Rep Power: 117

Hello everyone, I am wondering what you guys think of converting to a return type fuel system. I have a Y8 intake manifold with an AEM fuel rail, so I have a port on both sides of the rail so the fuel could flow in one side and out the other and I have a 3/8 fuel line running from the pump to the rail. I'm wondering what the benefits would be though. About the biggest benefit I can think of is that fuel would always be flowing through the rail instead of sitting there and getting hot, so the fuel being fed to the injectors would be much cooler. My fuel rail gets very hot in the summer, so hot that I can't hold my finger on it for more than a second, which is likely one of the main reasons my car feels slower when I get stuck in traffic in the middle of the summer, along with the intake air obviously being hotter.

So other than the fuel in the rail staying cooler, what benefits would I see from converting to a return style fuel system? Thank you very much in advance!

 
Rep Power: 209

I don't really see a benefit. Cooler fuel doesn't increase the volume significantly like air does. Back when cars had carburetors and fuel pumps on the engine that sucked gas fuel temperature and vapor lock was a concern. With a pressurized system that is no longer an issue.

 
Rep Power: 117

Thank you. So you wouldn't expect any noticeable power improvements with a heat soaked engine from reducing the fuel temp from probably up to 160 degrees to around 100 degrees? I have heard from a few sources that decreasing the fuel temp by 2 degrees F has about the same affect on charge density as decreasing the intake air temp by 1 degree F, which sounds pretty good since I could probably decrease fuel temp by up to around 60 degrees by installing a return setup. If that statement is true, installing a return setup could potentially have a similar effect on performance as decreasing the intake air temp by up to around 30 degrees, which is pretty significant and noticeable.

 
Rep Power: 242

Maybe in a forced induction application. Not sure how much it would help naturally aspirated.

 
Rep Power: 228

In order to supply enough fuel for super aggressive builds 20+ psi, you need to run one hell of a fuel pump. This pump flows so fast that it needs a fuel pressure regulator and return system to send excess fuel back, when your not using the fuel.

I'd suggest saving your money and buying a stage 1 camshaft instead; if you dont already have one.

 
Rep Power: 209

D17... I have a challenge for you if you'd care to accept it?

My car is a 1995 Civic EX with an Acura LS manual 5-speed.
Engine is a JDM B20 block with a non-vtec LS head.
The previous owner did all the mods but he disconnected and removed the charcoal cannister and evap purge valve it. The car is currently in Florida (no state emissions or safety inspections required) and I now live in North Carolina.

NC requires both emissions and safety inpections annually.
It old enough to where in NC it doesn't need to be emissions tested but must pass a visual inspection including emission parts such as the charcoal cannister., So potentially I could add a cannister and purge valve to make it " appear to work". However, I would like to actually connect and function properly but I haven't read anywhere online of any modders doing this Also, it could potentially be dangerous if not done right. Interested in solving the issue?



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Rep Power: 117

Thank you for explaining this! I already have a Crower stage 1 cam, thank god I got one before they discontinued them! So no real benefits to me other than cooler fuel in the rail. I'm going to do some research on how much difference fuel temp makes, but I'm guessing probably not very noticeable.

 
Rep Power: 117

Sure, I would be happy to help. I don't know about the 5th gen Civic's EVAP system specifically, but I have a good understanding of how EVAP systems work in general. I would suggest going to a junkyard, finding a 5th gen Civic, and taking pictures of the stock charcoal canister setup. After taking pictures of how it is set up, grab its charcoal canister and any missing hoses or brackets. Also, get a purge solenoid from whatever kind of vehicle the engine/ECU is from as it may be different and needs to be electrically compatible with the ECU. Then you need to install the charcoal canister in the back of the car as it was in the donor vehicle. In case you don't know, the charcoal canister absorbs fuel vapors in the tank so they aren't released into the atmosphere and the purge solenoid releases the vapors from the charcoal canister into the intake manifold when the ECU commands it open.

Once you get the charcoal canister installed as it was in the donor vehicle, then you will need to connect the purge solenoid to the pipe leading to the charcoal canister and to the intake manifold. If your intake manifold doesn't have an unused port, you can use a T fitting and splice into another vacuum source like the PCV hose or brake booster hose (before the check valve). Pay attention to the flow arrow on the purge solenoid as it needs to be installed with the arrow pointing towards the vacuum line going to the intake manifold. Mount the solenoid to a part of the engine, NOT the firewall. I made the mistake of mounting my purge solenoid to my firewall when I did my Y8 intake manifold swap and it is noisy as hell, it sounds like someone is tapping on the firewall with a hammer constantly whenever it is active. I need to move it when I have time.

Lastly, you will need to connect the electrical connector on the purge solenoid so the ECU can open it when it needs to. Presuming your engine harness has a connector for it then you just need to plug it in and you should be good to go. Let me know if you have any questions about this and I will do my best to help you.

 
Rep Power: 209

Thank you. that is very good info. The ECU is a refurbished/modified basemap tuned for a B20 from a company named Phearable. I'd have to call that company's owner and ask him if it can either work with a purge solenoid as is, or if I can send the ECU to him to be programmed to work with a purge solenoid.

 
Rep Power: 117

Glad I was able to help, let me know if you have any more questions