1M Diff and Transmission Specs

[jdmorris]

1M 6-speed

1st: 4.110:1
2nd: 2.315:1
3rd: 1.542:1
4th: 1.179:1
5th: 1.000:1
6th: 0.846:1
Final Drive: 3.154:1

135i 6-speed

1st: 4.11:1
2nd: 2.32:1
3rd: 1.54:1
4th: 1.18:1
5th: 1.000:1
6th: 0.85:1
Final Drive: 3.08:1

M3 6-speed

1st: 4.055:1
2nd: 2.369:1
3rd: 1.582:1
4th: 1.192:1
5th: 1.000:1
6th: 0.872:1
Final Drive: 3.846:1

M3 DCT

1st: 4.780:1
2nd: 2.933:1
3rd: 2.153:1
4th: 1.678:1
5th: 1.390:1
6th: 1.203:1
7th: 1.000:1
Final drive: 3.154:1

So the final drive came from the E9x M3 DCT final drive (same ratio) but the transmission ratios, and likely therefore the gearbox, are straight out of the 135i. That should answer some questions!

JD

[quackman]

Interesting that it has the final drive of the M3 DCT rather than the M3 6 speed. Why would they do that?

[ORIGIN M.]

I will give you one guess!

Originally Posted by quackman

Interesting that it has the final drive of the M3 DCT rather than the M3 6 speed. Why would they do that?

[Pete_vB]

Originally Posted by quackman

Interesting that it has the final drive of the M3 DCT rather than the M3 6 speed. Why would they do that?

Because with the 135 ratios and the M3 final drive the gearbox would be really short. As it is, they reduced the speed in each gear vs the 135i by a couple percent. So 2nd now ends at 41 mph rather than 42, etc. Interestingly, if you shift at 6700 (end of the power band) in the 1M the speed in every gear is now within 1-2 mph of the manual M3.

The M3 final drive would have made it very short, though- a redline 2nd to 3rd shift would be at less than 60 mph instead of 73, and 80 mph cruising would be spinning 3500 rpm...

[Robert]

Did a quick calculation. My first time doing this after doing 30 mins of reading.

For M3 6spd 8000rpm wheel size of 265/36/19

Gear Max Speed
1 40.46
2 69.25
3 103.70
4 146.59
5 164.06
6 188.14

1M 6spd 7000 redline

Gear Max Speed
1 42.59
2 75.62
3 113.52
4 156.59
5 175.05
6 206.92


Note: I did not factor HP into the calculation. Simply based on gearing

[Pete_vB]

Originally Posted by Robert

Did a quick calculation. My first time doing this after doing 30 mins of reading.

For M3 6spd 8000rpm wheel size of 265/36/19

Gear Max Speed
1 40.46
2 69.25
3 103.70
4 146.59
5 164.06
6 188.14

1M 6spd 7000 redline

Gear Max Speed
1 42.59
2 75.62
3 113.52
4 156.59
5 175.05
6 206.92


Note: I did not factor HP into the calculation. Simply based on gearing

The M3 looks right, the 1M looks off. What final drive did you use? For the 1M w/ 7000 rpm I get:
1 41.0
2 72.8
3 109.3
4 143.0
5 168.6
6 199.2

[JimD]

I do not think this is different from what has been said but is, perhaps, a little different way of saying the same thing. The motor of the 1M has more torque lower in the rpm range than the motor of the M3 (I've driven both although I own neither). It is common for the rear end of a manual transmission car to be geared to turn more rpm than the automatic. I believe this is done because the designer does not trust us to downshift when we need to so they gear it to turn more rpm so we don't need to.

So if you are building a car out of the parts bin - sensible for the expected volume of sales (if uninspiring) - then you choose the M3 automatic's lower ratio to avoid unnecessarily spinning up the N54 and loosing more gas mileage.

Jim

[grant]

Originally Posted by Robert

Did a quick calculation. My first time doing this after doing 30 mins of reading.

For M3 6spd 8000rpm wheel size of 265/36/19

Gear Max Speed
1 40.46
2 69.25
3 103.70
4 146.59
5 164.06
6 188.14

1M 6spd 7000 redline

Gear Max Speed
1 42.59
2 75.62
3 113.52
4 156.59
5 175.05
6 206.92


Note: I did not factor HP into the calculation. Simply based on gearing

If you're using redline for both, shouldn't you calculate 8,400 for the M3 (5% higher speeds)?

[Robert]

I used the final drive ratio above 3.154 for 1M

Corrected for 8400rpm

M3 6spd

Gear Max Speed
1 42.48
2 72.71
3 108.89
4 153.91
5 172.26
6 197.55


265/36/19 gave me 83.29" wheel+tire diameter

[grant]

Thanks, Robert!

[turbo8765]

Originally Posted by Pete_vB

Because with the 135 ratios and the M3 final drive the gearbox would be really short. As it is, they reduced the speed in each gear vs the 135i by a couple percent. So 2nd now ends at 41 mph rather than 42, etc. Interestingly, if you shift at 6700 (end of the power band) in the 1M the speed in every gear is now within 1-2 mph of the manual M3.

The M3 final drive would have made it very short, though- a redline 2nd to 3rd shift would be at less than 60 mph instead of 73, and 80 mph cruising would be spinning 3500 rpm...

Exactly.

I think the key is the need to hit 60 in second. People tend to zero in on this number and put way to much emphasis on it. If the 1M required a shift to third, thereby skewing the 0-60 time relative to its competitors, people would be very disapointed.

[MDORPHN]

BTW, despite the ratios being identical to the 135's, the tranny *may* be different.

According to the European media packet on the 1M (which has to be discounted for "marketing speak"):

"This newly developed transmission features dry sump lubrication.... The high transmission capability is combined with a compact design and a weight of some 43 kilograms, making it much lighter than conventional transmissions."

Neil

[Pete_vB]

Originally Posted by Robert

265/36/19 gave me 83.29" wheel+tire diameter

Check this number... it's 265/35/19. Tire Rack lists "Revs per mile", probably the most accurate way to do it. The OEM PS2s from the M3 are 790...
5280' / 790 x 12" = 80.2" per rev...

Originally Posted by formula M

You don't even need 1st gear in this car, it will easily come off the line in 2rd gear. (for dd)

Do you have something against your poor clutch?

[Fuerza]

Originally Posted by red-sauerkraut

I will give you one guess!

Turbo spool.

[Pete_vB]

Based on these gear ratios I ran some numbers.

I estimated a dyno curve with overboost for the 1M based on the 35is dynos; I assumed the factory under-rated the car a little- this assumes the car makes 350 hp, not 335. The results vs some M3 dynos (this obviously has some margin of error).

Using this graph, the US estimated weight of 3296 lbs and the gear ratio you can then figure out how hard the car pulls in each gear, which is the second graph. This ignores aero, transient turbo spooling, inertial effects, etc, but it allows for some comparison.

Each line represents a gear, and the higher the line, the harder the car is accelerating. So the blue line at the top is the 1M pulling in first gear; it's clearly going to kick hard when the boost hits, pulling harder than the M3 until about 35 mph when the torque rolls off and the M3 keeps pulling. The 1M is again slightly ahead up until about 60 mph in 2nd. In the higher gears, however, the M3 spends more and more time in front, and it's always in front above about 115 mph due to the higher top end power.

In reality aero would also take over at higher speeds and the M3's on the road advantage would be greater. At lower speeds, though, the 1M has lots of area under the curve. Looks pretty good stock, assuming the assumptions for power and weight are about right.

[grant]

Very interesting - thanks for doing that, Pete. That clearly shows that retrofitting larger turbos that would give the 1M better lungs at high revs would really give the little 1er an edge over the 3er (and is most likely the reason the factory did not do that, aside from cost).

[Pete_vB]

As requested- I was asked to compare the 135 3.08 R&P with the 1Ms 3.154. Very little difference:

[swamp2]

^ Your graphs are incorrect or at least minimally a misrepresentation. Heck you don't even have precise axis labels or units on them...ugh.

A much more informative way to look at a comparison of the cars is simply position vs. time, velocity vs. time or acceleration vs. time. What graphs vs. rpm can fail to fully represent is that except for the very brief pull to the shift point in 1st gear the M3 spends the vast majority of its times at a much higher rpm than the 1M, as such is is making more power for more of the time and hence accelerating more. A really rough range on WOT runs where the 1M spends its time is 5-7k rpm. The M3 is typically at 7-8k. I.e. it is operating where the 1M can not even reach from an rpm perspective! This emphasizes the importance of redline and hp over torque. The higher torque only really provides a performance advantage when you lug the M3 and use the wrong gear. For some particular speed contests such as low speed in high gear the 1M will win. Some describe this as a better daily driver type of characteristic whereas I perfer a better lazy driver.

Here you can look at the accelerative force vs. speed (1st two graphs), noting that at each shift you simply drop down one curve right to the next. For instance in 2nd gear the M3 is almost always producing more than 2000 lbs of accelerative force whereas the 1M typically producing less than 1750 lbs (again during WOT runs). The M3s green curve for 2nd gear does not even see the part of the curve below or to the left of the peak when doing a WOT run! These curves take into account power, torque, gearing, a plethora of losses, weight, aero effects, tire slip, you name it. It is a very rich physics based simulation. Do note that on these force curves I could not force my software to use the same scale so that can be a bit misleading (4000 peak vs. 3500 peak).

The radically downward sloping curves in the upper rpm ranges is that typical "running out of steam" feeling you get in a lower redline car with a much lower rpm torqe peak and narrow torque curve width.

When it comes to who is ahead or who is going faster that should be painfully obvious from the cars power to weight ratios. The next set of graphs only make it obvious. Not really much of a contest here. The M3 is ahead, always ahead and ahead from a distance or speed perspective. The only possible exception to this would be that somewhere in middle of the short 4 or so seconds to 60 mph the 1M might get just a few feet ahead of the M3 but by 4 seconds the M3 will have gained almost a wheelbase on the 1M.

Just for reference my 0-60 and 1/4 mi. times predicted for the 1M using this software were 4.6s and 13.1s respectively. The car might be underrated a bit by BMW like the 335i and in which case it wil fare a bit better but the trends won't be reversed. Not much tweaking of input parameters to the software was needed here nor was a super precise dyno curve required. Having those again would nudge curves very slightly here or there but no major change would result. Also note I have used the M-DCT M3 for comparison not the 6MT. You can see that by the very short shift times compared to the MT.

[HERR FSTIR]

Swamp, how much effort to redo the 1M dataset using the M3 DCT and final drive specs? I'd be interested to see what the 1M "could have been". Not sure cartest will account for DCT keeping engine on boost between shifts.

[rppwm3]

Could you possibly retrofit a DCT transmission with one from the Z4is and simply switch the ECU's since the engines are the same and they produce the same amount of horsepower?

[swamp2]

For you friend, it's fast. Two questions though need to be addressed perhaps separately. What would a 1M do with its existing ratios (gears and FD) just with faster shifting? Secondly would 7 gears and altered ratios help? I'll answer the first part quickly as the second part takes much more time.

In short a 6 DCT would provide about:

0-60: 0.2s improvement (just about the wasted time of a really fast shift in the MT)
0-100: 0.4s
1/4 mi: 0.2s, 1 mph trap
0-150: 0.9s
60-130: 0.4s

Not huge gains for no ratio changes.

Car #1 is 6 MT, car #2 is DCT.

[HERR FSTIR]

True - the gains are only incremental. But does cartest account for preserving boost levels during the shift? This factor is not insignificant.