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Futant3
07-05-2007, 08:34 AM
I guess my biggest question is why are so many sports cars electronically limited at 155 mph? What makes that better than say 150 or 175 or anything else?

Not like there are lots of roads that you can go that fast on anyway especially when you consider traffic. It just seems like such an artifical idea anyway and then you add in an arbitrary limit.

PhillyDRFT
07-05-2007, 08:49 AM
The idea of a speed governor is to limit the vehicle to the capacity of the suspension and drive train parts. For example the Bugatti (sp?) can reach 210mph and around that speed tires have a lifespan of around 10 minutes before they disintegrate from friction and heat. Also the limitations of the transmission gearing. RPM in relation to wheel rotation. The rating on the quality of wheel bearings/hubs is a factor of the cars speed governor also. It's not like EVERY car is capable of 200mph safely, but the governor is there to find a happy medium between performance, wear and reliability of your parts.

Edit: I think it was murg but a long time ago someone said in a thread about speed limiters. "The rev limiter is there to save your wallet but the speed limiter is there to save your life"

Gary
07-05-2007, 09:24 AM
155 mph = ~250 km/h
120 mph = ~200 km/h

Back in the 80's Germany suggested putting speed limits on the autobahn. Nobody (especially the car makers) agreed on this. To remedy the situation, all of the car companies in Germany (except Porsche, who wouldn't agree) signed a pact to put limiters on their cars instead of a set speed limit. Originally it was 120mph but has risen to 155mph today.

KoreanJoey
07-05-2007, 09:43 AM
I thought the Bugatti was limited at 253MPH...

PhillyDRFT
07-05-2007, 10:08 AM
I thought the Bugatti was limited at 253MPH...

Quite possibly could be. I just remember the video of it being test driven to top speed and it struggled. I think it was a Top gear clip.

hobbie2k
07-05-2007, 07:14 PM
I thought the Bugatti was limited at 253MPH...

253 is the max speed it can attain at the VAG test facility. It's electronically limited lower than that elsewhere.

In order to see 253 you actually have to take your car to their test track, then after an information session, deposit, and lots of waivers, they give you a special key or something that allows you to access the "top-speed" mode of the car. You can then make a run on their track to max it out.

Of course, they reset your car and you have to give the key back before they'll let you leave the facility. :hehe:

In the top-speed mode the car is fully lowered (less than an inch of clearance), the rear spoiler is fully lowered (seriously reducing downforce, but also reducing drag), and some other engine programming and suspension changes occur. Normally as you increas speed the computer automatically adjusts the aerodynamics for stability and downforce, drag limiting you to "only" about 220 I think.

Anyway, the reason most are limited to 155 as opposed to 150 is because they talk in km/h and 250km/h sounds better than 241.93548387096774193548387096776...and so on.

Futant3
07-06-2007, 01:58 AM
Oh I completely understand that for many cars the suspension, tires, and aerodynamics could be a problem before the engine has issues. I was more referring to cars that have adequate equipment to handle higher speeds than 155. Like the Bugatti, Ferrari, Porsche, Lambo, Saleen, etc.

Good Murg quote, certainly sounds like his wisdom. I knew it was a also a good spot as far as metric conversions go. The autobahn arguement seems very plausible to me. I just want to drive my Saleen S7 upside down in a tunnel without worrying that the speed limiter will bring me crashing down! :)

2kSnakEater
07-06-2007, 06:01 PM
wait wait wait!? I thought the Veyron came with that special Key? oh fuck that If Im spending 1mil on a car and the fucker doesnt come with that "special" key

nuclearhappines
07-06-2007, 06:20 PM
On the new Mercedes AMG cars ... they come in stock mode governed to 155mph. However there is a sport package (Designated by dealer option 030) which includes a limited slip differencial, an even sportier suspenision pacakge (or a coilover setup instead of airmatic where applies) and last but not least a raised/removed speed governer up to 175 or 180mph ...

Many german cars have the built in governers... but most of those can be removed with a simple 300-800 usd chip... you gain some 10-15hp, on BMW's you typically bump up redline by 1000 to 1500 rpms , and then you raise the governer to infiniti ...