Injection fuel connections
Turbo Mini Forums

Evening all.

Considering my options for when I come to plumb in my MPi manifold for fuel. Currently, I'm thinking of sawing off the the MPi push fit headers revealing the rubber flexi hose, putting some olive sleeves on the end of the supply and return copper lines and then just securing them with fuel hose clips.

My other idea is to machine two new flanges to fit on the ends of the fuel rail which would use screw barbs. This then enables me to use screw-on connection hoses and fittings between the copper fuel lines and the fuel rail, making it more secure.

Now, obviously, I would like to use the first option as it's easy, cheap and simple, but is it safe and secure enough to cope with 3 bar of pressure? Does anyone else run an MPi manifold without the standard MPi fuel lines (GrahamT comes to mind)?

Any help or suggestions are much appreciated.

Cheers, Carl.

Do you mean to do this ?
http://pagesperso-orange.fr/apavlov/mini/m...nt/dscf2623.jpg

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I run all home made stuff (well, it's run for a few hours anyway...) but re. the safety issue every location where a rubber hose connects to a rigid section I also created a raised part to the rigid tube so the fuel hose clip clamps behind it so can't slide over.

On the aluminium sections which are thick wall I machined a shallow wide groove in where the hose clip would be over but on all the copper piping, rather than olives, I used "end feed" solder fittings, straight joins, just soldered to the end of the pipe (not joining it to another) then cut in half with a standard tube cutter.

Just about visible in this photo


I didn't use olives because it would have meant cutting the sleeve nut off afterwards.

Schrödinger's cat - so which one am I ???

As long as you don't rely on a hose clip with a straight pipe, you should be OK.

3 bar is about 3 kg/cm2. 8mm pipe bore is about 0.5 cm2s, so the force pushing the pipe apart is only 1.5kg.

I use the basic principle that if I can't pull it off, it wont get pushed off by the fuel pressure.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I worked to that theory on the van Paul, nice to know I wasn't too far of the mark.

Yes alpa, that's what I meant.

Rod, that's essentialy what I meant when i said i would be putting olives on the solid fuel line, I think meant to say barbs insteaad of olives (raised collars on the copper pipe), and I think this would achieve the same effect as what you have done with soldering on new, slightly wider ends to the fuel lines.

Thanks Paul, i'll bare that in mind. I assume you mean straight pipe as in no raised edges or barbs preventing the flexible hose from just sliding off?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The only thing I would add to Paul's maths is that the roller vane pumps are capable of about 8-10 bar before the motor stalls.

So in the (very unlikely) event of a FPR failing shut or a pipe getting kinked by an overheight speed bump or in an accident, the loading on the clips could be three times Paul's figure.

OK, highly unlikely but I spent most of my working life in nuclear power generation where you have to consider everything.......

Schrödinger's cat - so which one am I ???

I think the only case there of any danger would be if the FPR was to fail Rod.

If the pipe kinked, the supply would be severely reduced or even stopped, causing the engine to cut out, in turn telling MS to shut off the fuel pump relay as the RPM is below cranking speed.

Well hopefully it would cut out! I suppose there is a chance that there could be enough fuel still flowing to create combustion, but it would be extremely lean so maybe you could use a bin to cut fuel and spark on MS if the AFRs were over a certain ceiling.

I know what you mean though, I like to think of every eventuality as well.

Edited by Carl S on 2nd Apr, 2010.

For the latter two of my scenarios, just make sure you add an inertia switch wired directly into the fuel pump +ve feed.

No relays, no relying on MS or anything else, just a straight inertia switch.

Re. the rest I'm sure just raised bits (soldered, compressed olives or whatever) are more than adequate to hold the flexible hoses on if proper fuel clips are used and fitted behind the raised bits.

Schrödinger's cat - so which one am I ???

Carl,
This setup made 10000km and I'd never had any leak. I use an external fuel pump from Alfa 33 16v (120hp I believe), it's probably a 120L/min pump, which means more than 200hp. Petrol smells a lot and any tiny leakage is easy to detect from the "vented" Mini.
Both hoses cover 2-3cm of the pipe.

Edited by alpa on 2nd Apr, 2010.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

That's excellent news about the distance you have covered with your setup with no leaks alpa, it puts my mind at ease substantially.

I picked up an external bosch pump fitted originally to a BMW 325i Touring, so it should flow enough to cope with a 998's fuel demands :)

Edited by Carl S on 2nd Apr, 2010.

2.5 has probably the same kind of 120L/min pump.
The only detail I'm still not sure of is the minimal pipe diameter I need for this pump. I used the original 6mm carb feed pipe for the return and added a larger 8mm pipe for the pump->engine flow.

Edited by alpa on 2nd Apr, 2010.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I'm torn as to whether i should use the standard carb supply line as a return, or take it off completely and put in two 8mm OD lines for supply and return.

The main reason I would use two 8mm lines is because the supply and return flexi hoses on the fuel rail are both 8mm ID.

Well my stuff worked during more than 1 year. Still I'd like to know. It also certainly depends on the pump flow capacity. I was not able to find any info about how estimate max flow in pipes, you can calculate the loss of pressure per linear meter (which in some way is an answer), but no general rules about usual numbers.
A return 6mm pipe just means more speed and loss. They seem to assume laminar flow.

Edited by alpa on 2nd Apr, 2010.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm