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intelligent fuel pump?

02GF74 - 7/4/06 at 11:55 AM

In the land rover I have a facet fuel pump that is powered all the time when the igntion is on.

Iam wondering whether an electrical pump exists that pumps petrol according to the demand of the engine?

A simple circuit driven off the igntion coil so the pump pumps more at higher rpm would be easy to tonk up; a more sophisticated version would use throttle position to increase the pumping according to engine loading.

the advantages are quieter operation, longevity and less power drawn (ok, the last one is miniaml but it all counts!)

muzchap - 7/4/06 at 12:03 PM

but if it goes wrong... then it's a dead pump!

Quiter operation - if ya can hear the fuel pump over the zorst - fair play

Your pump - give it a go ;-)

and more importantly

GOOD LUCK (if it works - I'll have one )

greggors84 - 7/4/06 at 12:24 PM

You would have to make it so it pumped more or less depending on engine speed/throttle position instead of just coming on or off.

Not sure if you can get a variable pump. If you can then im a system has been designed as otherwise variable pumps would exist (if they do!)

oliwb - 7/4/06 at 01:41 PM

What about a motorbike fuel pump such as one from a goldwing?? They pump to a specific pressure and then cut out like an SU pump....obviously the less the engine is revving the less demand for fuel so the pump reaches its threshold pressure sooner and cuts out, then when your ragging it its on all the time....also removes the need for a regulator and prevents overfilling of the fuel bowl and subsequent flooding.....Clever stuff! Oli.

procomp - 7/4/06 at 02:02 PM

Hi they do. Facet interupter type one.

cheers matt

JAG - 7/4/06 at 02:07 PM

Isn't this what more recent fuel injected petrol engines do - that's why they don't have a fuel pressure regulator or fuel return line to the fuel tank.

The pump supplies just enough fuel at just the right pressure hence all fuel delivered to the engine is consumed whilst keeping the pressure with certain tolerances.

Peteff - 7/4/06 at 02:22 PM

Old SU pumps worked on demand. when there's no pressure they pump, then they cut out till it drops again, nothing complicated though just pressure activated.

02GF74 - 7/4/06 at 03:06 PM

quote:
Originally posted by procomp
Hi they do. Facet interupter type one.

cheers matt

ah, I forgot one important bit of info., it is an open system so fuel is continuously pumped back from the carbs into the tank (stops air locks apparently) hence this would not work for me.

MikeRJ - 7/4/06 at 03:25 PM

The fuel pump in my MR2 turbo switches tro a low power mode at idle, though this is controlled by the ECU. It just switches a relay which puts a big power resistor in series with the pump. Locost method would be a microswitch on the throttle pedal I guess...

silex - 7/4/06 at 04:57 PM

One of the electronics wizzez on the site might know better, but using a potentiometer on the throttle pedal into a 555 timer or similar you should be able to create a PWM (Pulse Width Modulated) signal to the pump. This would act like a variable speed controller to the electric pump (I think).

You would need to put in a high power transistor or FET in the circuit to handle the current of the pump but I think it would work.

Johnmor - 7/4/06 at 04:59 PM

Alfa engine ECU,s only switch power to the pump when the engine is turning, and will not supplly power only if the ignition is on, prevents pump wear and means that if you have a accident the pump is switched of if the engine stops.
Means you dont need an impact cut off switch.
Detection is from the ignition timing pickup and switched through a relay.

Dont know if this is much help.

RazMan - 7/4/06 at 05:21 PM

quote:
Originally posted by Johnmor
Alfa engine ECU,s only switch power to the pump when the engine is turning, and will not supplly power only if the ignition is on,

That is how my MBE ecu trigger my Landy fuel pump - Ignition on (give a 2 second prime) Engine start (starts pump) Engine stall (stops pump)

the_fbi - 7/4/06 at 05:52 PM

quote:
Originally posted by RazMan

quote:
Originally posted by Johnmor
Alfa engine ECU,s only switch power to the pump when the engine is turning, and will not supplly power only if the ignition is on,

That is how my MBE ecu trigger my Landy fuel pump - Ignition on (give a 2 second prime) Engine start (starts pump) Engine stall (stops pump)

I believe thats the same for XE's too, unless there is a crank signal the pump doesn't operate.

MikeRJ - 7/4/06 at 05:53 PM

quote:
Originally posted by Johnmor
Alfa engine ECU,s only switch power to the pump when the engine is turning, and will not supplly power only if the ignition is on, prevents pump wear and means that if you have a accident the pump is switched of if the engine stops.

Most fuel injected cars do this. They often allow the pump to run for a second or two when you switch the igntion on to build up pressure in the fuel rail ready to start the engine.

Silex, you could do that but I'm not convinced the extra complexity is worth it on a 7. If the fuel pump is particularly noisy then it might be worth slowing it down at idle, but unless you have a particulary quiet 7 when as soon as you start driving the engine and wind noise will drown out most things.

By the way, I suspect the only fuel pumps that can be successfully slowed down this way are rotary based ones that take a continuous current ( i.e. with a motor) rather than the oscillating plunger type that takes current in short pulses.

Syd Bridge - 7/4/06 at 06:16 PM

I would think that you are correct Mike, regarding the rotary vs pulsed.

Although this discussion is somewhat academic, a pulsed pump could be controlled with a 555 firing a transistor in the pump feed. If you put a variable resistor in the timing side of the 555, the pulse frequency could be varied, ie slow to fast. A pot on the throttle, as in an efi setup may be able to do it.

Cheers,
Syd.