Disassembly: Speed Limit

**Greg E** · 03-26-2012, 09:07 PM

I was going to leave this out of v2 but it occurred to me that this might be handy. Say you're leaving your car with a friend or a mechanic and you don't trust them with your car.

The speed limit function is disabled by default, but it can be enabled via Periphery0 Bit6. There is another function to this bit as well, but I'm having trouble figuring out what is going on. It appears the speed limit operates just like the rev limit where it cuts fuel AND spark and I believe this is the other sub enabled with this bit.

The values you see here are the stock ones already programmed in memory.

To test this I set the Enable speed to 20mph and the Disable speed to 15, then gave my car to the inspection guys. Here in PA, state inspections are done with private garages. Now, all they were supposed to do was drive the car from the parking lot into the garage, hook up the OBD computer, then slap the sticker on it. Well... I got a phone call during the day about my car having a "problem" where it cuts out at 20mph and nearly caused an accident.

My reply was "How do you know this?"

**ChargerX3** · 03-27-2012, 01:34 AM

Would be awesome to automatically set this without having to reflash, but im not sure how you could do that.

**MR2** · 03-27-2012, 03:39 AM

I love that, I'm going to ask my tuners to give me a switch for that too!

**BigTyla** · 03-27-2012, 01:46 PM

Brilliant!

**Greg E** · 03-27-2012, 02:24 PM

Originally Posted by ChargerX3

Would be awesome to automatically set this without having to reflash, but im not sure how you could do that.

its not that hard but we only have a few inputs and I'd rather leave them for something else.

**Toni** · 03-27-2012, 05:23 PM

Speed is just a frequency input. It would be fairly easy to come up with an external device that handles limitation. Not sure I'd feel safe with it though in case it accidentally activates. Although solid state hardware once written correctly doesn't fail that often.

**stealthee** · 03-27-2012, 06:10 PM

Hey Greg, as part of PA state inspections they are technically supposed to take it for a drive to make sure everything is alright. I've only ever had my car taken for a drive twice, as most garages ignore that part, but it is actually what is supposed to be done.

**Greg E** · 03-27-2012, 06:53 PM

Originally Posted by stealthee

Hey Greg, as part of PA state inspections they are technically supposed to take it for a drive to make sure everything is alright. I've only ever had my car taken for a drive twice, as most garages ignore that part, but it is actually what is supposed to be done.

Got my sticker without the joyride.

**BigTyla** · 03-27-2012, 07:23 PM

Originally Posted by stealthee

Hey Greg, as part of PA state inspections they are technically supposed to take it for a drive to make sure everything is alright. I've only ever had my car taken for a drive twice, as most garages ignore that part, but it is actually what is supposed to be done.

I would NEVER go for that.