So why return fuel system?

lx347cid

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Are there any 700 plus hp cars out there on returnless fuel systems?
All the tuners say its easier to tune with return system vs returnless but yea so is switching to carb.
Seems like its going backwards in technology but what do I know- kinda like when fuel injection came out and everyone was scared to tune it. Just said carb is easier to tune.
So whats the deal. Why did the OE go to so much trouble to come out with a returnless system and then we need to change it?
 

Black02GT

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The OE uses it for emissions and fuel heating issues. Problem is the lag due to spinning the pump up and down and adaptive feedback loop used to try to maintain pressure is tough to tune. If you have something like a regulator maintaining constant boost referenced pressure tuning is way easy. Do some looking into PID controllers and tuning the returnless and you'll see why at high HP it's a beast.
 

cj428mach

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C6Zhombres car is a high horsepower returnless car and there maybe a few others but they're rare.

A return system is vastly superior to a returnless system because the fuel supply and pressure is always there on a return. People will argue that returnless can be made to work and it obviously can in some cases but its not better. The reason you never see returnless systems is because when you go to install a new fuel system the price of both systems are very close so people just choose the better of the two.

I think I've heard that the oems are going back to a return style, dead head system.
 

Black02GT

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C6Zhombres car is a high horsepower returnless car and there maybe a few others but they're rare.

A return system is vastly superior to a returnless system because the fuel supply and pressure is always there on a return. People will argue that returnless can be made to work and it obviously can in some cases but its not better. The reason you never see returnless systems is because when you go to install a new fuel system the price of both systems are very close so people just choose the better of the two.

I think I've heard that the oems are going back to a return style, dead head system.

Aren't the new 5.0 and GT500 essentially deadhead but in the tank "mechanical returnless"? Don't think they try to vary the pumps like the older returnless.

Isnt C6zhombre like 700 on E85 too, think 04sleeper tuned his, impressive for sure? I had a bitch of a time trying to tune mine, I think the stock line was maxed though making it pretty much impossible. After I get inspected and registered on this build I have a Fore return style going in. Then start playing around with getting it to pass NY inspection for next year.
 

Steve Cea

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Running my car with a 93 tune , Whipple and 19 lbs of boost while spraying Methanol I'm damn close to 700 hp to the wheels and nope still on the stock fuel system minus the 80lb injectors and Kenny Bell BAP

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01yellercobra

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Aren't the new 5.0 and GT500 essentially deadhead but in the tank "mechanical returnless"? Don't think they try to vary the pumps like the older returnless.

My understanding is it's a mix of the two. There's a mechanical limit in the tank. I want to say around 50psi. But the ECU still modulates the pumps in the lower end of things. Which is something that's good about the returnless. At least in the newer systems. The pressure can be dropped at idle and part throttle to better control larger injectors. I don't know if the 03/04 ECU's can do that.
 

choate

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I'm going through this right now. By the time I'm done getting the tank dropped twice, dealing with a popped FRPS (hasn't happened to me yet but I have been stranded and had to get a tow - car still won't fire btw), weird drivablity issues that has taken 3 revisions to get right and would have to do this all over again (new tune, drop the tank etc) if I ever want to go E85, i'll likely end up paying more than just doing return style the first time. It's expensive but way worth it. You only find out the hard way when you try to cheap out. If you are upgrading the blower, I'd do return style fuel. You also get the added benefit of upgrading your what 50k miles stock pumps to brand new ones while you're at it. Once and done. Do what I say though, not as I "did". Lesson learned
 

Black02GT

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My understanding is it's a mix of the two. There's a mechanical limit in the tank. I want to say around 50psi. But the ECU still modulates the pumps in the lower end of things. Which is something that's good about the returnless. At least in the newer systems. The pressure can be dropped at idle and part throttle to better control larger injectors. I don't know if the 03/04 ECU's can do that.

I'd be curious if your running Dual FPDM if you could run return and have the bottom two rows of your voltage half and the rest maxed out to make kind of a speed controller. I'd have to think a little more about that. I don't think you could drop pressure though since there is only 1 target pressure in the tune though just pump speed for heating.
 

01yellercobra

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I'd be curious if your running Dual FPDM if you could run return and have the bottom two rows of your voltage half and the rest maxed out to make kind of a speed controller. I'd have to think a little more about that. I don't think you could drop pressure though since there is only 1 target pressure in the tune though just pump speed for heating.

I think in the newer ECU's there's a commanded pressure that can be changed. At least that was my understanding. The guy I spoke to was tuning his own car and this was awhile ago.

But eventually the computer learns the needed voltage. So if it did work, the computer might null it out.
 

TRBO VNM

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But I want to go to a return style system just not sure what's involved to do so ? What does everyone recommend?

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Fore Innovations. I don't know if e85 is available by you or not, but I would just go with the Level 1E kit and 465 pumps. It will be setup for higher HP and e85 if you want to upgrade and at a later date you can easily add rails as well.
 

Steve Cea

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Fore Innovations. I don't know if e85 is available by you or not, but I would just go with the Level 1E kit and 465 pumps. It will be setup for higher HP and e85 if you want to upgrade and at a later date you can easily add rails as well.
E85 is very hard to find by me not impossible but I gotta drive like 15 miles into a not so good area so to me it's not an option , what's the price of a Level 1E kit with 465 pumps ? Difficult install ? Not that I can't wrench I am a GM and ASE certified tech and shop manager however battling a brain tumor at the moment so I'm a bit limited but still love to get in there ! Tumor son far has robbed me of my left eye ! But I intend to win this battle !!

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TRBO VNM

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Prayers are with you man. Beat it and make a recovery.

I'll drop you a pm about the system and other things tomorrow. It isn't hard to install and I am available for help during the install 7 days a week.
 
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04sleeper

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There are advantages and disadvantages to both. One advantage that is not thought about on a returnless system is voltage draw is kept to a minimum. When driving around 99.9% of the time, you don't need 100% of the fuel flowing. So that helps the voltage draw off the alternator and charging system It also helps in keeping fuel cooler due to not running the pumps 100% all the time either.

The down side is that they have their limitations as far as performance. Return systems are more common and can provide 100% fuel flow which is easier to predict. Down side to them is latent heat from the pumps and voltage loss.

Both can be made to work. Most choose return due to easier install and availability/predictability.
 

c6zhombre

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There are advantages and disadvantages to both. One advantage that is not thought about on a returnless system is voltage draw is kept to a minimum. When driving around 99.9% of the time, you don't need 100% of the fuel flowing. So that helps the voltage draw off the alternator and charging system It also helps in keeping fuel cooler due to not running the pumps 100% all the time either.

The down side is that they have their limitations as far as performance. Return systems are more common and can provide 100% fuel flow which is easier to predict. Down side to them is latent heat from the pumps and voltage loss.

Both can be made to work. Most choose return due to easier install and availability predictability.

Great explanation. I had not thought about the lower voltage draw
 

Quick Strike

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Are there any 700 plus hp cars out there on returnless fuel systems?

Why did the OE go to so much trouble to come out with a returnless system and then we need to change it?

Milne is in the mid 700s with a returnless system. It is at 65% duty cycle on a 93 octane and Torco tune. It was tuned almost seven years ago and still has no issues. The system is composed of a Fore hat, GT pumps, MDM Jr. (two channel FPDM), KB BAP, wiring upgrade, stock lines/rails and 60# injectors. Similar results could be reached with two FPDMs since the MDM Jr, is no longer available. The GT500 used a similar returnless dual FPDM system for a while that could be driven over 1000 RWHP with just a BAP.

The returnless system can be difficult to tune retaliative to the tried and true return system that anyone can make work. These tuning issues increase as more is demanded of the stock returnless system. Pressure spikes can leave the returnless system sidlined if tuned incorrectly and the BAP increases the possibility of spikes when run full time. The other issue is that the system can not easily support the volume of fuel that is needed for E85. I am at 65% DC on 93 octane, but would be maxed or beyond maxed on E85.
 

lx347cid

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I want to go e85 without going return system to get 700 rwhp. Anyone doing this with larger pumps and returnless?
 

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