 psi and manifold absolute pressure is 14.7 psi. then your net fuel pressure is 35.3 psi

fuel pressure-manifold pressure= net fuel pressure.

50-14.7=35.3

so in order to maintain the same fuel pressure being injected into the manifold a vacumm line is routed to the fpr in order to account for manifold pressure. so in example lets say at 0 psi of manifold pressure you have 50 psi of fuel pressure. in order to keep that at 50 psi of fuel pressure when the manifold is at 14.7 psi of absolute pressure a diapraghm increases fuel line pressure so net fuel pressure is maintained. so your line fuel pressure would be 64.7 psi

50=fuel pressure-14.7

fuel pressure = 50+14.7=64.7

thats how a standerd linear rate fuel pressure regulater works.

in a rising rate fpr the fuel pressure is raised at a higher rate as compared to manifold pressure. so if its a 1 to 2 ratio fpr then for every psi of manifold pressure fuel pressure is increased 2 psi. the equation is.

net fuel pressure=fuel pressure-manifold pressure+x

where x=manifold pressure times fpr ratio.

so in example you have a 1 to 2 fpr and your fuel pressure at 0 pounds of manifold pressure is 50 psi. then if your at WOT in a NA and manifold pressure is 14.7 pounds then your net fuel pressure will be 64.7

net fuel pressure=50-14.7+29.4=64.7

x= 14.7 times 2=29.4

hope that helps! phew that was exhausting.

 

So if i install the fpr and it's not a rising one it won't harm the car, I don't want to f-----k up anything. Thanks

 

no it wont hurt anything, and in my opinion a linear rate fpr is much better from a tuning perspective... what are you trying to accomplish by installing an fpr?

 

I want to do the parallel fuel lines while i have the uim off the car. But now i'm wondering if i should just stick with the stock set up. I'm open for any advice. Thanks

 

umm... i've never heard of anyone running parrallel fuel lines...doesnt mean people dont do it, but i've never seen it. why would you want two seperate fuel lines?...what modifactions do you have done to the car and if running a turbo how much pressure are you looking to run?

 

I'm not sure how to visually tell the difference. If you still have the box it came in it will clearly state if it's a rising-rate one. If it doesn't, it isn't.

You don't need a RRFPR. They're just a band-aid for undersized injectors. An adjustable linear-rate one is fine.

It will work exactly like the stock one, except for being adjustable. You'll need a fuel pressure gauge to set it correctly, either screwed into the FPR itself or teed into the fuel line after the fuel filter.

That's not really needed unless you're planning on making serious power. Mildly modded engines do fine with the stock arrangement.

Your explanation's pretty good, but this statement is very misleading. The FPR's job is to maintain a constant pressure differential across the injectors, so fuel pressure must rise and fall with manifold pressure. All linear-rate FPR's do this, including stock ones. Put a fuel pressure gauge next to a manifold pressure (vac/boost) guage and while driving the two should move in sync, the fuel pressure always the same amount higher than manifold pressure.

It's actually parallel fuel rails, not lines. The stock fuel rails are in series.

http://fc3spro.com/TECH/MODS/FUEL/fsystem.htm

 

i see that makes alot more sense, i was confused as to why someone would want parrallel lines, but obviously i was mistaken...as far as whether you should do it or not...judging by the description of parrellel fuel rails nzconvertible provided it may not be necassary, but if it makes you feel warm and fuzzy inside that you think you have a better designed system then stock, go ahead and do it. it doesnt look like a teerribly expensive mod so why not!

Since i dont take anyones word that something is better then stock just beacause its different...what is the thoery behind why parrallel is superior to in series fuel rails?

 

Yes i ment parrellel fuel rails. NZConvertible The fpr has a gauge right on it What should i set the psi at, what is stock psi on a 87 TII. Thanks

 

Stock static pressure (i.e. engine not running) is 36-37psi.