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Tuning The Mpi Engine


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#1 DoubleHB176

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Posted 17 October 2012 - 09:54 PM

Hi all,

I am currently restoring a late Cooper Sport, and would like to uprate the engine. I am proposing a specification along the lines of 1380cc, ported, polished and machined cylinder head, uprated camshaft, throttle body etc.

What is the best way to tune the electrical side of things ? Can the ecu be mapped ?If not, can a mappable system be obtained ? Failing all that, what sort of power figure can I expect with the standard ecu ?

Cheers guys,

Alex

#2 DoubleHB176

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Posted 17 October 2012 - 09:59 PM

Hi again,

Founda similar thread recommending 'Calver ST' ecu's, anybody recommend anything different or have any experience with these ?

Cheers,

Alex

#3 jimmyH

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Posted 17 October 2012 - 10:02 PM

Im sure someone will come and either correct me or give you alot more info than i can, but for now all i can tell you is:

I dont think the MPI unit can be re mapped due to its constantly changing and adapting status. It learns... for want of a better word.
As a result the best that you can get out of the standard unit is around 90bhp, which can be obtained "fairly" easily, pending money of course.

And then there are the emission woes which are apparently very hard to meet with even a lightly modified mpi.

That has to be the MPI's biggest downfall in my opinion, being so much more complicated to tune, modify.

Edited by jimmyH, 17 October 2012 - 10:02 PM.


#4 WillRunci

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Posted 17 October 2012 - 10:39 PM

Yep emissions are the problem with tuning i have an 1275 mpi with a weber and programable ECU. both cause problems

#5 toplessmini

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Posted 18 October 2012 - 08:13 AM

Yep emissions are the problem with tuning i have an 1275 mpi with a weber and programable ECU. both cause problems


Can you program the ECU when going to the MOT so the emissions are low? I realise it may not run as good.

#6 cian

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Posted 18 October 2012 - 06:11 PM

Imo if you are going to that spec of engine you need to throw away the standard ecu and gor for a mappable ecu, the standard one cant be mapped and cant cope with the mods, my mpi had a stage 3 set up with cam etc and it ran badly with the standard ecu then bought the sc 5 port management system and it transformed it

#7 DoubleHB176

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Posted 18 October 2012 - 08:45 PM

Thanks very much all, much appreciated.

Is there a website where I can read up on the management system you mention ? Where would it be available from ?

Given all these complications, would I be better to go down the more usual carburetor route (with a different engine) ? I have one available to me.

Best regards,

Alex

#8 bluedragon

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Posted 18 October 2012 - 10:21 PM

I don't think the Calver stuff will be any good for an MPI - I don't think he even offers anything. Calver himself has stated he's tried to mod the MPI computer and it's too tough a nut to crack. Not only is the ECU hard to program, but you also have to decode the very unique injection algorithm Rover (Mike Theaker) created to do true port injection on a head with only two intake ports. It's not just a matter of cranking in higher injector numbers, to say the least.

The MPI unit should be good for a true 80, perhaps 85 hp if you are fortunate. But, what is the intended purpose of the car? If one's driving style is to flog the motor to 5000+rpm to get into the powerband, then a carb'ed engine will have much more peak power potential. But it will hard for it to be as tractable, flexible, and economical at part-throttle.

If you're going to the drag strip, carburetors all the way.

If you're daily driving it, commuting, yet want a livelier motor, then I'd stick with the MPI. Get all 80 hp you can, and if that's not enough, then switch the final drive gearing from the super-tall 2.76:1 ratio to 3.1:1 or 3.4:1. Give that MPI motor the same final drive ratio as a carb'ed Mini, and you may be very surprised how well it goes - possibly much better on real roads than many built-up carb'ed motors.

The MPI's have a very broad powerband, developing good part at the low and mid speed ranges. This broad powerband is what helped Rover to get away with the super-tall 2:76:1 ratio to beat the sound output regulations then.

#9 cian

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Posted 19 October 2012 - 06:31 AM

Yes as blue dragon says change the fd ratio i went with a 3.4 and its really livley on the street, the ecu company are called specialist componants cant remember the site name but google it and they are at the top i believe, ps wouldnt go to a carb set up as its a defficult conversion on the mpi i believe

#10 jamesmpi

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Posted 19 October 2012 - 02:37 PM

As above but I would also recommend a swiftune SW5 CAM.

Also if you'really want big power then you will need to uprate your gearbox. Mpi boxes are known to be fragile. Up to 80 or 90 horses you should be ok (unless its done a lot of miles) but pushing higher could be too much for it.

#11 DoubleHB176

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Posted 21 October 2012 - 08:50 AM

Thanks again all, very useful and interesting information,

I am only intending to use the car on the road, and am hoping for a livelier engine with enough power to pull the 2.76 final drive, I like the way it cruises at 65-70 mph without overstretching itself, but don't like the way my brother just pulls away from me all the time ! Ha ha. I had already converted the car to ten inch wheels, which may compensate a little for this ?

I think I will stick with the MPi set up and go for a reliable 85bhp if I can !

Many thanks for your advice on this topic, much appreciated.

Cheers,

Alex

#12 Chris99

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Posted 21 October 2012 - 03:04 PM

This may well be stating the obvious but if you want an MPI to pull away quickly you have to really push it in each gear, far more than you would in pretty much any other car I've driven. Mine will happily go 40-50 in 2nd and 70 in 3rd if I really push. It's unmodified and I very rarely find lack of acceleration a problem, the car in front is usually what slows me up. Bought from John Cooper and their advice was to treat 4th more like you would 5th in a modern car.

It takes a bit of getting used to at first as it just feels wrong.

#13 cliche

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Posted 21 October 2012 - 04:17 PM

. Bought from John Cooper and their advice was to treat 4th more like you would 5th in a modern car.

It takes a bit of getting used to at first as it just feels wrong.


very interesting

#14 DoubleHB176

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Posted 21 October 2012 - 07:36 PM

This is true, I've had the car a number of years now. A bit of extra poke never goes amiss though does it ! And whilst I have the engine out anyway, and was intending to freshen it up a bit, I never found the car over-endowed with power so I thought I'd give it some extra. After all, a standard MPI has less power than an standard Cooper S, so I understand.

She'll do 70 in third, and about 80 in 4th ! My aim is to extract enough power to pull that 2.7 final drive better.

Edited by DoubleHB176, 21 October 2012 - 07:38 PM.


#15 cian

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Posted 22 October 2012 - 09:11 AM

Do you not find the gaps between the gears horrendous? I found when my mpi was standard it would only rev to four or five thousand rpm then the power totally dropped then changed gear and the gap between the gear totally ruined it




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