znod

Hi Friends:

I have seen the speedo and tach in the hidden iDrive menu characterized as providing "true" or "correct" speed and RPM readings. Does anyone know if these readings are different than those given in our instrument clusters, and, if so are they any more correct than the latter? If so, why.

If even different readings are provided, then I would like to check them out in connection with the possibility that my Step is shifting early. From numerous, but inconclusive eyeball observations, I have been unable to tell for sure. One thing I can say for sure is that my Step starts shifting earlier than it seems like it should for optimal shifting. Whether it completes the shifts at the points it should is a harder issue to discern. My car tends to start shifting at an indicated 30 MPH and 60 MPH--which is a not supposed to happed given the 545i's gearing. I would appreciate it if others especially with 545i's and 550i's would let me know the indicated speeds where their Steps start shifting.

This early-shifting-start observation overwhelmingly true if the 545i speedos really do read several MPH fast. Would someone confirm my recollection that the 545i's speedos read about two MPH fast?

Note that my GT2 data imply, IMO, that early shifting is a distinct possibility. Grogan, whose opinion I respect greatly, has not yet agreed. I am working on him.

cobradav

With very few exceptions (and some of those were outlandishly different) the 2 MPH high is the consensus. As a participant in some of those discussions my 2 MPH off was at 50, 60, and 75 (and many points in between) indicating that it is not a fixed % of speedo, rather a fixed bias of some sort. And that goes against my intuition, but several different radars made up my consistant results.

znod

That helps a lot cd. Thank you very much. So, my Step definitely appears to be starting to shift way early. Still, I wish I had watched the speedo more closely before 20.01.00.

If my Step is starting to shift at a true 30 MPH and 60 MPH, then the starting RPM's are given in purple below.

(5,687 / 6,500(34.28769707) = 30
(6,383 / 6,500)61.10243456 = 60

The second purple value would be bad, but the first one would be disastrous for ET's. And, the 1-2 shift is where I feel the weakness the most--except for no longer being able to get significant wheel spin. Given my wheels and tires, my calculations for top speeds in gears came out almost the same as what R&T, etc. show:

There are 807 revs per mile given 275 / 30-19 rear tires.
At 60 mph one would do a mile a minute, or 807 tire revs per minute.
If the effective rear-end is 1:1, then a mile a minute would take 807 engine RPM.
If the effective rear-end is 2.3322:1 (as below for 6th gear), then 60 MPH would take 2.3322(807)] = 1,882.0854 RPM.
Given the above, it the car could turn 6,500, then its top speed would be 60(6,500 / 1,882.0854) = 207.216952

Top speed in 1st gear would be 207.216952(2.3322 / 14.0946) = 34.28769707
Top speed in 2nd gear would be 207.216952(2.3322 / 7.9092) = 61.10243456
Top speed in 3rd gear would be 207.216952(2.3322 / 5.1376) = 94.06559005
Top speed in 4th gear would be 207.216952(2.3322 / 3.8532) = 125.42078674

I need to back up and check my speeds/RPM's at, say, 3,000 RPM calculated as follows:

(3,000 / 6,500)[207.216952(2.3322 / 14.0946)] = about 16
(3,000 / 6,500)[207.216952(2.3322 / 7.9092]) = about 28
(3,000 / 6,500)[207.216952(2.3322 / 5.1376)] = about 43
(3,000 / 6,500)[207.216952(2.3322 / 3.8532)] = about 58

I should have checked these values before, but assumed all was OK because my calculations agreed with those of others and my rear tire diameter should have barely changed if the manufacturer's data are correct. We shall see--on the way home pretty soon.

DD694

Could it be that the speedometer is calibrated in Km/H and the dial we see for MPH is merely overlayed, while speedo is not calibrated for MPH?

cobradav

Could it be that the speedometer is calibrated in Km/H and the dial we see for MPH is merely overlayed, while speedo is not calibrated for MPH?
[/quote]
No, I do not believe that is the case. Car mfrs as a group are making their speedos read high in nearly all countries that I am aware of and in some cases at the request of the respective government traffic safety agency irrespective of km or mph.

grogan545

Hi Znod
I have checked my speedo out at 70 mph it reads 2 mph fast(actually true 68).I did this by timing with a stopwatch for 10 miles on an interstate using the interstate mile markers for true distance.Time should have been 514 seconds for 70 mph,but was 529 seconds.

I just got my car back from dealer at noon today.It was updated with 20.01.My early observations are not definitive.Tried 2 starts in my usual manner and got very little wheel spin on first start,but lots of wheelspin on second start.I did notice that I saw 6500 rpm in M1 before the shift to M2,but I didn't notice at what rpm the shift actually started.I will observe better next time(probably monday weather permitting).

Your starting to win me over on the early shifting Znod.What I have been saying is the shifts may be slower and less firm.If thats true(slower shift)then you must deduce that the shift starts earlier in order to be complete by 6500 rpm.

My test road is on the way to my office so I will try to get some 0-60 runs on Monday morning weather permitting.

znod

Hi Znod
I have checked my speedo out at 70 mph it reads 2 mph fast(actually true 68).I did this by timing with a stopwatch for 10 miles on an interstate using the interstate mile markers for true distance.Time should have been 514 seconds for 70 mph,but was 529 seconds.

I just got my car back from dealer at noon today.It was updated with 20.01.My early observations are not definitive.Tried 2 starts in my usual manner and got very little wheel spin on first start,but lots of wheelspin on second start.I did notice that I saw 6500 rpm in M1 before the shift to M2,but I didn't notice at what rpm the shift actually started.I will observe better next time(probably monday weather permitting).

Your starting to win me over on the early shifting Znod.What I have been saying is the shifts may be slower and less firm.If thats true(slower shift)then you must deduce that the shift starts earlier in order to be complete by 6500 rpm.

My test road is on the way to my office so I will try to get some 0-60 runs on Monday morning weather permitting.
[/quote]
Thanks grogan. I hope your car is way better than OK. On the way to "work" today, I did a zero to above 60 after passing through each light. I was following along behind the traffic. Then, I'd catch up and do it again after the next light. I am beating my car into submission I hope. Keep in mind, however, that I only go 5 miles to "work."

I confirmed the two MPH offness also. Above, I say that my calculations imply the following:

(3,000 / 6,500)[207.216952(2.3322 / 14.0946)] = about 16
(3,000 / 6,500)[207.216952(2.3322 / 7.9092]) = about 28
(3,000 / 6,500)[207.216952(2.3322 / 5.1376)] = about 43
(3,000 / 6,500)[207.216952(2.3322 / 3.8532)] = about 58

At 3,000 RPM in first, my speedo showed 18 MPH rather than the correct calculated value of 16 MPH (with 30 MPH versus the correct 28 MPH in second, and 45 MPH versus the correct 43 MPH in third). I say the calculated values are correct, given my rear-tire sizes, because R&T calculated 1,900 RPM in top gear at 60 MPH for the sport package. I think this value is rounded. Consistently, using my manufacturer's revs per mile value (807) as a starting point), I calculated revs per mile at 60 MPH for my sports-package equivalent wheels/tires as follows:

Given that the sport package 545i's effective rear-end is 2.3322:1, then 60 MPH would take 2.3322(807)] = 1,882.0854 RPM--which looks like a likely value for R&T to have rounded up 1,900 RPM.

The implications of my speedo reading today are as follows. Note, first, that above I said:

"If my Step is starting to shift at a true 30 MPH and 60 MPH, then the starting RPM's are given in purple below.

(5,687 / 6,500(34.28769707) = 30
(6,383 / 6,500)61.10243456 = 60."

It now looks as though the step is starting shifting at a true 28 and 58 MPH which implies the RPM values in purple below--which are even worse:

If my Step is starting to shift at a true 28 MPH and 58 MPH, then the starting RPM's are given in orange below.

(5,308 / 6,500(34.28769707) = 28
(6,170 / 6,500)61.10243456 = 58

These RPMs are atrocious. Can they be right? Does anyone see any metal blocks I am having?

And, note that what you say is what I have been saying; it looks like early shifting and slow shifting are at least part of the issue. As you say, the Step needs to start shifting earlier to finish shifting at 6,500 if smoother shifting is the goal. But, we sure didn't need to shift more smoothly in DS!!! I don't notice enough of a smoothness improvement, if any, anywhere to matter over the shifting of 19.01.01. Bummer!!!

If we are right, then what still is to be explained is why no wheel spin for me. And, also, I am going to look closely at my RPM when I feel my car starting to shift. My bet is that it doesn't appear to be 5,308 and 6,170. I am beginning to think that BMW's programming is set so that the tach shows 6,500 when it fininshes shifting at full throttle no matter what (with one dysfunctional exception that I know about).

So, I am back to the issue of whether the tach and speedo in the hidden iDrive menu show different speeds and RPM than are shown in the instrument cluster. Has anyone ever hooked a "real" tach up to a 545i? Where can I get one. And, how hard would it be to hook one up? I haven't hooked a tach up since high school. Of course, that was just a few years ago.

Finally, note that I can't use, for example, the Pro SS to do what I want to do. This observation follows since one has to read RPM values from the tach into the meter for it to give suggested optimal shift points and to indicate when they occur. I suppose I could use the Pro SS to confirm the problems noted above though. Hummmm?

KAF

Could it be that the speedometer is calibrated in Km/H and the dial we see for MPH is merely overlayed, while speedo is not calibrated for MPH?
[/quote]


All the calibrations are in metric. The imperial readouts are conversions from the metric data.

Take a look at the consumption readouts and speed changes as you flick the cruise, they do not change in 1mpg or 1mph steps. Sometimes one tap on the cruise relates to 1mph sometimes it takes two, this is because each tap changes the speed by 1kph which of course is a touch less than 1mph.

znod

All the calibrations are in metric. The imperial readouts are conversions from the metric data.

Take a look at the consumption readouts and speed changes as you flick the cruise, they do not change in 1mpg or 1mph steps. Sometimes one tap on the cruise relates to 1mph sometimes it takes two, this is because each tap changes the speed by 1kph which of course is a touch less than 1mph.
[/quote]
EDIT: Nevermind on what I said here before; I misunderstood you.

DD694

All the calibrations are in metric. The imperial readouts are conversions from the metric data.

Take a look at the consumption readouts and speed changes as you flick the cruise, they do not change in 1mpg or 1mph steps. Sometimes one tap on the cruise relates to 1mph sometimes it takes two, this is because each tap changes the speed by 1kph which of course is a touch less than 1mph.
[/quote]
I have observed this same thing in driving Porsche and Mercedes-Benz cars. It is especially noticeable on Cruise Control Settings.