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07-06-2001, 02:22 PM
I read this SMG article below and got confused.. i have some questions..

so w/ SMG the m3 can choose to drive automatic (but with lag time in changing gear)? meaning the driver doesn't have to change the gears and the computer will change the gears??

about the lag time they denoted in the article.. does it mean SMG will have lag time if in manual mode?

Ray Koch
07-06-2001, 02:32 PM
You're confusing two different things. The SMG has several modes in which control the way it shifts. In the tamest mode, it trys to make the shift as slow and smooth as possible for comfort. In the max performance mode it shifts quick and hard for performance. This is one type of delay.

Now there is also a delay, even in it's highest performance setting, from the time you hit the lever till it performs the shift. The shift occurs in the blink of an eye but for reasons unknown there's this lag time. Perhaps the computer is performing some sort of calculation.

07-06-2001, 02:43 PM

07-06-2001, 02:47 PM

Simon (EvoSport)
07-06-2001, 02:48 PM
in S6 mode (the most aggressive), it engages the new gear in 8/100th of a second after the mechanism processes the shift. The question is how long does the "processing" take. This is the latency that is in question. The 8/100th shift time may be misleading. Likewise, the Ferrari F1's claimed shift time (0.150 I believe) may include the processing time that BMW may not be taking into consideration. We will find out soon enough...


Ray Koch
07-06-2001, 02:50 PM
The SMG will make faster shifts than a human and do so perfectly everytime. You'll just have to get used to the slight delay and learn to anticipate it.

07-06-2001, 03:03 PM

07-06-2001, 03:03 PM

07-06-2001, 03:04 PM

Randy G
07-06-2001, 03:04 PM
Has anybody tried to measure the delay between the click and the gear change that can be heard in the SMG sound files? This should be extremely easy, using a sound editor such as CoolEdit.

Randy G
07-06-2001, 05:30 PM
Using the changing_up.mp3 sound file from the BMW Web site, I measured the delay between the "click" and the change in pitch of the engine at approximately 0.45 - 0.5 seconds. This is 5 to 6 times the 0.08 seconds that BMW is claiming. Maybe the file was recorded with the mode set to S1? Weird.

Randy G
07-06-2001, 05:35 PM
I looked at the wrong number in CoolEdit's display, so it's actually .33 seconds, not .45 seconds. Still, 4 times the claimed time makes me think these sound files are not really supposed to illustrate the claimed 80 millisecond delay. If so, they do an incredibly poor job of it.

07-06-2001, 05:38 PM
BMW's times are likely quite accurate, and reflect the interval from throttle-off/clutch-in to throttle-on/clutch-out. Essentially the time where drive force is interrupted to the rear wheels, or if you prefer, the time that the clutch is disengaged.

What we're looking at is the half second or so from when the user indicates his desire to get a downshift, and the time that it is performed by the SMG. It appears there's some delay from clicking, to when the SMG goes for the shift - perhaps calculations are being performed, or it's seeing if you want a double downshift by giving a second click - only BMW can tell us.

Think of the two times just like a human would have. In one case you measure from when you decide to shift, to when it's done. That covers time for your right hand to leave the wheel, your foot to get ready, then time for you to perform the shift. That's going to be significantly more time than if we measure your human-fastest-shift from the moment your foot begins to move the clutch pedal...

Randy G
07-06-2001, 06:21 PM
If you subtract off the .08 second time during which there's no power going to the wheels, that leaves about 1/4 second from the time that I tell it to shift, to the time when it actually starts moving some gears around. To me, that seems like a big problem. One of the main reasons I like having a manual transmission is that I can shift NOW into any gear I want. The delay between moving the lever and the gear change is the biggest thing that put me off of systems like Steptronic (the other being the loss of power, of course). 250 milliseconds seems like way too long for the computer to make up its mind about what to do. When you see in-car footage of Formula 1 drivers, the downshifts go BANG BANG BANG BANG, with no perceptible delay between the driver's clicking the button and the BANG for each gear. I want a sequential shifter that's as close to that as I can get.

Maybe they will fix this by the time SMG gets to the US. Otherwise, I'm not so sure I'm going to like it.

07-06-2001, 06:37 PM
I would not expect any US version of the SMG to shift faster than Europe. If anything, BMWNA is worried that people will be expecting an autobox and think it's too harsh as is, let alone having it be more aggressive.

But hey, there's a computer in there making the decisions... Perhaps the engine chip tuning folks will get out the diagnostic clips, suck the eprom dry, and redecorate the microcode for those that want the full formula one experience? Sounds like a business opportunity to me.

I just had another nightmare thought of Microsoft buying BMW, and requiring all customers to install Service Pak 5 on their SMG systems if they wanted any oil changes.... Eeeeeeek! :)

Scott W
07-06-2001, 09:38 PM

07-07-2001, 06:00 AM
I perfectly agree with you...SMG is not like F1 race cars, so that I opted for the manual transmission.
If you buy an M3 i think you are a good driver, your foot is fast, your hand more, and you don't need an automatic transmission, which are to be left for taxies and daily car.....
Bye Bye
P.s. Don't believe that a good driver with SMG goes faster than a manual best friend has the SMG and he stays always behind me...

07-07-2001, 06:03 AM

07-07-2001, 06:06 AM
Ferrari is undoubetdly faster than the SMG...i tried both and there's are a lot of differences.
Try before to buy....

07-07-2001, 11:14 AM
I'll let you know as soon as I tried it myself.

However, I'm quite sure that you cannot just measure time from this strange clicking noise to the point when you think the car actually shifted. Furthermore nobody knows which program they were running when they recorded the sound file.

Honestly, I find it ridiculous to compare ANY sequential gearbox (for stock cars like the F360 or M3) to a F1-racer gearbox. Those gearboxes are designed to last as long as one GP (ca. 400 Km) and then they can fall apart.

An F1-racer can shift in 0.02 s ! This is still 4 times faster than SMG II. Do you really expect this from an affordable stock car ? You can't be serious ;-)


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