Beta VX Fuel Pump

[RickyJ]

Hi Everyone

Does anyone know what the Pressure rating is on the standard VX Fuel Pump? My understanding is that it's the same pump as on the 2000ie model but all I can find for it is the Flow rate (130 Litres/hour) rather than the actual pressure.

I'm unsure whether I need to buy an uprated (probably FACET) pump as I put a DCNF on my car a little while ago. I'm told I should really upgrade the standard pump as it can't keep up with the fuel demands of the 40 DCNF. I think I can get away with a Silver Top FACET which is rated at 5-6 PSI. Has anyone else done this and should it fit in place of the standard pump (i.e. on top of the rear transverse chassis beam)

Thanks
Richard

[Will]

AFAIK all the Volumexes are carbed, so NO, it's a different pump than the ie.

The ie models use a Bosch rotary-vane pump that puts out about 45PSI- the carbs will want a smaller, low-pressure pump such as facet, etc.

[rossocorsa]

I have a feeling that they are actually the same but it has always baffled me a little if they are, there is a pressure regulator though. if I have time I'll dig out the fiche reader from under a pile of junk in the garage and check

[andybeta]

The VX fuel pump will be ok to supply your 40 DCNF. It is the same pump I think as the IE which was high output to supply the Bosch injection system. However you will need an adjustable fuel regulator such as a Filter King or a Sytec regulator plus a fuel pressure gauge so you can set the fuel pressure to about 3.5psi at idle. Most Weber side draught carbs run at about this pressure. The std Vx fuel regulator is set at about 6-7psi so will flood your carb if you use this. It is also handy to plumb in a tap to isolate the fuel line if you need to for what ever reason. Hope this helps.

Andybeta

[Hamish]

Betacar supply the i.e fuel pump as a replacement for the VX standard pump and it works fine with the standard pressure regulator fitted to the car.
However a better option would be to do as Andy suggests and ditch all of the standard "plumbing" and pump in favour of a facet and a pressure regulator (filter kings are ideal) as this is a much more reliable system :wink:
Worth changing all of the fuel lines whilst you're at it 8O

[RickyJ]

Thanks for the pointers Guys

Andy - I'm slightly confused about the pressure regulator.
The DCNF that is now on the car is a Downdraft unit and is fairly similar to the standard 36 DCA it replaced, It's just a bit bigger. What I don't understand is why I would reduce the pressure to 3.5 PSI when the original (smaller) carb was limited to 6-7 PSI - Surely if anything you want more or at least he same, rather than less fuel pressure to stop the carb running lean? The Carb is a 40DCNF rather than DCOE.

At the moment I'm driving the car and it's running OK - I've avoided really
"booting" it until I've got the fuel pump sorted. I'm a little concerned of what will happen if I floor it and the fuelling can't keep up with the requirement of the new Carb.

[Will]

Wait a miuite- am I reading this right?
Are you guys saying the Vx Betas use the BOSCH ROTARY-VANE FUEL INJECTION PUMP????
What the heck for???
It's a Weber in a suck-thru application, not a blow-thru, so there is no need for additional pressure, and the cheap electric pump like the Monte uses can feed plenty of volume- so why would they have wasted a very expensive, high pressure, high volume pump for the fuel delivery system in the vx?
I have observed FIAT doing some illogical things, but never using a part that was other than the cheapest or most marginal in the parts bin! (ha ha)
What, did they have some Bosch pumps "left over" from the ie's or something??

Ricky-
Pressure and flow are two different animals. The amount of pressure a given Weber will accept is determined by its seat design, too much pressure will squeeze fuel into the bowl when the valve is supposed to be closed. The FLOW is determined by how much fuel you are burning, causing the float to drop. You need a pump that can flow adequately (and it won't take much at all) to keep the bowl full, at a pressure that's within range of what the carb can handle. Equating presure with flow is a common error, just bear in mind the valve controls the flow into the carb, the pump or regulator controls the pressure.

[andybeta]

I woudn't bother with the facet first off, just continue using the std VX pump. it's a high output pump anway. I was looking for the VX supplement last night but couldn't find it. But I think it pumps more than enough. As to the factory setting of the std pressure regulator I think this is about 6-7psi. I have no data for this. however with a DCOE installation it would flood the carb as the DCOE typically operates at 3.5psi max at tick over. Any higher and the pressure will lift the valve off it's seat and cause the carb flood. I suggest an aftermarket fuel regulator as you can acurrately set the pressure in the fuel line into the carb to your desired setting. as for your DCNF I don't know what setting will work. You will just have to suck it and see. If you have an in line pressure gauge this shouldn't be too hard. It is certainly going to be around this level anyway. Trial and error. There are no hard and fast recipes to follow.

But I would recommend getting an aftermarket adjustable fuel regulator such as the makes I've already mentioned plus an inline gauge. Don't go for the all singing all dancing Filter King with filter and a fitting for a pressure gauge on the edge of the bowl as this poorly designed. I couldn't get it to seal so fuel was spilling out everywhere. So instead I went for a basic ajustable regulator with separate in line pressure guage so I could set the line pressure. I have my own in line filters anyway.

Will is right the conventional carb works by the engine effectively sucking fuel out of the carb so you need adequate supply and pressure but not too much so it floods at any point.

As regards the interchangeability of IE and VX pumps, they are both high output pumps whether they are the same I don't know. I seem to remember the VX pumps at 27l/minute or 27l/? but I don't know the unit of time as I can't find my VX supplement. This figure is actually more than the Facet Silver Top pump. Why pay more than you need to?

And as Hamish says it is certainly well worth renewing all the old fuel lines and clips, ditching all the old electrics as well.

It will look so much neater.

Good luck,

Andybeta

[andybeta]

VX fuel pump - Bosch electric fuel pump , up to 130 litres/hour (as on 2000 IE).

Facet Silver top road, up to 18 gallons/hour
Facet silver top competition up to 27 gallons/hour

andybeta

[Will]

I wonder if those pump ratings assume no pressure, or assume a static line pressure of say, 6PSI?


Is so, then even a Facet red, at 18g/hr is adequate to fuel a nearly 190HP engine at a volumexy .60BSFC, so I'm wondering if they used the bigger pump in an effort to allow a greater return and thus keep the fuel at the carb fitting at a lower temperature? Even though, the standard vx with the bumped-down pistons is hardly "pushing the envelope" as far as dynamic CR, there would be some advantages to keeping the fuel at tank temerature rather than underhood temp. Other than that, I'm still clueless as to an explanation why they would have used it? Can somebody make some logical conclusion here that I'm just not seeing?

[RickyJ]

OK so I think on the basis that the Car is running OK at the moment I think I'm going to go with Andy's suggestion about regulator/pressure gauge and leave the pump for the time being. If it ain't broke and all that..

Thanks for the tip-off about the filter king as that would have been my first choice - The Sytec regulator looks fairly cheap/sturdy so I'll go with that.

Will - Not knowing enough technically about it I don't know why they would have used the ie pump - The only thing I can think of is that at the time the VX was being made, they'd stopped churning out regular Carb Betas/Trevis and so it may have made sense to use the components they had - Same goes for the VX airbox, part of which is the same as on the injection models.

[andybeta]

See the photo I posted in the album.

I ended up with a basic Filter King regulator without a filter bowl and without a fitting for a gauge having tried the poorly designed all singing all dancing one. This has worked fine. Sytec do offer regulators but have no experience of them. There is a basic regulator that has an adjustable dial to alter pressure rather than the filter king which has a cap nut under which are the adjustment and lock nuts. I am sure Sytec would be up to the job and I probably would have bought one had I seen it before the Filter King regulator as it looks simpler.

Anybeta

[Pope1]

Sorry, late to the party guys as I've been off-line for a few days.

I have the standard VX pump together with an aftermarket regulator and a DCNF on my car. No problems at all with fuel starvation and I think the pressure is set to about 4 psi.