Comments, suggestions, critiques from anyone who has used this diagram for their fuel system upgrade...

from the website The Rotary Beast
Thanks!

 

-08 seems awfully big, but I suppose it depends what you are trying to build...

 

I did mine with -6AN from to pump to motor and back. This was after reviewing all the Rx7 internet sites with fuel system info that included the diargam above, e-mailing questions to Max Cooper and Wade Linham, speaking with Pineapple and rx7.com, & lastly reviewing my plan with Kinsler Fuel Injection and some of my close friends that work for professional race teams.

At the time there was little info available that applied directly to the FD, many people have done this upgrade in the past year. If you haven't searched around there are some pretty good threads on here that have been written this year.

Anything bigger than -6AN is probably overkill unless building a 500+rwhp rotary. Larger lines will also work the fuel pump harder which can lead to higher fuel temps and decrease in pump life span. Some argue that -6AN is not much bigger than stock but a carefully designed system will have a lower pressure drop than the stock set-up. Cost will increase for larger sizes of hose and fittings. As the hose size get bigger, it is harder to work with.

Avoid using close turn or banjo fittings, they increase pressure drop and can possibly cause cavitation. I ended up having to use a banjo on the return side of the primary rail to avoid hitting the oil injector nozzle and still had to trim the nut.

If they were available at the time, I would have bought a top feed fuel rail for the primary to avoid close fittings and allow for use of lower cost Bosch injectors. A forum member (can't think of his name) now makes such a rail.

Another place that I probably sacrificed some pressure drop is I ended up tee'ing my returns together before the pressure regulator due to tight space but will seperate them if I go noseq or single in the future.

Get a fuel pressure gauge that can be monitored inside the car. You need to be able to monitor fuel pressure at wide open throttle with boost.

Check this page out, it shows some pictures of my fuel set-up. I've got many more pictures beside these if questions come up.
http://ourworld.cs.com/_ht_a/talvendi/id19.htm

Jack

 

Thanks for the terrific reply and pics. A lot of well thought out advice.

 

I've had a similar fuel system in my 7 for over a year now. But the difference in my system is that I ran two pumps forward, used the aeroquip FPR as the "Y" and used the charcoal canister line as the return line by putting a bulkhead fitting on the top of the fuel pump assembly. I used 2 stock FD pumps as my fuel pumps and I have enough fuel for a T-45S at 1.2 kilos of boost tuned at 11.0 a/f.

 

I didn't realize your FPR could come before the Fuel Rails. Or am I reading this wrong?

 

Yeah your reading it wrong. I've never seen that diagram but when i first was thinking of how to do my fuel system i though of that exact same method of running the rails in parallel. But when i was trying to prep the fuel system(get pressure) it wouldn't,But i was trying to use both sides of the FPR and come out the bottom. Then i swtiched to running them in series and found that i takes less connectors and i liked that for 2 reasons, saves me money(if i would of know before hand) and looks like a cleaner install. I ran the feed line in to the 2nd rail, some due it to the primary rail. I had no reason besides it was easier for me to do so. here is a quick little diagram. I also did use -8 lines but i'm going for larger HP numbers but i figured -6 might be enough but if i'm going to buy all the connections i might as well just get the -8 stuff cause it cost about the same and that one less thing i have to worry about limiting me.

 

Let me rephrase that question. Does that mean you are running 2 pumps/filters/lines to the 2 fuel rails? Then the other side of the rails go to the FPR to join them for the return?

When I asked am I reading it wrong, i was referring to jspecracer7's post and not the diagram... my mistake.

 

you talking about me? http://www.3rdgenrx7.com/keithsrails.htm

 

Not saying that any other arrangements won't work but I want folks to know the drawbacks to different set ups. This stuff was not well documented just a year ago. Lack of fuel and cooling issues are the two things that kill our motors so I don't mind going overkill on both.

The drawback to a series arrangement is that you risk starving the injectors at the end of the series. If using a series arrangement I would feed the rear rotor's secondary injector first since that rotor tends to run leaner.

Not sure why coolduke has problems with building pressure using both FPR inlets, that may have been a problem with the FPR itself or the pump, weird!

I wouldn't worry about two pumps unless you're building some high powered, single turbo beast. Its much easier having one pump that can satisfy your volume and pressure requirements. With dual pumps and feeds, you need two pressure gauges to know if one pump is losing strength otherwise you won't know until you go wide open throttle and possibly boom boom.

Before going dual pumps, I'd run constant 12V to the pump. Drawback to constant high voltage is shorter pump life and possibly higher fuel temps.

The Nippendenso pumps can move a large volume but they need higher voltage than the stock wiring provides. I bought an Apexi BNR32 thinking I would need it based on theoretical calculations but after flowing testing my RP/Nippondenso pump at Kinsler, I saw that its not necessary.

I have the relay and wiring in place in my car to give direct battery voltage through a 10ga. wire when the pump goes to high speed but ran into problems with power backfeeding through the stock relay and the new relay. At this point, I don't need it but will complete the project in the future with some diodes to eliminate the backfeeding.

Jack

 

Anyone else use this setup?

 

Why are people running dual feed lines or dual return lines?

 

I think -06 AN would be fine for almost any amount of horsepower you needed. People have run 500 rwhp+ on stock lines, so I don't think you need anything bigger than that.

 

I have nothing to add to this topic but laughed my *** off when I saw Jspecracer's sig. That still cracks me up. As far as the thread, Jon made a pretty picture to capture the essence of the fuel system..props.

Back to the normally scheduled and informative posts

Tim

 

http://www.mantissaconsulting.com/et...uel_system.htm

Gene

 

The smaller the line, the harder your pump has to work. On a car that's already vulnerable to fuel issues, do you really want to risk it? The worst thing that can happen is that some more fuel goes back to the tank after passing the rails.

 

What type of fuel starvation protection are you 7 owners running at the tank end? I had a chat with a mech on BMW raceteam the other day, he actually recommended a dual trapdoor system similar to what is used in nascar but on both sides of the tank. The flaps will swing to allow fuel in but once the fuel is in the boxes it is stuck because the flaps will not swing in the opposite direction. People also use fuel reservoirs and secondary pumps. I'm about to do some work on my fuel cell setup so let's gime some good ideas. ;o)

-Rob

right now I'm running a fuel cell with an aeromotive pump, filtered inline, through an-8 lines to singlr biased FPR then rails in series.

 

where is the FPD??

 

Read the thread.

Gene

 

FPD? We don't need no stinkin FPD!

 

I do not understand why when running the lines from the splitter in parallel, that both inlets on the FPR are not used. Why is it plummed back into one line?

I plan on running them in parallel as above, but from each rail the outlet would go into it's own inlet port on the FPR. I have an Cosmo fuel pump and that should provide more than enough flow.

 

what are you doing for fuel Jim?

I lied before, My new setup is using a 10AN feed to the the fuel pressure reg (A1000-6) and AN6 to the the rails and return lines. The rails share fuel via 2 hardlines. the Earl's fuel filter 10AN is mounted between the fuelcell and the pump (A1000).

I can take a couple pictures if anyone is interested.

 

You would need the two feeds to be independant of each other on driven by their own pumps in order to really get use out of your dual reference, I would think.

 

Twin Bosch pumps in the tank, -10 feed to an SX FPR, -08 out the bottom, back to the tank, -10 out the other side to the driver's side fuel rail, loop to the passenger's side rail, then dead end.

 

An FAQ from Aeromotive:

After 30 minutes or so of driving, fuel pressure starts falling, then the fuel pump gets louder and/or seems to quit running altogether. The pump also seems hot to touch. What’s wrong?
You may be experiencing EFI vapor lock. Fuel system hot spots, the cause of vapor lock in carbureted engines of the past, and modern EFI engines where no return line is employed, are eliminated with the use of a bypass regulator placed after the fuel rail, in the engine compartment. Still, thanks to underhood engine heat, fuel in the EFI bypass system does slowly warm up as it is recycled through the fuel rail(s) and back to the tank. The longer an EFI engine runs, the higher fuel tank temperatures can become. Unlike the more common carburetor vapor lock, where fuel is heated to boiling in the float bowl(s) or fuel line(s) under the hood, EFI vapor lock is often caused by hot fuel in the tank and/or cavitation. Excess pump noise along with fluctuating or dropping fuel pressure often indicate cavitation is occurring. The exact point where gasoline changes from liquid to vapor depends on its temperature and pressure. A combination of high fuel temperature and low pressure are the primary cause of cavitation. In a return style EFI fuel system, the most likely place for these conditions to exist in the same place, at the same time, is at the fuel pump inlet. The most common cause of cavitation is installation error. Once cavitation starts, it will feed upon itself. As vapor enters the pump, it displaces liquid fuel required to lubricate the mechanism, allowing metal to touch metal, creating even more friction and heat. Once the pump begins to super heat, a complete vapor lock may develop. In order to prevent cavitation and vapor lock, correct fuel system design and installation are vital. Ensure inlet filters meet hi-flow, low restriction requirements and they are kept clean. Keep the tank full on hot days. Reduce fuel pump speed during low load, idle and cruise conditions. Carefully route fuel lines and plan component placement to avoid exhaust heat. Do not overlook proper tank ventilation, if the vent line or vent valve do not allow ample air to move freely in both directions, fuel delivery problems will never fully resolve. Any conditions that restrict the pump’s access to fuel in the tank must be addressed. Read Tech Bulletin #101, Fuel Filtration and call the Aeromotive Tech Line if you need further assistance.

for those wondering about cavitation...