17 replies to this topic

[IronmanG]

I am fortunate to have come across a brand new hif44 at not brand new prices which I am very happy about. It will be going on my 1310.
I love reading about other options and I recently read up on aftermarket efi. After researching it a bit more I cam across a post on the turbo mini forum about efi.

https://www.turbomin...p=vt&tid=395643

It's 4 pages but it's interesting reading about how aftermarket efi doesn't really do as much as it promises. Was the MPI really good? Despite 30 years of advances in tech is the MPI still as good as it can get for the 5 port.
I've only driven 1 MPI briefly and it was unbelievably smooth

[Ethel]

I think we'd be fooling ourselves if we thought we could make much in the way of improvements over what BMW could achieve with their experience & budget. Even so, if we wanted something a bit different to what they offered with the MPI we might find a different engine management system can do a better job of that.

 

It's valid to think of the ol' A series as a 2 cylinder engine wrapped round a different 2 cylinder engine because of its siamese inlet ports in particular.  A cam sensor, like the MPI has, is essential if you want to cater for the specific needs of each of those 2 cylinders. Any aftermarket system that doesn't have a cam sensor input is at an innate disadvantage. Notable that a lot over on TurboMins also went to 7 port heads when they started moving over to fuel injection.

[mab01uk]

Also interesting to read Mike Theaker's (BMW/Rover Engine Development Engineer) account of the Mini MPI development story and how it was BMW's will and John Cooper's insistence that finally got the MPI into production in 1996, extending the Mini's life by 4 more years. Mike Theaker also later worked on powertrain development for the New MINI (R50).

Mike Theaker on the Development of the Twin Point Injection system for the Mini.
Link to PDF below:-
https://www.turbomin...ts/493117-1.pdf

 

(Article in the link above is from the September 2000 issue of Miniworld magazine)

 

MPi Mini Development Story:-

https://www.theminif...elopment-story/

Edited by mab01uk, 11 July 2026 - 01:03 PM.

[sonscar]

The MPI system is very good because it is fully sequential,something that aftermarket was slow,or never,adopted.the drawback is you need to control large injectors to be able to fully inject the charge into the proper cylinder.this may limit fuelling.Steve..

[IronmanG]

The MPI system is very good because it is fully sequential,something that aftermarket was slow,or never,adopted.the drawback is you need to control large injectors to be able to fully inject the charge into the proper cylinder.this may limit fuelling.Steve..

Can you explain sequential as opposed to.....
Do you mean large cc injectors? I thought that was a problem as then the control at low load or low rpm was difficult?

[IronmanG]

I think we'd be fooling ourselves if we thought we could make much in the way of improvements over what BMW could achieve with their experience & budget. Even so, if we wanted something a bit different to what they offered with the MPI we might find a different engine management system can do a better job of that.

It's valid to think of the ol' A series as a 2 cylinder engine wrapped round a different 2 cylinder engine because of its siamese inlet ports in particular. A cam sensor, like the MPI has, is essential if you want to cater for the specific needs of each of those 2 cylinders. Any aftermarket system that doesn't have a cam sensor input is at an innate disadvantage. Notable that a lot over on TurboMins also went to 7 port heads when they started moving over to fuel injection.

So the cam sensor is a big advantage over a crank sensor?

[Ethel]

The crank sensor will always do the timing of the injection & sparks. The cam sensor is needed to know which cylinder to inject for because (on a 4 cylinder engine) there'll be two cylinders moving together. One pushing the piston down the bore after firing, the other drawing in the next charge through the inlet valve. You can only inject fuel in to the second one, but if you fired its spark plug along with the cylinder about to start its power stroke it wouldn't matter: as there'd only be exhaust gasses in it. That's what's called wasted spark ignition and it doesn't need a cam sensor.

[sonscar]

The MPI injects into each cylinder with the right fuel at the right time.the cam sensor is to tell it when the inlet is opening so it can fire.the injectors are large as the opening gets smaller with rpm so it can get the fuel in in a shortening time.the MPI uses two injectors to do the same job as four would normally do.when introduced it was very advanced and is still the Siamese port gold standard in my view.Steve..

[Midas Mk1]

The MPi setup is a good 26 years old at least, I got fed up of the constant failures with it and went for the sc setup. Final straw was on a third date with the iacv holding the idle at 4k with a single box exhaust, didn’t get a 4th date 😂

[Cooperman]

The MPi setup is a good 26 years old at least, I got fed up of the constant failures with it and went for the sc setup. Final straw was on a third date with the iacv holding the idle at 4k with a single box exhaust, didn’t get a 4th date 😂

😀😀😀😀

[IronmanG]

The MPi setup is a good 26 years old at least, I got fed up of the constant failures with it and went for the sc setup. Final straw was on a third date with the iacv holding the idle at 4k with a single box exhaust, didn’t get a 4th date 😂

Is that the SC hardware that's the problem or the delta 400 that made it harder to sort out

[68+86auto]

Factory control systems had lots of money spent on the design and tuning. Aftermarket solutions may not have that, at least in the tuning area. The average person isn't going to replicate the amount of effort the factory spent.

Edited by 68+86auto, 12 July 2026 - 12:18 PM.

[timmy850]

There was some interesting information in this video (skip forward to 8:30 if you don’t want to see an 8 port mini) where he’s working on a 5 port fuel injected mini on the engine dyno.

He shows one of the issues with fuel injection on a 5 port head:
The firing order is 1342, or 3421. This means that cylinder 3 fill be filling with air and fuel just prior to cylinder 4 (and 2 just before 1).
Due to the cam timing this means that the inlet valve for cylinder 3 is still open when cylinder 4 starts to open, which adds to the charge robbing between each pair of cylinders sharing an inlet port

With a multi point injection system with one injector in each runner you need very well timed injection pulses to get fuel into each cylinder at the right time. Having a cam sensor is essential for multipoint injection

Most aftermarket injection systems use a single throttle body unit (but may have 2 injectors) as this does make it slightly easier to get the injection timing right

https://youtu.be/FKW...Qjh1s5j-CphwoH7

[Ethel]

Even without charge robbing the inlets of outer cylinders have a whole extra engine revolution. That could be an advantage or disadvantage depending on rpm, charge inertia.....

 

The A Series is a masterpiece of minimalist engineering, somehow giving maximal complexity of function.

[Authi]

https://www.km77.com...-con-inyeccion/

I built this mini quite a few years ago and it was tested by a famous Spanish motor journalist who wrote on paper many years and already later on the net.
It is a 998 with .040 pistons, The intake hardware is MPI, head 12G295, (10.5 CR) SW5 camshaft, ECU Canems and rolling road in ATSPEED. https://www.atspeedracing.co.uk/
The car has done many kilometers and goes very well, but out of curiosity (I thought many times that maybe it was excessive intake diameter) I put it a HIF 38 with a much better intake manifold.
I was surprised by the result, it has lost a bit of the initial instant push, but above 4,800, 5,000 rpm goes noticeably better. The only explanation I find is the design (and size ?) of the MPi collector and better final flow with the 38
Not Rolling road yet, They are not popular in Spain.
But i have done kilometers with gas analyser and find a very good needle.

Edited by Authi, Yesterday, 12:38 PM.