Opinions on S50B32 with 188 3.15 LSD.

[Alex0607]

Hi all, I am sure a lot of members here who have done an EVO engine swap would have similar setup to mine which is an S50B32 Euro engine mated to a 188 LSD. My LSD was off an M3 3.0L. The reason my setup is such is because I started out with a 3.0L swap. The engine had some issue from start and decided to swap that out and installed the EVO engine instead. Now that everything is working fine, I am just wondering how well the engine and diff work? This is a perfect match? OK match or not a good match? Can I improve on this in terms of acceleration, gear change, top speed and etc? Should I get the 6 speed manual transmission? Use a 3.23 210 LSD? Thanks in advance.

[Jim E.]

Hi all, I am sure a lot of members here who have done an EVO engine swap would have similar setup to mine which is an S50B32 Euro engine mated to a 188 LSD. My LSD was off an M3 3.0L. The reason my setup is such is because I started out with a 3.0L swap. The engine had some issue from start and decided to swap that out and installed the EVO engine instead. Now that everything is working fine, I am just wondering how well the engine and diff work? This is a perfect match? OK match or not a good match? Can I improve on this in terms of acceleration, gear change, top speed and etc? Should I get the 6 speed manual transmission? Use a 3.23 210 LSD? Thanks in advance.

The 188 diff is fine but 3.15 is not the ideal ratio for such a high rpm engine.

For a stock S50B32 with some miles under its belt I would at least use a 3.46 and preferably a 3.64 if it's a healthy engine. If modified then that's a different ballgame.

[Alex0607]

Hi Jim, thanks for your response. I am unlikely going to do any mod to the car to increase the power as I don't have the facility to tune the car after modding. So changing out the diff with a 3.46 or 3.64 will be good for my setup? What sort of improvement will I get? Currently with the setup, I am not feeling the power of the engine translated to the drive. The car feels heavy when I go through the gears. I saw videos of E36 M3 being run through their gears from 0 to 250KPH and I don't think my car can rev all the way up to redline without the car screaming its head off. And I can't seem to spin my wheels from a standstill. Love to do that once in a while. Maybe those cars in the videos have been modded to higher HP. I don't know.

[Alex0607]

OK. Been reading about diff ratio options. Looks like 3.46 is the way to go for me. Now looking for one. Anyone has a set lying around?

[Nugs]

I have a s50b30 with the 5 speed and a 3.91 188 LSD.
It certainly helps with acceleration, not ideal for cruising though, 3500rpm at 100kph.
Might be ok with the 6 speed.

[Alex0607]

3.91 might be too low. It is either 3.46 or 3.64. There is a video on youtube where this guy installed a 3.46 into his E46 and the review was good. I still like the cruising speed at low rpm. Only have 5 speed so got to go in between. The current 3.15 I am using is just isn't fun with 1st gear.

[SPhilly28]

I've got a 3.64 in mine. I wouldn't hesitate at all to go 3.91, but I am 6 spd so it wouldn't be as much of a nuisance on the hwy.

[MauiM3Mania]

I've got a 3.64 in mine. I wouldn't hesitate at all to go 3.91, but I am 6 spd so it wouldn't be as much of a nuisance on the hwy.

Same. It rips.

I should have said, I have the 3.91 and it rips. :-)

[Alex0607]

Good info guys. Now you are making me think. Lol! Changing to a 6 speed would be a possibility some day.

@Maui You have the 5 or 6 speed and on the highway what's your rpm sitting at when going around 120km/hr?

[MauiM3Mania]

Good info guys. Now you are making me think. Lol! Changing to a 6 speed would be a possibility some day.

@Maui You have the 5 or 6 speed and on the highway what's your rpm sitting at when going around 120km/hr?

My six speed (in sixth) runs at about the same rpm as being in 5th gear with a 5 spd and the 3.23 diff. 120k would be over our speed limit.

[SPhilly28]

I go just over 3000rpm jn 6th at 120kph with a 3.64 and 6 spd. If you have a buddy with an E46 M3 take it for a rip to get a good idea on gearing. Very close.

[Alex0607]

My six speed (in sixth) runs at about the same rpm as being in 5th gear with a 5 spd and the 3.23 diff. 120k would be over our speed limit.

Hehe.. On the highway where I am there is a 100kph limit but people rarely keep to that most time. 120kph is the norm or occasionally way more.

- - - Updated - - -

I go just over 3000rpm jn 6th at 120kph with a 3.64 and 6 spd. If you have a buddy with an E46 M3 take it for a rip to get a good idea on gearing. Very close.

With a six speed I guess 3.64 ratio would be a good match. I have driven an E46 M3 but only for a short distance and I think the car wasn't in tip top shape. It's an SMG version and if all SMG's are like what I have driven I am not a fan. So yeah, didn't get to feel the various speeds and rpm.

[kovrol]

I have the 3.64 with 6speed S50B32, I think its the best option for every use in city-highway-track, if you don't want to buy another diffs and change it weekly
I have a 3.46 8lamellen too, its also pretty good for street and better for highway but its wrong for track, 3.91 is better for track but its too much for daily drive if you have a load exhaust like me

[Alex0607]

I am waiting for a seller to get back to me on a 3.46 he has for sale. It will be to replace my current 3.15. Shipping in a whole diff would be too costly.

From all the posts I can say 3.64 is best suited for a 6 speed gearbox while 3.46 is best for a 5 speed gearbox. cool.

[=BA=]

I have done some highway pulls against my buddy. I ran 3.62 gears from a E46 M3 an he ran stock 3.23

On lower speeds its about equal and at higher speeds 3.23 is actually a bit faster. Ie he can do nearly 280 km/u in 5 and I had to upshift to 6th at 250 km/u or so. That is when he pulls a lot better and makes up the diffence.

All in all it feels more sporty but performance wise there is nothing in it. The reason is the shape of the S50B32's torque curve, it peaks between 3000 and 3500. On my car, doing 100-200 km/u is not much faster when I use 3,4 & 5 or when I just use 4 & 5.

And doing 120km/u on the highway @ 2500 RPM is actually nice too when you have a 6 speed.

Other disadvantages are that you are slower from a standing start, less traction and you have to shift earlier.

All in all I would not change it to a 3.62 again.


If you run a 5 speed I would just put the 3.15 on. The difference with 3.23 is not that big and it's really only used to offset the size in stock tire sizes, ie the 245/40/17 on the 3.2L is a bit taller than 235/40/17, the difference in ratio's cancels this out.

[Alex0607]

I have done some highway pulls against my buddy. I ran 3.62 gears from a E46 M3 an he ran stock 3.23

On lower speeds its about equal and at higher speeds 3.23 is actually a bit faster. Ie he can do nearly 280 km/u in 5 and I had to upshift to 6th at 250 km/u or so. That is when he pulls a lot better and makes up the diffence.

All in all it feels more sporty but performance wise there is nothing in it. The reason is the shape of the S50B32's torque curve, it peaks between 3000 and 3500. On my car, doing 100-200 km/u is not much faster when I use 3,4 & 5 or when I just use 4 & 5.

And doing 120km/u on the highway @ 2500 RPM is actually nice too when you have a 6 speed.

Other disadvantages are that you are slower from a standing start, less traction and you have to shift earlier.

All in all I would not change it to a 3.62 again.


If you run a 5 speed I would just put the 3.15 on. The difference with 3.23 is not that big and it's really only used to offset the weight in stock tire sizes, ie the 245/40/17 on the 3.2L is a bit taller than 235/40/17, the difference in ratio's cancels this out.

So that would leave 3.64 out of the question for me. There is a good deal for a 3.23 on ebay but being so close to 3.15 I was against the idea. Hence the thought of going for 3.46 instead. Looks like a sweet spot for my setup.