znod

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.
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What he is saying doesn't make sense to me assuming I now am understanding correctly. I think what he is saying that 60 MPH on the speedo, for example, really would be 62 MPH = 100 KPH. But, if that was true, then 100 KPH on the speedo would be in line with 60 MPH. But, in fact 100 KPH lines up with 62 MPH on the speedo.

DD694

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.
[/quote]
What he is saying doesn't make sense to me assuming I now am understanding correctly. I think what he is saying that 60 MPH on the speedo, for example, really would be 62 MPH = 100 KPH. But, if that was true, then 100 KPH on the speedo would be in line with 60 MPH. But, in fact 100 KPH lines up with 62 MPH on the speedo.
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I would expect that the speedometer, being analog, is likely to be less than accurate compared with all the microprocessors in the car that are measuring speeds over the road, engine speed, etc. My former Porsche 997S had an analog speedo, which was pretty much worthless, but also had a vbery nice large digital speed readout in the lower section of the center-mounted tachometer. I find myself missing this digital speedo readout when driving my 550i.

cobradav

An observation here. One of the pleasent surprises I found on the 6er was the fact that every measure of speed (analog center guage, HUD digital, and trip computer avg speed) all measured exactly the same. Do 10 miles at CC set 60, and all three indicated the same (wrong) thing. My Audi , on the otherhand, has no two of the three measures read the same.

znod

Well, that is good; consistent wrongness. Check above mi amigo.

EBMCS03

Didnt read the whole thread... but I'll ask my friend to see if he knows if the diagnostic menu speedo is "accurate" or not.

Also. my speedo is also 2 mph off at 65mph to 70mph... thats the time I've really noticed is when I cruise on the highway and my GPS always show 2mph less than the speedo.

P.S. My MINI is also just the same... 2 mph off so I think its a BMW std to make it 2mph faster.

grogan545

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?
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Just thought of another possible problem in trying to determine at what rpm a shift starts.The analog tachometer is dampened so there is a lag time in engine rpm's vs tachometer reading.As you are accelerating the engine rpm's at a given instant are higher than the tach reading.

I don't know about the wheelspin question.The only 2 reasons for this are less power or traction control not completly disengaged.

I would like to run some tests sooner but it is supposed to rain tomorrow and I will be busy Sunday.I do want to make my runs on my same test road to not introduce other possible factors for discrepancies.Also I will keep my GT2 at 10" rollout for direct comparison to original data.

znod

Hi EBMer: I appreciate the help.

EBMCS03

Hi EBMer: I appreciate the help.
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Ok I asked... he doesnt know for sure... he's still a student...

http://www.bmwstep.com

SaintK

Ok I asked... he doesnt know for sure... he's still a student...

http://www.bmwstep.com
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Ok read through most of the stuff...just a few questions to make sure.

Are the tire inflated to BMW specificed pressures on the sticker? And are you accounting for the final drive ratio of the rear diff? I noticed that you have calculations for direct drive and 6th gear overdrive but haven't noticed any final drive calculations.

Also as for the 2mph variation people are talking about...if speedo is indeed 2mph off then it's probably built in. The speedo is a needle but isn't based off of an analog signal. BMW pretty much use hall effect sensors (digital signal) for all rotating objects almost exclusively. The speedo gets a digital signal off the DSC and the motor just translates it into motor movement of the needle. So the speed discrepancy isn't in the needle speedo. Or at least shouldn't be.

The digital speed readout from the idrive or cluster display for non-idrive vehicles SHOULD be what the wheel speed sensors are reading. This is for techs to diagnose problems and should be true speed reading, since it is not meant for public knowledge.

znod

Others agree that the 2 MPH difference is built in.

Thanks EBMer.