Can an M3/4 hit 200MPH?

[overlook637]

Originally Posted by CanAutM3

If you look at the general shape of a car, you can see similarities with an airplane wing, where the air that travels over the car has to travel a longer distance than the air that travels under the car, which means it needs to travle faster creating lift in the process. There are indeed road cars that produce net downforce, but they have rather prominent aerodynamic appendages. For example, the M4GTS has net downforce.

The M3/4 were indeed designed with aerodynamic in mind and they designed some features to create some downforce to offset the overall lift, but the net result on the whole car is still net lift. I remember an Auto Motor und Sport article published some time ago where they showed the lift/downforce results on the front and rear axle of a few cars they wind tunnel tested. I'll try to dig it out.

EDIT, found it :

Thank You.

[GrussGott]

Originally Posted by CanAutM3

I remember an Auto Motor und Sport article published some time ago where they showed the lift/downforce results on the front and rear axle of a few cars they wind tunnel tested. I'll try to dig it out.

EDIT, found it :

ahHA! But they didn't test the 'vert top-down which generates ... who knows what it generates, but over a 100MPH it's so nuttyasfuck windy it makes ole Danny Bernoulli weep.

And I can confirm you can break 150MPH but not sure by how much.

[F83]

Originally Posted by GrussGott

ahHA! But they didn't test the 'vert top-down which generates ... who knows what it generates, but over a 100MPH it's so nuttyasfuck windy it makes ole Danny Bernoulli weep.

And I can confirm you can break 150MPH but not sure by how much.

Yes, 150 (track) is easy. Can also confirm. But huge difference between 150 and 200 obviously.

[GrussGott]

Originally Posted by F83

Yes, 150 (track) is easy. Can also confirm. But huge difference between 150 and 200 obviously.

lol, yeah, I don't know about yours with the mods, but I can guarantee a stock 2018 CP vert ain't coming close to 200 mph ... and if it did and you live through it they probably have an award or something for it.

[F83]

Originally Posted by GrussGott

lol, yeah, I don't know about yours with the mods, but I can guarantee a stock 2018 CP vert ain't coming close to 200 mph ... and if it did and you live through it they probably have an award or something for it.

I wouldn't take it faster than 150, 155. Plenty fast for that car. Plus (as we've discussed) the steering gets very twitchy at high speeds IMO.

[trey100]

Originally Posted by CanAutM3

Stumbled on that old thread revived from the dead, and I thought it might be pertinent to bring some more precision on the math. 500whp is not quite enough to get an M3/4 to 200mph due to rolling resistance, as pointed out by jwzimm . The formula for tire rolling restiance can be found below, we just need to multiply the result by the velocity to get the required power.

Further, we have the actual aero frontal area of the M3 and M4 at 2.29 and 2.23 respectively in the original published specs for more precision.

With the following assumption:
m = 1625kg vehicle weight
v = 89.39m/s (200mph) velocity
P = 1.225kg/m^3 air density
A = 2.29 / 2.23 effective aero frontal area M3/M4
Cd = 0.34 drag coefficient
p = 2.4bar (35psi) tire inflation pressure

With these assumption 457/445whp are needed to overcome aero drag for the M3/M4 respectively and 96hp are needed to overcome tire rolling resistance. So [COLOR="Blue"]540~552whp are needed to go 200mph in the M4-M3 [/COLOR]respectively . No stock M3/4 can achieve that.

Why engine HP and not actual force applied on the ground by the tire? With gearing, the same 500 hp at the crank means very different force at the ground in 1st gear vs 6th.

[CanAutM3]

Originally Posted by trey100

Why engine HP and not actual force applied on the ground by the tire?

It is quite possible to calculate the propulsive force needed, however it yields a number that is difficult to relate to. If I tell you you need 4607N or 1036lbf to travel at 200mph in your M3, does it tell you something?

Originally Posted by trey100

With gearing, the same 500 hp at the crank means very different force at the ground in 1st gear vs 6th.

Power equates to force times velocity. The faster one travels, the more power is needed to overcome the same force. Since power factors velocity, it is unaltered by the gear ratios and hence they become irrlevent to the calculation. The force needed to overcome aero drag increases with the square of speed, while the power needed increases with the cube of speed.

The math above figures whp and not crank hp, drivetrain loss in not factored in (usually 3~5%). Note that this is "true" drivetrain loss, which is much less than the "loss" seen on chassis dyno results that also include tire rolling losses and inertial effects.

[trey100]

Originally Posted by CanAutM3

It is quite possible to calculate the propulsive force needed, however it yields a number that is difficult to relate to. If I tell you you need 4607N or 1036lbf to travel at 200mph in your M3, does it tell you something?

Power equates to force times velocity. The faster one travels, the more power is needed to overcome the same force. The force needed to overcome aero drag increases with the square of speed, while the power needed increases with the cube of speed.

The math above figures whp and not crank hp, drivetrain loss in not factored in (usually 3~5%). Note that this is "true" drivetrain loss, which is much less than the "loss" seen on chassis dyno results that also include tire rolling losses and inertial effects.

I missed WHP. My bad.

But I still assume that due to your gearing, your peak WHP may not align with what you will have at that rpm and speed.

[Psychotic Mouse]

You could always take this to the nerd extreme, and show how altitude will help, and what barometric conditions you should be looking for when you try.

Then you would have to take into account the losses in HP due to Altitude, but the gains due to less resistance from thinner air. Without pulling out my calculator, I'm sure the losses due to altitude even with a Turbo'ed car will be greater than the gains made from thinner air.

[CanAutM3]

Originally Posted by trey100

I missed WHP. My bad.

Note that whp is not altered by gearing. The only difference between crank hp and whp in this case here is “pure” drivetrain loss.

[trey100]

Originally Posted by CanAutM3

Note that whp is not altered by gearing. The only difference between crank up and whp in this case here is "pure" drivetrain loss.

True but your peak WHP is not consistent throughout the rpm range. So at 200 mph you may find yourself a x rpm which is a place where you may or may not be producing that peak WHP.

[CanAutM3]

Originally Posted by trey100

True but your peak WHP is not consistent throughout the rpm range. So at 200 mph you may find yourself a x rpm which is a place where you may or may not be producing that peak WHP.

Correct. The math gives you the power needed at that specific speed and is not correlated to peak power.

[Bch53211]

I have no idea but no, it can’t. Not even if it was dropped from a plane.

[metomwhou]

Soon as i put my summer tires back on, I'll let you guys know....I'm close to the 500hp range with catless DP and AlpineMSS stage 2+. 2015 M4, 6MT, stock 19 wheels and rubber. I hit 170(indicated) in the fall, felt like it had a bit more to give and that was before the new tune and parts.

[cfm56d7b]

Where would one test this theory in a safe and controlled manner?

[ntg44]

Originally Posted by cfm56d7b

Where would one test this theory in a safe and controlled manner?

Where everyone else does, "Mexico"

[Za135i]

A few guys here have hit 330km/h repeatedly, most running about 400+ wkw hybrid turbo installs tho, on stock turbos most hit around 315-317km/h

[GlazierGlaze]

I've taken my car up to 150+ but I am FBO Stage II. I think it has the legs to get close.

[KoonerzF80]

I hit 180mph easily with my stock f80 dct!

[Wills2]

A stock 440hp Alpina B4S will hit 190mph from the factory which is quite impressive for the power.

[EricSMG]

Originally Posted by lippy

And that's not peak HP. The 500 HP calculated above would need to be at the RPM that corresponds to 200 MPH in gear. So the car would probably need to make 600 HP peak, roughly.

Bingo.

To go 200 requires redline. To make 500whp at redline means like 600whp peak, probably.

[Humdizzle]

its funny so many other things besides HP play into this. Past 150mph my ~500whp 458 feels every bit as fast, if not faster, than my old 600+whp GTR.

i think the GTR had a lower Cd, but the frontal area differences are huge between the two. The 458 NA motor loves to live up top, whereas the fbo gtr turbos are running out of breath. Lastly, the 7 speed vs 6 speed transmission.