12 replies to this topic

[mini-mad-mark]

Hi All,

Just about ready to embark on the rebuild/improvement of the mini you can see next to my name.

 

Many of the projects I see have an electric fuel pump rather than mechanical (not sure why - is there a specific reason to go away from the mechanical pump?) but thinking I would do this as it seems to be an improvement that people add.

 

These are mostly aftermarket (Facet generally I've seen) and I'm not all that keen on the installations (generally in the boot) as they just look "added on" which of course they are, and I know some/most of these require a fuel pressure regulator.

 

Would it be possible to use an SPi or MPi tank/pump set up with a carb engine  (preferably without a return fuel line for ease although I suppose it's not the hardest thing to add.....)

 

I guess I would need to use a fuel pressure regulator under the bonnet? Or do the SPi/MPi pumps generate too much pressure? Or is there something I haven't understood about electric fuel pumps in general?

 

Thoughts?

 

Cheers, Mark

[nicklouse]

An injection pump produces way too much pressure. 
 

it’s not to do with electric or mechanical pumps it is using the right pump.

 

carbs need about 3-4psi while fuel injection run at 30-60psi (and higher). I don’t know the exact spi/mpi pressures.

[timmy850]

Perhaps you could get a low pressure pump that’s a direct replacement for the SPI pump? Another option is a regulator in the boot and return back to the tank

Random example, don’t know if it would fit:
https://www.demon-tw...el-pump-240854/

In terms of the factory carb electric vs mechanical pumps:
Mechanical is probably a simpler option
Mechanical pumps can leak fuel into the sump if the diaphragm splits
Electrical will prime easier
Electrical is easier to replace on most cars

[mini13]

you can use the turbo style fuel reg, after all, turbo's run fuel injection pumps, and carbs.

[MikeRotherham]

My carb 1994 mini was produced during the changeover to spi and I always believed that the fuel tank and fuel lines were the same as the spi without the return but with a mechanical pump.

 

Perhaps someone could confirm this?

 

If correct could that be a solution?

Edited by MikeRotherham, 11 August 2022 - 07:35 AM.

[mini-mad-mark]

Hmm - thanks all for the responses - food for thought. Guess I will look at the Facet pumps after all and just try to make the installation as neat as I can

 

Cheers

[timmy850]

Does the spi tank have an outlet on the bottom for a fuel line? If the only lines out are on the top, then an external pump may not cope with lifting the fuel up and out

[Ethel]

I hardly think it's worth the cost of a fuel tank. If you have a carb fuel tank fit an electric pump as low as possible. Possibly on the rear subframe. A Facet solid state pump is a good option for most applications. Be sure to get one that's SU compatible. Pumps for Webers etc run at a higher pressure & are likely what you get from a general tuning shop / Fleabay unless specifically stated.

 

Most Miniists end up with a leccy pump to avoid clearance problems with aftermarket exhaust manifolds, but they are a bit more sophisticated & less wasteful than manual pumps that are constantly going at engine speed regardless of the fuel requirements.

[nicklouse]

I hardly think it's worth the cost of a fuel tank. If you have a carb fuel tank fit an electric pump as low as possible. Possibly on the rear subframe. A Facet solid state pump is a good option for most applications. Be sure to get one that's SU compatible. Pumps for Webers etc run at a higher pressure & are likely what you get from a general tuning shop / Fleabay unless specifically stated.

 

Most Miniists end up with a leccy pump to avoid clearance problems with aftermarket exhaust manifolds, but they are a bit more sophisticated & less wasteful than manual pumps that are constantly going at engine speed regardless of the fuel requirements.

Just want to pull you up on the Weber comment. They don’t run at higher pressure than SUs. And the new float chamber needles for the SUs are meant to be good for up to 10 psi. But with any electric pump I would run a regulator and if a performance build I do like the filter king filter in the engine bay as it did smooth out fuel supply issues.

[mini-mad-mark]

Just to clarify I have a "carb" tank now, I was only asking if the SPi/MPi could work - who would change the tank to an SPi/MPi and then use an aftermarket pump ???

 

I guess I really wanted to know if an electric pump was a worthwhile change; as I mentioned many of the nicer project minis seem to have them so I thought there must be some merit to changing from mechanical.

 

I do plan to use a Filter King regulator under the bonnet to dial the fuel pressure to exactly what is needed (assuming I do "go electric" - fuel pump, not engine as a whole !!!)

 

I haven't finally decided what engine/carb I will have but it may be a Weber - I have only ever had SUs so no idea if they are a good thing to do - as far as I read they are most benefit at the top of the rev range where I am not likely to spend much time, but they do sound good........

[Lplus]

If you decide to go for an electric pump it might be worth putting an emergency cutout in the power supply line in case of accident/overturning etc.

[timmy850]

If you already have a carb tank, then just add an external fuel pump inside the rear subframe like the factory did on early minis.

Buy the right pump and you don’t need a regulator

There’s absolutely no reason to buy an Spi tank if you just want an electric pump

Hope that clears it up for you

I have used a Dellorto DHLA (very similar to a Weber DCOE) on a std 998 & modified 1100 and I really like it. The throttle response is much quicker, sounds better and easier to tune in my experience. Yes there are compromises like any carb, but I think it’s worth it

As for who would use an Spi tank and change the pump:
If you had an Spi mini and were going carb
If you were planning on using injection in the future and found a good tank you could use for later
You had a small early tank and found a really good larger Spi tank

Edited by timmy850, 12 August 2022 - 09:09 PM.

[PeterG]

When I converted my SPi to carb (HIF44) I continued to use the SPi tank and pump but added a bypass regulator to reduce the pressure to the carb. I had a restrictor in the return line from the regulator so the SPi pump was pushing a load similar to the original injector. I recently changed the tank to a carb version with an electric pump (Facet) and took off the regulator and the fuel return line. Both approaches worked fine.