Fuel Line Size Article

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Worth a read

http://www.onallcylinders.com/2016/02/11/carbureted-vs-efi-how-fuel-line-size-effects-pressure-drop-in-your-fuel-system/

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

Interesting article, I wonder if that flow loss is based on a straight pipe/line only or includes the extra losses seen when you start adding in many 90° bends and/or fuel line types?

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

1x 90 = 10ft of straight the same diameter pressure drop wise.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Immortality wrote:

Interesting article, I wonder if that flow loss is based on a straight pipe/line only or includes the extra losses seen when you start adding in many 90° bends and/or fuel line types?

When did my mechanical engineering diploma we did a term on fluid losses etc, I know its not totally equivalent to fuel lines but certainly then you had factors as bends etc had a significant effect.  Maybe given the pressure and flow of the fuel it may even be worse.

[Heron SSVParticipant Central Coast NSW2009 Pajero Exceed 84 VK SL LS3 View build HERE Member since: May 5, 2015 Posts: 585]

I wonder how the location of a regulator affects fuel rail pressure. I’m mounting mine near my tank and running a single line to the rail, so the line between the intank pump and regulator will be short, but could there be a pressure issue at the rail if the regulator is sensing say 58psi, but the actual pressure at the rail/injector has dropped enough to impact injector flow? I’d say the line from the regulator to the rail would be around 8ft with a couple of bends

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

I’m not a fan of the return-less fuel system.  I’d much prefer the regulator at the fuel rail so that the fuel pressure is controlled where it is most critical.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Immortality wrote:

I’m not a fan of the return-less fuel system. I’d much prefer the regulator at the fuel rail so that the fuel pressure is controlled where it is most critical.

110% this, this is what Jack at Earls who imo is a walking encyclopedia on fuel systems told me.  You want the regulator right up at the injector end so as the demand rises rapidly (especially if its boosted) it can respond quickly. The other negative of a dead end system which is especially true for a streeter is that whilst running  at light loads the fuel is sitting in the rails heating up, with a full return system regardless of what demand is, the fuel is constantly circulating back to the tank keeping it cool.  That’s not so important for a race car, as at wot there is actually not a lot of fuel returning to the tank as its being used in the engine.

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

Dead head works fine otherwise just about every modern Commodore built in the last 20 years would be having issues, only place I can see much of a difference is if you run a boost referenced regulator there is a delay in the signal if you have the reg at the tank, only really noticeable if you’re logging the AFR during transitions.

Have ran it both ways and not seen a problem.

This is all dependant on a correctly functioning fuel system of course with clean filters and a pump capable of maintaining pressure/flow as required.

As for heating the fuel my old Supra ran a return system with a pair of 044 pumps after an hour of cruising it would heat the fuel tank to where it was uncomfortable to touch with a bare hand, this is why I ran fuel pump controllers to drop the pump speed for cruise and idle.

Hope this helps.

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

Dead head is harder on the pump because at idle there is almost no flow and then when you suddenly nail the throttle it has to get that whole column of fuel moving that is currently sitting still in the fuel line.  Probably not so bad on a road car but when you get into high HP drag cars that can pull substantial G loads when getting out of the hole can put even more strain on that poor old pump.

No doubt both system work but my preference is return style.

VRSenator065 knows all about knows all about vapour lock from boiling fuel

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Immortality wrote:

VRSenator065 knows all about knows all about vapour lock from boiling fuel

Sad but true.

Wouldn’t almost all race cars run full return?  But totally agree like most things any system designed right will work.

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Dead head has the regulator at the pump with a self bleed, so it’s not like it’s over loaded at low fuel demand scenarios.

It’s basically a return setup with the regulator at the tank.

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

Yep but it still has to get that column of fuel moving when the pressure drops at the engine and that creates a delay more so than having the regulator at the fuel rail.  I’m not saying it doesn’t work just that IMHO it’s not the best setup but certainly is cheaper for OEM with having to only run one one line up the length of the chassis.

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