Differential Time, 3.91 vs 4.10 on 6 speed ZCP

[0-60motorsports]

Bumping this thread up. I have 3.91's on the M3 and misplaced my stock 3.62's. Finally found a set of 3.62's and will be installing them, really thinking i should pair that with a wavetrac as I getting a good deal on it.

With the wavetrac they recommend New diff output flanges which I see no reason to do. Any of you using the wavetrac and 3.62 combo? I really like the point Obioban made about the wavetrac.

Anything else I should change while doing this job? I got output flange seals and all new OE diff bushings as well.

[bigjae46]

You can consider a 4.44 also if only doing track

With a 4.44 3rd gear almost becomes like 2nd gear. Wouldn't a 5 speed with a 3.91 be better for track use?

For reasons I can't explain and I'm sure someone else can and I know I risk sounding like a retard (can I even say that anymore?) ...but there is a certain gear that feels like the car pulls harder. In my E90 M3 DCT...its 4th gear. It just feels insane above 5k rpms to redline. Kind of the same for the E46, 4th gear. Then 5th gear always feels kind of lazy, likely due to increased drag but I would imagine 6th gear would be worse?

[youngblood750]

It depends. I like short gear ratio but at my local track (Le Circuit Mont Tremblant), depending of tires diameter and lap time, with my 4.10 I would need to get into 5th gear after corner 7 for like 200’ than brake and get into 3rd for corner 8. With 3.91, I would stay in 4th after corner 7 until corner 8 braking zone. So 4.10 was good before when I was slower but doing the track under 1:50 it would sucks.

So gear ratio depends also on the track, your speed and your tire diameter to match the curves.

I would say 3.91 usually is a safer choice. It was always fine for me with a 3.91 on the main 5 tracks I was doing. But I prefer shorter gear ratio like 4.10 for feeling!

You can consider a 4.44 also if only doing track

well, sound like I have to improve my skill first.

4.44 seems too extreme. I have to drive on the regular high way to the track

[Gt4]

So, there is no definitive answer for this topic. I have been wondering for long time which Final drive ratio is better for me. well, I drive my car mainly on the track. only one track I drive. and I only use 3rd , 4th gears for the track. even the longest straight, 4th gear hit the maximum speed. in this case, is it bettter changing Final drive into 3.91 or 4.1 than stock gearing?

It depends. I like short gear ratio but at my local track (Le Circuit Mont Tremblant), depending of tires diameter and lap time, with my 4.10 I would need to get into 5th gear after corner 7 for like 200’ than brake and get into 3rd for corner 8. With 3.91, I would stay in 4th after corner 7 until corner 8 braking zone. So 4.10 was good before when I was slower but doing the track under 1:50 it would sucks.

So gear ratio depends also on the track, your speed and your tire diameter to match the curves.

I would say 3.91 usually is a safer choice. It was always fine for me with a 3.91 on the main 5 tracks I was doing. But I prefer shorter gear ratio like 4.10 for feeling!

You can consider a 4.44 also if only doing track

[M3dragon]

Forgot I went 3.91 for CSL build

[M3dragon]

3.91 is still 2 changes to 60 while 4.10 is 3. So you will be working more at the start with 4.10 but on the same side once rolling you will get a bigger punch

[youngblood750]

So, there is no definitive answer for this topic. I have been wondering for long time which Final drive ratio is better for me. well, I drive my car mainly on the track. only one track I drive. and I only use 3rd , 4th gears for the track. even the longest straight, 4th gear hit the maximum speed. in this case, is it bettter changing Final drive into 3.91 or 4.1 than stock gearing?

[EthanolTurbo]

Awesome, thank you guys. Will probably be one of the last weight reduction mods I do. I'm at about 3200 lbs right now and will be down to 3100 hopefully soon.🤙

[Obioban]

I removed everything, including all stock stereo wiring, and just installed an Avin and plugged two super light speakers into it’s internal amp. Custom harness was really just a harness so the chassis plug works with an Avin adapter plug, so I can plug and play other head units in the future.

[repoman89]

Could you ever di a quick guide on the wiring harness and stereo stuff that's safe to remove? I know you said it's very tedious to remove, would just like some pointers on where to start and how.

Start by removing the entire interior, including dash, rear carpet, rear shelf (headliner can stay). I did something similar (nav to non-nav including wiring harness -- probably 20 pounds saved plus ~7 for trunk sub delete. The 50 pound figure must include pretty much all of the speakers, nav stuff including the full harness isn't THAT heavy). It's not hard or really even that time consuming, I probably spent 10-12 hours total. It will be obvious what can be removed once you're in there, and you have to get in there either way. This was a useful reference for me: http://www.diymybmw.com/e46/bmw-169-...-nav-retrofit/

Add extra time for making a custom wiring harness as I believe Obioban did

[EthanolTurbo]

Here and there in my build Journal.

The short answer is...
48 lbs of CF roof
50 lbs of battery
62 lbs of seats
50 lbs of wiring harness and stereo reduction
25 lbs of wheels
... and then a bunch of small things that are 1-2 lbs each, but add up when you do a bunch of them (airbox, cabin air filter housing, LATCH points, etc).

Could you ever di a quick guide on the wiring harness and stereo stuff that's safe to remove? I know you said it's very tedious to remove, would just like some pointers on where to start and how.

[Hyperboost]

Did you have Nick tune the car? He did the tuning on the Emtron, on my 2.7L DTM level S14 with slide throttles, and it drives like an OEM tuned it. He is amazing.

T

Of course he is the one who tuned it. He is easily the top 10 tuners in the US. He is not all about top dyno numbers but more about good power and safety and drivability. I made 358RWHP with all of my hardware IIRC. I have to look back at the dyno sheet. It was on DynoJet as well.

[Mr. Wolfe]

I remember having 4.10's. Was cool at first and then quickly realized 1st and 6th gear sucked compared to stock.

Mr. Wolfe

[///Mangler]

I mostly run on tracks that's longer than 1.5miles so I should be fine there. I am going to call Dan@Diffsonline to see what he recommends since I barely see the street with my car.

8500 Rev Limit is set regardless of the track. With EmTron and the safeties built in it, I could run it up there all the time. The coolant temp does run hot when it is over 90F surface temp.

Did you have Nick tune the car? He did the tuning on the Emtron, on my 2.7L DTM level S14 with slide throttles, and it drives like an OEM tuned it. He is amazing.

T

[Hyperboost]

I mostly run on tracks that's longer than 1.5miles so I should be fine there. I am going to call Dan@Diffsonline to see what he recommends since I barely see the street with my car.

8500 Rev Limit is set regardless of the track. With EmTron and the safeties built in it, I could run it up there all the time. The coolant temp does run hot when it is over 90F surface temp.