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Fuel Injection Line - stub or flow through?
Nevtiger - 14/1/21 at 01:47 PM

Afternoon.

I am just about to fit a set of Heritage Throttle Bodies rather then my original modified 40DCOE's (modified to throttle bodies that is). Going from 40 to 45's.

On my original set up i used the standard set up of a fuel rail fed one end and returning the other end.

On my new set up and as the inlet is now the opposite side of the car (the cylinder head is now a cross flow configuration) than it was it will be more beneficial in packaging to run the fuel rail as a 'stub' from the pressure line at the regulator.

I have thoroughly convinced my self that this will be of no consequence - after all OEM do it like on the AJ30. However, any one have any reasons that it is not such a good solution?

Cheers

Nev

peter030371 - 14/1/21 at 02:01 PM

Run a dead end system on my Duratec with zero problems. The regulator is as close to the fuel rail as I could get it then a dead end coming from there to all 4 injectors. Maybe if you are pushing power high it could be a problem but for 95% of us I suspect it would be fine

Nevtiger - 14/1/21 at 02:07 PM

Excellent - thank you.

Power will be high for me but not in the overall scheme of things!

coyoteboy - 14/1/21 at 04:30 PM

I should be flow through to be correct, apart from anything it helps bleed the fuel rail and reduces fuel heating at low speed/power.

peter030371 - 14/1/21 at 09:15 PM

Just to be clear this is how I run mine (not my picture but it's exactly what I have)
https://forum.wscc.co.uk/forum/uploads/monthly_2017_03/58bf241ef3d9a_fuelinjectiondeadheadsetup.png.83ff2872e82ca13acde88f1ccc1d026f.png

No problems on the rolling road whilst having the nuts thrashed out of it being tuned, road or track. No air locks and no hot fuel. In fact some tuners claim this way the fuel is cooler as its not all passing a hot engine before going back to the tank

kingster996 - 14/1/21 at 10:40 PM

quote:
Originally posted by peter030371
Just to be clear this is how I run mine (not my picture but it's exactly what I have)
https://forum.wscc.co.uk/forum/uploads/monthly_2017_03/58bf241ef3d9a_fuelinjectiondeadheadsetup.png.83ff2872e82ca13acde88f1ccc1d026f.png

No problems on the rolling road whilst having the nuts thrashed out of it being tuned, road or track. No air locks and no hot fuel. In fact some tuners claim this way the fuel is cooler as its not all passing a hot engine before going back to the tank


Yes me too - it’s my drawing of my setup

Edit: but now have a swirl pot too - can post a pic of that setup if anyone wants it.

[Edited on 14/1/21 by kingster996]

ianhurley20 - 15/1/21 at 09:55 AM

That is the system we used on a Ford ST170 engine running throttle bodies with 225bhp on the rolling road, no issues with fuel. Hearing was probably damaged at 7400rpm and full throttle though!

40inches - 15/1/21 at 10:43 AM

quote:
Originally posted by kingster996
quote:
Originally posted by peter030371
Just to be clear this is how I run mine (not my picture but it's exactly what I have)
https://forum.wscc.co.uk/forum/uploads/monthly_2017_03/58bf241ef3d9a_fuelinjectiondeadheadsetup.png.83ff2872e82ca13acde88f1ccc1d026f.png

No problems on the rolling road whilst having the nuts thrashed out of it being tuned, road or track. No air locks and no hot fuel. In fact some tuners claim this way the fuel is cooler as its not all passing a hot engine before going back to the tank


Yes me too - it’s my drawing of my setup

Edit: but now have a swirl pot too - can post a pic of that setup if anyone wants it.

[Edited on 14/1/21 by kingster996]


Same as mine. I think all/most modern engines use the dead end system, I know that Jaguar engines do

MikeR - 15/1/21 at 10:45 AM

So how long can the line be between the circular flow and the injectors? I'm just wondering about could you run a single pipe the length of the car and have all the regulator gubbins and return line in the boot?

(perhaps idle curiosity, as i'm expecting bleeding the air out of a high pressure fuel line the first time you fire up would be 'interesting' on a run that length)

40inches - 15/1/21 at 11:37 AM

quote:
Originally posted by MikeR
So how long can the line be between the circular flow and the injectors? I'm just wondering about could you run a single pipe the length of the car and have all the regulator gubbins and return line in the boot?

(perhaps idle curiosity, as i'm expecting bleeding the air out of a high pressure fuel line the first time you fire up would be 'interesting' on a run that length)

Jaguars fuel pressure is controlled at the tank with a single line to the fuel rail, that's a long run with no problems.
There is a schrader valve on the rail for checking fuel pressure/purging and I think the fuel line is purged for a few seconds after
the ignition key is turned, Megasquirt does this.
You can see the single fuel line and schrader valve in this photo.
Description
Description

[Edited on 15-1-21 by 40inches]

coyoteboy - 15/1/21 at 01:02 PM

quote:
Originally posted by peter030371 In fact some tuners claim this way the fuel is cooler as its not all passing a hot engine before going back to the tank


That's not a logical argument though, if there's not enough heat to heat up the stationary fuel in a stub end, there's not enough to heat a larger volume that also gets cooled by a massive pipework network the length of the car is there

There's a bunch of reasons that most OEMs do it as a loop. MS, as I remember it, has it as a purge pulse to purge the injectors prior to start, not as a fuel line purge.

Check out the installation instructions for decent aftermarket fuel pressure regs - they're designed as bypass fuel regs, to go after the rail, to maintain full fuel flow capability to all injectors all the time. The far end of the stub will see a drop in pressure otherwise at full chat, which may lean out your distant cyls enough to cause issues. If your rail is centre-fed between injectors, the effect may be minimal. And if you have an over-sized rail you may get away with it too. I'm not saying it doesn't work, just that it's not right and may cause issues.

[Edited on 15/1/21 by coyoteboy]

kingster996 - 16/1/21 at 08:17 AM

My current set up with swirl pot. Works perfectly.


40inches - 16/1/21 at 10:16 AM

quote:
Originally posted by kingster996
My current set up with swirl pot. Works perfectly.




Exactly the same as mine

kingster996 - 16/1/21 at 07:24 PM

quote:
Originally posted by 40inches
Exactly the same as mine


Shhh - don’t let everyone know about the bright green petrol!