Max speed design

[john970]

Just noticed that the theoretical top speed for the 335 and 135 is exactly 300kmph/186mph which is the exact speed rating of the tires. Given this, I have no idea why there is a speed limiter on the cars set 36 mph lower than this.

Also figured out (using someone else's calculator) the horsepower required to overcome aerodynamic drag at 186mph using a Cd*A of .69 = 87 horsepower. Not sure what else comes into play at those speeds, but seems like we have lots of power left over to hit the rev limiter given enough road.

[clived]

Originally Posted by john970

Just noticed that the theoretical top speed for the 335 and 135 is exactly 300kmph/186mph which is the exact speed rating of the tires. Given this, I have no idea why there is a speed limiter on the cars set 18mph lower than this.

Also figured out (using someone else's calculator) the horsepower required to overcome aerodynamic drag at 186mph using a Cd*A of .69 = 87 horsepower. Not sure what else comes into play at those speeds, but seems like we have lots of power left over to hit the rev limiter given enough road.

1) The speed limiter is not, as you suggest set at 168mph
2) A 135i or 335i with 300bhp will not reach 186mph in any case - I don't know how you've worked that out as the theoritcal top speed, but you've missed something

Edit: Hmmm.. wondering if 186 is a typo on your behalf?

[mikeo]

There is a 150mph speed limiter on the 135i becuase BMW AG lawyers say so.

[john970]

Originally Posted by clived

1) The speed limiter is not, as you suggest set at 168mph
2) A 135i or 335i with 300bhp will not reach 186mph in any case - I don't know how you've worked that out as the theoritcal top speed, but you've missed something

Edit: Hmmm.. wondering if 186 is a typo on your behalf?

The typo is the 16, meant 36mph lower. Everything else is correct. I used the gearing for the theoretical top speed, which it will hit given enough power.

[wnta135]

According to my excel chart(posted somewhere here),
redline in 6th is about 196 mph.
That is if 300 hp can get the 135i up there.

[Troyn]

If I remember correctly, the 335i's top speed is limited by wind drag, never reaching redline in top gear.

Not sure if that would be true for the 135i, but may be a good guess.

[john970]

Originally Posted by wnta135

According to my excel chart(posted somewhere here),
redline in 6th is about 196 mph.
That is if 300 hp can get the 135i up there.

Can't find that post... did you include wheel size?

[aesthetect]

Originally Posted by john970

Just noticed that the theoretical top speed for the 335 and 135 is exactly 300kmph/186mph which is the exact speed rating of the tires. Given this, I have no idea why there is a speed limiter on the cars set 36 mph lower than this.

to give bmw a margin of safety preventing people from hitting the max speed which is when the tires could potentially blow out?

Originally Posted by john970

Also figured out (using someone else's calculator) the horsepower required to overcome aerodynamic drag at 186mph using a Cd*A of .69 = 87 horsepower. Not sure what else comes into play at those speeds, but seems like we have lots of power left over to hit the rev limiter given enough road.

just to be sure

drag force = (1/2)*(air density)*(velocity^2)*(cross sectional area)*(Cd, drag coefficient)

where did you find the cross sectional area of a 1 series? you would need to be sure to use wheel torque values divided by wheel radius to get force

or drag "power" = the same thing but velocity^3

double check units

[john970]

Originally Posted by aesthetect

to give bmw a margin of safety preventing people from hitting the max speed which is when the tires could potentially blow out?



just to be sure

drag force = (1/2)*(air density)*(velocity^2)*(cross sectional area)*(Cd, drag coefficient)

where did you find the cross sectional area of a 1 series? you would need to be sure to use wheel torque values divided by wheel radius to get force

or drag "power" = the same thing but velocity^3

double check units

I used BMW's numbers for cd*a, they are posted on the board somewhere.

I wasn't attacking the problem of actual top speed in a 1 series, that would depend on a ton of variables. I'm not sure a 1er can hit redline in 6th with a stock motor, probably depends on conditions.

[john970]

Just realized bmw numbers might be m^3 and not ft^3, i'll refigure when i get a chance if they are wrong

[aesthetect]

right on, i just knew i had seen the Cd value before but that was all. dont know how else youre going to find the answers youre looking for but good luck.

dont most 6spd cars hit top speed in 5th? ie due to higher torque values from the gearing and 6th is just a gas friendly highway cruiser. not sure but i know my cousin's Z06 does.

[john970]

Originally Posted by aesthetect

right on, i just knew i had seen the Cd value before but that was all. dont know how else youre going to find the answers youre looking for but good luck.

dont most 6spd cars hit top speed in 5th? ie due to higher torque values from the gearing and 6th is just a gas friendly highway cruiser. not sure but i know my cousin's Z06 does.

Wow, can't hit top speed in 6th? was it a C6? That is surprising, if it has the 505hp motor they must have super tall 5th gear as it'll hit 200mph.

I'm guessing the 135 with the sport pack produces a lot of drag trying to eliminate lift/generate some downforce so I doubt it will hit 186, but it would be interesting to see what the true top speed is.

[john970]

Just looked at a post over at bimmerfest, someone had a 335 w/ flash to 175 and climbing and had to stop due to lack of road, seems plausible a flashed 135 could hit 186 on a good day.

Oh, and get different tires before you try this so you can tell us about it afterwards.

[aesthetect]

C6. and yeah, tall gearing, lots of torque, and high rpm/redline (>7k in an OHV??) allow top speed in 5th. it gets to ~60 in first, IIRC. 6th is just crazy tall

[john970]

Originally Posted by aesthetect

C6. and yeah, tall gearing, lots of torque, and high rpm/redline (>7k in an OHV??) allow top speed in 5th. it gets to ~60 in first, IIRC. 6th is just crazy tall

I remember clarkson doing a top speed run in 6th... the whole time. he started from 0 in SIXTH... insane torque.

[aesthetect]

Originally Posted by john970

Just looked at a post over at bimmerfest, someone had a 335 w/ flash to 175 and climbing and had to stop due to lack of road, seems plausible a flashed 135 could hit 186 on a good day.

Oh, and get different tires before you try this so you can tell us about it afterwards.

ill never know from experience but the 3 series' lower drag should make more of a difference in top speed than the 1 series' 200lbs

Originally Posted by john970

I remember clarkson doing a top speed run in 6th... the whole time. he started from 0 in SIXTH... insane torque.

seriously! first time ive ever been genuinely scared in a car. and i have some stupid stupid friends.

[E82tt6]

The fact that the 135i is considerably faster to 140 indicates that it probably actually has lower drag than the 335i

[aesthetect]

from another thread (thanks john haha)

Originally Posted by john970

335i - .30
135i - .33

as stated cross sectional area plays a role as well but i would (unfortunately) think the 135 xs > 335

[TwinturboBMW07]

Originally Posted by aesthetect

ill never know from experience but the 3 series' lower drag should make more of a difference in top speed than the 1 series' 200lbs



seriously! first time ive ever been genuinely scared in a car. and i have some stupid stupid friends.

HOLY SHIT thats crazy

[1ToBeOn2Wheels]

Originally Posted by mikeo

There is a 150mph speed limiter on the 135i becuase BMW AG lawyers say so.

That's the way I understood it as well, and if I remember hearing correctly, it also has to do with German Govt. regulations (which is why Mercedes-Benz and other German manufactured cars have the same limiter).

[Evolution Racewerks]

With a chip raising the speed limiter and some basic bolt ons, reaching max speed should not be a problem, in Germany. I dunno where you guys are at but here in SoCal, there is no way one could drive that fast. If you didn't get killed by the idiot driver changing lanes into your lane, Highway Patrol and the ghetto bird would get you.

Drive safely guys. "With power comes responsibility" :wink:

[clived]

Originally Posted by john970

Just looked at a post over at bimmerfest, someone had a 335 w/ flash to 175 and climbing and had to stop due to lack of road, seems plausible a flashed 135 could hit 186 on a good day.

Oh, and get different tires before you try this so you can tell us about it afterwards.

Firstly was that speedometer indicated 175, or a scientifically measured 175, say laser timing beams across the road? Even a 3 or 4% over-read (which I'd say is pretty likely at those speeds) sees that car actually doing somewhat less than 170. And there is a MASSIVE difference in the power needed to get a car to 170 to 186 - it is very far indeed from linear. I've had experience of high power cars trying to reach their Vmax over a 2 mile runway. The lower power cars often reach pretty much their top speed in that space, whilst the higher power cars are still, very very slowly, gaining speed. But if you take a look at this list of recent results, to see the (typically very modified) cars that reach 186, you'd have to wonder if that speed is really within the reach of a 135i, chipped or otherwise. http://www.vmax15000bhp.com/results.htm I'd suggest not. These speeds are all laser trap verified, not readings from the speedo.