10 replies to this topic

[germini30]

Went out yesterday for the first time since fitting the mg metro engine. Originally the mini was fitted with a 998 and is a1989. The metro is a 1982. Pulls like a train and spun the wheels in second off a roundabout. It seemed as though the gears are short . The speedo was showing 65mph and I was on 5000rpm in forth.i realise that the speedo will be out but is it likely to be miles out or am I going to have to swap diffs. If the speedo is miles out and I was nearer 80mph at 5000rpm then I will have to compromise top end speex for acceleration. Does anyone know how far I can expect the speedo to be out.my mini is on 12 inch wheels.

[Tamworthbay]

Went out yesterday for the first time since fitting the mg metro engine. Originally the mini was fitted with a 998 and is a1989. The metro is a 1982. Pulls like a train and spun the wheels in second off a roundabout. It seemed as though the gears are short . The speedo was showing 65mph and I was on 5000rpm in forth.i realise that the speedo will be out but is it likely to be miles out or am I going to have to swap diffs. If the speedo is miles out and I was nearer 80mph at 5000rpm then I will have to compromise top end speex for acceleration. Does anyone know how far I can expect the speedo to be out.my mini is on 12 inch wheels.

The speedo could be miles out. Easiest way to check is to drive along with a sat nav on and see how it compares. If it's just a matter of swapping speedo drive then Guess works website has a page where you can work out what you need. Its a damn fiddly job but can be done with the engine and box in situ. If you need to swap the FDR then its an engine out job.

[germini30]

I see on some websites that you can change the final drive in situ.but its awkward. Would going from a 3.1 to 3.4 have made such a difference? Mini is surely better with acceleration than top end.

[Dusky]

With that diff you should still ride 91mph @ 5000 rpm with 12 inch wheels..

 

http://www.tomsminis..._calculator.php

[germini30]

Speedometer must be out by loads then.will give it a spin when the weather is better

[Guess-Works.com]

The metro used a 1000 tpm speedo as standard, where as the mini's are generally between 1200 and 1300 tpm, which means your speedo will be reading approx 20% higher than your actual speed..

 

If the gearbox is original to the mg metro engine then it'll have a 3.4 final drive and a 5/17 speedo worm & pinion, if your speedo is original to the 1989 specification then it'll be a 1242 tpm 90 mph Nippon Seike, and what you'll need to do is change the 5 tooth worm to a 6 tooth worm... Unfortunately to do this you're going to have to remove the radiator and n/s engine mount and bracket so you can access the worm drive, but at least it can be done without removing the engine from the car.

Edited by Guess-Works.com, 05 January 2014 - 03:34 PM.

[germini30]

Ok job for when I got nothing else to do

[germini30]

So when I was showing 60mph what speed was I actually doing using the percentage you mentioned abovw

[germini30]

Sorry its 72mph.i am not too good at maths

[dklawson]

There is an alternative to opening up the gearbox or changing the speedometer to get the reading correct.  Contact a vendor such as Speedograph Richfield Ltd and discuss a speed correction gearboxbox with them.

 

You will need to tell them the turns-per-mile value of your current speedometer and they will ask you some related questions either about the car's current gearing OR the known error (such as 65 MPH displayed is really 72 MPH... whatever it really is).  In addition to that information you would probably need to provide them a couple of new speedometer cables and an indication of where you would want to locate the correction gearbox.

 

They will build a custom gearbox (about the size of a pack of cigarettes) which mounts INLINE with the speedometer cable (that's why you may need to supply a couple of new speedo cables and indicate where you want the gearbox located along the resulting new cable length).  The gearbox will convert the cable turns "in" from the gearbox, to the correct cable turns "out" that the speedometer needs to read correctly.  

[AVV IT]

As above the other option is to have your speedo recalibrated, "Speedy Cables" offer this service for £65 + vat & shipping. http://www.speedycab...alibration.html