[choppedliver]

Originally Posted by WretchedRefuse

Would you mind sharing the final drive ratios of the M5 and 550? Also, are the transmission gears the same between the two?

I've never driven an M5 but would love to do an A/B comparison between the M5 and a modded 550 (either JB4 or BM3 Stage 1 plus xHP trans tune.)

Here you go:

2019 M5 Competition
First (:1) 5.00
Second (:1) 3.20
Third (:1) 2.14
Fourth (:1) 1.72
Fifth (:1) 1.31
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 4.17
Final Drive Axle Ratio (:1) 3.15

2021 M550i
First (:1) 5.5
Second (:1) 3.25
Third (:1) 2.20
Fourth (:1) 1.20
Fifth (:1) 1.32
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 3.99
Final Drive Axle Ratio (:1) 2.81

M850i
First (:1) 5.5
Second (:1) 3.52
Third (:1) 2.20
Fourth (:1) 1.72
Fifth (:1) 1.31
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 3.99
Final Drive Axle Ratio (:1) 3.40

The M850i is geared closer to the M5 than the M550i

[choppedliver]

Originally Posted by choppedliver

The ECUMAP seems to offer OTS tunes which is "650hp" but they say "700hp" in the video so I suspect it's a custom tune. Who knows what it's making at the wheels but this seems about as fast you are going on stage 1 custom tune + XHP.

They replied to my comment on the video confirming it's a custom tune.

[WretchedRefuse]

Thanks choppedliver. Are you sure that the figure for 4th gear in the M550i is correct? Anyway, I crunched the numbers to calculate the total torque multiplication for each car in all eight gears. In general, the M850i has more torque multiplication in every gear than the M5 Comp and the M550i has less. This is especially true in gears 1-3. Does this mean anything? Could we get better acceleration by swapping in the final drive gears from an M850i? Or maybe we shouldn't mess with the meticulous tuning done by BMW engineers to calibrate each car's powertrain to its chassis?

[choppedliver]

Originally Posted by WretchedRefuse

Thanks choppedliver. Are you sure that the figure for 4th gear in the M550i is correct?

Ahh, I see 1.67 here.
https://www.caranddriver.com/bmw/5-s...ies-sedan_2016

I think wherever I got the 1.4 from is incorrect.

Nice work on the table!

With fourth at 1.67 the M550i has taller gears and less torque multiplication in each gear. That alone could account for the bulk of why it is relatively slower compared to the M5.

The final driver from an M850i might work, but I've really no idea. I'm sure it could confuse the car.

[choppedliver]

Just looking at the M850i.

Faster than ours and I think heavier from other references. It's all down to that final drive ratio.

https://www.caranddriver.com/reviews...y-the-numbers/

[WretchedRefuse]

That's interesting; 3.3 seconds 0-60 is 0.3 seconds faster than the M550i spec. I assume that changing the final drive ratio would be a matter of swapping the gears in both differentials? Or is it maybe in the transfer case? Regardless, the speedometer would also have to be re-calibrated and who knows what else. I don't recall ever seeing somebody offer that service so maybe it's just not practical. Here's to hoping that somebody clever comes up with a solution.

[M550bernina]

Originally Posted by choppedliver

Here you go:

2019 M5 Competition
First (:1) 5.00
Second (:1) 3.20
Third (:1) 2.14
Fourth (:1) 1.72
Fifth (:1) 1.31
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 4.17
Final Drive Axle Ratio (:1) 3.15

2021 M550i
First (:1) 5.5
Second (:1) 3.25
Third (:1) 2.20
Fourth (:1) 1.20
Fifth (:1) 1.32
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 3.99
Final Drive Axle Ratio (:1) 2.81

M850i
First (:1) 5.5
Second (:1) 3.52
Third (:1) 2.20
Fourth (:1) 1.72
Fifth (:1) 1.31
Sixth (:1) 1.00
Seventh (:1) 0.82
Eighth (:1) 0.64
Reverse (:1) 3.99
Final Drive Axle Ratio (:1) 3.40

The M850i is geared closer to the M5 than the M550i

Where did you find that the M850 has a 3.40 final drive?

Everything I googled shows it's a 2.81 same as the m550.

[choppedliver]

Originally Posted by M550bernina

Where did you find that the M850 has a 3.40 final drive?

Everything I googled shows it's a 2.81 same as the m550.

https://www.caranddriver.com/bmw/8-s...50i-coupe_2020

[M550bernina]

Originally Posted by choppedliver

https://www.caranddriver.com/bmw/8-s...50i-coupe_2020

Ok. Got ya.

I've been trying to find a final drive differential off an M850, but there all 2.81.

[choppedliver]

Originally Posted by M550bernina

Ok. Got ya.

I've been trying to find a final drive differential off an M850, but there all 2.81.

I guess it begs the question. If they are all 2.81 how come the M850i is faster than the M550i?

[M550bernina]

Originally Posted by choppedliver

I guess it begs the question. If they are all 2.82 how come the M850i is faster than the M550i?

I agree the higher gear ratio would make sense of why it's faster.

https://parts.bramanmotorsbmw.com/oe...BoCWrUQAvD_BwE

https://www.bmwpartsnow.com/oem-part...xoCAH0QAvD_BwE

https://www.ebay.com/itm/25601733415...mis&media=COPY

https://www.ebay.com/itm/25601733449...mis&media=COPY

https://www.ebay.com/itm/18557849896...mis&media=COPY

[WretchedRefuse]

Originally Posted by M550bernina

I agree the higher gear ratio would make sense of why it's faster.

https://parts.bramanmotorsbmw.com/oe...BoCWrUQAvD_BwE

https://www.bmwpartsnow.com/oem-part...xoCAH0QAvD_BwE
...

Interesting that the first two links show the same part for both the 550 and the 850. Is the final drive ratio determined by the differential (in which case we would need two) or somewhere else like the transfer case?

[M550bernina]

Originally Posted by WretchedRefuse

Interesting that the first two links show the same part for both the 550 and the 850. Is the final drive ratio determined by the differential (in which case we would need two) or somewhere else like the transfer case?

The gears are in the differential. I'm still working on trying to figure out if I would need the front and rear differential or just the rear.

The other issue I have is, there are not a lot of m850s on the road. I use a website that is designed for body/repair shops to buy parts from salvage yards. Right now they're not showing any m850s and I won't buy from eBay - too expensive.

[M550bernina]

Originally Posted by choppedliver

I guess it begs the question. If they are all 2.81 how come the M850i is faster than the M550i?

I just got off the phone with BMW parts. They ran every m850 model and they all have a 2.81 final drive.

Now back to your question, why the hell is it faster than an m550?

[Manley00]

Originally Posted by M550bernina

I just got off the phone with BMW parts. They ran every m850 model and they all have a 2.81 final drive.

Now back to your question, why the hell is it faster than an m550?

Could simply be in the tune? Motor or trans side…

[M550bernina]

Originally Posted by Manley00

Could simply be in the tune? Motor or trans side…

Could be. I was hoping it came from the final drive in the differential so i could upgrade.

[choppedliver]

Originally Posted by M550bernina

I just got off the phone with BMW parts. They ran every m850 model and they all have a 2.81 final drive.

Now back to your question, why the hell is it faster than an m550?

Apologies for the error. I guess even reputable magazines make errors.

[WretchedRefuse]

We could still in theory swap in the M5 Comp differentials, correct? Maybe they are more available than the 850i.

[M550bernina]

Originally Posted by WretchedRefuse

We could still in theory swap in the M5 Comp differentials, correct? Maybe they are more available than the 850i.

M cars have a special active M differential. I'm pretty confident there's no way we can use one off an M5.

I haven't looked much into the full drive train of an M5, but I know on our engines, there are no parts except for two that are shared. Rods and throttle body. (Although the s63 block starts its life as an n63 block)

[Bsm550]

Maybe the m850 has better aero thats why it is faster

[WretchedRefuse]

The BMW USA web site says that the 0-60 time for the M850i Coupe is 3.6 seconds, and the Grand Coupe is 3.7 seconds. Where did the 3.3 figure come from?

[choppedliver]

Originally Posted by WretchedRefuse

The BMW USA web site says that the 0-60 time for the M850i Coupe is 3.6 seconds, and the Grand Coupe is 3.7 seconds. Where did the 3.3 figure come from?

https://www.caranddriver.com/bmw/8-series