Got An Mi Box Fitted To My Mi At The Weekend

[SweetBadger 91]

I can't believe the difference having an MI box instead of a 1.9 box makes. By far the best mod I've done, the car is way more driveable and feels so much quicker - there's no horrible put your foot down and wait for it to get in the powerband anymore it just goes!

 

If anyone is considering using a 1.9 box with an MI my advice is don't, you just won't get the most out of the conversion!

 

Only problem is my speedo is reading too fast (shows 90 when I'm doing 80). I'm using the speedo drive out of the 1.9 box am I right in thinking it needs changing to the MI speedo drive? If so does anyone have a spare I can buy?

 

Cheers,

Alex.

[Anthony 1,000]

You need to use the complete speedo drive (ie both of the cogs) from the 1.9 gearbox, as if you use the ones from the Mi (or mix and match) then the speedo will be miles out.

[SweetBadger 91]

You need to use the complete speedo drive (ie both of the cogs) from the 1.9 gearbox, as if you use the ones from the Mi (or mix and match) then the speedo will be miles out.

 

Hmm, sounds a bit more tricky than I first thought! What exactly needs to be done? Do you mean I have to replace the metal cog in the diff housing and the plastic speedo drive assembly? If so I really can't be arsed with removing the driveshafts again! Think I'll just stick a handy mph per rpm guide infront of the speedo instead!

[Ryan 99]

There is a large plasic gear that fits over the longer drivershaft. The smaller gear on the end of the speedo cable engages with it.

 

You have to take the driver's side driveshaft out and remove the alloy housing on the end of the diff (only 3-4 bolts iirc).

[Ahl 4]

You need to use the complete speedo drive (ie both of the cogs) from the 1.9 gearbox, as if you use the ones from the Mi (or mix and match) then the speedo will be miles out.

Im using a bx16v gearbox on my 1.9. The tyres on my car are just a little smaller than the 185/60/14's of the bx and an online program tells me that my speedo will read only 2.3% faster than im actually going? If I put the 1.9 cogs in it, it'll still read 0.9% too fast due to the 195/50 instead of 185/55 so surely it doesn't make much worthwhile difference?

 

Perhaps sweetbadgers speedo difference is mostly down to it being inaccurate itself rather than the small gearbox drive difference.

 

tyre size calculator

[SweetBadger 91]

Im using a bx16v gearbox on my 1.9. The tyres on my car are just a little smaller than the 185/60/14's of the bx and an online program tells me that my speedo will read only 2.3% faster than im actually going? If I put the 1.9 cogs in it, it'll still read 0.9% too fast due to the 195/50 instead of 185/55 so surely it doesn't make much worthwhile difference?

 

Perhaps sweetbadgers speedo difference is mostly down to it being inaccurate itself rather than the small gearbox drive difference.

 

tyre size calculator

 

With the 1.9 box my speedo was almost spot on, in fact it slightly under-read at higher speeds.

 

I'm running 1.6 wheels and tyres iirc 185/60 R14 and using the online program it only shows a 3% error if the box came from an MI (think the MI had 195 55 R15). Mine is more like 10-12% out at the moment, so does that mean I can reduce the error by just fitting the MI speedo drive, or is the MI speedo differently calibrated anyway? I'd settle for a 3% error if it meant not getting the drivers driveshaft off again. Undoing the intermediate bearing bolts is one of the most awkward jobs, and I've gone through more engine and gearbox oil that petrol lately!

Edited July 4, 2006 by SweetBadger

[jackherer 543]

some people must mean a BX 16v box when they say Mi16 box I guess... I didnt think the BX box affected the speedo so if the 405 mi16 one does I guess they have different speedo drives, makes sense as the BX runs 14" wheels with the same size tyres as a 205 1.6!

[petert 554]

Mi16 has 22T/19T gears, 1.9L 8V has 19T/17T gears, which is a 3% difference.

[d-9 0]

in kates mi the other sunday indicated 70mph was an actual 57mph on the GPS, thought it was a bit quiet!

[S33GAV 0]

If anyone is considering using a 1.9 box with an MI my advice is don't, you just won't get the most out of the conversion!

Spot on that

[SweetBadger 91]

some people must mean a BX 16v box when they say Mi16 box I guess... I didnt think the BX box affected the speedo so if the 405 mi16 one does I guess they have different speedo drives, makes sense as the BX runs 14" wheels with the same size tyres as a 205 1.6!

 

Yep looks like that's the case and I've deffo got an MI box but it shouldn't be that far out. Assuming that the MI speedo is calibrated the same as the 205, if I was using both the speedo drive and plastic cog that drives it off the MI I should only see a small error - 3% overread.

 

So hopefully there should be an improvement in accuracy if I source the plastic bit that connects to the speedo cable from an MI box.

 

Does anyone know how many teeth are on the 1.9/1.6 speedo drive and how many are on the MI?

 

 

Edit: Ooops, question already answered! Must remember to check for new posts after making cup of tea. Cheers!

Edited July 4, 2006 by SweetBadger

[kate205gti 4]

mines about 10-20mph out since putting the mi box on (was 1.9), have been old its because i used the mi cog not the 1.9 one so plan to swap them over at some point

 

bit unnerving doing 100-110mph to work every morning

[ashley peddle 3]

mines about 10-20mph out since putting the mi box on (was 1.9), have been old its because i used the mi cog not the 1.9 one so plan to swap them over at some point

 

bit unnerving doing 100-110mph to work every morning

 

at least it dropped your 0-60 time by about 3 seconds

[SweetBadger 91]

Mi16 has 22T/19T gears, 1.9L 8V has 19T/17T gears, which is a 3% difference.

 

That'd make sense,

 

so the 1.9 speedo drive is 1 : 1.118

MI speedo drive is 1 : 1.157

 

I'm currently running 22T/17T which is 1 : 1.294

 

a whopping 15.7% out!

 

I'd guess you've got the same problem Kate!

[dazEmad 0]

Good choice of box there which enables to keep more in the powerband and faster acceleration. Ive got the 1.6 box which is great too just a bugger when on the motorways (4000rpm=70mph). It doesnt bother too much as i hardly travel on the motorway except for events. Also i will mention when i had the engine changed from 1.6 to 1.9 guttman i had it rolling roaded, 90mph was actually 96mph (higher the speed greater effect on the reading being out).

[TEKNOPUG 3]

When I changed the diif on my 'box it didn't alter the indicated speed at all. Then I changed the whole speedo clock unit for another 1.9 one and it instantly started showing the correct speed. Weird.

[C_W 3 1 Cars]

Yea I think some clocks are differently calibrated so they must just have a matched gearset to the gearbox sendor gears.

[S33GAV 0]

All this makes it rather worrying when going through speed cameras :s

[KRISKARRERA 2 1 Cars]

I never had any of this baloney when I had my 309 Mi16.

[Henry Yorke 269 3 Cars]

I now have an Mi16 box with a 1.9 final drive in my CTI turbo and it is loads better to drive and less time is lost flapping about changing gear.

 

However my Speedo reads up to 20mph too low versus the GPS. Do I need to put the two cogs back on from my old 1.6(ish) gearbox? It has the diff from the original BE3 box in it, but am I missing something?

[pug_ham 242 3 Cars]

Henry, as I thought today there is definately something wrong with the speedo.

 

Just checked on a ratio calculator & your car should be doing about 2900rpm with your current fifth gear @ 70mph.

 

What was it doing when the GPS said 70mph?

 

Graham.

[Henry Yorke 269 3 Cars]

About 3200 IIRC. I will have to do some proper tests!!