3.62 Limited Slip Differential

[jmflukeiii]

Originally Posted by stega

You must be excited.. I know I was. Shit is ridiculous first time you get to rev it all the way. And the exhaust sound from 5.5k up is simply amazing.

I am excited. I'm sick of being so cautious about how high I run the engine. It makes me have a sort of uneasy feeling about driving, not making me perfectly comfortable in the car because I'm always worried about where I am on the tach. As you know, the car starts to rev pretty damn quick once at 4k. So i'm excited to just have the car and all its power available

[jmflukeiii]

Originally Posted by SehrSchnell

Going 80 mph with my 4.10 diff bumps the RPM's up to around 3.5K... not too bad if you ask me.

@jmflukeiii: The pulley only really adds power in your very high RPM's... so you gotta flock it hard in order to feel it. It's a nice mod.. and most of some aren't really expensive, I think the Dinan one is around $800...

Drone doesn't play a role with a new diff... if you have the right exhaust set-up. Basically if you had drone before the new diff - you'll have drone with the new one as well, otherwise you'll be fine.

As for the pulley, of course it would be Dinan. I only will accept Dinan parts on my car.... and the pulley is very cheap, maybe $700 with install. But like you said, I'm going to hold off. I'm probably just doing the intake and differential to get the badge and then probably through a pulley on when I get that itch again to do something.

And that was exactly my thought about the RPM.... in a car with an 8600 red line, who cares if you're at 3750 (I think thats where the 3.65 puts you) versus 3500 at 80..... there's plenty of room left.....

[stega]

Originally Posted by jmflukeiii

As for the pulley, of course it would be Dinan. I only will accept Dinan parts on my car.... and the pulley is very cheap, maybe $700 with install. But like you said, I'm going to hold off. I'm probably just doing the intake and differential to get the badge and then probably through a pulley on when I get that itch again to do something.

And that was exactly my thought about the RPM.... in a car with an 8600 red line, who cares if you're at 3750 (I think thats where the 3.65 puts you) versus 3500 at 80..... there's plenty of room left.....

I will do a highway run later today and tell you my rpm in 7th @80mph...

[jmflukeiii]

Originally Posted by stega

I will do a highway run later today and tell you my rpm in 7th @80mph...

Awesome, yeah I'd be interested to know instead of just throwing out estimated calculations

[pbonsalb]

Just plug your diff, tires and gear into the RPM/MPH spreadsheet here:

http://www.diffsonline.com/techinfo/index.shtml

Those with DCTs will be able to do only 6 gears at a time, but for this discussion, the issue seems to be just one gear, the top gear, and that can be plugged into the 6th spot even though it is the 7th gear.

[stega]

Originally Posted by jmflukeiii

Awesome, yeah I'd be interested to know instead of just throwing out estimated calculations

Sorry did not get a chance yesterday. I am going to get in my car and whip turns right now for a bit and will test the rpm in 7th @80 and report back.


Ok went for a ride. 7th gear 80mph I am at exactly 3500 rpm...

[jmflukeiii]

Originally Posted by stega

Sorry did not get a chance yesterday. I am going to get in my car and whip turns right now for a bit and will test the rpm in 7th @80 and report back.


Ok went for a ride. 7th gear 80mph I am at exactly 3500 rpm...

I forget and am too lazy to look at the other thread... do you have an LSD or not? I seem to remember you saying you were going to get the 3.45.... sorry

EDIT: I went and looked. You do have a 3.45, but is that from Dinan? You didn't write Dinan in front of it like your other Dinan stuff. So I'm still thinking 3750 maybe for the 3.62 at the same speed... or am i way off?

[tlv]

Related to the previous posts - anyone have any thoughts on the below e90 M3 upgrades. I've read the various posts regarding "overreving" with the 3.62 FD, and that the Dinan software doesn't correct for this (?). I have not found anything regarding whether this issue has been corrected, on Dinan's webpage or any other posts/internet sources. And there still seems to be conflicting information on whether this is a good way to go (?). Does anyone have any recent information about this, or have a new opinion? I'm like 3.62 (14.9% torque increase), and think it would offer the "response," I am looking for, but wouldn't want to sacrifice engine life? Here are the the mods considering:

HP Torq
Base 414 295 Dinan Cost
Trottle Body 7 5 $2,499
PerfTuning 9 8 $999
BMW middle 23 21 $2,699
Drive Pulley 11 7 $549
Total: 464 33
FD 3.62 (14.9%) $2,999
Total Gain & Cost: 464 386 $9,745

[arter]

That's about the cost of the VT1-535 ESS tune installed. ( 535Hp plus).

Sorry but couldn't help but insert that option......

[swamp2]

Originally Posted by stega

The diff for sure make a difference in low end acceleration.

Uhhh no, it does not. Did you read the threads in the links rldzhao provided? A FD mod may get you one tenth to 60. ONE TENTH. It is basically in the noise or a drivers race.

FD mods can make a car feel faster but not really faster by any significant amount.

There has not been a single instrumented and statistically significant test showing any real world gains from FD mods for this car. Just a lot of folks justifying their huge expenses with "it feels awesome" "X % more torque", etc.

There is no such thing as a free lunch. If all a FD did was to give you more wheel torque you would simply increase it to some absurd level and have a magic car with infinite (or near infinite) wheel torque. Until you understand why this does not work you shouldn't waste your money. Hint it is not just mpg as to why the OEMs do not do this. It is about time averaged power.

Get some pulleys or a cat delete or software, these are the biggest bang for the buck mods that will give more power and thus more performance.

[RichMattB]

Get out of here with that technical mumbo jumbo. I don't wanna hear that...I wanna spend 3g's and feel more TORQUE!

[RichMattB]

Originally Posted by tlv

Related to the previous posts - anyone have any thoughts on the below e90 M3 upgrades. I've read the various posts regarding "overreving" with the 3.62 FD, and that the Dinan software doesn't correct for this (?). I have not found anything regarding whether this issue has been corrected, on Dinan's webpage or any other posts/internet sources. And there still seems to be conflicting information on whether this is a good way to go (?). Does anyone have any recent information about this, or have a new opinion? I'm like 3.62 (14.9% torque increase), and think it would offer the "response," I am looking for, but wouldn't want to sacrifice engine life? Here are the the mods considering:

HP Torq
Base 414 295 Dinan Cost
Trottle Body 7 5 $2,499
PerfTuning 9 8 $999
BMW middle 23 21 $2,699
Drive Pulley 11 7 $549
Total: 464 33
FD 3.62 (14.9%) $2,999
Total Gain & Cost: 464 386 $9,745

To respond, I don't have any information about how a shorter final drive ratio would cause you to overrev, per se. Your redline and fuel shut off (absent the Dinan remap) remains the same as it was prior to changing your rear end.

You will spend more time at a higher RPM point than you would with the OE gears, but that doesn't equal overrev. It just means that you will use more gas and potentially wear the engine (a little) faster.

No one asked my opinion, but I don't think that the torque modification you get from the shorter gears is worth the fact that you will be able to spend less time in each gear, necessitating more shifting if you are trying to get a faster quarter mile time or whatever. On a real track, I think there are some benefits because you can take advantage of that extra torque when coming out of corners, etc. But in a straight line speed competition, like swamp said, you arent gaining much with the rear end. You are better off getting the pulley, a filter, the x-pipe, and getting a good tune to maximize the benefits from your mods. I would skip the gears and the throttle bodies.

Also, for the middle, you may want to look at a Turner test pipe. I think its like $399.

[eeeboy]

My biggest complaint was the kick down over rev..however, recently BMW called me about a recall for DCT software. Now the kick down problem is gone...sweet

[FVM3]

Why the slip differential will affect the rev ? I am noob about this but really like to know

[bchang2001]

Originally Posted by eeeboy

My biggest complaint was the kick down over rev..however, recently BMW called me about a recall for DCT software. Now the kick down problem is gone...sweet

are you talking about the rev limiter? do you happen to know which DCT software you got? thank you

[eeeboy]

Not sure which one, but Crevier BMW called me and made me bring it in. Now when I gun it, the RPM needle doesn't bounce of the rev limiter.

[cloud8r]

Just wanted to chime in. Dinan has always been quick to return my emails when I had questions about their products. Yet every time I've contacted them about potential dct issues or possible firmware upgrades for the dct when paired with their LSDs, I get zero responses.

[tlv]

Originally Posted by ramyar

Just wanted to chime in. Dinan has always been quick to return my emails when I had questions about their products. Yet every time I've contacted them about potential dct issues or possible firmware upgrades for the dct when paired with their LSDs, I get zero responses.

Me Too!!! - On three (1, 2, 3) different occasions I've inquired about the same potential "issue," and No/Zero Response! - WTF ?

[klammer]

Think the 3.62 would be too much, get the 3.45. Have over 20k on it with over 15 track days as well and have had zero problems and really love it for city and track driving. Personally think the 3.62 is pushing it and think the 3.45 is more than enough. Btw, "worth it" is a reactive term.

[klammer]

Meant relative, not reactive, but it is that as well.

[cloud8r]

Originally Posted by tlv

Me Too!!! - On three (1, 2, 3) different occasions I've inquired about the same potential "issue," and No/Zero Response! - WTF ?

Bummer so that implies that there is indeed an issue with the 3.62. Pretty shady for them to not acknowledge it though. Wouldn't have expected that from Dinan. Kinda lessens their credibility to me.

[tlv]

Originally Posted by klammer

Think the 3.62 would be too much, get the 3.45. Have over 20k on it with over 15 track days as well and have had zero problems and really love it for city and track driving. Personally think the 3.62 is pushing it and think the 3.45 is more than enough. Btw, "worth it" is a reactive term.

Thanks, appreciate your response/experience ! - and good to hear you like the 3.45 - still researching options, but probably looks like the 3.45 is best way to go.