Fuel system help!!!

[Ponderthis]

can someone explain why a return style system is needed for E85 and 700-800whp and not just a pump upgrade? The factory lines that restrictive?

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[phunk]

can someone explain why a return style system is needed for E85 and 700-800whp and not just a pump upgrade? The factory lines that restrictive?

The factory lines could support 700-800 if all else was ideal, but it's not. None of it is.

The stock pump found inside the stock fuel pump module is already a good pump. I don't have a flow chart for it but if a Walbro 450 is an upgrade at all it's not going to be a huge one. So you're looking at twin pump to move forward. The twin pumps do not have returnless setups built into them like the stock one. The stock pump housing has a regulator integrated to it (and the fuel filter). So by virtue of installing a twin pump you automatically need to add a regulator and you'll need to bypass the stock feed pipe to add an inline filter.

Now even if someone came out with a 800LPH pump that fits in the stock fuel pump module, returnless is not ideal for high power anyway. Returnless cars control fuel pressure at the tank/pump... thus any pressure drop through the plumbing is effecting pressure at the rails, meaning fuel pressure will be dropping as fuel consumption increases. There is no way around this other than to go with grossly oversized plumbing, and by now if you're running new lines there is no reason to not make it a return system too. Return fuel systems regulate rail pressure (as opposed to pump pressure like a returnless setup), so any pressure drop in the plumbing does not hit the rails until you have literally outran your fuel pump(s).

A return system will use a regulator that increases fuel pressure as boost increases. This keeps the effective fuel pressure static. A fuel system that does not increase rail pressure with boost will lose effective fuel pressure. Imagine an exaggerated example, if you had 50psi boost and 40psi fuel rail pressure... your effective fuel pressure is -10 and your injectors would be injecting air into your fuel system rather than fuel into your intake. A return fuel system with 1:1 referenced regulator would have increased fuel rail pressure by 50psi to match the boost, keeping effective fuel pressure 40psi higher than intake manifold pressure.

Basically the entire setup is handicapped when your fuel consumption gets to that level, and all roads point to return conversion.

 

[Ponderthis]

Just trying to put things into perspective, back in my 4G63 turbo 4 cylinder days we ran twin 450LPH pumps in tank with just 6AN line upgrades from tank to rail, that car made 700whp @ 45 psi boost... The car did have a Fuel RETURN line which ran to a Fuelab Regulator then back to tank... So that was a Return style system? They returned from the factory we just ran larger lines of course, I think im starting to catch on since our fuel rail only has FEED line, never actually thought about it damn.

 

[phunk]

Just trying to put things into perspective, back in my 4G63 turbo 4 cylinder days we ran twin 450LPH pumps in tank with just 6AN line upgrades from tank to rail, that car made 700whp @ 45 psi boost... The car did have a Fuel RETURN line which ran to a Fuelab Regulator. So that was a Return style system??

Ya most turbo cars, or all of them that I can think of right now, use a return style system from the factory.

Lower boost applications can do 700whp e85 with a single 450 with 6an, we can get that from high compression 6 cylinders. But at 45psi boost and especially with lower compression too, definitely need that second pump to do it.

 

[Ponderthis]

Ya most turbo cars, or all of them that I can think of right now, use a return style system from the factory.

Lower boost applications can do 700whp e85 with a single 450 with 6an, we can get that from high compression 6 cylinders. But at 45psi boost and especially with lower compression too, definitely need that second pump to do it.

This was some old 90's AWD DSM junk, Talon/Eclipse GSX...Ran 9s though lol

 

[TooSoonJunior]

Thanks for taking the time with helpful info. I'll tell you this, I've never touched 1000whp on two pumps, e85, and a single 8AN feedline. But maybe I was too conservative in the setups ability

 

[beefcake]

our fore level 1 system is as good a quality as it gets, and upgradeable later on, you really can't go wrong with it.

feel free to give us a ring and bend our ear on your needs and goals

 

[phunk]

Thanks for taking the time with helpful info. I'll tell you this, I've never touched 1000whp on two pumps, e85, and a single 8AN feedline. But maybe I was too conservative in the setups ability

Not all cars will be able to hit 1000 e85 on just 2 450 pumps, it depends on what is in your favor. Higher compression ratio (more efficiently converts fuel to torque), displacement and good cylinder heads that allow you do it at lower boost pressure (keeps fuel system pressure lower thus fuel pump output higher), and optimum ignition timing tuning, are the main contributors to success in that regard and are all common attributes of a boosted S550. I think that the parasitic losses from the supercharger are the only obstacle to seeing the higher end of power per given volume of fuel.

But the single 8AN line would not be the hold up seeing as that it's only contributing to a 2psi increase in pump pressure. That ~1psi pump pressure over a 10AN in this flow range is going to reduce fuel pump output by less than 1 GPH per pump. As I'm sure you already understand, if you're cutting it that close that 1-2GPH is the difference between lean and safe for you, you need another pump. That increase in flow from a 10AN is not going to provide a meaningful margin... the pump is what needs attention.

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