Twin 40s, What Fuel Pump Pressure?

[Rally Slag 0]

OK got a 1.4 8 valve ally engine, got big cam, big valves, uprated springs, ported and polished, the works, using twin 40s. Any ideas on what the fuel pressure should be, planning on running a facet pump in the boot, im pretty sure 7psi will be fine, but just wana check and see if anyone else is running something similer. Im not going to be running a regulater, theres no need when you can buy a pump to provide the correct pressure to start with, facet do quite a range or pumps with different opperating pressures.

 

Cheers guys

[burr_2000 1]

i have known people to use 2 regulators to get the pressure correct and constant. when i removed my mechanical pump and fitted facet plus a filter king regulator.

[Rally Slag 0]

yeah there is that route but i cant see the issue in running a pre set pump. Fuel pressue on a carb engine doesnt change, EFI is different, the pressure in the rail is constantly changing under driving conditions. So i cant see why i would need a regulator and stuff when all I need to do is buy the correct pump to start with, a few people have said 7psi will do, but there on about different engine. I will be removing the mechanical pump and fitting just 1 electric one, just need to know what pressure rating to go for.

[samc 1]

i used 1 malapassi regulator from the injection pump down to 3.5psi when i had my gti on 40s, so 3-4psi i say lol could go buy a fuel pump of a bike with carbs, got last 1 for a fiver and its preset at the right pressure

[Rally Slag 0]

See i was toying with the idea of running the standard injection pump and just fitting a regulator, this way no messing with fuel lines or wiring, just a small change the to fuel pipes under the bonnet. I cant remember what the standard single point injection pump puts out though, did have it written down somewhere but im forever loosing things. If it makes over 50psi though then this is far from ideal for my liking and id rather ditch that set up and try to run a carb pump at the correct pressure.

[Baz 421]

Nothing wrong with either way, my current carb equipped car runs an uprated (although as OE) fuel pump in the tank, and a single regulator to drop pressure to around 6-7psi iirc.

 

The one previously had the in tank pump removed and a facet lift pump, with a single regulator, and the one previous to that was as my current one above but with 2 regulators.

 

All work/ed well.

[MrG 3]

I run the std set up then onto a regulator which has been set to a constant 5psi, so far so good!

[205Rallee 59]

I run a 1.3 Rallye with what sounds a very similar spec to yours and I run the standard mechanical pump and it's still going strong at 203,000 kms and 17 years of sprints, hillclimbs, autosolos etc. No fuel pressure problems at all.

[Rally Slag 0]

hmmm i was told the mechanical pump wouldnt be able to cope with twin 40s and that it puts out roughly 4 psi. I duno what to do now lol

[205Rallee 59]

Try it with the standard pump and if it doesn't work change it for an electric one, you never know it might work and if it does it'll save you some cash to spend on something else!

[Rally Slag 0]

well the problem is the car is a 1.1 single point injection at the minute, i have this other engine to go in, just need to sort the fuel situation out

[Guest dean-191]

Best thing is to get the biggest facet carb pump in the boot as close to your tank as you can then a regulator set to 3-4psi as close to the carbs as you can. You really do need the regulator, you'd be lucky to get the exact pressure from just the exact pump. Also it'll probably flood through tight bends and under braking. Use 8mm hose as a bare minimum, 10mm is better. Fuel surge on my ax was the bain of my life for a while. I've heard of people regulating down the standard injection pump though but never done it so can't really speak for it.

[Rally Slag 0]

I allready get bad fuel surge with the standard engine and pump lol, the standard set up really cant keep up with my driving on uprated suspension and brakes.

 

OK well that sounds like the best option, will look into doing it that way then, thanks.

[drmo 5]

205 1.3 euro rallye (twin Weber DCOM 40's) also had a mechanical pump. It didn't have any fuel problems, not as standard, not modified. The AX sport engine was the same...

[205Rallee 59]

I run a 1.3 Rallye with what sounds a very similar spec to yours and I run the standard mechanical pump and it's still going strong at 203,000 kms and 17 years of sprints, hillclimbs, autosolos etc. No fuel pressure problems at all.

 

DRMO just as I said above!

[Rally Slag 0]

hmmmm ok then, guess i will just try and use the standard mech pump then.

 

What to do in terms of the fuel tank, obviously current unit is an injection tank, i'd prefer not to have to swap the tank for a carb model tank, i know its a straight swap but i have heard the MK1 tanks have a different gauge sender unit than the MK2, any ideas?