[rak299]

The whole concept doesn't make sense. Rev matching is more useful on downshifts of more than one gear, where the RPM change would be greater. This thread is in in the B58 board. To me, that means that the change wasn't done on the 4-cylinder engines, making the whole thing sound more like some engineer's screw-up. I could imagine someone deciding that NOT doing rev matching on single-gear down shifts was OK, thinking that the adjustment would be more minor, and then doing it backwards. I am taking my '17 440ix in for its first service Monday, and I will ask ahead of time whether they think it needs some sort of software update. I would prefer that things work "the old way".

[Araemo]

Originally Posted by rak299

The whole concept doesn't make sense. Rev matching is more useful on downshifts of more than one gear, where the RPM change would be greater. This thread is in in the B58 board. To me, that means that the change wasn't done on the 4-cylinder engines, making the whole thing sound more like some engineer's screw-up. I could imagine someone deciding that NOT doing rev matching on single-gear down shifts was OK, thinking that the adjustment would be more minor, and then doing it backwards. I am taking my '17 440ix in for its first service Monday, and I will ask ahead of time whether they think it needs some sort of software update. I would prefer that things work "the old way".

Software updates aren't done just because. Either to fix an identified issue, or due to a service campaign to proactively fix an issue (I haven't heard of any of those for the b58 cars yet).

As for whether it applies to the B48? No clue.. how many B48s are sold with manuals? And does the 330 manual have downshift rev matching?

[kern417]

Originally Posted by Araemo

Software updates aren't done just because. Either to fix an identified issue, or due to a service campaign to proactively fix an issue (I haven't heard of any of those for the b58 cars yet).

Exactly. For all we know, someone went 5th-2nd instead of 5th-4th and blamed over-revving their engine on the rev matching. It sounds stupid but it's pretty much impossible for us to say since we're not seeing the warranty claims/customer surveys. It could even be a by-product of another upgrade that they did to engine mapping for emissions or anything really. the only thing we do know is it cost the company money to change the programming, and they won't spend that money unless it a) makes them money or b) stops them from losing money.

I'm curious why people are getting updated software flashes to begin with? Is something being fixed or are the dealers just doing it as protocol?

[rak299]

Originally Posted by kern417

I'm curious why people are getting updated software flashes to begin with? Is something being fixed or are the dealers just doing it as protocol?

I am going in tomorrow for a normal, 12-month service (only 7k miles). I will try to ask the protocol and see whether they have some normal procedure to flash or some service advisory. I'll post back after.

[Araemo]

Originally Posted by kern417

Exactly. For all we know, someone went 5th-2nd instead of 5th-4th and blamed over-revving their engine on the rev matching. It sounds stupid but it's pretty much impossible for us to say since we're not seeing the warranty claims/customer surveys. It could even be a by-product of another upgrade that they did to engine mapping for emissions or anything really. the only thing we do know is it cost the company money to change the programming, and they won't spend that money unless it a) makes them money or b) stops them from losing money.

While you're basically correct, software development is a more complex animal. The change could have been due to a specific request from someone on a specific product team, but the software is shared among multiple cars, or it could have been the original intent all along, and the programmers made it 'low priority' to 'fix' the incomplete implementation, so after they got the production-critical features done, they went back and started refining the software's more minor features that they couldn't complete in time for initial release... I don't really care the reason, only the fact that it worked one way when I test drove the car and for months after purchase, and no longer works that way, without a good rationale for why it was changed.

Originally Posted by kern417

I'm curious why people are getting updated software flashes to begin with? Is something being fixed or are the dealers just doing it as protocol?

As I noted in my post, that was the explanation I was given. In my case, it was specifically to address a drivetrain malfunction message. They scanned the car, escalated to corporate, corporate said to do a software update to address the issue. The drivetrain malfunction message has not recurred since, but it only showed up once for me anyway (annoyingly enough, it showed up after they pulled up my car to give it back to me, but before I got in it, after an oil change).

[Dinan_Rated]

Originally Posted by eluded

2016 - Never updated since the factory, running same version of factory software, rev matches in all the gears

11/14 rev matches

[kern417]

Originally Posted by Araemo

While you're basically correct, software development is a more complex animal. The change could have been due to a specific request from someone on a specific product team, but the software is shared among multiple cars, or it could have been the original intent all along, and the programmers made it 'low priority' to 'fix' the incomplete implementation, so after they got the production-critical features done, they went back and started refining the software's more minor features that they couldn't complete in time for initial release... I don't really care the reason, only the fact that it worked one way when I test drove the car and for months after purchase, and no longer works that way, without a good rationale for why it was changed.

I'm very aware, which is why i said it could be anything. Moreso, you likely won't get the answer you want from a dealer for that reason. When I worked in automotive we ran into the issue all the time because so many vehicles shared components. Sometimes you received design changes that you didn't know why they were being implemented, the only thing you were directed is to verify there was no degradation to vehicle function. For something like this, i'd imagine it could easily be swept under the rug even if an engineer did identify it as an unexpected or unwanted change. but we'll most likely never know.

[B58 parts]

Is there a way to outright disable this? I'm perfectly fine blipping my own throttle and do not need a computer in the way. The computer and I are walking on each other...

I'm really confused why so many people WANT this 'feature'

[kern417]

Originally Posted by YuminNuman

Is there a way to outright disable this? I'm perfectly fine blipping my own throttle and do not need a computer in the way. The computer and I are walking on each other...

I'm really confused why so many people WANT this 'feature'

It's disabled in Sport + or if you disable traction control.

To be honest i didn't like the idea but it doesn't bother me that much anymore. Especially when I tried to heel-toe and realized how crappy the positioning of the pedals is. It took a while to get used to because holding the brake while shifting shifted my focus a ton, so mentally I had to be at ease with it. But now it's a force of habit.

Plus, per the point of this thread, i still have plenty of opportunity to rev match myself when i skip gears.

If they had a button or coding to turn it off, i probably would. But imo it's not as big of a headache as people make it out to be.

[B58 parts]

I've read that, but it still happens on my 340 in all modes, even sport+ .... or any mode and messing with the TC button. I've read conflicting reports that coding the 'clutch pedal on start' / 'brake pedal on start' kills it. Some say it does, some say no difference.

As far as I understood it, it triggers when the shifter starts to pass into the gate for the target gear. So idk how going from 6-5 would be any different than 6-4, as both just pass through N to each gear. I do wonder how this works......

In my day the only electronics near an MT were A) the ground wire, B) the starter, C) the speed sensor, and D) the reverse lights... that's it!

Anyway .. not to thread jack, hope you get it 'fixed' whatever that entails.

[jpsimon]

If you turn traction control off (by holding down the DSC button) rev matching will be disabled.

Originally Posted by YuminNuman

I've read that, but it still happens on my 340 in all modes, even sport+ .... or any mode and messing with the TC button. I've read conflicting reports that coding the 'clutch pedal on start' / 'brake pedal on start' kills it. Some say it does, some say no difference.

As far as I understood it, it triggers when the shifter starts to pass into the gate for the target gear. So idk how going from 6-5 would be any different than 6-4, as both just pass through N to each gear. I do wonder how this works......

In my day the only electronics near an MT were A) the ground wire, B) the starter, C) the speed sensor, and D) the reverse lights... that's it!

Anyway .. not to thread jack, hope you get it 'fixed' whatever that entails.

[B58 parts]

Originally Posted by jpsimon

If you turn traction control off (by holding down the DSC button) rev matching will be disabled.

Ah .. nobody ever told me that you can hold that button in and something else happens... Interesting. I will have to try that later. Thanks.

I will try to find out a little more on how this works .. i'm wondering if you change the tire size if it's smart enough to adjust or if that can be programmed... i.e. your tires are 10mil taller over OE, does the computer always overblip.

I haven't 'used' it enough but was also wondering if it continuously adjusts the revs if the car's speed changes if you jokingly take an inordinate amount of time between gears.. And I can't imagine why the programmer would now look at the source gear either..

[Araemo]

Originally Posted by YuminNuman

Is there a way to outright disable this? I'm perfectly fine blipping my own throttle and do not need a computer in the way. The computer and I are walking on each other...

I'm really confused why so many people WANT this 'feature'

I can understand that, and if it was a configurable option, I'd have tried the car without it. But with it doing it for every downshift, I just got used to it - it's nice when driving lazily, and it works well when driving hard.

The current configuration where it only automatically rev matches on single gear downshifts... really pisses me off, because as I've been re-developing the muscle memory to rev match myself, now I screw with it when it's trying to rev match as well, and it fucks up my timing, because most of my down shifts are more than one gear, but sometimes I only downshift one gear and it steps in as well.

Originally Posted by YuminNuman

Ah .. nobody ever told me that you can hold that button in and something else happens... Interesting. I will have to try that later. Thanks.

Yep, pressing the button once is 'traction' or 'DSC sport' mode. Press and hold turns DSC off.

I will try to find out a little more on how this works .. i'm wondering if you change the tire size if it's smart enough to adjust or if that can be programmed... i.e. your tires are 10mil taller over OE, does the computer always overblip.

Tire size won't have any effect on it. The difference in gear ratio from one gear to another stays constant, so it will always aim for the correct RPM. And if you change tire size (overall diameter change), the car doesn't know any better, it will still think your speed at 2000 rpm in 6th is the same, even if you're really going faster/slower due to a larger/smaller tire diameter.

I haven't 'used' it enough but was also wondering if it continuously adjusts the revs if the car's speed changes if you jokingly take an inordinate amount of time between gears..

Basically, yes. Because it's both smarter and simpler than you think. When the computer activates rev matching, it commands the engine to rev to rpm (vehicle speed sensor / diameter of the stock wheels / vehicle final drive / gear ratio of the gear you're entering) (I may have the math slightly wrong, but the idea is the same - there is a set multiplier between engine RPM and measured vehicle speed for each gear. They can determine that during design and program a single # into that formula, since first:
Vehicle speed sensor's raw output is actually transmission output shaft RPM, which then gets multiplied by final drive and (divided by?) diameter of the tires to determine the speed in mph, so the first division isn't necessary. Final drive never changes, so instead of dividing that by the gear ratio in real time, you can just program in what ( final drive / 1st gear ratio ) is, (final drive / second gear ratio ), etc, etc. are, so it's a very simple math problem, updated multiple times a second, so if your speed changes, the target rpm changes in direct relation to speed.

And I can't imagine why the programmer would now look at the source gear either..

That's the surprising part, to me. Before it was a super simple block: "If shifting into gear (IE, shifter in gear and clutch depressed), command engine to hit <target rpm>", where <target rpm> is a calculation as described above...

Doing it for only some downshifts requires tracking state a lot more. What gear were we in previously? etc, etc.

[B58 parts]

My point was if you change the tire size the speedo will always be off... so it for sure matters for the blip calculation. It will misblip every time if you change nothing aside from the OD of the tires from stock.

Likewise obviously if you change your FD gear out it will radically misblip and your speedo reading is far different from actual speed.

I bet they have a hard coded number in there for the FD and the stock tire OD as well. Put 22s on yo and see how the blip works.

[rak299]

When I had my car in for service today, I asked the "service adviser" and he didn't know what rev matching was or why you might want it or not want it. He said I had no software updates suggested for my car, but said he would talk to the foreman to see what he knew. They were going to call back, but I heard nothing.

[kern417]

Originally Posted by YuminNuman

My point was if you change the tire size the speedo will always be off... so it for sure matters for the blip calculation. It will misblip every time if you change nothing aside from the OD of the tires from stock.

it doesn't matter what your actual speed is. when rev matching, the car is comparing the hub speed (wheel sensor) to the engine speed. and the hubs diameter will not change regardless of your wheel size. what will change is the speed on the dash vs your actual moving speed, which is irrelevant to rev matching.

[eluded]

Originally Posted by kern417

If they had a button or coding to turn it off, i probably would. But imo it's not as big of a headache as people make it out to be.

I generally double down and on my gears and the rev matching never shows up. I think if you blip the throttle between gears it doesn't match. I will confirm tomorrow

[PushingRedline]

Originally Posted by rak299

When I had my car in for service today, I asked the "service adviser" and he didn't know what rev matching was or why you might want it or not want it. He said I had no software updates suggested for my car, but said he would talk to the foreman to see what he knew. They were going to call back, but I heard nothing.

Please let us know if you do hear anything. My SA hasn't contacted me back yet so I am guessing he just doesn't care.

[Araemo]

Originally Posted by YuminNuman

My point was if you change the tire size the speedo will always be off... so it for sure matters for the blip calculation. It will misblip every time if you change nothing aside from the OD of the tires from stock.

Likewise obviously if you change your FD gear out it will radically misblip and your speedo reading is far different from actual speed.

I bet they have a hard coded number in there for the FD and the stock tire OD as well. Put 22s on yo and see how the blip works.

No, changing your FD will not effect it. Even if it were based on MPH reading, it would still be fine, because the amount of error would be equal in both cases. If your wheel diameter is 2% larger, your MPH reading will be 2% lower than it should be, but your engine rpm will be the same as it was at the same MPH reading. It will just be 2% lower than it 'would' be at your real speed. The only thing that would cause it to mis-blip is changing your gear ratios without reprogramming the ECU with them. And if you're doing that invasive a change, you should probably be able to disable this feature.

Originally Posted by eluded

I generally double down and on my gears and the rev matching never shows up. I think if you blip the throttle between gears it doesn't match. I will confirm tomorrow

It does still, but if you blip to above the target rpm before pushing the gear lever into gear, it has nothing to do, but if you watch it, RPMs should drop to the 'correct' rpm, then stop dropping for a moment (1-2 seconds, I think?) before it gives up on rev matching and lets them drop again.

[B58 parts]

Ok, I didn't know about this ABS hub sensor ... I didn't realize is it's reading the hub rpm in gear A vs the hub to gear B, which is a relative calculation only between gear A vs B. I didn't know about that sensor and figured it would be MPH (VSS/FD/tire) based. Interesting... I guess this is a 17 BMW vs my 96 honda I was about to put the 4.9 FD in.

So, I can freely move to slightly different tire diameters (not that I will) and my speedo will still read correctly (as this is also hub based), and I won't worry about the computer misblipping. (Though I will always do that manually and still seek to disable it outright, preferably keeping DSC on).

My whole point was it would really suck if a simple tire change caused it to always underblip.

[Beek]

Originally Posted by rak299

When I had my car in for service today, I asked the "service adviser" and he didn't know what rev matching was or why you might want it or not want it. He said I had no software updates suggested for my car, but said he would talk to the foreman to see what he knew. They were going to call back, but I heard nothing.

Sad ... just sad.

[Araemo]

Originally Posted by YuminNuman

Ok, I didn't know about this ABS hub sensor ... I didn't realize is it's reading the hub rpm in gear A vs the hub to gear B, which is a relative calculation only between gear A vs B. I didn't know about that sensor and figured it would be MPH (VSS/FD/tire) based. Interesting... I guess this is a 17 BMW vs my 96 honda I was about to put the 4.9 FD in.

So, I can freely move to slightly different tire diameters (not that I will) and my speedo will still read correctly (as this is also hub based), and I won't worry about the computer misblipping. (Though I will always do that manually and still seek to disable it outright, preferably keeping DSC on).

My whole point was it would really suck if a simple tire change caused it to always underblip.

You are really misunderstanding things. You can freely change tire diameters without effecting automatic rev matching at all. You cannot freely change tire diameters and expect your speedometer to be accurate.

Vehicle speed sensors in BMWs (and every other car I've owned) read the RPM of the transmission output shaft, and the control unit that converts that to MPH has a ratio it applies that's based on the final drive ratio and tire diameter. Which is why changing either will make your speedometer inaccurate. However, since the spot the 'vehicle speed' is measured is before either final drive or tire diameter are involved, changing either of those will not impact the automatic rev matching.

Lets break it down further...
In third gear, at 45 MPH, the engine is at 3000 RPM. So if you're driving in 5th at 45, and want to downshift to 3rd, you blip to around 3000 RPM to rev match.

If you then increase your tire size by 11% (255/40R18 to 255/50R19.. ridiculous, but just pretend you did it).

When your speedometer says 45 MPH, you'll actually be going 50 MPH.

But, if your speedometer says 45 MPH, and you are in 3rd gear, you'll still be at 3000 RPM, even though you're actually going 50 MPH.

So, even though you're going 50 MPH, if you're in 5th and want to downshift to third, you'll still be blipping to around 3000 rpm to match the 3000 rpm at an indicated 45 MPH. And this is basically exactly what the computer will do, so it won't be bothered by tire diameter changes.

So, even if the engine control unit based the rev matching on vehicle speed in MPH, it would still work accurately if you changed final drive or overall tire diameter, because those multipliers apply after where it measures vehicle speed, which is why your speedometer is inaccurate after changing either of those.

None of this has anything to do with the wheel speed sensors on the wheel hubs, which are used for ABS, ESC, etc.