27 replies to this topic

[RobinSherwood]

Hello,

 

I have a set of original twin tanks (and all the fittings) from an older project that is not worth continuing with.

 

How would I go about fitting the pair of 5.5 gallon tanks to a later 2000 MPi Mini Cooper?

 

Many thanks in advance for any help with this.

 

Kind regards,

 

Robin

[brivinci]

There will need to be a decent amount of fab work done to make these work. The injection cars use in-tank fuel pumps. Carb cars do not so plumbing was a LOT easier. You just had two fuel lines meet in a Y, before the pump and off you went (very basically). With FI cars, you need high pressure to feed the injectors. I'm sure this has been done but my guess would be that, at the very least you would need to modify the left tank to accept the in-tank pump, and then fab up a pipe that ran from low on right tank to low on left to transfer the fuel. I can think of a few issues already so interested in hearing anyones thoughts who have possible seen or done this.

 

[RobinSherwood]

There will need to be a decent amount of fab work done to make these work. The injection cars use in-tank fuel pumps. Carb cars do not so plumbing was a LOT easier. You just had two fuel lines meet in a Y, before the pump and off you went (very basically). With FI cars, you need high pressure to feed the injectors. I'm sure this has been done but my guess would be that, at the very least you would need to modify the left tank to accept the in-tank pump, and then fab up a pipe that ran from low on right tank to low on left to transfer the fuel. I can think of a few issues already so interested in hearing anyones thoughts who have possible seen or done this.

Thank you for taking the time to answer 

 

Robin

[Bobbins]

Why not retain the left hand 7.5 gallon tank and work with the existing pump setup? Would it then need anything more than top and bottom connecting pipes?

[Gaz66]

Put the 5.5s in with a T piece to a facet competition pump.

[brivinci]

If you did that you would have to put the pump outside of the tank? Also, what is the max PSI needed for these cars? Probably a good idea to add an external pressure regulator.

Edited by brivinci, 05 August 2022 - 09:32 PM.

[stoneface]

I'm running twin tanks to multi point injection, although not the standard MPI setup.

Tanks are connected with a link pipe at the bottom and a T piece in the middle going to an external pump and filter.

From memory the only mod to the tank was to add a fuel return pipe to the top of one.

If you search the site you will find this has been discussed a few times. Best search using Google.

[viz139]

I tried this on a turbo with external pump but the flow rates of the tanks didn't match and one tank would end up with all the fuel , I ended up fitting a single SPi tank. My twin tank Lotus has a 1" link pipe.

[coopertaz]

need to put both feed pipes to a y piece and use facet external pump, but as said origainal tank would be fuller due to return from pressure reg so would need a balance pipe from left to right at bottom of tanks to balance them. or just fit balance pipe and leave feed / return as is. either way you need to fabricate mpi tank at least

[brivinci]

I think I have asked this before but since we are talking tanks...I am in the US and the US/UK gallon is different. The Rover owners manual I have in from of me stats the injection cars have a 7 gallon tank? Is that UK or US? I assumed it was always UK, so for me, it would be an 8.4 US gallon tank. 

On the original twin tanks, were they stated in UK or US gallons? They were 5.5 gallons each, correct? So, you would be going from 7 UK gal to 11 UK gal, or 8.4 US gal to 13.2 US gal? 

Some mention fitting the RH 5.5 gal but retaining the standard injection tank. That would certainly give you more capacity (but only an added gallon), have less fab work (welding in balance pipes between them still) BUT would take up the most boot space. 

[bluedragon]

Any official Rover documentation is going to cite Imperial gallons instead of the smaller US gallon since Rover Minis were never sold in the USA. The 5.5 gal figure is Imperial as well.

 

Interesting that it says 7 gallons - I've always read 7.5, and in fact was able to squeeze over 9 US gallons into my MPI tank (early in my ownership when, unused to the non-linear fuel gage, I ran it dry.)    Maybe the .5 gallon difference represents the reserve.

 

Dave

Edited by bluedragon, 09 August 2022 - 11:53 PM.

[brivinci]

In my glovebox manual from 94, it states that the carb models have a 7.5gal tank and the Injection have a 7gal. My only guess was that was down to the injection cars having in-tank pump and all that. Half a gallon worth? Not too sure.

[Bobbins]

So if the LH injection tank is retained complete with internal pump, and a RH tank is added with an injection filler cap, the system would function fine as long as the breather from the RH tank is connected to the top of the LH tank (keeping the system sealed) and a suitable size fuel transfer pipe was connected across the bottom, ideally being as big as 1"?

I've read of various issues where the RH tank becomes pressurised and full of fuel as the LH tank empties, is the solution just to have a much bigger fuel transfer pipe?

[Steve220]

MPi tank is 7.5 Gallon. No idea where people are getting 7 from..

[bluedragon]

1" pipe! The water supply for my entire house is supplied by a 1" line! 

 

I have no experience with twin MPi tanks but I have thought about doing it - I even have a couple 5.5 gal tanks stored away. (one was a neat plastic tank I got from a seller from either New Zealand or Australia, the other a regular steel tank.)

 

The idea of a pressurized RH tank being a flow problem I don't understand. I would think that a pressurized RH tank would actually help force fuel into the LH tank. And even any or both tanks were pressurized, I'm not sure how it could block fuel flow, since the fuel pickup is immersed. It's unclear to me how air pressure in the tank could prevent fuel from flowing.

 

Personally, when I thought about doing this, I had wished to put an electrically controlled fuel valve between the tanks so I could start the flow at my discretion (when the LH tank starts reading low.) I probably would be OK with an unvented cap for the RH tank since the sealed cap is for the emissions vapor control system. The ecologically minded would want to connect a RH vent to the LH tank and use a sealed cap to keep things clean.

 

 

Dave