Hey I was monitoring my peak injector duty with my PFC and noticed that it was hitting about 90-94% injector duty at its peak. Is this too high? I know with my settup (see my sig) that i probably need 1600cc secondaries, but right now i don't have the cash for injectors and rail, and i need a boost controller first and foremost. Should i turn the boost down a little so that i'm keeping it under 85%. Right now i'm running about 1.10-1.15 bar (16-17psi) Should I just keep it a little lower until i can upgrade the fuel system or am i ok where it is. It has never hit 100% but i've been told once it passes 85% its at full flow.

Oh also, i've seen this mentioned before, but whats too high of a number for the knock sensor reading on the PFC? Is it relative to something? I'm hitting about 30 at max boost and high rpms (It's at like 3 or 4 at idle)

I would really appreciate any help that anyone can offer. Thanks guys!!!
-Rob

 

The stock injectors can only support up to 1bar, nothing above it.

 

you only wanna be doing 85% dutycycle cuz anything above that is pretty much going static/nearly full on all the time. lower boost or get better injectors. btw, have you put your car on a dyno with a lambda meter yet?

 

Don;t get bigger injectors, it wouldn;t be the best diea for max power, atomization, an high boost, where accurate fuel delivery is required.

I would get a RRFPR, an dbut he fuel pressure, then you wil be fine. Even if you increase injectors size, you nee dot get a RRFPR with anything that big. I fyou plan to run really high boost like 20+ you may not be able to get the fuel pressure high enough safely without fuel line mods, etc. But for your boost levels now, I am sure bumping fuel pressure is teh best way to go.

 

You've got the 1200CC secondaries, but I don't see an upgraded fuel pump on your list. If your running the stock fuel pump that would be the first thing you should replace.

 

sorry, running Nippondenso fuel pump

RRFPR would be what exactly?

And no i havne't been on a dyno with a lambda meter. What is a lambda meter?

 

RRFPR = Rising Rate Fuel Pressure Regulator. It increases fuel pressure as boost pressure increases, ie: every 1psi boost = +1 psi fuel pressure or more depending on which one you get, some are even adjustable.

 

Run a higher fuel pressure. Also, what are your A/F ratios like?

 

OK correct me if Im wrong but don't our cars have a RRFPR stock?

at 0 psi my FP gauge reads ~31 at 10 psi ~41.. sounds rising rate to me.
what you all mean is adjustable FPR

 

i think rising rate has to be 2:1 ratio or higher, 1:1 ratios are linear fpr?

 

how does the RRFPR effect the amount the injectors flow? I thought the injectors can only flow so much, and the raisng the fuel pressure doesn't effect that.

 

actually that can only OPEN so much, not flow. the more pressure the more flow when it is open. And a matter of fact, higher fuel pressure through injectors is generally better for atomization. This is not so important with stock injectors, btu it becomes paramount when using monsters like 1600cc. the larger the injector the more pressure it requires to operate the most efficiently.

 

I was under the same impression zoomspeed was.
So is this rrfpr a piece of hardware, or is it some sort of electronic device. Can the PFC not control the fuel pressure? Sorry if i sound ignorant, just trying to figure all this out. Thanks for your help Kz1 and everyone else.

 

yeah, thanks for clearing that up KZ1.

So would it be possibe to run 14 PSI on just an upgraded fuel pump, RRFPR?

Does the RRFPR absolutly have to be tuned? Because nobody around here would know how to do it. IF so, does the RRFPR get "tuned" or is it the ECU. I have a pre programed ECU.

 

OK thanks for the clarification on rising rate.

for everyone having problems thinking about flow, pressure, and atomization and how they all relate. Think garden hose.




It should all make sense now.

 

Yes it would have to be tuned, but so would larger injectors for that matter. I think the biggest thing that deters people from RRFPR is the tuning involved, it requires a lot from my understanding, or at least more than that for larger injectors where you just change a few settings and not actually the cell values.

If you want to run any setup that exceeds 100% on stock injectors, you shoudl be getting the car dyno tuned with wideband, etc anyway. at which time who cares if more tunign is involved.


My opinion is that yes I would go with RRFPR before larger injectors.even though that is not what I did( I regret it). I would first get a PFC, Haltech, AEM, etc.

 

you mean before upgrading from stock injectors? or in this guys case before going larger then 1200 secondaries?

One thing that should be pointed out here for everyone.

The increase in flow rate on an injector is not linear with the rise in pressure.


Our cars have FPRs that increase 1:1 fp for boost.
what this does is keep the delta (differential) pressure across the injector the same (say 37 or what ever base fuel pressure is) so when your FP is 37 at 0 psi your delta is 37. When you add 10 PSI boost the delt is still 37 because your FP rises 10 PSI also. so you have a rise of 10 psi on the outlet/intake side of the injector and I rise of 10 psi on teh Fuel line side also.

NOW what you'll need to realize before getting a rising rate FPR the relationship between flow and pressure is not linear.

Raise the FP 25% you will not have 25% more fuel. if memory servs correct it's more like half that (so 12% more flow)using these numbers. Again it's not a linear relationship. Ill see if I can dig up some more info on the relationship between an increase in pressure and the resultant increase in flow.

 

OK found that link.
look about 1/2 way down to see the formula to calculate flow rate with a new pressure...

http://www.rceng.com/technical.htm

 

now for the next obvious question. who makes rising rate FPRs and which one do you recommend?

 

where is the stock FPR. I would assume an aftermarket one would take its place? Is this a common mod? I havne't noticed it in anyone's sig's. I'd at least like to find one FD that has done this. Anyone know of anyone on the board with an aftermarket RRFPR??