Cruise Control: Set Minimum Speed

'The cruise control in my Passat 3B TDI AJM '99 with 115 hp can only be activated above 30 km/h, which seems to be a deliberate design choice. It's also not possible to activate the cruise control in first gear above 30 km/h, which is illogical, but I wanted to test it. The cruise control must be getting information about speed and the gear selected, with the speed signal being a direct input and the gear likely being derived from the speed and engine RPM. Is there any way to bypass this limitation of the cruise control, so that it can be used both below 30 km/h and in first gear? The purpose of this exercise is to use the cruise control in traffic zones where the speed limit is below 30 km/h, in order to strictly adhere to it. It's likely that the cruise control was disabled below 30 km/h by VW engineers to prevent users from making mistakes – what would happen if you pressed the acceleration button on the lever in first gear and the car over-revved? It probably doesn't make sense to drive slower than 30 km/h in second gear, or why was the area below 30 km/h locked out for the cruise control? I'm looking for a way to bypass this lock, so that I can use the cruise control below 30 km/h and/or in first gear!'

Hi,
The GRA (presumably a control unit) regulates the speed (v), so it should also receive the speed as a measured value. It doesn't need to perform any calculations, because the speed (v) is already available in the engine control unit (ECU) and is sufficiently accurate at a resolution of 3 clicks per meter.

I don't know the exact meaning of the 30 km/h speed limit, but it's not "over-revving" because even when idling, the engine control unit, which regulates everything, doesn't over-rev.

You can certainly remove the limit if you can reprogram the MSTG. It's nothing more than chip tuning. You just need to figure out how that limit is stored on the chip and have someone reprogram it with something else.

m;

Hi,

If I have to drive at a constant speed of 10 or 20 km/h and I'm too lazy to press the accelerator, I don't need a cruise control. I can simply put the car in first or second gear and let it idle. This would result in a speed of around 9 or 17-18 km/h, which isn't really a problem.

Best regards,

Jan.

hb2000 wrote:

Der Tempomat bei meinem Passat 3B TDI AJM '99 mit 115PS lässt sich erst ab 30 km/h aktivieren - das scheint ja irgendwie vom Werk aus gewollt zu sein. Auch ist es nicht möglich, den Tempomaten im ersten Gang bei über 30 km/h zu aktivieren - ist zwar unsinnig diese Konstellation aber ich wollte es einfach ausprobieren. Also bekommt der Tempomat irgendwo her die Information von Geschwindigkeit und verwendetem Gang, wobei das Geschwindigkeitssignal direkt anliegen sollte und der verwendete Gang sich wahrscheinlich zusammensetzt aus Geschwindigkeit bei verwendeter Drehzahl. Gibt es irgend eine Möglichkeit, diese Beschränkung des Tempomaten aufzuheben, so dass der Tempomat sowohl unter 30 km/h als auch im ersten gang verwendet werden kann ??? Sinn und Zweck dieser Übung wäre das Verwenden des Tempomaten in Verkehrszonen, wo die Geschwindigkeit unter 30 km/h vorgegeben ist und um diese penibel einhalten zu können. Wahrscheinlich wurde der Tempomat unter 30 km/h von den Ingenieuren von VW gesperrt, damit keine Idiotenfehler damit passieren können - was passiert, wenn man im ersten Gang auf die Beschleunigungstaste am Hebel drückt und die Karre komplett überdreht ??? Wahrscheinlich macht es keinen Sinn im zweiten Gang langsamer als 30 km/h zu fahren oder warum wurde der Bereich unter 30 km/h gesperrt für den Tempomaten ??? I am looking for a way to remove this restriction, so that I can use the cruise control at speeds below 30 km/h and/or in first gear!!!

You've already answered your own question - of course, it doesn't make sense to drive with GRA below 30 km/h, just like it doesn't make sense to drive in first gear above 30 km/h, unless it's purely for fun. However, since the people at VW usually prioritize reason over fun, this limit was set.
Andrere Frage, wenn du diese Grenze festlegen müsstest - wohin würdest du sie legen, aber bedenke du verkaufst 10 Mio. Autos?

As dieselmartin correctly pointed out, there's nothing you can do.

dieselmartin wrote:

I don't know the exact meaning of the 30 km/h speed limit.

"This is a requirement for type approval. The cruise control must not function below 30 km/h. Similarly, the ABS must not function below 6 km/h. These are safety regulations mandated by law."
The gear identification is performed simply by calculating the relationship between speed and velocity.

Okay.

Good evening.

With any mechanical cruise control system, such as one that draws its speed reference from the alternator, it is quite possible to drive at speeds as low as 5 km/h while using the cruise control. The system simply doesn't know how fast it's going and bravely maintains its set speed.

"Contrary to what's supposedly legally required, DEKRA didn't even look at this part during the vehicle inspection (TÜV) or ask about any ABE/CE approvals. It's probably just a matter of product liability/avoiding problems, so maybe it could be changed?"

That would be great!

Peter K.

PeterK wrote:

.... "Contrary to what's supposedly legally required, DEKRA didn't even look at this part during the vehicle inspection, nor did they ask about any ABE/CE approvals. It's likely just a matter of product liability/avoiding problems, so perhaps it could be changed?"

Read the instructions!
The speed limiter I installed for my father in his G3 ADY specifically states that it should not be used at speeds below 30 km/h. While it is possible to connect it to the alternator or the tachometer signal, this is not covered by the approval certificate (ABE) that came with it.
At the technical inspection, the TÜV inspector immediately asked for the ABE (General Operating Permit). Different TÜV locations, different practices.

I consider it technically impossible to set a 30 km/h speed limit with Lima, because at 5th gear, there's something like an idle speed of 1000 (t4) RPM, and with first gear, it clearly goes significantly below 30 (5?! ).
The manufacturer wouldn't have been allowed to obtain the necessary approval for that..., and the device could have been connected directly to the alternator, since that wouldn't cost anything.

Peter K.

Okay, I'll check my manual to see what it says. Then, if it's applicable (i.e., if the validity period is less than 30 days), the sentence about the expiration of the approval certificate (ABE) needs to be included.

Mechanically, it should work without problems with the cruise control at speeds below 30 km/h; the issue is more that it's not supposed to function at those speeds. Electronically, the cruise control won't be easily bypassed in the control unit, unless there's another activation code for different countries that would allow it to be activated even at speeds below 30 km/h. And there are definitely still some codes for the control units that are kept secret by the engineers and will never be released publicly. Every system has its hidden features or traces left over from development; you just have to find a way to discover them.