BlueSprite

It migth be a goofy question, but i just want to make sure be4 i spend the money

FPR is really needed for modified car, such as street or race port, upgraded turbo ?? Currently, i have Race port with t78 and PFC, dp,mp and etc.....; and i m running 550/1300 with stock FPR and rail.

I m deciding to upgrade the fuel system, but first I want to know is it really needed to have upgrade the FPR and rail ??? If i dont do it, will it cause a problem in future??

BTW, can i reuse the current injectors on aftermarket fuel rail, such as (kgr??) some others

thx

Snook

iTrader: (12)

well even 1300s and 850s in the primaries (if you were to upgrade to that) wont be enough fuel for high boost. Maybe if you got 1000 primaries it would be enough

when people upgrade the secondaries to 1600s they fit into a different rail because they feed differently. At that point its hard to use the stock fpr so an aftermarket one is used. It's not needed as far as I've seen but it would be a nice idea to upgrade it for safety. They are so cheap it would be pointless to get the stock one to fit in there.

Bacon

iTrader: (12)

The Stock one is a POS; get a rising rate one so you can control your base Fuel pressure, also so it accurately holds pressure under boost. Most out there are 1:1 Rising rate

You need to get top feed injectors with all of the aftermarket rails. Keith (kgparts) rails are awesome, hee’s a great guy I’ve known him for years. I’m also running his rails, “not only am I a spokes man but I am a client” lol his prices are also super reasonable.

Based on mod’s it would seem like you should just upgrade to the 1600 secondaries, and might as well stay 850 in the primaries. Fuel is the most important thing next to oil in a rotary.

JONSKI

Bacon lives!

KevinK2

new rail or new high rate fuel pumps trigger need for new fprs. Need higher flow rating for big pumps, to correctly control pressure at low loads.

you don't want a rising rate reg ... thats for when you bolt a turbo on a dodge dart.

standard 1:1 fpr's will properly let pressure rise directly with boost ... 10 more rail psi at 10 lbs boost. Rising rate would kick pressure up ... like 20 psi more rail pressure at 10 lbs for a 2:1 rrfpr.

BlueSprite

thx all of you, these infomations are great help to me.

Since i have stock injectors(550/1300), can i use it on the aftermarket fuel rail (kgparts - they have very good price on the rails; cuz i had told the aftermarket fuel rail need to use aftermarket injectors, is that ture ??)

Btw, how can i setup the FPR in standard 1:1 !? Can i just install it and it will set it by itself ; or i need to play around the adjustor on top

maxcooper

Most aftermarket FPRs are 1:1 and don't have an adjustable multiplier. You just install it, including connecting the manifold reference (vacuum hose), and it will be 1:1. The adjustment is for the base pressure, not the multiplier. This includes FPRs from Aeromotive, SX, etc. -- the ones you are used to seeing.

The term "rising rate" is used inconsistently in the industry, but in my opinion, it should only be applied to FPRs with a rate higher than 1:1, usually with an adjustable multiplier. For those FPRs, the effective fuel pressure (rail pressure minus manifold pressure) increases as the manifold pressure goes up, effectively making the flow rate of the injectors rise. These FPRs are typically round and are sometimes called an "FMU". They are especially useful when you are trying to turbo a car that wasn't a turbo before. But they have no place on a car with adequately sized injectors and a programmable fuel injection system that can read boost. It is useless adjustability on an FD with a PowerFC. Useless adjustability is bad.

A typical "adjustable FPR" and a "rising rate FPR" are two different kinds of devices.

It isn't totally clear to me at what point you MUST upgrade, or why. Some say the stock FPR is unreliable, but I haven't heard of many (any?) failures. Perhaps the stock FPR is too slow or otherwise inadequate to deal with large injectors or high pump flow rates. That seems reasonable, but I'm not sure where the line is.

I run 850 primaries and 1300 secondaries in the stock rails, and I have upgraded my FPR to an Aeromotive unit (and replaced the stock FPR with a brass fitting in the process). I did it because I wanted control over the base pressure, and because I thought it might deal with the large injectors and high-flow pump better (faster).

-Max

BlueSprite

thx, nice post, it lets me understand more now.....

Can i use my stock injectors on the kgparts fuel rail ??

rynberg

No offense, but from reading your posts in this thread, it doesn't seem like you have much of a clue what you are doing with the fuel system. For some reason, you seem to feel the need to spend a decent chunk of money on something for no good reason.

You say you are running a T-78 on a ported motor. Is it tuned properly? How much boost are you running? Are you seeing uncomfortably high duty cycles, unstable fuel pressure, or other signs your fuel system isn't up to snuff. If you aren't or you don't have the capability to monitor such things, I think it's pretty damn silly to throw several hundred dollars at something that may be working just fine.

Just my 2 cents.

And NO, your stock injectors won't fit with a KG Parts rail, which is designed for top-feed 1600cc injectors. Why would you buy a fuel rail to run your stock injectors when the stock one works fine?

rynberg

damn dp

GoodfellaFD3S

iTrader: (213)

my 850s/1300s with stock FPR provided enough fuel for 421 at the wheels, but they were about maxxed out......

KevinK2

new car regulators are in the tank, and supply single pressure level to rail,for all conditiond. Ecu must sort out the more complex maps.

maxcooper

For semi-steady-state running (like on a dyno), I have no doubt that the stock FPR works just fine. The question is how well does it maintain pressure under more dynamic conditions, like a 3-4 shift with a throttle lift, hard launch, etc. It is hard to measure -- you aren't going to see it on a gauge. I suspect does at least okay there, too, but it isn't a simple determination to make.

-Max

DaleClark

iTrader: (55)

One problem I've seen with stock FPR's on the FC is a beefier fuel delivery (big fuel pump, rewired fuel pump, etc.) will overrun the stock FPR. The base fuel pressure is increased, and you have too-rich problems at idle and low load. An aftermarket fuel pressure regulator will let you set the base fuel pressure, overcoming that problem.

BTW, a rising rate FPR generally refers to one that increases fuel pressure with boost at more than a 1:1 ratio, and lets you set the amount and rate of rise. This is a typical bandaid fuel system for small turbo kits - they're a royal pain to tune, and you will typically end up with a sloppy fuel curve with lots of too-rich spots. There is a difference between a rising rate FPR and a typical 1:1 FPR.

Dale

rx7f4n4tic

bryan at bnr runs stock rails, walbro pump 850 primaries and 1200 secondaries with the stock FPR and puts 420 to the wheels all day long and he said has 40k miles on the motor and over 140 dyno passes.

Id say the stock FPR is fine for 90% of the applications on the forum.

BlueSprite

The car is not tuned yet because it needs to break-in. i m not trying boost the car in this period. Meanwhile the car has a lot of burning gas from exhaust, so that i m thinking does the regulator or injectors causing the problem; and it has hesitation under 3k.

I understand it is pretty silly to throw money on sth that i m not sure, so that i want to get as much as infomation before i buy. In fact, i m very appreciated your help and post. Since i have that sitation with burning fuel, do you think i should do dyno before i setup a new fuel system. (i will do it after the break-in)

I was thinking the stock injectors are comparible to top-feed 1600 injector, so i thought i can use it.

rotorbrain

1300 + 850 = 2150
1600 + 550 = 2150

. . .

maxcooper

In that case, it is just that the stock FPR can't flow enough fuel back to the tank so the pressure rises above the base pressure. I think if you keep the stock 2-speed pump setup you'll be fine (mine was fine with stock FPR and my beefy BNR-32 pump), but it wouldn't surprise me if this happened with the pump wired to run full voltage all the time (i.e. no more 2-speed system). And come to think of it, I think I did have an otherwise unexplained bump in fuel pressure when the ECU switched my pump to high speed (full voltage).

-Max

BlueSprite

If i want to change 850 as pri. should i change the Pri. fuel rail ?? or stock fuel rail is ok !?

If i want to install FPR, should i go ahead to change the fuel rails too; i know the stock fuel rail cant put aftermarket FPR on it.

maxcooper

Before selecting components, continue your research to learn about what is available. And decide how much fuel flow you need for your power goals. I have a web page that will do the grunt work of the calculations for you, but you do need to figure out what numbers to put in. Figuring out what the numbers mean is a useful exercise, IMO: http://maxcooper.com/rx7/how-to/fuel_system/calcs.html

Here are some facts about FD rails and injectors:

1. The stock injectors are side-feed and work with the stock rails. The primary injectors are 550 cc/min and the stock secondaries are 850 cc/min. The size rating means that if you hold the injector open (by applying an electric signal to it) for one minute, the injector will flow X amount of fuel, measured in cubic centimeters (=mL) at the standard effective fuel pressure of 43.5 psi.

2. You can have the stock secondary injectors modified (bored out) to flow 1200 or 1300 cc/min, but they are still stock secondary injectors.

3. Stock secondary injectors are shorter than the stock primary injectors, but it is pretty easy to modify the stock primary rail to work with the stock secondary injectors. You just shave about 1/8" of material off the top of the rail. It is even possible to leave the rail as-is but use extra o-rings to take up the space and seal the injector in the rail.

4. Aftermarket injectors that are commonly used are top-feed and will not work with the stock rails. They are available in many sizes, including "1600s", which are really 160 lbs/hr injectors that flow 1684 cc/min.

5. Aftermarket rails are for top-feed injectors and will not work with the sotck injectors. You can get aftermarket rails for both the primary and secondary injectors.

6. You can tap the stock secondary rail and install a fitting in place of the stock FPR to use the stock secondary rail with an aftermarket FPR. That is what I did to mine. I used a 90 degree, 1/4 NPT to 5/16" hose barb brass fitting.

-Max

BlueSprite

Thx max, i have nothing to ask !!!! it is a great help to me, after this post i have gain a lot of knowledge about the fuel system.....I appreciated for all of your answer

Improved FD

good thread....worth a bump

do the aftermarket FPRs eliminate the need for the stock fuel pulsation dampner?