Speed Limiters

What’s with this new trend towards speed-limiters in new cars and trucks nowadays? Besides that, how do they decide which cars have them and which don’t? I’ve been thinking about this since a recent Motor Trend Editorial brought it up. I don’t really understand the point of some speed limiters on cetain cars. I find some that are just, like putting a speed limiter on a Lamboughini Diablo 6.0 or a McLaren F-1 simply for the purpose of keeping them from out-running the police helicopter, but for other cars, like a Honda or Toyota that has its speed limiter set at 125, what’s the point when the car’s actual speed limit (when the car just won’t go any faster) is only 130? Plus, if you’ll notice, Imported cars often times have speed limiters whereas their American equivalents don’t. Take, for example, a BMW Z3 and a Pontiac Firebird. They aren’t exactly in the same class, but you get the idea. the Bimmer has a speed limiter set at 135, but the Firebird is free to go way past 150. Does anyone know why the government does this?

They are called “govenerors”, and AFAIK, the Federal Govt does not require them.

However, I believe that the German government does require a cutoff around 200 km/h (125 mph), which is why the BMW has it. Maybe the Japanese government has something similar.

I don’t agree with a cutoff on cars like the Diablo, though… at least ones that can’t be easily bypassed. If I’m going to spend that much money on a car, I expect it to go as fast as it can. :wink:

In any case, for many (all?) modern cars, you can easily and legally (in the US) remove the cutoff by replacing the chip.

I have not read the Motor Trend article, however I am not sure that the goveners are mandated by the goverment. I can only speak from experience regarding one car manufacturer and that is Honda. On Honda’s, there is actually no govener per se, but rather a rev limiter and a ful cut-off. The rev limiter is there to stop the car from being rev’ed to high. The redline on a stock Honda Prelude is around 7200 RPM. (The actual limit is 7200 but the stock tach is so in-accurate that it will often read anywhere from 7200 - 8000) What is significant is that the rev limiter can be changed, but you only do this if you have modified your car to be able to handle the additional rev’s.

Now the fuel cut-off is a different story. This is something that can never be changed (so I have heard) and is designed to stop a person from creating a monster car that will destroy itself. A stock Prelude can not handle 200 mph (this is a made up number, I have no idea what the “terminal velocity” of a Prelude is) so the fuel cut-off is there to make sure that no matter what kind of crap you put on the car to speed it up, it will never reach a speed it was not designed to handle. Reasons being saftey, most likely.

Please understand this is my knowledge of Honda’s ONLY. I would assume it applies to domestics and other imports, but I have no idea.


I do know that on a Z-3, you have to get special tires and then they will bump the governor from 125 to 138 or something lke that.

This helps to prevent tire blow-outs a-la Ford Explorers.

I had a new Grand Prix in 1996 and the goveneror kicked on at 105mph. I wish they had set it at 120. I think that car would have done it.

Speed limiters are being applied voluntarily by the big 4 Jap bike manufacturers. In the UK this is supposed to be around 186 mph but this is a matter of p.r rather than any meaningful limit on speed.
Their view is that they should limit their speed voluntarily to something less than the emotive 200mph barrier rather than have it done in an ad-hoc way with differant levels in differant countries which would mean that there would have to be differant spec models and a consequent increase in cost, or decrease in profit.
If you look in the latest bike magazines you will also read that they are moving over to digital speedos, not just to reduce weight, but also so as not to display the speed markings on the clocks when the bike is parked up.

In Europe they have a 100hp limit on bikes but usually this can be derestricted or an import brought in from somewhere that does not.We in the UK have no upper limit
On the unrestricted speed German autobahns, and not all are, there is an insurance disclaimer which states that if you travel above a certain speed then you are no longer insured, however you may go as fast as your vehicle will allow you.

Personally I think that power limiters can be a bad idea , the last thing you need when accelarating to get out of a sticky situation, like a dodgy overtake, is a loss of go.

The real problem of speed is not addressed by such measures anyway simply because they do not stop you doing 50mph when the conditions do not allow like in ice or fog.Many if not most accidents occur not on the safest roads there are(such as the freeways) but on urban roads where the speed limits are much lower.

Someone has to say it so it might as well be me…

Speed kills.

How many cars are actually designed to be driven at high speed and how many drivers have the needed skills? I don’t think there are many in either category.

It seems like a good idea to set cars up with systems that will protect the driver from making a car outperform it’s design specs. I have lost count of how many times I have been passed on the highway by people driving compact economy cars that are not built for the speed they are being driven. Your minivan wasn’t designed to be driven down the highway at 90 mph. I can see building a minivan with decent horsepower because they are designed to haul people and stuff but are they built for high speed? Definately not.

We have laws against speeding so why would anyone object to having their car restricted to let’s say, 80mph? You’d be able to pass people on the road but wouldn’t be able to fire that 4000 pound missile also known as your car down the highway at 100mph.

I believe that the specified top speed of my car is 135mph but you won’t see me testing this out at any time. I was thinking the other day that my car could actually use an off switch on the turbo because in poor driving conditions it is all too easy to get the wheels to break free and start spinning. I want to be able to switch things back on for when the roads are dry and clear… I admit that I sometimes drive a little over the speed limit and love acceleration.
A governer shouldn’t restrict the power available to the driver but should limit the top speed of the vehicle. I don’t see this as being a bad idea but I am sure there are more than a few people that will scream that this would be another attempt by the government to legislate and control our behaviour.

Feynn, I agree that most cars out on the roads nowadays are not designed for high-speed driving, e.i. above 75, I’d say. However, these cars are not what I was complaining about in the first place. There are many cars out there that are certainly capable of high speeds and wouldn’t be in any mechanical danger doing so, but they also have speed-limiters on them. I’m talking about cars like Camaros (They used to have speed-limiters on them, I’m not sure if they still do) and Bimmers that are designed for superlegal speeds, however will never achieve them because of a speed-limiter. I agree whole-heartedly that econocars that get 60mpg shouldn’t really be going 70, let alone 90. However, if you’ve got a car that’s capable of going really fast, well then I don’t think the government (or anyone else for that matter) should be able to take the ability to go fast away from us. Sure, people will say stuff like its against that law to go above 75, but they’re wrong. There are literally thousands of places that are in fact free to go to that will permit high speed driving. One of these places is the Utah Salt Flats. Even in a Geo Metro, you could probably hit 140 out there (if the gears went up that high). All I’m trying to say is why should a car company design a go-fast car if it’s just gonna be limited from its full potential of doing what it was designed to do?

My friend had a Camaro, it had a fuel cut-off that would kick in at 120. He demonstrated it to me once.

BTW, I have a '92 Honda Civic hatchback that was surprisingly fast. I tested it and took it up to close to 110 and it felt like it could go quite a bit faster, but the front end started feeling floaty, like it was wanting to come off the ground. It could probably go 120, but I think it would be highly dangerous even on the most gradual curve at those speeds.

threemae wrote:

… which is an opinion more suited to this thread: http://boards.straightdope.com/sdmb/showthread.php?threadid=41865


Lately I’ve been driving between Spokane and Seattle every few weeks. The speed limit is 70 most of the way, but I regularly drive between 80 and 90. So does everyone else. It cuts 30-60 minutes off my trip, and hey, I like driving fast.

Before I bought this car I drove a VW Diesel Vanagon with a top speed of 65 mph, and then an Isuzu Trooper with so many problems I could rarely reach 60 on the freeway. Let me tell you, getting passed by every semi on the road is no fun.

I can drive 300 miles between 80 and 90 mph and still get 29 miles per gallon. I can take every turn the freeway has to offer and slow down quickly if I need to. I use good judgment and keep my eyes open. I see no need for a device that prevents me from driving at speeds my car was designed to handle.

In many (most?) cases the rev limiters are there to prevent you from exceeding the speed rating for the stock tires. Tires come in various speed letter ratings, with the highest being ‘Z’ I think, at 135+ or something like that.

Most stock tires are rated at 90 or 100 MPH (guesses, the numbers are somewhere around there) so the car manufactures want to keep the cars under that speed. At those speeds, unless the tires are designed for it, the internal friction from the belts will cause the tire to overheat and blow out.

If you want to go fast, make sure your tires (and brakes) are rated for that speed, not just the engine.

Mr. 2001 - So you get to make what is normally a four hour trip in three and a half hours. If your car can handle it and you don’t mind the possibility of being ticketed go for it. 10 over the limit isn’t a big deal. Just don’t kill anyone or yourself.

I once drove from Vancouver to Penticton in two and a half hours in what is normally a four hour trip. Not much of the route I took was straight for any length of time. Average speed was 100mph as I had to slow down for the corners and make a stop for fuel.

Scariest moment? Passing a cop while doing 130mph. If he didn’t have someone pulled over already I would have been toast. I would have deserved to have my license pulled but the driving gods were smiling on me that day.

My thanks go to Ferdinand Porsche for building such wonderful cars.

Are you sure about this? You may be correct, but I have had a personal experience that has led me to think differently.

My 2000 BMW was originally slated for German delivery. It ended up in the states almost by mistake. I know for a fact that my car is not limited to 128 mph the way it’s supposed to be according to the technical information offered by BMW of North America. This has led me to think that BMW only employs limiting devices for autos intended for American delivery.

Also, the BMW Z3 is manufactured in the United States - specifically, South Carolina. That model does indeed have a limiting device even though the vast majority of Z3’s are delivered to US dealers.

What we need here is testimonial from a German driver of a new, fast car. I’ve tried to search German law archives, but they make my head hurt.