3.23 lsd with m30 conversion?

[blingsta]

would this ratio be any good?

[leeparkes]

I think winx is running one on his M30

[winx]

think mine is a 3.25 from an M3, it's a bit long really... Great for cruising around and should get half decent economy. I find second isnt great for fun on roundabouts and 1st isnt long enough, judging by a trackday though I reackon it would pull to 150 easily and probably beyond.

[blingsta]

So I take it the best and ideal ratio would be 3.64 or 3.46

[ImysE30]

3.64 quicker acceleration and top speed

3.46 better for all round driving i believe

I've got a standard 3.46 diff still in the box

[DRIFTBOY]

3.64 quicker acceleration and top speed

Now that is having your cake and eating it, but sadly not true!

The 3.64 will get through the gears slightly quicker, the 3.46 will give a slightly higher top speed (I suspect that's what you meant Imy).

There is only 5% difference in these two ratios though, so 100mph with the 3.64 will work out 105mph with the 3.46, not a lot of difference at all, so it won't radically change the car!

[zaust]

On a 3:64 lsd at the moment, But i'm after a 3:46 lsd too. I'm on the motorway when i'm not spanking it, so the 46 is better for sitting at motorway speed's and still gives short enough gears to have some fun with.

[ImysE30]

3.64 quicker acceleration and top speed

Now that is having your cake and eating it, but sadly not true!

The 3.64 will get through the gears slightly quicker, the 3.46 will give a slightly higher top speed (I suspect that's what you meant Imy).

There is only 5% difference in these two ratios though, so 100mph with the 3.64 will work out 105mph with the 3.46, not a lot of difference at all, so it won't radically change the car!

Yeah something like

Tend to get mixed up between the 2

[Ziggy]

3.64 quicker acceleration and top speed

the 3.46 will give a slightly higher top speed (I suspect that's what you meant Imy).

Only if it's got the power to hit the rev limiter (or at least get past peak power!) in top on a 3.64 surely - I've never tried but I'd be surprised if it'd manage that!

[Rav335uk]

I've gat a 3.46 on mine, and it will still hit 60 in just over 6 secs, and top end will be beyond 150mph , I have tried it(on private land of course)
I might try a 3.64 or have a go in Lees as he's just finighed his and see the difference.

[DRIFTBOY]

3.64 quicker acceleration and top speed

the 3.46 will give a slightly higher top speed (I suspect that's what you meant Imy).

Only if it's got the power to hit the rev limiter (or at least get past peak power!) in top on a 3.64 surely - I've never tried but I'd be surprised if it'd manage that!

Good point, very true.

And anyone who has tried to max out a 5-speed Capri 2.8i will know all about that!
They have stupidly long gears, they won't even hit the limiter in 4th!

But for a given speed the engine will be revving slightly less, so a little better for (non-flat out) motorway cruising.

[gareth]

i'm (veeeery slowly) building up a 3.38:1 LSD, using the CWP from a wierd E34 525ix diff.
i get the feeling that gearing is not such an issue with a M30 as they pull about the same in any gear. i do know that a 3.91 is bloody annoying and anything over 70mph feels like i'm trying to kill it to death!
with a 3.91 on, i can hit the rev limiter in 5th which is a GPS verified 132mph (145 on the speedo) and before anyone complains, that was on the 'ring, around a corner
it does pull very hard into the limiter though so has plenty of balls left. oh, and when i did that, i had a broken inlet gasket blocking half of number 1 inlet port can't fail to be better now surely
so with the 3.38 and no increase on my rev limit (5750rpm on an auto ecu?), it should be good for 152mph

[Rav335uk]

~Somebody did do all the calcs for me on here, with tyre sizes, g/box, and diff size.
All in all, it was 0-60 6.4 secs and top end of 162mph.
But due to the box shape of the car, i'll be happy to get 150mph

[Jon_Bmw]

3.91 is the diff for a track car. I bet that would be fun.

[DRIFTBOY]

3.91 is the diff for a track car. I bet that would be fun.

Yes, but as first gear is next to useless it is effectively a four speed gearbox!

[Rav335uk]

Blinsta maaaaan,
It will not be ok if your going to boost up the engine , but a n/a engine its short, depends on how or what you use the car for

[gareth]

3.91 is the diff for a track car. I bet that would be fun.

Yes, but as first gear is next to useless it is effectively a four speed gearbox!

i wonder if there are any benefits to be had by changing gearboxes? i have no idea what the ratios are but mine has a E34 530 box fitted.

[Jon_Bmw]

3.91 is the diff for a track car. I bet that would be fun.

Yes, but as first gear is next to useless it is effectively a four speed gearbox!

I have never ever used first on any gearbox on track, bar using it to start the first warm up lap. By having a too long ratio, a la 2,93 or something, you will make it a 3 speed box, as 1st and 5th won't be used!

[DRIFTBOY]

3.91 is the diff for a track car. I bet that would be fun.

Yes, but as first gear is next to useless it is effectively a four speed gearbox!

I have never ever used first on any gearbox on track, bar using it to start the first warm up lap. By having a too long ratio, a la 2,93 or something, you will make it a 3 speed box, as 1st and 5th won't be used!

I see your point, especially if talking track cars, but as Gareth said, the torque curve of the M30 makes higher gears far more useable than with the higher revving screamers!

There will always be corners , and whole tracks even, that suit a certain car with certain gearing over a taller or shorter geared car.
There are advantages and disadvatages with both, depending on when and where they are used.

Racing teams have gear sets for each track, us lot just have to make do with finding a happy medium that suits us I suppose!

Horses for courses and all that, I don't think there can ever be a right or wrong.

[gareth]

just do what i do when i'm being lazy... treat 3rd as 'drive' on an auto box. i can go everywhere and do any sesnible speed in 3rd! bloody quickly too

i do enjoy overtaking people at a fair rate without bothering to downshift from 5th

[Jon_Bmw]

Agreed Martin. I am just a short diff hooligan.

[Driftben]

in which BMW had that 3.91 diff?

[gareth]

most late 325i's afaik

[Driftben]

Lovely I'll have to keep my eyes peeled for one of them. Or a LSD with a similar ratio?

[gareth]

just noticed your sig... a 3.91 will be far to short geared with a blower

aaaanmnway, i've not seen and details on your conversion on here, what's the score? do you have a build thread on here or any pics?

[Driftben]

Well I'm slowly battling through the build. And taking pics as I go. I'm not so good at making a build thread. I have kind of got one but just need to get my rear end into gear and update it. I'm a-shamed

What sort of ratio would be best for my build?

[gareth]

i'm guessing a 3.25 would be about right... you'll have an absolute gob load of torque to play with so short gearing will only end up in smokey tyres

might be worth looking what toby unna ran on his M30B35 turbo

[DRIFTBOY]

Toby was running a 2.93:1 open diff.

I'm running a 2.93 slipppaaahhhh!

Although I've not tried it properly in mine yet, Toby's wasn't exactly sluggish under acceleration!

There is a short video that Toby took of it in 3rd and 4th gear on here somewhere but the STUPID search function on here won't find it!

[TheMoose]

No hijack of post intended.

Will a M88 engine from the E28 M5 match nicely with a 2.93:1 lsd and a Getrag Sport Box 265/5?
Alpina in South Africa matched the M30b32 with the 2.93:1 lsd and the Getrag Sport Box 265/5. The car is an absolute blast to drive!

[Driftben]

Oh wouldn't a slipper be nice .

Maybe a slightly shorter ratio as I do like to make them lines
Wouldnt mind seeing the turbo m30. Interested to see how it goes.

Sorry for the hijack by the way. I'll rub your feet later.

[DRIFTBOY]

I found it!

http://smg.photobucket.com/albums/v334/ ... 020824.flv

Now working!

[TheMoose]

No hijack of post intended.

Alpina and BMW Motorsport South Africa matched the M30b32 with the 2.93:1 lsd and the Getrag Sport Box 265/5. The car is an absolute blast to drive!

Sorry for incorrect info, now corrected as above.

[Driftben]

That's too much practice you have on the search button driftboy

[DRIFTBOY]

The link is working now, my internetz is going reeeaaallly slllooowwwly tonight, so it's taken me ages!