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View Full Version : Has anyone run a 3.91 LSD in their tracked E36?


Nolimit77
07-03-2012, 04:30 PM
As title states... Has anyone run a 3.91 LSD in their track car? I have found during the last 4 events I have done that my car is needing a higher gear. Currently I have a 3.15 LSD in my car and it has been a very good upgrade, but it seems I am still out of the powerband of my motor during 3rd gear corners, especially at TMP. I found the same thing at shannonville but it was not quite as bad. My only concern is running out of gear on the TMP/Shannonville straights which are 4th gear. Mosport is of no concern as 5th gets me to 215KPH and with my lightly modified motor, I won't be seeing those numbers anyways. So far, I have done mid 1:23's at TMP and I am looking to take the GT2 track record during this weekends OTA event but to do so, I need a little more. In preparation for this weekends event, I have so far removed the complete A/C system, AUX fan, fan clutch and installed a SPAL electric fan kit. Along with all of that, I will be finally installing my M50 manifold w/tune! *wiggle*

Btw, I am only looking for first hand experience as I have already done my research and know what numbers(speed wise) to expect! This is a track only car.

Thanks in advance!

sb_600
07-03-2012, 05:10 PM
Yup, that's what I've got in my car.

I love it - I basically always run 3-4-5, and never have to drop to 2. With my motor (built M52 - 232WHP), I don't run out of gear at Calabogie, Shannonville, and just BARELY at Mosport on a good run, but nothing serious .... watch some of my vids and you'll see my shift points.

sb_600
07-03-2012, 05:15 PM
This year -

CMP Short Track:

<iframe width="560" height="315" src="http://www.youtube.com/embed/Dg3DuZVU5MQ" frameborder="0" allowfullscreen></iframe>

ASE (Autodrome Ste-Eustache):

<iframe width="560" height="315" src="http://www.youtube.com/embed/EuqPuYIoRGI" frameborder="0" allowfullscreen></iframe>

Last Year -

CMP Long Track:

<iframe width="560" height="315" src="http://www.youtube.com/embed/Mbj-XJMB7ZA" frameborder="0" allowfullscreen></iframe>

Shannonville Long Track:

<iframe width="560" height="315" src="http://www.youtube.com/embed/My8VG_zyj4I" frameborder="0" allowfullscreen></iframe>

Nolimit77
07-03-2012, 05:29 PM
Thanks for the response! :) I wasn't worried about topping out in fifth, just 4th gear. Having to shift to 5th before turn one at TMP or after the back straight at SMP would not be good but judging by what your saying, I should still be ok.

Btw, what time have you done at SMP Long? I just did a time attack event a couple weeks back and managed a 2:03.8.

Nice vids too!!

sb_600
07-03-2012, 05:36 PM
I've only ever been to shannonville twice, and it's never been a timed event. On that vid I think my best is a 2:02-2:03, just judging by the clock at the bottom lol... i didn't have many (if any) clean laps - always stuck in traffic, a couple drifts...

Last year I was sitting at around 2500lbs (plus me and the passenger), on 255/40R17 starspecs

If you watch my SMP video starting at 7:45, you'll see that I lied lol. I take that tight corner in 2nd, then do 2-3-4-5 on the back straight - you'll see there's lots of room to keep accelerating before the downshift back to 4th for the right-hander.

Again, not "declaring the law" for how to drive that track, as I don't have much experience on it.

Nolimit77
07-04-2012, 01:58 PM
Wow, 2500LBS is light! Right now I am sitting at around 2820LBs without me but I have another 60LBS to go to be optimized for my class.

If I go with the 3.91, I will be sure to update this thread with my findings!

Discostar
07-04-2012, 07:01 PM
Yup, that's what I've got in my car.

I love it - I basically always run 3-4-5, and never have to drop to 2. With my motor (built M52 - 232WHP), I don't run out of gear at Calabogie, Shannonville, and just BARELY at Mosport on a good run, but nothing serious .... watch some of my vids and you'll see my shift points.

Is that a large case, or medium case your running?

If its the med case, have you had any issues with boiling the fluid or durability?

sb_600
07-05-2012, 11:09 AM
It's a medium case.

According to this: http://forums.bimmerforums.com/forum/showthread.php?t=1650106, only the euro M3 has a large case diff.

No I've never had any issues, and I don't even run a finned cover. I had Royal Purple 75W140 in it for the past 2 years (before that was OEM fluid). Last year the input seal started leaking and I changed the fluid this year to Redline 75w90.

When I bought the car in 2005, the diff was already in, and it's now on it's 4th season of autocross/track and still holding strong!

Discostar
07-05-2012, 06:31 PM
It's a medium case.

According to this: http://forums.bimmerforums.com/forum/showthread.php?t=1650106, only the euro M3 has a large case diff.

Yes, we never got the large case in the E36 over here. But both the 7 series and M5 came with large case diff in North America, and many people swap it over. There are a few ways to do it.

Either way good to hear the Med case is holding up. That will prolly be the route I end up going anyway.

doogee
07-05-2012, 09:22 PM
Only info I have to provide is that I run out of gear for a few seconds at Mosport with a 3.73.

Nolimit77
07-05-2012, 10:25 PM
Only info I have to provide is that I run out of gear for a few seconds at Mosport with a 3.73.

How much power are you making and what wheel/tires sizes?

Using a 3.91 I would top out at 215KPH and I don't see that happening..

doogee
07-05-2012, 10:27 PM
Power I'm not positive of. It a fairly stock S52. No more than 270 crank.

Tires are 225/40/17 Hoosiers.

I top out around 200

BMXWill
07-06-2012, 01:14 AM
^I thought you were in the 210-215 range from where I was sitting.

doogee
07-06-2012, 08:16 PM
^I thought you were in the 210-215 range from where I was sitting.

I guess I need to pay more attention lol.

According to diffsonline, I should top out around 215. So maybe I'm wrong. Either way, I don't like having the motor at 7000rpm for the amount of time it sits there.

LVP
07-07-2012, 10:43 AM
Same as doogee. I ran the 3.91 lsd. Great on the shorter tracks, but at Mosport, I was running the car hot and topped out on the back straight. The my oil temps were also a lot higher, as I ran it near the top range all the time. I pulled it and I'm now running a 3.23. I believe the 3.46 is the sweet ratio for this car.

ScotcH
07-09-2012, 11:04 AM
3.73 all the way if you're choosing an all around ratio.

sb_600
07-09-2012, 11:13 AM
Tires are 225/40/17 Hoosiers.


Better driving + shorter tires must be the difference... I run 245-255/40R17s

It'll be fun to compare on Thursday :)

craz azn
07-09-2012, 11:27 AM
Better driving + shorter tires must be the difference... I run 245-255/40R17s

It'll be fun to compare on Thursday :)

Oh SNAP! lol!!

sb_600
07-09-2012, 11:28 AM
LOL I meant better driving on Kurt's part, :P I still have a lot to learn :)

Nolimit77
07-09-2012, 11:33 AM
Well, I think I have my answer based on this past weekends OTA event at TMP. If I were to switch to the 3.91, I would have to shift into fourth through the short shoot before the chicane which would not be ideal. Good thing I didn't make the move on the diff before the weekend. I was however able to remove my fan clutch, AUX fan and A/C before the weekend and I bettered my PB by a few tenths. Now sitting at a 1:23.3 In the next couple weeks I will most likely try out a 3.38 LSD and see if there is an improvement along with the M50 manifold swap.

Anyone else here have times from TMP?

craz azn
07-09-2012, 11:50 AM
LOL I meant better driving on Kurt's part, :P I still have a lot to learn :)

Haha you sure? :P

Anyways, those tires he runs are about the same as yours no? They are the 225/45 Hoosiers... same as the Contis. They have about the same diameter as the 245 Contis, give or take a 1/4"

Well, I think I have my answer based on this past weekends OTA event at TMP. If I were to switch to the 3.91, I would have to shift into fourth through the short shoot before the chicane which would not be ideal. Good thing I didn't make the move on the diff before the weekend. I was however able to remove my fan clutch, AUX fan and A/C before the weekend and I bettered my PB by a few tenths. Now sitting at a 1:23.3 In the next couple weeks I will most likely try out a 3.38 LSD and see if there is an improvement along with the M50 manifold swap.

Anyone else here have times from TMP?

I've also done a 1.23.3 at TMP, but it was my second time ever driving there, and in a car I literally jumped into and was forced to get a lap time within 3 laps. I am sure with at least a session of practice I could have gone faster. It was a 97 328is with TCK coils and super heat cycled out Yoko slicks (and a 3.23 diff FYI). I probably could have gone faster on R comps right out of the box as those slicks take a few laps to heat up :(

sb_600
07-09-2012, 11:59 AM
Haha you sure? :P

Anyways, those tires he runs are about the same as yours no? They are the 225/45 Hoosiers... same as the Contis. They have about the same diameter as the 245 Contis, give or take a 1/4"



Then it's even more about the driver!

Nolimit77
07-09-2012, 01:31 PM
Haha you sure? :P

Anyways, those tires he runs are about the same as yours no? They are the 225/45 Hoosiers... same as the Contis. They have about the same diameter as the 245 Contis, give or take a 1/4"



I've also done a 1.23.3 at TMP, but it was my second time ever driving there, and in a car I literally jumped into and was forced to get a lap time within 3 laps. I am sure with at least a session of practice I could have gone faster. It was a 97 328is with TCK coils and super heat cycled out Yoko slicks (and a 3.23 diff FYI). I probably could have gone faster on R comps right out of the box as those slicks take a few laps to heat up :(

Interesting, I have an option to go to the 3.23 but I don't think it is enough as I am currently using a 3.15. My car is running on 255 Hankook RS-3's and OEM shocks/H&R spring setup due to the class I am in. Unfortunately I haven't optimized the car yet due to lack of funds but I won this past event by 1.1 seconds(2nd place guy was also driving my car) so I am very happy to say the least. Track record for my class is 1:22.7 and next time we go, I plan on changing that! *th-up*

On a seperate topic, anyone ever have a belt shift in their tire? It was the only problem I suffered the entire event- seems like the left front just gave up completely due to being run consecutively all day. Started to get a big vibration on the straight and even more when turning right so we swapped it to the rear and I had less vibration in the steering wheel but more in my butt. Was able to go quicker once we did the swap but I still felt nervous through turn 1-2.. Thinking of just going with a new set seeing as how mosport is the venue for our next event. :eek:

craz azn
07-09-2012, 05:59 PM
On a seperate topic, anyone ever have a belt shift in their tire? It was the only problem I suffered the entire event- seems like the left front just gave up completely due to being run consecutively all day. Started to get a big vibration on the straight and even more when turning right so we swapped it to the rear and I had less vibration in the steering wheel but more in my butt. Was able to go quicker once we did the swap but I still felt nervous through turn 1-2.. Thinking of just going with a new set seeing as how mosport is the venue for our next event. :eek:

I had a belt shift on some Kumho street tires that I ran on my old E30... It happened at Mosport, and seemed to happen almost instantaneously (almost from one lap to another). I didn't know what it was at first, I figured maybe the wheel was loose or something because it was way worse than a missing wheel weight. It developed a bump on the inner section of the thread, about half way around the wheel. Interesting experience, but I didn't feel confident driving on that set anymore so I just gave the 3 remaining ones to a buddy to drift on. Definitely recommend to get a new set of tires for a higher speed track like Mosport.

doogee
07-10-2012, 03:26 AM
Better driving + shorter tires must be the difference... I run 245-255/40R17s

It'll be fun to compare on Thursday :)


Racewars. It's on. Lol :D

sb_600
07-10-2012, 11:41 AM
I can't wait - My parts are being overnighted from Japan as we speak.


;)

doogee
07-10-2012, 12:10 PM
I can't wait - My parts are being overnighted from Japan as we speak.


;)

Perfect. Hopefully I can get my diamond plate floor riveted back in by Thursday. It mysteriously fell off in a previous battle.

sb_600
07-10-2012, 12:29 PM
Too much boost!!!

craz azn
07-10-2012, 12:32 PM
Be careful of the welds on your intakes guys!

exbmwtech
07-10-2012, 12:43 PM
No granny shifting

sparf328
07-10-2012, 10:06 PM
http://www.youtube.com/watch?v=X1IE-ERnEBw&feature=fvwrel

lmao

doogee
07-10-2012, 11:54 PM
<iframe width="640" height="360" src="http://www.youtube.com/embed/X1IE-ERnEBw" frameborder="0" allowfullscreen></iframe>

lmao

That will definitely be the scene in the paddock around 5pm.

sb_600
07-11-2012, 11:04 AM
Someone's going to owe someone a 1:3X car ;)

sb_600
07-14-2012, 12:33 PM
And the results:

http://www.maxbimmer.com/forums/showthread.php?p=1574839#post1574852