12 replies to this topic

[mini1976]

Im thinking of getting a 1380 engine to fit to my mini. I do quite a few motorway miles and would like to be able to fit a final drive ratio that will able me to be a low ish revs while on the motorway but have the torque to still be fun to drive with the FD ratio. I was thinking of something like a 2.9 to 1 FD and a 1380 engine. Was looking at this engine on ebay. What do people think. My main concern is weather it is actually a 1380 but like i said what do people think? Link

[Dog]

I was going to go 1380... but the feeling of knowing how thin the Bore walls were.. made me change my mind to a 1330.

a 3.2/3.1 diff would be better for you

[mini1976]

so with a 3.2 or a 3.1 what sort of revs would i be doing at 70? Is what i really want a 5 speed box? or is the extra gear a ratio between 2nd and 3rd rather than a ratio for motorway driving?

[Dog]

Maybe good GuessWorks will post his wonderful Box program!

By the info and questions I have pestered with John with, a 3.2 would be good, as this'll give about 3800 rpm at 70mph

me personally, as I want quick 0-60 I have gone for a 3.44, this is a very vesitale FD, slightly higher rev'd at 70, but it'll pull a bit quicker than a 3.2 would. But a 3.2/3.1 would have a slow RPM at 70

[Dog]

Have a nose at this;
http://www.rcmoc.org...uff/Ratios.html


It's fairly simple...

There are 4 selections..

1. The tyre size of your chioce, this provides the calculator with the rolling circumference of the tyre and hence the turns per mile of the wheel

2. The ratio of the drop gears, which is defaulted to a 1:1 ratio which is standard for all but the most modified minis. These transfer the rotation of the crank to the 1st motion shaft of the gearbox.

3. The type of gearset ratio used. Over time there have been a number of different ratios used within the mini gearbox, from the early 3 synchro magic wand boxes to the latest A+, each will have a slight impact on the final speeds in 1st 3nd and 2rd. 4th on 4 speed gearboxes is a direct 1:1 ratio, so if you're only interested in final top end speed then any selection in here will provide that.

4. The final drive or Diff ratio. This is the ratio provided by the crownwheel and pinion and is the main component for the final road speed calculation.

Using these 4 parameters it is possible for you to make an informed choice about what type of road speeds are available, not only as a top end but also through the gears, maybe allow you to make better use of the power available and also designed to you driving needs. This is why I have included a number of after market SCCR gearsets in the parameters.

I should also be said that this is theoretical speeds, obviously it's unlikely that you're going to get to 8k rpm in 4th but it's handy for finding out what sort of rpm you're going to be doing at motorway speeds, or if for example you are running ministox cars and wish to keep to using 1st and 2nd, a change in diff ratio or drop gears could increase your competativeness on particular tracks (within regulations of course)

[Sprocket]

so with a 3.2 or a 3.1 what sort of revs would i be doing at 70? Is what i really want a 5 speed box? or is the extra gear a ratio between 2nd and 3rd rather than a ratio for motorway driving?

Depends which 5 speed box you get, some have a 1:1 fifth and others have somewhere in the region of 0.86:1 fith (over drive) But final drive ratio the two types will need selecting carefully

A 1:1 fifth with a 2.7:1 diff or a 0.86:1 fifth with a 3.2:1 diff will both give the over all final drive around 2.7:1 but give the acceleration characteristics every wana be racer desires

[Guess-Works.com]

IMO, 5 speeds are just too much money for the extra cog, if you can get one for under 500 then maybe... but 4 with the right gears, and FD should be enough...

If you want a cruiser, then go for a 2.9

If you want to play country lanes and cruise, then a 3.1 or a 3.2

But if you want to go chav baiting, sorry you may not be familiar with my current sporting exploits but commonly know as leaving tricked up corsa's, pug's and Rover 220's standing... then a 3.44 is the baby to have...

As for the engine, the only real way to tell is to take the head off and measuer the bore, you could either request the vendor to do this, or check it when you get there.. either way if it isnt then the ebay contract is null and void because you have not been sold what is advertised...

(happened to me with an engine which was meant to have a SC box and drops) checked the box when I got there by removing the diff cover, found to be helical, so we agreed a new price... then when I got it home and stripped the fylwheel and transfer case off, no straight cut drops to be found either.. after a threat of legal action, we agreed a very reduced price on the engine, or he had the option of a full refund and comming an collecting the engine)

also be prepared to strip and rebuild the engine and add in the cost of that to your calculations... I would never use an engine asis unless it was from a trusted source or guarenteed

[mini1976]

I believe i have got a 3.44 FD at the mo its what ever comes standard on what i believe to be an 86 MG metro engine. I had a look at the link above and with my wheel size and a 3.44 FD ratio and an post 84 metro selected the speeds seem to tally with the revs and speeds that my car does. I do love driving down the country lanes but find all too often i end up driving on the motorway. I like the acceleration and speed of what i have ( although it will only just do 100 and i mean just) but its just so noisy with the rev's so high. So i was hoping larger engine different FD and i would keep the acceleration or atleast not loose much but gain on the comfort when cruising. Will this be the case? Or will I loose lots of acceleration and it become horible to drive except on the motorway?

[vasi]

From what you've written, the only gripe you have with the current 3.44:1 CWP is noise. You didn't mention fuel consumption or anything else.

So invest in better soundproofing

[mini1976]

What sort of millage would it be reasonable to expect from a 1380? I know its all down to build quality but im more thinking along the line of that you cant have it reboared and would have to replace the block if this required doing wouldnt you?

[mini1976]

What sort of millage would it be reasonable to expect from a 1380? I know its all down to build quality but im more thinking along the line of that you cant have it reboared and would have to replace the block if this required doing wouldnt you?

OH and i have no idea what my fuel consumption is as my speedo under reads quite a bit but im under the impression its not too good maybe say 120 ish on a tank and i would normally be putting about 4 gallons in ish. But like i said the milage is not too acurate its more i know how far it is to get somewhere and i drive there and back and make a few short trips while im there so i huess i did about 120 miles. rather than thats what my speedo said ive done.

[Guess-Works.com]

think 30 to the gallon, I get more than that out of my 1330

[mini1976]

yeah about 30 to the gallon and thats with my 1275 mg metro engine