Fuel pump.flow pressure

General Chat About Exhaust, Cylinder Heads, Fuel Systems And Intake

Moderator: phpBB2 - Administrators

Post Reply
Lmy78kstag
Newbie
Newbie
Posts: 4
Joined: Tue Jul 16, 2019 12:26 pm

Fuel pump.flow pressure

Post by Lmy78kstag »

Hi
Need help I am running a 3.9'efi disco engine in my stag
Running a bosch 070 external fuel pump an rpi boost fpr
And have got a fuel pressure gauge set the fuel pressure at 2.0 bar which rises to 2.5 bar when I accelerate
Have I got the right set up ie fuel pump set pressure or is there not enough flow the engine misfire,s under load
Thx



DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Re: Fuel pump.flow pressure

Post by DaveEFI »

The nominal pressure on a flapper is 36psi which is 2.5 bar - checked vacuum disconnected, so the maximum. But when I had an FSE rising rate, it didn't seem to be right, so raised it to 38 psi. Not sure if the hotwire is the same. But if the EFI mapping is correct there shouldn't be a need to use such a crude way to increase the fuelling.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

User avatar
Eliot
Top Dog
Top Dog
Posts: 1765
Joined: Sat Nov 18, 2006 9:46 am
Location: Milton Keynes
Contact:

Re: Fuel pump.flow pressure

Post by Eliot »

hotwire is 3 bar iirc (tested with engine off and fuel pump running)


actually its 2.5 bar:
http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

but you set the pressure with engine off (atmospheric pressure) and force the pump on (bypass the relay)
Eliot Mansfield
5.7 Dakar 4x4, 4.6 P38 & L322 TDV8
www.mez.co.uk / www.efilive.co.uk

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Re: Fuel pump.flow pressure

Post by DaveEFI »

Just a comment :D Setting the pressure with the engine stopped may be fine on a brand new vehicle. But with an older one, where there will likely be more voltage drop - and possibly a tired pump - I'd have thought engine running with the voltage that gives a better way?
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

User avatar
Eliot
Top Dog
Top Dog
Posts: 1765
Joined: Sat Nov 18, 2006 9:46 am
Location: Milton Keynes
Contact:

Re: Fuel pump.flow pressure

Post by Eliot »

DaveEFI wrote:
Wed Jul 17, 2019 12:04 pm
Just a comment :D Setting the pressure with the engine stopped may be fine on a brand new vehicle. But with an older one, where there will likely be more voltage drop - and possibly a tired pump - I'd have thought engine running with the voltage that gives a better way?
With the engine off, you will be setting the pressure as a worse case scenario (lowest voltage) - with the engine running and hence higher voltage, the regulator will do it's job and regulate it to 2.5 bar - no?
Also my understanding is that it's a static pressure - with no flow across through injectors.
Eliot Mansfield
5.7 Dakar 4x4, 4.6 P38 & L322 TDV8
www.mez.co.uk / www.efilive.co.uk

stevieturbo
Forum Contributor
Forum Contributor
Posts: 3979
Joined: Sat Nov 18, 2006 6:22 pm
Location: Northern Ireland

Re: Fuel pump.flow pressure

Post by stevieturbo »

IMO set base pressure ( if adjustable of course ) to desired pressure, vac disconnected and engine running.
9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

User avatar
SimpleSimon
Knows His Stuff
Knows His Stuff
Posts: 620
Joined: Mon Apr 25, 2011 10:36 pm
Location: East Sussex

Re: Fuel pump.flow pressure

Post by SimpleSimon »

Lucas Hotwire stock pressure is 2.5 BAR if your using just 2 BAR that may well be your misfire from an over lean AFR (dangerous for the motor) :(
TVR Chimaera RV8 Mods & Megasquirt

Post Reply

Return to “Exhaust, Cylinder Heads, Fuel And Intake Area”