c00lduke

I was just wondering if it matter really which one was fead first? I know the primaries get feul first in the stck system but i was wondering if feeding the 2nd rail first would be fine.

Thanks
~Luke

BigIslandSevens

iTrader: (4)

I think the names say it all: PRIMARY= first.....SECONDARY=second...Geeeezzz!! Mars is causing people to think crazy!!! WHAT are you guys smokin in Kansas?!!!

es

Most people that upgrade the fuel system split the main feed & supply both rails in parrallel.

That's how mine will be.

es

The primary rail is called that because it's injectors are on first. Then once you reach a certain RPM the secondaries come on line.

Just like the old 4 bbl carburators you pops used to drive. Only different.

BigIslandSevens

iTrader: (4)

Sorry !, Didn't mean to offend anyone! (It's early here, i just woke up) I understand completely how they work . Read my profile and you'll see that I am a mechanic and own a shop out here. But thanks for the school lesson. His question is a little confusing. I also have the feeds split to both rails with the FPR in between the secondary. Someone on this board sells a bitchin fuel set-up for like 650 bucks I think! It has everything you need! ( except the fuel pump)

BigIslandSevens

iTrader: (4)

Hey coolduke! If you want some pics of my set-up to get an idea let me know your e-mail. I'm rebuilding know so everything is easy to get to and snap a pic. Let me know.

lane_change

iTrader: (20)

I run mine in parallel instead of in series. It will help with your transition if you are running larger secondaries.

jdhuegel1

Yup. That's rxrotary2_7. Great product and service. I'd recommend him in a HEARTBEAT!

jdhuegel1

Can you explain the "transition"? I've heard this several times... Wondering if there is a safety precaution involved... Like a lean condition?

rxrotary2_7

thanks man. https://www.rx7club.com/forum/showth...hreadid=217667

duboisr

The big injectors need all they can get and with all the fuel pressure there both will get plenty . Garfinkle does feed the sec first then the pri . The name primary and sec does not have any thing to do with how it works for flow .He has biger steel lines from the fuel pump bell connector to the fuel pressure regulator . The lines have very few bends and the ones on the engine are mostly stright . No fuel damper is used as he has the sx fpr . But yes the sec is first in line then the pri . The pri rail is drilled out to match the line size and he made custom fittings for each end .

supracosworth

I'm about to install a pair of additional injectors on the Greddy elbow but haven't quite decided whether to run these in series or convert the primary, secondary and the additional injectors all to a parallel system. The additionals are 550cc injectors. Do you think there's likely to be a pressure drop problem if I just join these in series to the existing fuel circuit?

duboisr

With out looking at what you have I for one am guessing because , Most on the forum know all. With that said I am thinking that with an upgraded fuel pump , adjustable fuel pressure regulator and bigger size fuel lines you will be all right . The bigger fuel lines do not need to be as costly as many say . The system Garfinkle made did not cost much and I bet it will flow as much as any reasonable system out there . I think he did not spend more than $ 40 for the tubing,clamps hose ect . The time spent was another matter, ask exstacy 7, or rotorbrain about it . The lines and hand made fittings look great .

tmiked

I would definitely go parallel to any aux injectors. If you dont you will be flowing all the fuel through both fuel rails and all the elbows etc. required (pressure drop).
The names may be primary and secondary but for racing the 'secondaries' are the most critical and feed the most fuel. So if you were designing from scratch for racing you would feed the primaries first or go parallel.

duboisr

If you are designing from scratch I think Garfinkle is correct and you should go to the sec first . Why is this wrong . The above said to feed the primaries first or go parallel . If gar is wrong I will get him,hahahaha

rotarypower101

iTrader: (1)

I have a question for you guys, has anybody came up with a good idea of how much flow area we need to properly feed the upgraded injectors that we are running?

I have been considering if I should move up to 8 from 6 but really don't know if I should. what are the stock lines capable of safely providing in terms of capacity to the injectors?

These are some rough estimates of the sizes and are percentages more than the stock system bottlenecks.

-8 = 9.6mm=.378"
-6 = 7.5mm=.296"
stock fpr=6.2mm=.246"
stock banjo bolt=6mm=.236"

so to go from stock to 6 it is 1.56 times the flow area.
to go from -6 to -8 is 1.63 times the flow area
and to go from stock to 8 is 2.56 times the flow area.

So how much flow area do we really need for a given HP range, assuming standard fuel pressures?

what is just right and what is excess?

Any thoughts?

duboisr

Good math, You need to know the horse power and how much fuel to support that range. Then the flow rate of the size tube in question .

tmiked

You could calculate the theoretical size needed. However, as the cost difference is minor to a tuner, the best choice is plenty big. AN-6 should be fine up to 400HP. AN-8 to the 'Y', and AN-6 to each rail if you are going for more.

rotarypower101

iTrader: (1)

That is how I plan on running my setup, with the y in the system so the FPR controls each rail independently.

Does anyone know what the limits in terms of HP of each system is?

What can the stock system provide without pressure drop in the system with a reasonable factor of safety? What about -6, and -8.

And just a thought how does the fuel pressure gauge on the fpr indicate the correct pressure for two independent fuel lines going into it?

Wouldnt each line be different if only slightly.

For example, hypothetically if we were to starve the primary before the secondary were to even kick in wouldnt the pressures be different and the dial indicator on the FPR would still read full pressure because of the secondary pressure?