12 replies to this topic

[Mojito]

Hey all,

 

As a potentially first time mini buyer, I have been scouring this forum to help me decide what car to buy.

 

Here are the sort of specs I'm looking for:

-Good MPG (ie north of 40  ) because petrol is so damn expensive in France.

-Decent amount power, I wont settle for anything less than around 75hp (at the fly wheel) (at the wheels would be awesome).

 

 

Here is what I gathered after reading threads in the forum

MPi is more reliable and slightly more fuel friendly than SPi. Haven't found any numbers though.

MPi is slightly more difficult to mod than the SPi and way more than the carb.

MPi engine has a stock power of 63hp (flywheel?), don't know about the SPi.

MPi is more reliable than the others.

 

 

I know MPG and power don't mix very well, but I would still like to know if its possible. Obviously this would demand modding and/or tuning the car to achieve that but that's not a problem for me. I'm more electricly inclined than mechanicly but I learn fast  . I'm not looking for some high performing little thing, just a regular commuting car that has a bit more oompf. I've got a motorcycle if I want to go Speedy Gonzales.

 

If what I'm asking for inst feasible then I am prepared for an engine swap, this does open a lot more opportunities but I don't know how much that is going to cost nor do I know anything about the French laws on that.

 

Your expertise and opinions will be much appreciated.

[brivinci]

SPi and MPi had the same output. 63-64hp. Are you dead set on an injection car? From my understanding, a carb Mini is WAY easier across the board; tuning, making power, easier to work on; cheaper parts.

 

That said, I do love my injection car. I know I will never get the kind of power you can with a carb...for anywhere close to the same money. The Spi motors are a little more simply of the two. I have never owned an MPi so I have no idea but with the radiator moved to the front, things seem to be even harder to work on.

 

Maybe its just me but my stock SPi almost never got 40mpg...even stock. I dont drive it on super long highway drives though. The few trips I have done on looooong, straight US highways I have just tipped into the 40's. I am about to add a head to my motor now and that added to the cam and exhaust, I should be looking at around 80-83hp per Calver. I doubt very much that I will see better fuel economy.

 

If you want 75+, you will need a head, header, cat-back exhaust and either a cam or high lift rockers. Bringing you to 80 or so. What do people on here with a similar setup get for MPG? One HUGE factor in all this is the driver behind the wheel. If you are going to add all those bits and spend that kind of money, how are you going to drive? I am not planning to spend this money so I can putt around. I want the added power so I can drive it faster. You need to figure out what you want more and what you can give up on a bit. Power or fuel economy. Have you ever driven a Mini before? That is the first step. Take a well sorted injection car out and see if it has the power you need. If its feels way too slow, hand back the keys and find a different car because to make these injection cars REALLY fast, you need deep pockets...and I am not sure what kind of MPG's you will be getting if you are looking for power.

[HarrysMini]

I don't know why everyone thinks that injected Minis are more reliable than a carbed equivalent, that really is not the case. 

 

Providing you actually maintain your car, there's no reason why a carb engine can't be more reliable than an injection one.

 

SPis and even more so, MPis suffer from electrical problems (like all modern cars), which are far harder to diagnose than any other problem.

 

Also, I'm not sure if you actually can get above 40mpg and have 75hp. There are many factors contributing to that though.

[brivinci]

Yes, the second these car went FI, they became very complicated and even harder to work on. Theres just a lot of stuff crammed into that tiny space. MPi's look even worse.

 

I didnt fully read the OP and see that engine swaps are an option. I do not know all the options out there but I am sure there is a motor that has the power stock and maybe the fuel economy. Most likely that motor is going to weigh more so there is that to consider. In the end, you may be asking for too much.

[FlyingScot]

SPIs don't all have the same power output....standard SPi is only 52bhp (53PS) only the Cooper models of SPI with a different compression ratio ECU etc have the 63bhp quoted.
Simple fact is that the more complicated something is the more chance of a failure overall. Mini electrical connections were never great so add additional complications in the same design and you could have trouble.

Fuel injection cars suffer from the fact it is more difficult to trace faults especially if you don't have the specialist diagnostic equipment (don't believe me ? Look how many posts we have with what look like similar problems but have different root causes)

Modification of the fuel injection cars is more difficult due to the very narrow operating conditions imposed by the basic design of the a series in relation to fuel injection timing.
Don't take my word for it "Improvements could always be made but remember any modification to the engine means re-calibration of the fuel metering system which is far from simple" these words were written by Mike Theaker the engine development engineer at Rover who developed the SPi and devised the later MPi systems.

It doesn't mean it is impossible as others will testify just more difficult!

FS

Edited by FlyingScot, 25 April 2014 - 04:42 PM.

[bluedragon]

Peak power isn't everything. If you look at the shape of the power curve, you'll probably find that an MPI's curve is much broader than that of a carb'ed 1275 or even an SPI. 

 

That power curve is why Rover was able to fit the 2.76 final drive into the MPI to meet drive-by noise regulations - it would have been unbearable for the stock SPI. Indeed, the cited Mike Theaker, also said the 3.1 FD MPI's "went like a bomb" and showed what the MPI could really do.

 

So as far as power goes - if one's style to rev the engine hard and stay in the upper reaches of the powerband, then a carb'ed 1275 may well be a better choice. For all around driving, including cruising and commuting, the broader power curve of the MPI may be the better choice (but you won't get sky-high revs out of it due to that max fuel limitation.)

 

Of course, now that the cars are 14+ years old, problems may crop up. But if well kept up, I do believe the MPI to be more reliable than a carb'ed/distributor fitted engine. No points, distributor cap, or carb floats/needle wear, etc. to deal with. That stuff isn't a big deal for a hobby car, but if you were to daily drive the thing, I would get a sorted MPI and enjoy. Once sorted, just change fluids and adjust valves regularly. That's all that's needed.

[Fast Ivan]

bluedragon very well put.

 

the standard mpi has 63bhp and 70 lb ft torque, pretty impressive figures for standard trim

 

getting 75bhp out of an mpi is no more expensive or difficult than a carbed engine, in fact it could well be cheaper as the ecu will adapt to the modifications where as a carbed engine will require a rolling road session.

[Fast Ivan]

edit

[Mojito]

Thanks for all the input guys.

 

I'm just looking for commuting car with a little more power and a lot more soul than a Renault Twingo . I want the extra power to be able to go on the motorway without the engine screaming it's head off. With my current Twingo I get 47mpg in town, 56mpg on B roads but 31mpg on motorways!

 

What about engine swapping? I would have thought that with a more modern engine the fuel consumption would be better. Nobody has talked about it except Brivinci briefly, is that because it's really difficult to do?

[brivinci]

Well, the short answer is YES IT IS!!! The mini is small so that makes fitting a different motor and running gears in that much harder...sometimes impossible. If you search around for Mini motor swaps, plenty have been done. You can fit a honda single cam vtec motor under the original shaped body but a twin cam vtec has you extending the front end a bit. There are plenty of vtec conversion topics out there. i have also see a street bike motor in the front of the Mini, Suzuki Swift motor, etc. Your are really limited only by your imagination, skill level and wallet thickness. Hell, check this out for inspiration:

 

 

This is an AMAZING build series. These guys need their own show.

[brivinci]

If you are thinking about a motor swap, some things to keep in mind are.

 

1. Total weight of Mini

2. Total weight of Mini minus original running gear

3. Power output of original running gear (lets say 80hp)

4. Fuel economy for 80 hp motor. No idea but lets round up to 30mpg average

 

Now, start shopping for a new motor to squeeze in there. When you find something, look at these things:

1 HAs been done before and is there a kit

2. Total cost (if that matter)

3. Total weight of running gear

4. New total weight of Mini

5. Power output of new setup, ie Power to Weight Ration!

6. Claimed fuel eco when in original car at that cars original weight.

 

From this you can start to get an idea what you are getting. The mini is light so the power to weight as well as eco will improve with a more powerful motor. If this was going to be purely a commuter car that needed good fuel, maybe some standard Honda motor would do the trick. The power to weight should go up a bit and because the Mini is lighter then any Honda you would be getting a motor from, the fuel eco should be even better. Most people doing motor swaps are after one thing, POWER. That is why vtec motors are a popular choice. They tear the wheels off a Mini. If you shoot for around 120hp (no idea what a honda civic motor puts out or what they way) you might get what you want.

[bluedragon]

If you're looking for a commuter car with a bit more zip, a engine-swapped Mini seems to be a very roundabout and troublesome way to do it.

 

Even though there are many kits and it's been done many times, these swaps are not plug and play. You can expect to spend some time debugging the swap even if the mechanical work is perfect. And you won't find a Haynes or factory manual to troubleshoot. Unless the swap itself is the point of the project (you want to take on the challenges and work of doing the swap) - it seems like a very expensive way to get more fuel mileage and more pep from a Mini.

 

As far as fuel mileage goes, it may not improve to the extent desired either. Many of the swaps end up with gearing that's too short (higher numerically) than is optimum, because they were targeted for cars with 15" and 16" wheels. And the coefficient of drag for a Mini is horrendous compared to a modern car (.48 for a standard Mini, .54 for a SportsPack.) Only the small frontal area of the Mini salvages this somewhat.

 

If you cruise at higher freeway speeds, you may find you consume more fuel that you would think. Ultimately, if you have never owned or driven a Mini and think it needs a engine swap to be satisfactory without having this experience, I would advise looking for a different vehicle.

[brivinci]

Very well put