Return Fuel System
 

If you have experience with a return fuel system then you'd be a great help if you could answer some questions for a write-up that I'm doing.

My single turbo 13B REW installation has a return fuel system that is a complete bodge. I'm now getting around to sorting it out and have spent over 10 hours searching here and on the internet to see what I need to do. I found getting information difficult and often confusing so I decided to help those coming after me by doing a write-up of the available options (Simple pump upgrade, return system, external fuel pumps, surge tanks, twin fuel pumps, etc)

I'll do the write-up over the next few days and will put it up here for comment. However, I'm having difficulty in getting answers to some questions because I can't find any info, the info is confusing or posters say contradictory things. For a car used on road and track:

Using the siphon venturi to drain RHS saddle
If you replace the stock fuel pump with an in-tank pump such as the Walbro 255 and pass return fuel through the stock venturi tube to siphon fuel from the RHS tank:
1. How did you connect the return hose?
2. How did it perform and what modifications, if any, are needed, for example a pressure relief valve to stop the back pressure in the return line from rising too high?

Reduced pump speed at low rpm, say below 4000 rpm for cruising
3 If you have some system to reduce a pump's speed in order to reduce noise and heat build-up at low RPM, for example when cruising at 60-70mph for several hours, how did you do that and what advice do you have eg on voltages?
4. For a fuel pump speed controller such as the Aeromotive 16306 can you safely connect it to 2 pumps (Aeromotive have said 'No', but IMO they'd say that if even you could)?

Thanks for any help.

All you had to do was look at the threads on the first page of this forum area

https://www.rx8club.com/series-i-maj...system-168996/

sigh ....

What are your issues with your setup?......how do you have it set up?. It will be easier to give you answers if we now :)

Thanks for the steer.

I did though have look at that before posting but was still left with my questions. I also had a look at loads of other posts here, on the various RX7 and RX8 and at other club sites.

For example, yes, dznutzuk has a description of his system that includes his saying he connected the return line to the siphon but he doesn't go into detail and someone from another club said that he did that but took it off as it wasn't picking up the fuel from the RHS tank and had problems on WOT. Hence I'd appreciate a 3rd (or more) opinion despite the comments in that thread.

I'm open to any system that best meets my needs (400 bhp, road and occasional track use, retaining all 4 seats and as much boot/trunk as possible).
The current system consists of a Walbro GSS342 255lph in place of the stock pump (no other mods to the fuel pump unit) feeding a cheap fuel regulator in the engine bay via what measures as non-armoured AN-4 tubing/hose, return hose/piping of AN-4 and AN-2 piping ending with some solid piping shoved into the top of the fuel pump unit. It gets it's power through the original wiring.
It doesn't get any fuel from the RHS tank, won't pump much beyond half full on the fuel gauge and struggles to maintain pressure on WOT.
The GSS342 is very noisy, as expected from reviews I've seen.


Ian

I would replace the passenger side cover with drivers side fuel pump assembly, and use twin pumps, one per tank. Then have the return line Y into each fuel tank.

You're serious? Sounds like a bit of a mess....the OEM line is -5 equivalent... so -4 is a downgrade

This is how I originally had it, nothing wrong with it, just got aluminum fittings instead( https://www.google.gr/search?q=an-6+...or%3B178%3B225 ). The original feed line is used as the return-which you connect to the siphon valve, and ran a new an-6 feed line. I don't have any problem with the fuel not being siphoned, if anything at one point I removed the fuel pump basket and all the fuel was on the driver's side, weird but... Make sure you melt the edges on the valve so it won't pop open. Now the top feed part is a little tricky, installing a regular an-6 bulkhead fitting and then using a straight push on fitting doesn't really leave aany room for the line to connect to the fuel pump. You can find something like this: Bulkhead Flare AN 6 TO 1 2 Barb Fitting With AN 6 NUT | eBay for a more direct approach and more room. At some point soon, I'm going to try getting a Walbro 485l pump in there.

ps. I don't see a need to install a a fuel pump speed controller, I'd rather have it as straightforward as possible.

First; I do not have experience with return system, but with electronics.

If you sense a signal that changes with RPM, for example pulse going to coils, then you can use this to regulate pump speed proportionally. This would be far superior to the vegetable way its done from factory(resistor if i remember correct). Now pressure relief valve would bleed less fuel, generating less heat and less noise.

Dannobre, when are you going to post pictures of your swap???

Not for a while. Motor is out...waiting for machine shop to do the internal work...and designing the dry sump. Hope to have it back together by Mar :)

Guys, thanks, that's a big help.

Yep, there's a resistor the size of a cigarette packet in the engine bay. If your engine builder doesn't secure it properly then on a track day it can easily find its way next to your turbo's exhaust, short out its leads, blow fuel pump fuses and then hide from sight; if you don't know this, as 20+ RX8 owners at a track day didn't, then you can find your track day cut short and your wallet lighter from paying for a recovery truck home (been there, done that, don't want to do it again).

good info

There are others too .....

Boost-A-Pump

Pump capacity isnt the issue N.A...... getting the fuel to the pump is.

^^E85 and six ID725 injectors, better safe than sorry ...

Can you be more specific as to where?

srsly, stinky???

It's underneath the air pump at the front bottom of the RH front shock tower

https://www.rx8club.com/series-i-tec...equest-220470/