25 replies to this topic

[Midas Mk1]

What does the standard MPI have ?

2.7, as much as I loath it in my sportspack on 10's (going for a 3.2 soon), its awesome cruising just over 4k at 85..

[pete l]

Why do you loath it ?

So does the mpi suffer from diff pin failure seeing as it has a very high final drive and a very torquey engine ?

[Ethel]

It has a reputation for knocking teeth off the final drive.

[tiger99]

If my engine developed good low down torque (some highly tuned ones don't) I would go for 2.95, because I like high speed cruising. But 3.2 is not too much for many driving conditions. 3.9 would be dreadful in long distance road use.

I fitted a Metro 998 power plant once and it was useless till I changed the final drive. About 60 flat out, guessing it was at least 3.9.

Actually that was a great power plant, and needed no other attention except routine maintenance. It came from an offshoot of General Accident Insurance in Tolpits Lane, Watford, and so came from a low mileage write off but was cleaned, tested and guaranteed. I don't think they are still in Tolpits Lane, but would certainly like to know if the operation is still in business somewhere as it was a very satisfactory way of buying an engine. But off topic, apologies....

[Cooperman]

The 3.44 is very good unless you do a lot of motorway driving.

[martin_mini]

Yes the 3.44 was fitted to the Mk.1 Cooper 'S' and it worked well.
It will give 16.5 mph per 1000 rpm in top which means about 83 mph at 5000 rpm.

 

Allow me to roughly sum this up... I would like to know more about mph/rpm in top gear for other FDR 2.7, 2.9, 3.1, 3.2, 3.7. Can anybody help fill out the puzzle here? Cooperman already gave two, if you know some more please share. Thanks.

 

 

3.44
It will give 16.5 mph per 1000 rpm in top which means about 83 mph at 5000 rpm (Credit: Cooperman)

 

4.1:1
It will give just under 13 mph per 1000 rpm in top gear. So 5000 rpm would be something like 62 mph. (Credit: Cooperman)

 

2.7?

2.9?

3.1?

3.2?

3.7?

 

[alex-95]

have a look here

http://www.guess-wor.../Tech/ratio.htm

[Cooperman]

So much depends on the engine specification and the shape of the torque curve, as well as how you wish to use the car.

The mph/1000 rpm in top is just a measure of that and does not consider the fact that as the FDR gets 'taller' the gaps between the gears gets 'longer' as well. The correct gearing enables the engine to stay nicely 'on the cam' when changing up or down the gears.

With the standard gears, which are quite wide ratio, if the cam and head have been changed to give more power wand a narrower torque band, then a slightly lower FDR will help the overall performance.

That is why, for a mildly tuned road engine, say with around 70 to 80 bhp, a 3.2 or 3.44 FDR is about ideal.

[martin_mini]

have a look here

http://www.guess-wor.../Tech/ratio.htm

Thanks Alex, I have tried the site but seems like the site doesn't respond to me? weird.....

[martin_mini]

So much depends on the engine specification and the shape of the torque curve, as well as how you wish to use the car.

The mph/1000 rpm in top is just a measure of that and does not consider the fact that as the FDR gets 'taller' the gaps between the gears gets 'longer' as well. The correct gearing enables the engine to stay nicely 'on the cam' when changing up or down the gears.

With the standard gears, which are quite wide ratio, if the cam and head have been changed to give more power wand a narrower torque band, then a slightly lower FDR will help the overall performance.

That is why, for a mildly tuned road engine, say with around 70 to 80 bhp, a 3.2 or 3.44 FDR is about ideal.

 

 

So much depends on the engine specification and the shape of the torque curve, as well as how you wish to use the car.

The mph/1000 rpm in top is just a measure of that and does not consider the fact that as the FDR gets 'taller' the gaps between the gears gets 'longer' as well. The correct gearing enables the engine to stay nicely 'on the cam' when changing up or down the gears.

With the standard gears, which are quite wide ratio, if the cam and head have been changed to give more power wand a narrower torque band, then a slightly lower FDR will help the overall performance.

That is why, for a mildly tuned road engine, say with around 70 to 80 bhp, a 3.2 or 3.44 FDR is about ideal.

 

Cooperman, thanks for the info. My car is currently a stage 1 and it is a Cooper engine. I use it as a daily driver and drives a lotttt on motorways( top cruising speed ) I have no idea what FDR is in my car since the current owner said he was thinking of building it for track use.

 

From engine plate identifier of minispare, the specs are suppose to be 3.1 FDR. BUT, I assume that it is currently a 3.44 FDR, because it cruises at the same rate as what you mentioned.

 

"3.44 - It will give 16.5 mph per 1000 rpm in top which means about 83 mph at 5000 rpm (Credit: Cooperman)"

 

I am thinking of going for original 3.1 or 3.2 like you've mentioned. I do lots of high/top speed cruise. Also, thinking of porting the head and uprating the O/S valves, but still unsure about changing to Kent 266 cam kit.

[Cooperman]

With a standard gearbox I wouldn't go any higher than a 3.2:1 FDR if using a 266 cam. The 266 (or similar MG Metro cam) give excellent mid-range torque and a 3.2 will be fine and on long straight roads it will cruise well. It will stay nicely 'on the cam' through all the gears and in top will cruise well at around 4200 rpm and 70 mph, which is about ideal.