Surge Pump Return Hose

[Dave 53]

My return hose from the fuel rail back to the tank is 1/4", even though the fuel rail barb seems to be 5/16" (previous owner). No obvious issues. All other hoses such as fuel pump to the fuel filter, then filter to the fuel rail are 5/16".

I'm in the middle of plumbing in a surge tank. So now, I'll have not just the fuel rail return using this 1/4" hose, but now also the return from the surge tank using the same hose. Fuel rail returns to surge tank - surge tank returns to gas tank via 1/4" hose.

Replacing this 1/4" return hose with a 5/16" will be a pain in the *** requiring removing the fire wall. Willing to do it if this forum says I need to, but hoping this forum says don't worry about it - 1/4" return hose is fine.

[Bob_n_Cincy]

Dave,
Here is a chart that you can use to calculate if 1/4" hose is enough.

hose-friction-loss.jpg

here is a link on summit racing page https://help.summitracing.com/app/an...4879/related/1

[RPGs818SNA]

Dave,

While the surge tank is initially filling or recovering from a surge, there is no flow in the ¼” return tube. Once full and not surging, the return flow is the same as before. During surge operation, there is no flow in the return tube. So the return flow never exceeds the original flow rate.

Assuming a 1 gallon per minute fuel pump and a 10’ return hose, the pressure at the top of the hose is at most 5.4 psi per the chart Bob references. That won’t affect a return style regulator as shown here.
https://help.summitracing.com/app/an...5243/related/1

However, Summit recommends the return hose be as large as or one size larger than the supply hose here.
https://help.summitracing.com/app/an...4752/related/1

I disagree with Summit. If the pressure at the regulator return is close to the fuel rail pressure, maybe 60 psi, that could impact the fuel rail pressure. I don’t see a situation where your return pressure could exceed 5 psi with an unrestricted ¼” return hose, so it won't impact your fuel rail pressure. I don’t think you need to change it.

RPG

[Dave 53]

Part of the fun of building this car is learning all kinds of things. Those Summit links look like they address a standard setup with fuel rail return directly back to the tank. There must be different kinds of surge tanks because mine has constant flow in (via the in gas tank pump) and returning to the gas tank with a pump in the surge tank supplying the fuel rail.

Without the surge tank, the fuel rail returned excess gas back to the tank via the 1/4' hose - no obvious issues. With the surge tank, the fuel rail is now returning excess gas to the surge tank container. The gas tank pump is now constantly pumping gas into the surge tank. Now the return hose from the surge tank back to the gas tank needs to handle both the fuel rail return and the excess gas constantly circulating through the surge tank container. I was worried about this combined flow squeezing through the 1/4" hose.

Moot point. I took the fire wall out and replumbed the surge tank return to the 5/16" tank barb. The 1/4" barb is now my vent to the top of the tank filler neck.

I mentioned it in a previous post... if you're building a track car, the Holly Hydromat isn't enough. You're gonna need a surge tank or fill up the gas tank every 40 minutes of track time.

[RPGs818SNA]

My favorite part of building an 818 is the chance to learn more about how cars work, both from my own experience and from that of others via this forum. Thanks for sharing about the benefits of a surge tank and how it works. I suspect you’ve nailed fuel starvation.

One nagging question I have is where the surge tank pump gets its fuel. I thought it pumped fuel from the contents of the surge tank toward the fuel rails, and any fuel the engine didn’t use was returned to the surge tank. If that’s the case, the fuel returned to the surge tank would be somewhat less than what was pumped out, for a net loss of fuel to the engine from the surge tank. So wouldn’t the return hose only need to handle what the main tank fuel pump is pushing up to the surge tank as before?

A novice still learning,
RPG

[J R Jones]

I built a prototype motorcycle on contract for an OEM, putting a 120hp water cooled EFI engine into a (80hp air cooled engine) frame. The original fuel pump was a tiny (Vega?) unit in the frame/tank. The new pump was huge. I had to build a surge-like remote accumulator for the big fuel pump. I gravity fed fuel to the (lower) canister with a large diameter hose. I may have put a breather between the top of the canister and the top of the frame/tank. Worked great. It would be hard to position an accumulator lower than an 818 fuel tank. Maybe a deep sump would work.

[Neeraj Ahluwalia]

For my surge tank setup I bought a cheap tank off ebay for about $100, which came with a knock-off bosch 044-style pump. I ran the 5/16 lines from the main tank to the surge, and the same back - with a 5/16 to 1/4 reducer (I had the same issue - didn't want to remove the firewall).

I have AN6 lines running to everything after that but my regulator won't go lower than 70psi. Thinking this is a function of the regulator to surge tank hose size - AN6 being restrictive

[Dave 53]

Pulled the firewall and plumbed the 5/16 return hose to the 5/16 tank barb. Yes, pulling the firewall was a pain in the ***. But as it turns out, very necessary for wiring.

SURGE PUMP WIRING

I have an iWire harness, 2002 WRX. I wanted the pump feeding the fuel rail to be connected to the fuel pump controller and the in-tank pump to be ran on a relay. I pulled the dash off and tried doing the wiring switcheroo under the dash (cut the wire from the pump controller to the in tank pump and rewire it to surge tank pump). I studied the FSM wiring diagrams and probed every wire with my multi meter. The wiring switcheroo cannot be done under the dash. I believe there is a wire spliced in the harness run somewhere between the controller and tank pump. If you cut the wires to the tank pump and attach the surge pump wires at the controller end, you are cutting this spliced in wire out of the circuit and it won't work correctly. The switchroo must be made that the tank end of the wire harness to make sure this spliced wire is included. Also, the ground for the pump controlled by the controller, now the surge pump, must use the ground from the controller and not a general chassis ground. The controller plays with this ground.

I wanted the relay for the tank pump to be triggered by the (surge) pump controller. The controller will run the pump only when the engine is running. I'm most concerned about the tank pump continuing to run after an accident. The controller varies the voltage to the pump as low as 9.0 volts to 0 volts when the engine isn't actually running. My plan was to trigger the tank pump relay off this wire. I tried 2 Amazon relays that were supposed to trigger at 7 volts, but neither of them did at 9 volts, so this plan failed.

Next plan is to trigger the tank pump off the main fuse box pump relay thinking if the relay was giving voltage to the pump controller, it knows something that also applies to the tank pump. After studying the wiring diagrams, it turns out the main fuel pump relay is triggered by the key being in the "on" position and the relay switching controls more complicated aspects than just supplying voltage to the pump controller. That being the case, I wired the tank pump straight to an open key "on" fuse - no relay. So, the tank pump runs when the key is "on" regardless if the engine is running. I'm not really liking this. I need to find a relay that truly triggers around 8 volts. Any leads?

If you left the tank pump wiring alone (so it is still being controlled by the pump controller) and simply added a new circuit for the surge pump, I kinda hate to say this, but I think you did it wrong because now your fuel rail isn't getting fuel from a pump controlled by the pump controller - the fuel rail is getting fuel from a pump running full tilt at all times. And short of ripping the wiring harness apart to find this spliced in wire, I see no alternative other than to pull the firewall and do the wiring switch at the tank. Running the surge pump full tilt whenever the key is "on" will work, but the ECU/pump controller will be controlling the voltage to a pump that isn't feeding the fuel rail. You might as well delete the pump controller. THIS MIGHT EXPLAIN WHY YOUR FUEL PRESSURE WON'T GO BELOW 70 PSI. Note: at least for my 2002 year, but I believe other years too, only turbo motors have a fuel pump controller - NA do not.

Had the car out at Willow Springs over the weekend and the surge pump worked flawlessly. Prior to the surge pump, I was getting fuel starvation in right hand turns at half a tank of gas. Willow Springs is very much a giant right-hand turn, and I had no fuel issues with a nearly empty tank.

[Ottw]

This is what you need, they are a little pricey but will not be dependent on your factory wiring. Aeromotive 16306 Billet Fuel Pump Speed Controller, I have a extra new one fs. You don’t have to hook it up to your tach, just your speed sensor on your transmission (lot easier to get to)
5CADD740-C489-4AAD-B4A2-5344AFDF2B0A.jpg

[Dave 53]

Thanks for the lead, but... I found a solid-state relay that advertises triggering at 3 volts. Currently have the fire wall out and gas tank exposed, so planning to rewire the pumps with the solid state relay controlling the tank pump this week after I finish installing the oil cooler.

https://www.amazon.com/SSR-25DD-3-32...NrPXRydWU&th=1

BTW, before the surge pump, I had a 5/16 tank vent to the top of my filler neck and fill ups were never a problem. I wanted the surge tank to have a 5/16 return, so I used the 5/16 barb on the tank for the surge return and switched the filler neck vent to a 1/4 tank hose barb. Fill ups became a problem. The win-win solution was to have the surge return and filler neck vent share the 5/16 tank barb.
Surge pump return T.jpg

[Ottw]

That will work but it’s on or off, and it’s noisy sitting behind your seat, the 16306 lets you setup the fuel pump based on demand.

[Dave 53]

Looks like that controller would be great for a pump feeding the fuel rail, but I just need on/off for the pump feeding the surge tank. The pump will be on only when the engine is running which is the goal, so the noise isn't an issue. It will always be running at full tilt, but under very little pressure as it's just circulating fuel through the surge tank.

What would be cool is an amplifier that doubled the amps so that both pumps could be ran off the same controller. Couldn't find such a device.

Also thought about a second OEM controller with power to the controller from a separate power circuit, but shared ECU inputs.

Or a $10 relay...

[DSR-3]

Be careful buying electronic components on Amazon, and/or be sure to have easy access...

[Dave 53]

Be careful buying electronic components on Amazon, and/or be sure to have easy access...

Excellent point and your advice will be taken. It will be effortless to by-pass a failed relay, but who want's a failure while driving? I wonder if they fail making contact or fail breaking contact?

One problem I had looking at higher quality relays was finding an advertised trigger voltage. I probably should just buy a quality one and test it.