Vehicle Speed Limit Controller
dunecherng
03-06-2005, 03:30 PM
I'm doing a project titled Vehicle Speed Limit Controller. I'm not familiar with the car's part so I hope that I can get some useful information at here. The case is: speed limit for expressway is 110km/h and 60km/h at cities. So if I want to design a device to control the vehicle highest speed in different places, where should I start? How I can control the limit? connecting the device to ECU? Then I have to change the ECU's setting? connect the device to fuel pump to control the fuel distribution? but how if too much air gets into engine while the amount of fuel reaches the maximum quantity so that the speed won't exceed the limit? connect to fuel injection system? or just control the throttle valve position? Anyone can answer me? thank you.
Ridenour
03-06-2005, 07:00 PM
Is this just a hypothetical situation for like a class?
Well anyways the route I would go with would be air to fuel ratio, as well as throttle plate position. Most modern speed limiters kick in by leaning out the mixture and cutting timing. However, leaning it out too far can be very dangerous for the engine. So I would go with a combination of leaning it out as lean as it will safely go, and then beyond that have the ECU start to close the throttle plate.
Well anyways the route I would go with would be air to fuel ratio, as well as throttle plate position. Most modern speed limiters kick in by leaning out the mixture and cutting timing. However, leaning it out too far can be very dangerous for the engine. So I would go with a combination of leaning it out as lean as it will safely go, and then beyond that have the ECU start to close the throttle plate.
Autopro
03-06-2005, 09:18 PM
You can also check two other systems. Trucks use a Governor to contol its speed. Also check to see the how cruise control system for a vehicle works. You can search online or go to the store and buy a manual. That should give you an idea how to design a device.
Hope this helps.
AutoPro
Hope this helps.
AutoPro
CBFryman
03-06-2005, 09:57 PM
i dont understand why you would need to do this. it will never happen. regulateing speed by govenor to the exact speed limit is just asanine. there are times when exceeding the speed limit is perfectly alright, for instance if someone is dying.... i wouldnt wait on an ambulance in the county i live in.... i would have someone drive me. also, acceleration may be needed to get out out of a dangerous situation, such as on an on or off ramp on an expressway or even on a multi lane road where you end up next to or near a big rig.
dunecherng
03-06-2005, 11:15 PM
Original posted by CBFryman:
i dont understand why you would need to do this. it will never happen. regulateing speed by govenor to the exact speed limit is just asanine. there are times when exceeding the speed limit is perfectly alright, for instance if someone is dying.... i wouldnt wait on an ambulance in the county i live in.... i would have someone drive me. also, acceleration may be needed to get out out of a dangerous situation, such as on an on or off ramp on an expressway or even on a multi lane road where you end up next to or near a big rig.
Well although each road has different speed limit but most of the drivers still exceeding it most of the time. Don't you think this is making a risk for other road users? So this system is to limit the speed by force. But for instance if someone is dying, i also wouldn't wait on an ambulance but, how you be sure that the person can just be move like so easy into the car, for example, if someone has bone fracture or internal bleeding. Besides, if you speed up to send the person to hospital, aren't you also risking others' life?
i dont understand why you would need to do this. it will never happen. regulateing speed by govenor to the exact speed limit is just asanine. there are times when exceeding the speed limit is perfectly alright, for instance if someone is dying.... i wouldnt wait on an ambulance in the county i live in.... i would have someone drive me. also, acceleration may be needed to get out out of a dangerous situation, such as on an on or off ramp on an expressway or even on a multi lane road where you end up next to or near a big rig.
Well although each road has different speed limit but most of the drivers still exceeding it most of the time. Don't you think this is making a risk for other road users? So this system is to limit the speed by force. But for instance if someone is dying, i also wouldn't wait on an ambulance but, how you be sure that the person can just be move like so easy into the car, for example, if someone has bone fracture or internal bleeding. Besides, if you speed up to send the person to hospital, aren't you also risking others' life?
Moppie
03-07-2005, 03:03 AM
If you want to debate the morality of speeding please don't do it in this forum.
Its a good way to get your posts deleted.
We have a variety of forum in the Coffee Break/Off Topic forum you can use for this discussion.
As for speed limiters and how they work?
Most use an ignition cut. A fuel cut creates a lean condition, which is a good way to destroy an engine.
They are then hooked up to some kind of electronic speed sensor, which cuts the ignition at a predetermined speed.
Rev limiters work the same way.
If you can reprogram the ECU, or convince car manufactors to install lower speed limits then it easy to set them to what ever speed you want.
The problem with your idea will be changing the limit for the differnt speed zones.
The car needs to know what speed zone its in, and given the hundreds of thousands of differnt speed zones in a small country like NZ thats a lot of information for the car to have collect, or a lot of sensors and transmitters.
The simple fact is such an idea is simply not practicle.
Its a good way to get your posts deleted.
We have a variety of forum in the Coffee Break/Off Topic forum you can use for this discussion.
As for speed limiters and how they work?
Most use an ignition cut. A fuel cut creates a lean condition, which is a good way to destroy an engine.
They are then hooked up to some kind of electronic speed sensor, which cuts the ignition at a predetermined speed.
Rev limiters work the same way.
If you can reprogram the ECU, or convince car manufactors to install lower speed limits then it easy to set them to what ever speed you want.
The problem with your idea will be changing the limit for the differnt speed zones.
The car needs to know what speed zone its in, and given the hundreds of thousands of differnt speed zones in a small country like NZ thats a lot of information for the car to have collect, or a lot of sensors and transmitters.
The simple fact is such an idea is simply not practicle.
curtis73
03-07-2005, 04:39 AM
Not to mention thousands of studies show that traffic problems would be infinitely worse if speed were controlled like this. If you could watch what happens to traffic from overhead and be able to mathematically decipher what is going on, you'd see that one of the few things that keeps traffic moving is its diversity of speed.
On an interesting sidenote, the mathematical minds that study this used blood as a model. They radioactively marked red blood cells, then injected them into a test subject. By watching how slow (faster) cells and larger (slower) cells merge in and out of restrictions, splits, and intersections, they were able to write algorithms as a pattern for traffic.
But enough about Big Brother :)
Speed limiting should never be done with A/F ratio. It can be done with an electronically controlled throttle. Cars like C5 and C6 corvettes don't have a throttle cable, they have a sensor on the pedal and a servo-driven throttle. They limit top speed by controlling the actual position of the throttle, which I think Ridenour was saying in a manner of speaking. If you just limit fuel you can easily do damage. By limiting throttle, you limit air and fuel just as if you lifted your foot.
Dropping the ignition is a very good way to limit top speed and that's how most accomplish it. Some of the early speed-limited cars would shut down the ignition (and injectors if so equipped) at the top speed for a few seconds. In effect, turning off the engine for enough time to drop speed. I had a Beretta that would do that. It was limited to 110. It would shut down everything for 2.5 seconds. If I held my foot to the floor it would go to 110, shut of and drop down to about 95, then kick on and go back up to 110.. etc. More modern ignition-controlled speed limiters use a floating or random misfire technique where it starts dropping random sparks. On the first time around it might drop cylinders 2 and 6, then 3 and 8, and so on. This way, any cylinder only ever misses a spark for one revolution preventing fuel load up.
On an interesting sidenote, the mathematical minds that study this used blood as a model. They radioactively marked red blood cells, then injected them into a test subject. By watching how slow (faster) cells and larger (slower) cells merge in and out of restrictions, splits, and intersections, they were able to write algorithms as a pattern for traffic.
But enough about Big Brother :)
Speed limiting should never be done with A/F ratio. It can be done with an electronically controlled throttle. Cars like C5 and C6 corvettes don't have a throttle cable, they have a sensor on the pedal and a servo-driven throttle. They limit top speed by controlling the actual position of the throttle, which I think Ridenour was saying in a manner of speaking. If you just limit fuel you can easily do damage. By limiting throttle, you limit air and fuel just as if you lifted your foot.
Dropping the ignition is a very good way to limit top speed and that's how most accomplish it. Some of the early speed-limited cars would shut down the ignition (and injectors if so equipped) at the top speed for a few seconds. In effect, turning off the engine for enough time to drop speed. I had a Beretta that would do that. It was limited to 110. It would shut down everything for 2.5 seconds. If I held my foot to the floor it would go to 110, shut of and drop down to about 95, then kick on and go back up to 110.. etc. More modern ignition-controlled speed limiters use a floating or random misfire technique where it starts dropping random sparks. On the first time around it might drop cylinders 2 and 6, then 3 and 8, and so on. This way, any cylinder only ever misses a spark for one revolution preventing fuel load up.
charles27
04-24-2005, 04:16 PM
can i turn it off if yes tell me
Automotive Network, Inc., Copyright ©2025