Mi16 Gearbox In Road Rally 1900 Rebuild

[Guest oilburner]

hi Everybody,

I am busy preparing my car for next seasons road rally championship. This time i am changing from std 1600 to a lightly modded 1900 engine.Mods are lightly worked head, GRP N Cam. So note a wild engine but a fair bit more power than before with hopefully good reliability as we,ve stripped it & renewed anything that might have given trouble.

I will be fitting a 4.4 CWP inlo of the std 4.6.1 we have been using - a good thing to do so i understand to increase performance.Now i also have come across an MI16 gearbox in perfect order.What,s the crack here? I was going to go with my 1600 box & CWP but is the MI16 box worth fitting instead ? - or is there a way of using some of the ratios to make if you like - a better ratiod box to go with the fresh 1900. I,m not familiar with MI16 ratios so would any of you gearbox/ratio experts have any comment or suggestion as to what,s best, before we put it all back together ?

I would be grateful for some opinions as i know alot of you have mixed engines/boxes etc with varying degrees of success. I,m just looking for any bit of performance gain i can get in the lanes....

Cheers all Ian..........

[Miles 331 1 Cars]

To cut it short for small lanes etc I would keep the box you have and if you have got a 4.6 (Never seen this before thou) keep that as it's higher than the 4.4 of the MI16 box, But if it's the std 1.6 box it will have a 4.05 CWP so fitting the 4.4 will give you better acc and lower top end but I can't see you doing 120 down the lanes,

[Guest oilburner]

To cut it short for small lanes etc I would keep the box you have and if you have got a 4.6 (Never seen this before thou) keep that as it's higher than the 4.4 of the MI16 box, But if it's the std 1.6 box it will have a 4.05 CWP so fitting the 4.4 will give you better acc and lower top end but I can't see you doing 120 down the lanes,

 

Miles,

Thanks for your advice - makes good sense,so it would seem then : - 1600 gearbox,4.4CWP,Quaife ATB.

That,s the way we,ll go now. As regards the 120 mph "in the lanes" I have road rallied since 1981 & maybe

you can remember the "Motoring News " championship ? Well i got clocked & of course penalised by the powers

that be for doing a "genuine" clocked on vascar - 118mph!!!! on the 1984 Cilwendeg Rally. The competitive -

section was near Aberaeron in west Wales. The car - Avenger Tiger ! As they say " Those were the days"

[Miles 331 1 Cars]

Christ I remember that Championship and those car's,

Had a Avenger 1600 built to almost that spec as a first car back in 86, Or are we showing out age.

[Anulfo 22]

How different would the end results be putting a 4.4cwp in a 1900 box and in a 1600 box? Any idea what your top speeds mite be? I suppose the key is with road rallying you want the gears close together so you can keep the engine up there revving in its peak power band!!!

[philfingers 5]

I run an Mi16 CWP in basically a 1900 box for road rallying. The 1600 boxes are the same ratios other than 1st (unless it's a more rare 'close ratio' 1.6 fitted to later car I believe). Std 1600s have a short 1st which means that when you change into 2nd there a big drop in the revs. The best std ratios (for performance) are the 1900. BUT the std 1900 box is ruined by the final drive., for our application anyway

In basic terms a std 1900 box will redline in 2nd at around 60mph, with a 1900 ratios/ 4.44 CWP it will redline in 3rd at about 65mph. So up to 6o (ish) mph you have an extra gear to play with

My 'conversion' cost me 20 quid (for a Mi16 box with damaged housing) and it's the best money and time I've spend on the car, without doubt.

 

Top speeds (in 5th at the redline, which a std 1900 would never pull on a 1900 box anyway) are:-

1600 box ~122mph

1900 box ~137mph (70mph is ~3400rpm in 5th)

1900.4:44 ~110mph (70mph is ~4000rpm in 5th)

 

Sorry not about to post my email address on here but if anyone wants a copy of the excel gears spreadsheets I have drop me a PM with your email address and I'll send them.

 

You can play around with tyre size, ratios, final drives. These files will give you revs at change up, max speed in each gear etc.

The only downside of th hybrid 1900/4.44 is that cruising on the motorway is noisy. I used to run my car between Birmingham and Aberdeen for work and fuel consumption wise compared to the 1900 box at 70mph wasn't a lot different in the 309. Only 1mpg difference probably, but much when you drive above 70mph and it starts to drink it. My car is trailered mostly now so it's not a major issue anymore, which is why i have 4.8 to go in.

 

In short 1900/4:44 is the way to go for road rallying. I've hit 100mph a couple of times on single track road at night, it's quick enough!

[Craigb 2]

This is an interesting one, since in the last three years; I have had three combinations of boxes.

 

I started out with a 1600 box with a 4.8 FD, this went tits up during a rolling road session, But don’t get me started on that one!!!

 

This was replaced with a STD 1900

 

This was then updated to include a 4.4 FD.

 

The 1600 box and 4.8 was rapid, despite running an engine that had 126 bhp , the std 1900 , I used for two events , as I had no choice , it was pants , used only three gears all night and was not competitive , even with the 150hp engine.

 

Since I have fitted the 4.4, I know find I use 4 gears, and that it is competitive.

 

But I still have the nagging doubt that a 4.8 would be better with my engine. As Philfingers has pointed out, the downside is long motor way journeys to and from events, which are quite noisy and tedious.

 

If I had the cash in my pocket, I would go and try a 4.8 ….. Next year maybe

[Guest oilburner]

This is an interesting one, since in the last three years; I have had three combinations of boxes.

 

I started out with a 1600 box with a 4.8 FD, this went tits up during a rolling road session, But don’t get me started on that one!!!

 

This was replaced with a STD 1900

 

This was then updated to include a 4.4 FD.

 

The 1600 box and 4.8 was rapid, despite running an engine that had 126 bhp , the std 1900 , I used for two events , as I had no choice , it was pants , used only three gears all night and was not competitive , even with the 150hp engine.

 

Since I have fitted the 4.4, I know find I use 4 gears, and that it is competitive.

 

But I still have the nagging doubt that a 4.8 would be better with my engine. As Philfingers has pointed out, the downside is long motor way journeys to and from events, which are quite noisy and tedious.

 

If I had the cash in my pocket, I would go and try a 4.8 ….. Next year maybe

 

I had intended using the BE3 1600 Box with the 4.4 CWP. Are you boys running BE1 OR BE3 Box,s ?

So just for me to get this clear - The 1900 box & 1600 (BE3) are the same except for 1ST Gear ? Hence then 1900 box/4.4CWP is the answer to

avoid the rev drop from 1st to 2nd gear. Am i right ?

[philfingers 5]

I had intended using the BE3 1600 Box with the 4.4 CWP. Are you boys running BE1 OR BE3 Box,s ?

So just for me to get this clear - The 1900 box & 1600 (BE3) are the same except for 1ST Gear ? Hence then 1900 box/4.4CWP is the answer to

avoid the rev drop from 1st to 2nd gear. Am i right ?

 

The 1600 (late close ratio one excepted) and 1900 boxes are the same except for 1st gear AND final drive. Yes the idea is to use the 1900 box (less 1st to 2nd drop) and the 4.44CWP.

If you were running an Mi16 for instance then you may be better with a 4.8, as the Mi revs to 7500 ish, where as the 8v only really runs to about 6k.

Oilburner, drop me a PM and with your mail address and I'll send you the files

 

Phil

[philfingers 5]

Craig

You're probably right a 4.8. I've yet to try it. It was all up and running in the 309 I had then it got pulled to pieces (rust). Thing is (and I'm going to put a 4.8 in mine to try it) if you're using 4th already then you'll be chnaging gear even more.

In fact std 1900 is great road rally box, you only need 1st and 2nd, occasionally 3rd! Far less changes!!!!

 

As an example how good the 1900/4:44 hybrid is. The car I just bought (205 8v tarmac car, 'cooking' spec, LAD head, high comp pistons, Gp A PTS cam, std inlet/ fuel system) finished Mull last year 61st with this box configuration. This is my new road rally car, interior getting fitted next week. . ... . . .

[Anulfo 22]

Craigb,

So if you were to fit a 4.8cwp to the 1900 box then what kind of top end speed would that be giving you at full revs in 5th?Im guessing a tad over 100mph?

I do sprints and some tracks are faster than others so i want the best of both really-good acceleration and 110-115mph flat out top end.Dont know whether to go 4.4 or 4.8 for next season.

[Craigb 2]

theoretically

 

122 as I'm revving to 7200rpm

 

110 at 6500

[Anulfo 22]

Ah thats not badas im revving to around 8000.The 4.8cwp is the proper £500 purpose built bit of kit isn't it?

[Guest oilburner]

:wacko:Use

Ah thats not badas im revving to around 8000.The 4.8cwp is the proper £500 purpose built bit of kit isn't it?

 

I think maybe the 4.8 would be perhaps a bit too much of a restriction on long straights where top end counts.

Certainly from what has been said on this box/FD discussion from my point of view -road rally with loads of

twisty tight lanes etc, i,m going the 4.4 route. Again it,s down to i suppose the type of events your going to be doing

most of the time. You have to take into account your engine aswell & of course your driving style.

It can drive you barmy going over & over the different set up,s. It,s so easy to throw time & of course loads of money

into these things, only to end up dissapointed at the end of it all !