Why Are Many Sports Cars Electronically Speed Limited?

[diamondjo]

I was driving home from work the other day and I was thinking about how my 33 is electonically limited to 180km/h and while this is massively over any posted speed limit in our country, I got to wondering why manufacturers do this.

I figure it might have something to do with reaching the limit of the vehicle's aerodynamic stability - while a stock engine might be capable of powering on for another 30-50 km/h, perhaps higher speeds go outside of the rest of the car's safe operating parameters. At what point would a stock 33 start generating lift and leave the road? I suppose we don't just need to consider aerodynamics, but the propshaft, gearbox and other moving components could be reaching the limit of their safe operation as well.

Now everyone knows there are 300km/h+ Skylines out there, but I think you'll find most of them have massive spoilers and diffusers providing truckloads of downforce, sucking the car into the tarmac - and I also wouldn't be surprised to find carbon-fibre propshafts, upgraded diffs and high-speed tires.

So I guess the question is this; is the above a reasonable assessment of why we have elecronic limiters, or are the manufacurers just being kill-joys?

And semi-related; I'd be interested to know if anyone has driven a stock R33 gts25t without a limiter on something straight and flat like an airstrip and how fast you got it up to.

[madbung]

Japanese government legislation, they also have kw restrictions...it's a safety and emissions issue I believe.

Nice tangent though

[diamondjo]

Japanese government legislation, they also have kw restrictions...it's a safety and emissions issue I believe.

Nice tangent though

Thanks for the reply madbung. I know the Japanese have what they call a "gentleman's agreement" on power restriction - but speed limiting is not just a japanese thing. The latest BMW M5 is elecronically limited to 250km/h (and is capable of 330 without), this from the country that brought you the Autobahn. Closer to home, the new HSV W-427 will also be limited to 250.

[borko08]

Thanks for the reply madbung. I know the Japanese have what they call a "gentleman's agreement" on power restriction - but speed limiting is not just a japanese thing. The latest BMW M5 is elecronically limited to 250km/h (and is capable of 330 without), this from the country that brought you the Autobahn. Closer to home, the new HSV W-427 will also be limited to 250.

With most German cars being speed limited, I remember topgear saying that it was to keep the autobahn without a speed limit.

[VB-]

yeah i was under the impression it was to keep the guys in suits happy, government officials and that type

[ras1983]

Jeremy clarkson gave an opinion which presents yet another thing to think about. If a car s limited to a certain speed then it only has to be engineered to cope at that speed i.e. brakes, suspension, tyres etc that can withstand 180kph or 250kph for example.

If a car is allowed to run to 200mph (around 320Kph) then the whole car will need to be engineered to hold up at those sorts of speeds.

Maybe its the law of dimishing returns?

Unfortunately I can't remember which episode of top gear he said that on, but I do remember that he was talking about why Mercedes chose to limit its CL cars to 155mph or something.

Edited October 25, 2008 by ras1983

[Johnny]

Put it this way; when the r34 gtr was imported into the UK, extra oil coolers had to be added for the european market as in germany the autobarn could see cruising at more than 180km/h for a few hours so extra cooling is required.

Tyres might have to be changed to cope with the extra stresses.

[Johnny]

oh forgot to add; the new HSV thingys antenna would rattle at over 240km/h

the range rover sports tyres would only hold just over 200km/h so it had to be limited to stop the tyres from bursting.

Basically the speed is limited to whatever various components were made to cope with for long periods of time, not just a quick blast to 300km/h and stop. etc!

[baron25]

I'm pretty sure the japanese 180km/h thing is legislation, as for other markets i'd assume as above.

[PM-R33]

Jeremy clarkson gave an opinion which presents yet another thing to think about. If a car s limited to a certain speed then it only has to be engineered to cope at that speed i.e. brakes, suspension, tyres etc that can withstand 180kph or 250kph for example.

If a car is allowed to run to 200mph (around 320Kph) then the whole car will need to be engineered to hold up at those sorts of speeds.

Maybe its the law of dimishing returns?

Unfortunately I can't remember which episode of top gear he said that on, but I do remember that he was talking about why Mercedes chose to limit its CL cars to 155mph or something.

Correct, he said it on the Super Car Special (The one where he keeps pouring all sorts of alcohol into a big cup to describe the Lamborghini and how they keep adding more power hahahaha).

Said the mercedes would need 300km/h tyres, 300km/h brakes, 300km/h suspension etc etc and that would make the car so much more expensive, therefore they speed limit it so they don't need to build it for such a high speed. Makes a lot of sense when you think of it from an Engineering point of view when you have to build a car to a certain budget.

[Kinks]

after just reading the misinformation thread i should probably stay quiet but I thought* it was a marketing thing, so the GTS-t's top speed is 180km/h and the GTR's is 200+.

* I have no solid basis for this claim

[PM-R33]

But the GTR is speed limited to 180km/h aswell.

Both cars can reach way above this with the limiter removed. Top speed of a vehicle is determined by the top rpm the engine can reach or is rev limited at multiplied by the gearing ratio in the top gear of the car (5 speed/6 speed), then multiplied by the final gear ratio in the diff (3.73:1, 4.11:1, etc). This gives a hypothetical top speed of the vehicle, however the vehicle then needs the power behind it to over come the force from the air pushing against it trying to slow it down. Hence why the Veyron and other cars need so much power behind them to reach over 400km/h.

Looking at this, you can see that most vehicles can reach quite a high speed, especially ones with tall gear ratios and a lot of power, therefore the only logical thing to do is limit them to a certain speed electronically to stop people pushing the car to its top speed when the rest of the car (tyres/brakes/aerodynamics/supsension/cooling) aren't designed to withstand that high speed and strain on the vehicle.

[diamondjo]

oh forgot to add; the new HSV thingys antenna would rattle at over 240km/h

the range rover sports tyres would only hold just over 200km/h so it had to be limited to stop the tyres from bursting.

Basically the speed is limited to whatever various components were made to cope with for long periods of time, not just a quick blast to 300km/h and stop. etc!

Yeah, in spite of the price tag, I get the feeling that the 427 will still feature Holden's trademark bogan-pack build quality and dodgy electrics. I'd like to see what Clarkson thinks of it. I seem to remember he was bagging the cheap interior of the Monaro - anyone remember which episode that might have been?

[PM-R33]

Yeah but he said he loved the Monaro at the same time aswell Said it was a great non-nonsense rear wheel drive platform. Can't remember what episode it was, but they pretty much spent the whole time drifting it around the track and then tested it against the supercharged Jaguar and i cant remember what the other car was....an american car of some sort maybe? I dunno, can't remember.

[diamondjo]

Jeremy clarkson gave an opinion which presents yet another thing to think about. If a car s limited to a certain speed then it only has to be engineered to cope at that speed i.e. brakes, suspension, tyres etc that can withstand 180kph or 250kph for example.

If a car is allowed to run to 200mph (around 320Kph) then the whole car will need to be engineered to hold up at those sorts of speeds.

Maybe its the law of dimishing returns?

Unfortunately I can't remember which episode of top gear he said that on, but I do remember that he was talking about why Mercedes chose to limit its CL cars to 155mph or something.

Yeah ras (edit: and PM-R33, sorry for missing you the first time), that makes the most sense to me. More of a cost saving thing. I suppose this also brings up the question of why not set the gear ratios so that at the point the limiter kicks in, you're already pushing the redline in top gear?

Hmmm, just after I typed that I started thinking about power bands and how that probably wouldn't be such a good idea after all. But you know what I mean? It seems a bit of a waste to have another few thousand RPM left and not be able to use it.

Edited October 27, 2008 by diamondjo

[Johnny]

Yeah, in spite of the price tag, I get the feeling that the 427 will still feature Holden's trademark bogan-pack build quality and dodgy electrics. I'd like to see what Clarkson thinks of it. I seem to remember he was bagging the cheap interior of the Monaro - anyone remember which episode that might have been?

Id rather have anthrax then buy that holden for 150k + who know what taxes are thrown in.

audi rs4 with an 8000rpm v8 and amazing handling + build quality

bmw m3 with an engine which requires a supercomputer to run it

mercedes c63 amg with a 6.2litre engine which fries the tyres + quality

r35 gtr that does everything and ticks all the boxes

Id rather blowtorch my nipples and lick a toiletseat used by a hairy greek or eat the money then pay 150+k for a GM holden.

[Johnny]

Yeah but he said he loved the Monaro at the same time aswell Said it was a great non-nonsense rear wheel drive platform. Can't remember what episode it was, but they pretty much spent the whole time drifting it around the track and then tested it against the supercharged Jaguar and i cant remember what the other car was....an american car of some sort maybe? I dunno, can't remember.

Yeah buts that the 70-80ish k monaro or vxr or clubsport etc

thats a good car for the money; uses the same shock absorber technology as the ferrari 655

[PM-R33]

A W427 came to work the other day, so had a good look at it. First one in Townsville from what im aware. Dude said he paid $170k for it! F**k that! Honestly i don't see where the extra money is over a VE GTS. The bigger brakes, bigger engine and the few other tweeks here and there are not worth an extra 90k.

[scathing]

I was driving home from work the other day and I was thinking about how my 33 is electonically limited to 180km/h and while this is massively over any posted speed limit in our country, I got to wondering why manufacturers do this.

Japanese legislation requires their cars to be speed limited to 180km/hr. Hence why the JDM R35 has a 180km/hr speed limiter when it's not on a race track even though the entire car will cope with going much faster safely, and why Nissan had to spend the time/effort coding in all the race tracks into the GPS.

For other countries, I think other people have covered it. The law requires that your tyres be able to cope with the top speed of your car. Setting a 250km/hr speed limiter means the car can get away with W-rated tyres...which may also explain why a lot of the Euro luxo-barges have a "soft" 250km/hr speed limiter that lets them go a tad faster, since W-rates go to 270km/hr. I can imagine that the other engineering requirements (having an engine sit high in the rev range, with high load due to wind resistance, requires specific tuning) to make sure it's safe.

Most of the German manufacturers have a "voluntary" 250km/hr speed limiter in place, aside from Porsche. I remember reading a piece a while back that said that even CEOs of other German manufacturers didn't think Porsche should be limited even while their companies did.

[BigDirtyJase]

isn't also due to road conditions?? The UK gets the GTR at the end of this year without the speed limiter. IMO, Speed limiter or none you can only take out all the anger and speed on the race track (or the autobahn if you are Germany) unless you are foolish enough to do it on the street and risk losing your car.