Mclaren Lm

[joe911]

Originally Posted by joe911

Production F1
- 627 bhp
- 225 mph (240.1 mph with no rev limit)

F1 LM
- 680 bhp
- 225 mph (according to Driving Ambition)

F1 GTR (1997)
- 600 bhp
- 215 mph (according to Driving Ambition)

Thanks to comments from my learned friend ...

The 680bhp LM engine is 1.084 times more powerful then the standard with the 627. For a given CdA, your multiple in max speed is the cube root of the increase in bhp. The cube root of 1.084 is 1.027. Therefore, if you put an LM engine in the standard body shape, your resulting top speed would be 1.027 (ish) times 240, or 246.5 mph, at best.

A standard road F1 with HDF will do, in fact about 190mph.

Another friend had an HDF car with an LM engine and it would do about 195 mph - which all adds up.

If you do the math for the lower power of the GTR - they would max out at about 186 mph.

[amanichen]

Originally Posted by joe911

Thanks to comments from my learned friend ...

The 680bhp LM engine is 1.084 times more powerful then the standard with the 627. For a given CdA, your multiple in max speed is the cube root of the increase in bhp. The cube root of 1.084 is 1.027. Therefore, if you put an LM engine in the standard body shape, your resulting top speed would be 1.027 (ish) times 240, or 246.5 mph, at best.

I actually did some calculations a couple of months ago involving installing an LM engine into a standard road car. Here's the results if you're interested:

http://s94779296.onlinehome.us/McLarenF1/McLarenF1.html

[ClioRacer_72]

They just fast aint they ? lol

[joe911]

Originally Posted by amanichen

I actually did some calculations a couple of months ago involving installing an LM engine into a standard road car. Here's the results if you're interested:
http://s94779296.onlinehome.us/McLarenF1/McLarenF1.html

Interesting numbers, thanks for sharing. The document says engine power is 698.4400 horsepower - and yet McL and BMW claim 680 - where did the 698 come from?

[amanichen]

Originally Posted by joe911

Interesting numbers, thanks for sharing. The document says engine power is 698.4400 horsepower - and yet McL and BMW claim 680 - where did the 698 come from?

That's the necessary power output for the standard F1 to travel 251.8 mph speed, which is a bit of a problem because the LM engine is rated for a power of 680BHP @ 7800RPM. I first raised my eyebrows at it, but then I realized that this data is taken from a dynamometer.

Unlike top speed tests, dynamometer tests aren't conducted with air being forced into the intake at 240mph, they're conducted on test stand. This means that my over-estimate of the engine's ability isn't necessarrily a bad thing, because the LM engine might actually be able to crank out 698HP when the air is being forced in by a 240mph headwind.

Additionally, the 240mph run that the F1 did meant it was putting out 539 N*m of torque at the wheels @ 8300RPM. This, however is a gross overestimate of the engine's capability according to the dynamometer test data. Again, the 240mph headwind must improve the volumetric efficiency of the engine at high speed because it acts as a forced induction. In non-technical terms, this is a "ram-air" effect.

I have since updated the web page to include this effect.

[peter i]

Additionally, the 240mph run that the F1 did meant it was putting out 539 N*m of torque at the wheels @ 8300RPM. This, however is a gross overestimate of the engine's capability according to the dynamometer test data. Again, the 240mph headwind must improve the volumetric efficiency of the engine at high speed because it acts as a forced induction. In non-technical terms, this is a "ram-air" effect.

This is the fact of race car been design this way , But still lots of people do not believe the force of nature.....

[joe911]

Originally Posted by amanichen

That's the necessary power output for the standard F1 to travel 251.8 mph speed, which is a bit of a problem because the LM engine is rated for a power of 680BHP @ 7800RPM. I first raised my eyebrows at it, but then I realized that this data is taken from a dynamometer.

Unlike top speed tests, dynamometer tests aren't conducted with air being forced into the intake at 240mph, they're conducted on test stand. This means that my over-estimate of the engine's ability isn't necessarrily a bad thing, because the LM engine might actually be able to crank out 698HP when the air is being forced in by a 240mph headwind.

Interesting.

Forgive my lack of maths and physics (which I did study 25 years ago but have forgotten nearly all of) - but the aim of your paper seemd to be to calculate the top speed. However, you seem to be assuming the top speed and calculating the engine power required to meet your number?

Your point about ram air seems relevant - however - I understood that some dynos do have the ability to add air to the equation (for valuable cooling as well as a more realistic air temperature/density scenario) - however I had assumed that whether some amount (maybe too little, maybe too much) of ram air was used that the derived engine power would factor it in.

I think you can assume that BMW and McL understand these things and factor them in. They say 680 bhp. Should that not be an input parameter to your equations, rather than an output?

[peter i]

i think I should remind about this topic , the power from wheels are diffrent, compare to direct power output from the engine .......all thats factor count...

[joe911]

Originally Posted by peter i

i think I should remind about this topic , the power from wheels are diffrent, compare to direct power output from the engine .......all thats factor count...

Yes, of course - the figures being discussed are engine figures, not at the wheel figures (which are of course always lower).

[amanichen]

Originally Posted by joe911

Interesting.

Forgive my lack of maths and physics (which I did study 25 years ago but have forgotten nearly all of) - but the aim of your paper seemd to be to calculate the top speed. However, you seem to be assuming the top speed and calculating the engine power required to meet your number?

I think you can assume that BMW and McL understand these things and factor them in. They say 680 bhp. Should that not be an input parameter to your equations, rather than an output?

If cars were operated on pure force alone, such as a jet engine, then I could simply use:

Power = 0.5 * Cd * A * density * V^3

However, cars must physically push from the ground, so I have to include the effects of gearing. The power that I calculate is based off of the estimated engine torque and the RPM where that torque occurs.

For cars in general: the actual top speed might not come at peak power, because the wheel speed is constrained by gearing. Some cars have 6th gears which are actually slower than their 5th gears, to promote good fuel economy. The F1 is one of the few cars where the highest gear will take it all the way up to its top speed, due to the almost linear power curve of the engine, and the gearing.

Your point about ram air seems relevant - however - I understood that some dynos do have the ability to add air to the equation (for valuable cooling as well as a more realistic air temperature/density scenario) - however I had assumed that whether some amount (maybe too little, maybe too much) of ram air was used that the derived engine power would factor it in.

I don't doubt that that McLaren and BMW both have the capability to simulate 240mph air being fed into the engine, and this is often done for Formula 1 cars. However, I don't think this was done on the F1's engine: if you compare the dynamometer data to the F1's 240mph run, you'll find out that the dynamometer data just can't move the car at 240mph. There has to be some ram-air effect happening.

Remember, Murray only asked for a 550HP engine, but BMW gave him one that was slightly heavier and produced 627HP. He obviously designed the car's air intake to be in an advantageous position, but I doubt he sat down to figure out exactly what the effects of the ram-air would be. He also didn't purposefully make the F1 go 240mph, he just designed it to be his vision of the ultimate driver's car for the road.

[amanichen]

Originally Posted by peter i

i think I should remind about this topic , the power from wheels are diffrent, compare to direct power output from the engine .......all thats factor count...

I account for this in my calculations. The F1 only needs about 602HP at the wheels to go through the air at 241mph. The engine is probably producing more than the quoted 627HP because of the ram-air effect.