m50 info please

[penton08]

your sport should have a 3.91.1, if you want it a bit quicker i have a 4.10.1 LSD on the shelf but the price will make you shake. i would stick with your 3.91.1 and get it sent off to gareth!

[DanThe]

You wont want to go any shorter than 3.91 for a road car

[town325i]

A 4.10 will be topping out on the motorway at around 100mph flat out nearly on the limiter

[DanThe]

Nah it wont be that bad gearing with his sport diff wont be much different to what I have with the E36 box and 3.25 diff

[DanThe]

[penton08]

A 4.10 will be topping out on the motorway at around 100mph flat out nearly on the limiter

No way!!! 70 mph comes at around 3800 rpm and 100 mph is still under 5000 rpm on a 4.10 with the iS box, at a guess i would say it would do about 130-135mph flat out. i swaped my 3.23 for a 3.64 a while back and 70 mph moved from 3200 rpm to 3600 rpm so there is not the world of difference between the two.

[town325i]

A 4.10 will be topping out on the motorway at around 100mph flat out nearly on the limiter

No way!!! 70 mph comes at around 3800 rpm and 100 mph is still under 5000 rpm on a 4.10 with the iS box, at a guess i would say it would do about 130-135mph flat out. i swaped my 3.23 for a 3.64 a while back and 70 mph moved from 3200 rpm to 3600 rpm so there is not the world of difference between the two.

What i said was exagerated to get a point across

[penton08]

A 4.10 will be topping out on the motorway at around 100mph flat out nearly on the limiter

No way!!! 70 mph comes at around 3800 rpm and 100 mph is still under 5000 rpm on a 4.10 with the iS box, at a guess i would say it would do about 130-135mph flat out. i swaped my 3.23 for a 3.64 a while back and 70 mph moved from 3200 rpm to 3600 rpm so there is not the world of difference between the two.

What i said was exagerated to get a point across

fair play

[Baz666]

What about a 2.93 diff would this be ok ??

[Brianmoooore]

What about a 2.93 diff would this be ok ??

Perfect, IMO. The equivalent of a 3.62 on a 'normal' E30.

[Baz666]

Thanks Brian but would there be any benefits or shell i stick with the 3.91 i have.

[DanThe]

A 2.93 would only be any use with an E36 or E34 non overdrive gearbox,

A 3.91 is only any good with an E30 overdrive gearbox

Personally I wouldnt use a 2.93 with an M50B25 as I feel its not got quite enough power

As a comparison the E36 325i used a 3.15 ratio diff as standard

[Baz666]

so Dan stick with the 3.91 yeah

[mick_318is]

Depending on what you want to use the car for.

For everyday driving I would think a 3.64 or 3.73 would be better.

3.91 imho is a bit tall for the M50B25, unless your going to be using it on the track a bit.

Considering that a regular 325 came with 3.64 or there abouts.

[Alpina99]

I'm not confused, this is just a good impression !!
I'm putting an M50 (2.5) into a 320 Cab & using an E36 318is gearbox & I've been told not to use the 320 diff,
I want a car with reasonable acceleration but will be using it more for long distance touring so will be more after sensible economy as well,
What diff ?

[Baz666]

Hmmm is the e36 box the same as the e30 318iS box because that`s what i got told to use, i`v just brought a 3.91 which is really clean and only done 70,000 miles, i will only be using the touring for light use no track days.

i`m the same as you alpina99 looking for good economy so the 3.91 was the wrong one to go for then

[DanThe]

Baz, are you converting to go faster or to save petrol?

If you use an online gearing calculator you will find that an overdrive gearbox with a 3.91 diff ratio gives virtually the same gearing as a non overdrive box with a 3.15 ratio diff, so using the 3.91 and iS box Baz you will have the closest gearing to an E36 325i

[Baz666]

all this ratio stuff is head banging, but i see what your saying now Dan i did say from the start of all this i dont have a clue.

[DanThe]

Ok, with 205/55/15 tyres @ 3000rpm the speeds in fifth are as follows

3.15 diff, E36 box = 67.62mph

3.91 diff, iS box = 67.26mph

3.73 diff, iS box = 70.5mph

3.64 diff, iS box = 72.2mph

The speed difference is not worth the loss of acceleration

[Baz666]

Dan your a star fella i`v got it now so for speed i could have gone for the 3.64 but as it goses the 3.91 so very much ok as it`s not going to knock my mph out to much

[Alpina99]

Thanks Dan,
Even I understood that,
My question now is how do you identify which diff is which ?
(Are they coded & what are the codes ?)
Thanks

[Baz666]

There a tag on the casing fella.

[Alpina99]

Thanks,
And that tag actually states the ratio outright ?
(If I'm reading the picture correctly, that's a 3.91 ?)
Thanks,

[Baz666]

Yeah dude s3.91 ratio

[Alpina99]

Thankls Baz,
Another trip to the breakers then soon,

[Baz666]

Right i`m looking at buying some H&r springs would you guys know what set up i would need ie 60/40 or can i get 40/30 as i`m going 16x 9 wheels.

[penton08]

either should be ok mate, mines lowered 40mm at the back with 17 x 9 rims and 235 tyres. just make sure you get touring springs, from memory H+R touring springs where the wrong side of £300

[Baz666]

Well guys Penton started the car and it fired up first time on the button, untill it run out of fuel yes my fault didn`t check to see if it had any, all sounds good and pulls well but has a bit of a nosiey vanos which i`ll have to get sorted at some point.

should be back with me on Monday to get on and start sorting stuff out.

[Baz666]

[ImysE30]

Looks right at home Baz

[baptie0]

Nice one Baz

[Baz666]

Thanks guys, got my tech2 kit to get on and the sports interior to put in get it insured and taxed all next week and were good to go.