Return VS. Returnless Fuel System...Which way to go?

[skwerl]

Sam, you looking to break 1000hp?

 

[19COBRA93]

Sam, you looking to break 1000hp?

Yes, absolutely. I'm hoping to be over 1100 ultimately. But short term, I'm looking to break 1000rwh at about 26-27lbs on 110 unleaded. I'm just taking baby steps to make sure everything is playing nice together.

I'm currently upgrading my lines and pumps, but retaining the returnless configuration (for now). I'm hoping to make just over 900rwh with that setup at about 23lbs and 100 octane. I'd like to find the limit of a returnless system. As it is, I think a lot of people go return when they're miles from needing to.

 

[Bobby]

If you are down here at mustang week get up with me tomorrow or sat and i can talk to you about both.

 

[BruceH]

Is there anything you can do with a return that can't be done with a returnless?

 

[blownGTvert]

Is there anything you can do with a return that can't be done with a returnless?

Either system will work, but for big fuel demands, a return style is optimal. You will have a much more stable fuel pressure. Most tuners will recommend a return style system for anything over 650hp. Especially when the additional fuel demands of E85 fuel are in play. The Aeromotive A1000 or Eliminator are single drop in pumps for the S197 that will support big power. there are advantages to a single pump over muliply pump systems as well. I have the Eliminator pump and it rated at 875lph and support 1000hp+ on corn. Combined with the Aeromotive pump control and vapor lock is eliminated for a street application. The pump control is "pulse width" modulation just like the OEM fpdm.

 

[Department Of Boost]

Someone might correct me on this but all a return style really does is make it easier for the tuner. Set the regulator and that's it. The downfall is at lower power levels because that 5 bar needed to run wot is still there for normal driving. This means very short pulse widths are needed to run the motor at low loads.

I run 40psi base pressure and it goes up 1psi/psi (of boost).

 

[BruceH]

I was talking about the fuel injector pulse width. As the delta pressure goes up the injector has to be on for a shorter amount of time, at lower fuel demand levels in can be a liability.

I'm trying to learn, not argue. However, it's going to sound like I'm debating but I'm not.

I can understand how a return system is going to always have the same psi. It's regulated to blow off or return any fuel over the setting and not used.

What I don't understand is how a returnless has issues? I only have experience with my builds. With that said I've never had a problem with fuel pressure being stable. It's very easy to command different delta or base pressures for different air flows. I do quite a bit of data logging and am not seeing anything that would be dangerous. As the airflow increases the psi increases. The computer adjusts for the increased delta pressure and a/f doesn't suffer at all.

Is it possible that the s197 is refined to a point that it's more reliable than earlier returnless systems?

Either system will work, but for big fuel demands, a return style is optimal. You will have a much more stable fuel pressure. Most tuners will recommend a return style system for anything over 650hp. Especially when the additional fuel demands of E85 fuel are in play. The Aeromotive A1000 or Eliminator are single drop in pumps for the S197 that will support big power. there are advantages to a single pump over muliply pump systems as well. I have the Eliminator pump and it rated at 875lph and support 1000hp+ on corn. Combined with the Aeromotive pump control and vapor lock is eliminated for a street application. The pump control is "pulse width" modulation just like the OEM fpdm.

 

[Department Of Boost]

I can understand how a return system is going to always have the same psi.

A return system doesn't have a constant psi. For example, mine is 40 base and 60 at WOT under boost.

As the airflow increases the psi increases.

Same with a return system but it's as the boost increases the fuel pressure increases.

 

[05yellowgt]

A return system only drops and raises fuel pressure as a function of boost if you have a boost referenced fuel pressure regulator. Should be a no brainer, but I wanted to make sure that part was clear. You can also use a Hobbs switch to disable or turn down the voltage on return style fuel pumps to reduce the flow and therefore the amount of heat that gets transferred to the fuel in the tank, but I think that was covered too.

 

[19COBRA93]

Anyone have any reason not to run a "deadhead" system? It's a return style system, but is returnless at the motor. This is what I have planned for mine.

It goes; supply line to regulator. Return line from regulator. Then two supply lines from the regulator to the rails. No fuel returns from the rails which are capped at the ends.

 

[crownaviation]

I would haeve to dig thru all my old logs but I have been running a complete Fore Innovations return system with the 4i regulator, dual Walbro 465 pumps, -8AN feed and return. ID1000 injectors and always run e85 on that setup. 4ga wire to the pumps from the battery in the trunk but will soon change to the Fore innovations controller for simplicity

Fuel temps were rediculous before I installed a hobbs switch to control the second pump. It comes on at 3psi of boost so system is ramped up/ready when needed.

Ran just a hair over 23psi of boost at 55psi base pressure. Also using the frps signal..

I will need larger injectors for my build which sucks cause they were $2k alone. The ID1000 will not support 1,000rwhp on the corn

 

[blownGTvert]

Anyone have any reason not to run a "deadhead" system? It's a return style system, but is returnless at the motor. This is what I have planned for mine.

It goes; supply line to regulator. Return line from regulator. Then two supply lines from the regulator to the rails. No fuel returns from the rails which are capped at the ends.

That's not correct. The supply line feeds the front of both rails. Out of the back of each rail to the regulator. From the regulator, fuel returns to the tank. Fuel is always circulating and not "deadheaded".

I would haeve to dig thru all my old logs but I have been running a complete Fore Innovations return system with the 4i regulator, dual Walbro 465 pumps, -8AN feed and return. ID1000 injectors and always run e85 on that setup. 4ga wire to the pumps from the battery in the trunk but will soon change to the Fore innovations controller for simplicity

Fuel temps were rediculous before I installed a hobbs switch to control the second pump. It comes on at 3psi of boost so system is ramped up/ready when needed.

Ran just a hair over 23psi of boost at 55psi base pressure. Also using the frps signal..

I will need larger injectors for my build which sucks cause they were $2k alone. The ID1000 will not support 1,000rwhp on the corn

Neither will a -8 supply line. You may want to consider a -10 supply if your goal is 1000hp on corn. Also the return line should be the same size as the feed at a minimum for a return system. If the return is too small you get inaccurate pressure readings at the regulator.

 

[19COBRA93]

That's not correct. The supply line feeds the front of both rails. Out of the back of each rail to the regulator. From the regulator, fuel returns to the tank. Fuel is always circulating and not "deadheaded".

I get what you're saying, but that's not how I plan to run mine. There's no reason the fuel has to pass through the rails.

This is my regulator:

 

[lito]

I was talking about the fuel injector pulse width. As the delta pressure goes up the injector has to be on for a shorter amount of time, at lower fuel demand levels in can be a liability.

I'm trying to learn, not argue. However, it's going to sound like I'm debating but I'm not.

I can understand how a return system is going to always have the same psi. It's regulated to blow off or return any fuel over the setting and not used.

What I don't understand is how a returnless has issues? I only have experience with my builds. With that said I've never had a problem with fuel pressure being stable. It's very easy to command different delta or base pressures for different air flows. I do quite a bit of data logging and am not seeing anything that would be dangerous. As the airflow increases the psi increases. The computer adjusts for the increased delta pressure and a/f doesn't suffer at all.

Is it possible that the s197 is refined to a point that it's more reliable than earlier returnless systems?

ERFS is probably the best of the returnless systems as it has a lot of flexibilty, tuning very high pump volumes gets tricky and peak pressure issues may get into play. Yes, it has the flexibility of programmed deltas which a return wont. I think there lies the confusion, 1:1 regulator will keep delta (somehow) and the PID controller of the ERFS will do the same by raising RAP (but we always measure delta) so is the same thing.

Anyone have any reason not to run a "deadhead" system? It's a return style system, but is returnless at the motor. This is what I have planned for mine.

Only issue you may run into is if you choose to work on switch pumps, pressure spikes may kill FRPS.

That's not correct. The supply line feeds the front of both rails. Out of the back of each rail to the regulator. From the regulator, fuel returns to the tank. Fuel is always circulating and not "deadheaded".

Says who?

Neither will a -8 supply line. You may want to consider a -10 supply if your goal is 1000hp on corn. Also the return line should be the same size as the feed at a minimum for a return system. If the return is too small you get inaccurate pressure readings at the regulator.

Also depends on how your system is laid out, if working on stepped pumps you will have basically no issues keeping -10/-8 or -8/-6. Is not bad to have a big return line though.

This is my regulator:

That thing looks is going to start walking any moment, lol. Why all 90s? not a single line coming from a side or front at least?

 

[blownGTvert]

I get what you're saying, but that's not how I plan to run mine. There's no reason the fuel has to pass through the rails.

This is my regulator:

Having the regulator before the rails will work. However, most manufacturers recommend the regulator after the rails. This reason is the regulator maintains the fuel pressure between the pump and regulator. With the rails in between the pump and regulator the pressure in the rails is very consistent.

I can say with certainty the 2 largest aftermarket fuel system manufacturers - Aeromotive and Magna recomend to install the regulator after the rails.
Not saying having the regulator before the rails won't work. It's just not preferred for most EFI installations. In the end its your car, install the system in the manner recommended by the manufacturer using the method you and your tuner are most comfortable with.

 

[19COBRA93]

That thing looks is going to start walking any moment, lol. Why all 90s? not a single line coming from a side or front at least?

I just put them all on there to keep them in one place. Once it's actually installed, it will have a bunch of different ones.

Having the regulator before the rails will work. However, most manufacturers recommend the regulator after the rails. This reason is the regulator maintains the fuel pressure between the pump and regulator. With the rails in between the pump and regulator the pressure in the rails is very consistent.

I can say with certainty the 2 largest aftermarket fuel system manufacturers - Aeromotive and Magna recomend to install the regulator after the rails.
Not saying having the regulator before the rails won't work. It's just not preferred for most EFI installations. In the end its your car, install the system in the manner recommended by the manufacturer using the method you and your tuner are most comfortable with.

This is an Aeromotive regulator designed specifically to be run in the way I describe. It has been proven to work really well, and eliminates the fuel heating of a conventional return system.

Lethal has been running their systems like this for a while without a problem.

 

[01yellerCobra]

Lethal has been running their systems like this for a while without a problem.

That's what I was going to say. It seems to work. I've been looking at a dead head set up just because it'll be the cleanest set up. I don't have a lot of room to run lines from the rails to a regulator. My only concern is if the regulator fails in some that causes a lean issue. If it's after the rails then the fuel will always be there. But then I might be over thinking it.

 

[BruceH]

A return system doesn't have a constant psi. For example, mine is 40 base and 60 at WOT under boost.


Same with a return system but it's as the boost increases the fuel pressure increases.

A boost referenced regulator. Ok, I get that. How is it better than returnless with a vacuum/boost regulated fpdm getting it's signal from the frps?

It sounds very similar except for the return line. If fuel pressure is regulated by a signal then why have the return line?

 

[01yellerCobra]

IMO, reaction time. With a return system the ECU has to sense that you've floored it and then tell the pumps to speed up to increase pressure. While it happens fast, it still takes time. With a return style the volume is always there ready to be used.

 

[BruceH]

If it's a boost referenced regulator then it's also dependent on a signal to raise the pressure.

BTW an electronic signal travels at close to the speed of light.

IMO, reaction time. With a return system the ECU has to sense that you've floored it and then tell the pumps to speed up to increase pressure. While it happens fast, it still takes time. With a return style the volume is always there ready to be used.