Speed governor/limiter (EU)

[npole]

OP is arguing about how two displays disagree with each other or one onboard system doesn't match GPS

Where did you read this? I never said a such thing, neither the two could match, for a matter of reasons that aren't part of this topic.
We're discussing about how the speed governor works, and why it didn't kicked in at the supposed read speed (not the "real" vehicle speed). Please do not deviate the topic with stupid argumentations.

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[npole]

You assumed a top speed and went past it

I did not "assumed" anything, It's the speed shown on the speedometer, and it doesn't count if it's the speed in the "real world", the instrumentation is aboard of the car and the governor relies on the calculated/read speed.
As I already wrote in the previous message: here we're discussing why the governor didn't kicked in, NOT the real speed of the car.

 

[Vlad Soare]

The easiest and most obvious explanation would be that Euro Bullitts are not electronically limited. But frankly I find this unlikely.
Another one would be that the PCM disregards the intentional error built into the speedo. The speedo is intentionally programmed to read a bit higher. But I don't know at which point in time this error is added into the equation. Is it embedded into the very algorithm that calculates the speed based on the input from the ABS sensors? Or is the real speed calculated first, then the PCM (or is it the BCM?) adjusts it and sends the adjusted value to the speedo? In the latter case, the PCM could take the real speed into account when deciding when the limiter should kick in.

 

[ZeroTX]

I don't care about GPS (it was just a coincidence, that it shown the real "declared" speed).. I'm more curious about the speedometer reading 273. If it's limited to 263, it should never have reached that speed.
So with a recent updated they increased the top speed further.. or the governor is calculating the speed in a different way.

Automotive speedos are known to read high intentionally. However, legally, they cannot read high for odometer reading purposes. In other words, your speedo is lying.

 

[npole]

The easiest and most obvious explanation would be that Euro Bullitts are not electronically limited. But frankly I find this unlikely.
Another one would be that the PCM disregards the intentional error built into the speedo. The speedo is intentionally programmed to read a bit higher. But I don't know at which point in time this error is added into the equation. Is it embedded into the very algorithm that calculates the speed based on the input from the ABS sensors? Or is the real speed calculated first, then the PCM (or is it the BCM?) adjusts it and sends the adjusted value to the speedo? In the latter case, the PCM could take the real speed into account when deciding when the limiter should kick in.

The speed could be intentionally programmed to read higher to comply with the law to mitigate a reading low error (of effective speed) and potentially having you speeding more than you think? It's an explanation.. however it's all speculation, like the others. I think we'll have more info if I'll manage to read the value discussed above, if it's effectively higher than 262, then maybe all the EU Bullitts have been "upgraded" or mine has a different software (coz they "played" a lot with it...).

 

[npole]

Automotive speedos are known to read high intentionally. However, legally, they cannot read high for odometer reading purposes. In other words, your speedo is lying.

If that's the case, it can be tested with a GT as well (EU non-EU doesn't matter). We know they are limited to 250, if so, the speedo should show more that that before the governor kicks in... if I'll found someone with a non-tuned GT that has "tested" the effective max speed.

 

[Vlad Soare]

The speed could be intentionally programmed to read higher to comply with the law to mitigate a reading low error (of effective speed) and potentially having you speeding more than you think?

Not only that it could, but it definitely is. We know it is.
What we don't know (I mean I don't know) is whether the PCM is aware of this intentional deviation and disregards it when it comes to triggering the speed limiter. I'm not sure which module is responsible with determining the current speed, but my guess would be the BCM. Does the BCM apply a certain coefficient as part of the speed calculation algorithm? Or does it calculate the speed correctly, then it sends the real speed to the PCM and an adjusted (increased) value to the IPC? I don't know. If it's the latter, then it could explain the behaviour you've experienced.

When you reached 263.5 km/h and couldn't accelerate any further, did it feel like an electronic limit? Or did it feel like the car simply could not do more?

 

[npole]

When you reached 263.5 km/h and couldn't accelerate any further, did it feel like an electronic limit? Or did it feel like the car simply could not do more?

Not a "break feel" (like in example you feel when hitting a rpm limiter), the car was rising slowly but steady, it gave me the feel that it would have gone up more than that, but suddenly it stopped at 273 like it was me maintaining that speed with the accelerator (I was obviously floored).
I know the feel of reaching the max speed due to the aerodynamic (vs the power), it's not like that, the max speed is reached more and more slowly as you approach its limit, and it's also not constant. While I can't bet for sure that it was effectively a limiter, the feel was that.

 

[raptor17GT]

Where did you read this? I never said a such thing, neither the two could match, for a matter of reasons that aren't part of this topic.
We're discussing about how the speed governor works, and why it didn't kicked in at the supposed read speed (not the "real" vehicle speed). Please do not deviate the topic with stupid argumentations.

your first post states two speed readings therefore you had the car speedo and a GPS read out hence me pointing out two different readings, that's what you said originally. Moving on

I have read information on the output shaft speed sensor sending signals to the PCM and the speedo getting information from the ABS sensors but the speedo works on the rolling road when the fronts aint moving so that doesn't sense check entirely.

Does your cruise control setting match 100percent with the speedo reading? I'm sure my cruise control is a couple mph lower than the speedo but mt82 MY17 so maybe not the same. Be interesting if the same difference is noted on digital equipped cars.

Get it read by a forscan reader, can't change it but it can read its value. 263kph aint slow, well done.

Speed limiters tend to work by pulling fuel so it will feel a soft limit rather than the hard limit of a rev limiter so that matches what you said?

 

[WD Pro]

Just some comments that may / may not be applicable to the Mustang.

Based on a car I've had in the past (Euro spec e36 M3 evo) I seem to recall some owners reported that the limiter would allow some overshoot (to 163 mph ish) before slowly bring it down to a constant 155.

I didn't experience that in my car, mine simply stopped accelerating, just like I had got up to speed on a motorway and then backed off the throttle to hold it at a constant speed. In the case of the M3, mine stopped accelerating at 155 mph (exactly as per spec) in fifth. I didn't look at the speedo (kind of regret that) as the car had gone a little floaty at the front, but the handheld garmin clocked it at 155. I don't even know what it was reving at, I just had the mentality that if the shift light blinked I would have put it in sixth lol

Maybe the stang has a similar soft limiter at the top end ? I'm sure that would be more preferable at those speeds than a hard limiter that could unsettle the car or driver ...

WD

 

[raptor17GT]

found this topic, basically speedo says 273 but car is doing 263..... and you're in the thread lol
https://www.mustang6g.com/forums/threads/gear-to-speed-limits.143305/post-2963622

 

[Vlad Soare]

Not a "break feel" (like in example you feel when hitting a rpm limiter), the car was rising slowly but steady, it gave me the feel that it would have gone up more than that, but suddenly it stopped at 273 like it was me maintaining that speed with the accelerator (I was obviously floored).
I know the feel of reaching the max speed due to the aerodynamic (vs the power), it's not like that, the max speed is reached more and more slowly as you approach its limit, and it's also not constant. While I can't bet for sure that it was effectively a limiter, the feel was that.

Then I think that explains it. The PCM knew you were doing 263 km/h even though the IPC was showing 273. And the speed limiter kicked in.

 

[npole]

your first post states two speed readings therefore you had the car speedo and a GPS read out hence me pointing out two different readings, that's what you said originally.

The GPS speed matched the expected speed, was just a coincidence, it has nothing to do with the speedometer and the speed limiter.

Does your cruise control setting match 100percent with the speedo reading?

Never checked.

Get it read by a forscan reader, can't change it but it can read its value. 263kph aint slow, well done.

If it can be read with ForScan, i can do it. Is there any guide on "how"? I've only used it to read the PCM errors so far.

Speed limiters tend to work by pulling fuel so it will feel a soft limit rather than the hard limit of a rev limiter so that matches what you said?

Yes, like you would do by maintaining the gas pedal to a certain position to maintain that speed.

 

[npole]

Hi again... so the explanation was the most obvious one, and my assumption that the EU version is limited to 263 km/h was wrong, it is in fact limited to 273km/h, and it happened with an update released back in Nov. 2019.

I've found the thread where they were discussing this on the German mustang forum: https://mustang6.de/viewtopic.php?f=67&t=14694

Why 273? I guess it's because they wanted to match the "real" advertised top speed, so they accounted in the speedometer reading "error" and went for that number. The other EU chaps that have tested it (from the same thread above) ended with the same GPS speed as of me (263Km/h), while the speedo was reading 273.

There's another "interesting" finding: some time the governor kicks in lower (260Km/h on the speedometer). None knows why, a supposition is that it is variable depending of the external a/o engine temperature.

 

[npole]

found this topic, basically speedo says 273 but car is doing 263..... and you're in the thread lol
https://www.mustang6g.com/forums/threads/gear-to-speed-limits.143305/post-2963622

Yup, and because of that I "remembered" the discussion about the "increased" governor limit with an update, but I thought it was 263 Km/h, while effectively it is 273 Km/h. So the "mistery" wasn't a mistery at all, and there's no "two speed read", nor anything odd. The max speed is simply set to 273... with an exception (see the post above).

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