Changin my diff today from 2.92 to 3.38

[Pho3niX90]

So went to Rustenburg the weekend and have to say compared to my previous trips to Rustenburg the fule consumption hasn't increased, or atleast not any noticeable increase, filled up before I went and wen I got there the consumption was around 7.5L/100KM, after I "played" in Rustenburg and drove back it was sitting at 9.0L/100KM. Was cruising there at 120KM in 6th (about 3000rpm) and back was cruising at 160KM in 6th (about 3500rpm), can't remember the rpms.

 

[SP33DYV]

IIRC my ex e46 330i was at 2600rpm at an indicated 120km/h and around 2750rpm at an indicated 130km/h.

 

[moranor@axis]

acceleration graph of a stock e46 323i against a 3.38 ratio:

blue is the 3.38 all other parameters are equal... slight acceleration advantage from ratio change alone but not much... it sure has hell makes the car way more fun to drive and thats what counts the most unless you chasing numbers :rollsmile:

 

[Yuben]

IIRC my ex e46 330i was at 2600rpm at an indicated 120km/h and around 2750rpm at an indicated 130km/h.

Mine at 120km/h revved at approximately 2500rpm with the stock 2.93 ratio and increased to 2900rpm with the 3.38 diff.

 

[sclass]

So in summary this mod is for feel more than anything, zero or marginal gains in accelaration (according to Sean's graph)? Or should this be assessed on a model by model basis? I ask because if the gains are only marginal I'd rather replace my auto with another one rather than do a manual 'box swap + diff only to find I'm going at the same pace.

Sorry for going slightly off topic, feel it's kind of related though :fencelook:. Glad you're enjoying though Phoenix90, that's the main thing :thumbs:

 

[moranor@axis]

auto box alone eats alot of torque....

 

[ChrisBrand]

The Diff-mod has also been tagged as the poor mans supercharger. Just because its one of the mods on a N/A car that is most noticeable.

According to that graph there should not be much difference and should only feel different.

Luckily i had some real world experience with this when freerider still had his e36 328i. I had decatted exhaust, chip and few other mods and he had a shorter ratio diff. Rolling start he instantly opened up a car length on me. We both were very suprised at the outcome.\

Even though the graph doesn't show it it does make a difference. Now to find a 3.46/3.38 diff....

 

[moranor@axis]

graph does not show how much easier it is to drive the car with gear ratios closer together...

best way I can describe it is with the old ratio it felt like it was in the wrong gear the whole time

 

[sclass]

Thanks for your descriptions guys, that sounds good :thumbs:

Diff,M50,and software should completely transform an M52!!

 

[Pho3niX90]

So in summary this mod is for feel more than anything, zero or marginal gains in accelaration (according to Sean's graph)? Or should this be assessed on a model by model basis? I ask because if the gains are only marginal I'd rather replace my auto with another one rather than do a manual 'box swap + diff only to find I'm going at the same pace.

Sorry for going slightly off topic, feel it's kind of related though :fencelook:. Glad you're enjoying though Phoenix90, that's the main thing :thumbs:

I honestly can say the difference you feel is well worth the cash spent, but if I am not mistaking if you have an autobox then you already have a 3.38 diff? Just do the manual swap and you will feel hapiness :rollsmile:

graph does not show how much easier it is to drive the car with gear ratios closer together...

best way I can describe it is with the old ratio it felt like it was in the wrong gear the whole time

Agree, the drive is so much funner and shifting is a delight, snap change makes you grin like a little girl and the torque mocks you if you TRY and drive like a normal human.. When I am off the highway I gunn it the whole time,

When I think back of how the car drived with the old diff it just seems that the bmw had a too long diff for the 6sp box and weight, the 3.38 fits in much better with the rest of the car.


Currently my average is sitting on 9.5L/100KM, that's 80KM a day highway (centurion to sandton) and 10KM hard town driving.

 

[Crash_Nemesis]

Gentlemen, I shall let the following video show you the gains of a diff swap on an e46 M3.

Camera car is stock diff. Middle car is 4.10, and far right is 3.91. ENJOY

[video=youtube]

 

[moranor@axis]

and look at how small the difference is on the graph for the 4.11 vs stock 3.64

 

[osiris]

A diff can make a big difference in off the line acceleration, it also helps you push through the gears faster, your top speed may be affected slightly but you will get to that speed faster.

I changed the gearing on my first Yamaha R6 which is essentially the same as changing the diff in a car and it made a MASSIVE difference. My first gear was much shorter but the acceleration was rediculous, On the race track it was so much better for out of corner acceleration, my front wheel used to lift as I was accelerating out of the corners but it was still smooth acceleration. The only downfall was that the revs sat a bit higher on the highway.

Definately a worthwhile mod :thumbs:

 

[individj]

i am not really clued up on the topic but i am doing a few bmw's currently & i am doing a 330i swop into a 325i both e46 so which diff would be better? am i right in assuming the 325i...when i say better i mean acceleration etc.

 

[moranor@axis]

i am not really clued up on the topic but i am doing a few bmw's currently & i am doing a 330i swop into a 325i both e46 so which diff would be better? am i right in assuming the 325i...when i say better i mean acceleration etc.

e46 330i has a 2.93 diff and the 325i has 3.15 i would stick with the 3.15 or go 3.38...

 

[individj]

thank you. i will leave the diff as is...will now have a 330i diff for sale

 

[Inactive]

not a nice experience......but at least worked out in the end.

Just out of interest, are the bolts on the rear of the diff that broke the standard bolts? They dont look like it.