M3 CSL Max speed

[alexk]

I had 300km/h in the tacho in Germany.
The unlimited cars have speed limiter set to 280km/h.
So I am sure the 300 indicated is 280 or so real.

I am not planning to attempt this again, with my current suspension.
It's possible that I will fly to the space and beyond with the German bumps $*$*&$*$@*#*$#*@

[The Gorilla]

Hi,

Quote- ''7000rpm in 6th (0.83) on standard final drive 3.64 and 265/30 x 19 tyres = 174mph true speed and would be 181mph with the 35 profile tyre (so no science defiance]

So no drag ?

Your not going to see past 170mph in std CSL
its all down the science.

Regards,

The Gorilla.

[Mike R]

Originally Posted by The Gorilla

Hi,

Quote- ''7000rpm in 6th (0.83) on standard final drive 3.64 and 265/30 x 19 tyres = 174mph true speed and would be 181mph with the 35 profile tyre (so no science defiance]

So no drag ?

Your not going to see past 170mph in std CSL
its all down the science.

Regards,

The Gorilla.

Your science is flawed....

This is something I am extremely experienced in, having held the top speed record for Cosworths back in the day . It was crucial to work every thing out to get the correct gearing and peak power point at exactly the right rpm to achieve the required figures within the confines of Bruntingthorpe's 1.7mile straight. I've been up against all sorts, including a 700bhp GTR and a Yamaha R1 and with just 515bhp, beat them .

If you're seeing 7000rpm, you're seeing 7000rpm. Multiply it by the gear ratios and tyre sizes and you get the true road speed. The drag (which increases exponentially), only holds the car back when it reaches it's choke point (or aerodynamic brick wall if you prefer), which is where it won't physically go any faster unless conditions change (i.e. tail wind, down hill stretch of road, increase in peak power (at the right rpm point of the choke point) or alter the gearing to suit the power band better (but this would only gain you a few mph by lowering the gearing so that it can use the peak power to go faster). Given the CSL makes peak power at 7900, altering the gearing to be a fraction lower, could give it a slightly higher top speed.

But as it happens, 174mph is I believe what BMW quote as the top speed of a derestricted CSL .

I've verified this gearing calculation numerous times to not only back up the Datron timing gear, but to see how best to alter the gearing to suit where the peak power is to achieve the best top speed .

The only thing that could skew the equation is if the rpm reading is incorrect.

[Rick H]

Originally Posted by The Gorilla

Hi,

Quote- ''7000rpm in 6th (0.83) on standard final drive 3.64 and 265/30 x 19 tyres = 174mph true speed and would be 181mph with the 35 profile tyre (so no science defiance]

So no drag ?

Your not going to see past 170mph in std CSL
its all down the science.

Regards,

The Gorilla.

Fastest CSL at VMax200 looks to be 170 mph officially recorded - not on speedo or GPS.

[Mike R]

Originally Posted by Rick H

Fastest CSL at VMax200 looks to be 170 mph officially recorded - not on speedo or GPS.

Which is in the confines of Bruntingthorpe's runway. Give it a longer stretch and it would do its 174mph . But at 1.7miles total distance, you soon run out of runway at these speeds .

I have done 172mph there with similar power, so it looks like the CSL and Sierra have a similar aerodynamic choke point. It then took an extra 130bhp just to do 10mph more .

[The Gorilla]

Hi,

Quote- ''Your science is flawed...

Drag is drag, the calculations are
just pure calcs as such, if you have
a warmer day, tyre drag is higher,
if you have a warm day and full tank
drag is even higher, if you have a warm
day, full tank and slicks its even
greater.

If Billy Bunter is driving it gets worse.

Thus any Car geared to do say max of
175 mph will never hit it, may get close
but will never do what the calcs say.

The other item is lift, which when combined
with drag will make hitting the calculated
speed impossible.

Regards,

The Gorilla.

[Mike R]

Originally Posted by The Gorilla

Hi,

Quote- ''Your science is flawed...

Drag is drag, the calculations are
just pure calcs as such, if you have
a warmer day, tyre drag is higher,
if you have a warm day and full tank
drag is even higher, if you have a warm
day, full tank and slicks its even
greater.

If Billy Bunter is driving it gets worse.

Thus any Car geared to do say max of
175 mph will never hit it, may get close
but will never do what the calcs say.

The other item is lift, which when combined
with drag will make hitting the calculated
speed impossible.

Regards,

The Gorilla.

You are obviously very knowledgeable on all things mechanical, but in this regard you haven't got a clue .

The only factor drag has on a car is requiring more power to overcome it.

If a CSL on standard gearing / tyres is pulling 7000rpm it IS doing 174mph FACT and that is irrespective of what drag is acting on it LOL. It just shows that what ever the drag is/was the CSL in the photo has sufficient power to overcome it in the picture posted (as it is clearly showing 7000rpm).

IF it had been your car with all the aero appendages on it (and you had changed back to standard gearing and tyre sizes), and assuming for the sake of this arguement it has standard CSL power, then your car would not have been able to pull 7000rpm, as your aero would have lowered the speed at which the choke point would be reached (due to the increased drag). However, if your car had managed to pull 7000rpm with all that aero on, it would also be doing the same 174mph, BUT the only way it would be able to do that is with a LOT more power than a standard CSL has to overcome the increased drag. This is the balancing act that F1 teams are constantly playing with gearing and aero wize to achieve the fastest laps possible. You often see them getting it wrong though (they either hit the hit the rev limiter or fail to pull the gearing).

Alternatively, you could lower the gearing on your car and then it would pull 7000rpm in top, but the speed achieved would be considerably lower (and below the original choke point) and that is why it could then pull it.

The only way 7000rpm would not equate to 174mph in a CSL is if one of the fixed gear ratios / tyre sizes were different from factory.

It is also irrelevant who is driving - 7000rpm is 174mph in a CSL whoever is driving it.

Just like in my Escort, 7800rpm in fifth is 172 mph - it won't go any slower or faster at 7800 irrespective of drag or driver. The gearing dictates the speed and the power dictates if it can overcome the drag to pull the required rpm to achieve that speed. A standard Escort (with only 227bhp) will only pull 143mph top speed, as it has insufficient power to overcome the drag.

Let's say conditions changed - like a head wind, this would increase the drag, and the car might be then only able to pull 7600rpm (which would be a slower speed), or with a tail wind it would then pull 7900rpm (which would be a higher speed).

[shane@mbtech]

I'm with mike on this one.

Although forget the viscous fan coupling mike

[Mike R]

Originally Posted by lawsy

I'm with mike on this one.

Although forget the viscous fan coupling mike

Can you elaborate?

I'd be really interested in knowing the parameters of how the viscous fan works in a CSL, as I have no experience of these and just want to know in my own mind where the inefficiencies might be?

[northernjim]

Originally Posted by Mike R

But as it happens, 174mph is I believe what BMW quote as the top speed of a derestricted CSL .

I am sure that I have been faster than this in a csl on the munich trip, according to his gps....


Standard size road tyres by the way, not cups