F1 Engine friction

[xpensive]

I was thinking about internal friction-losses in today's 18k Rpm V8's, which should predominantly be viscous losses within various oil-films, in bearings and pistons.

The the way I understands things, the majority of said losses should be conveyed out of the engine with the lubricant, to finally exit the car through the oil cooler?

If today's engine's have a mechanical output of 720 Hp or so, anyone have a number for friction losses as described above?

[F1_eng]

This type of approach won't get you in the ball park for frictional losses I'm afraid.
Rotating elements friction such as bearings increase with the square of the speed but bearing friction is only a portion of the total friction. Most significant of all is the friction caused by the pistons, the heat generated through this does not find its way in to the oil system so an oil system heat rejection approach will be far from the truth.
When calculating the theoretical frictional losses in the movement of the piston and its rings, you will find some interesting occurances. If you are interested you could build up a piston friction model, can be done in Excel or Simulink or whatever. I can give you cylinder pressure data for an engine, but bare in mind I won't give out an F1 engine data.

Models like this are very good when learning as you often find interesting discoveries that change how you approach the system. In the piston model you can then calculate the effect of changing con-rod length or offseting the crank or whatever and its effect on engine friction. You must remember is it theroetical and not hugely accurate in the actual numbers but the trends do follow actual test data closely, the oil film thickness and friction coefficient are very difficult to predict theroetically.

[xpensive]

Thank's for sharing, sorry if my type of approach was not adequate for the intriguing world of piston-friction though.

However, far more than the theoretical analysis, I am looking for typical numbers on the matter, anyone?

[flynfrog]

fuel energy in - completness of combustion - exaust enrgy temp volume and velocity - heat energy from combustion to radiatior.

also you have to take into account the energy absorbed by teh fuel when its injected it will pull some heat from the pistion.

the easiest way to figgure it is find the power of the starter used and the rpm it works at.

[xpensive]

Interesting thinking flyn, given that the starter only has to overcome the internal friction?

[flynfrog]

Interesting thinking flyn, given that the starter only has to overcome the internal friction?

there are also pumping losses too you could make a guess on those based on power displacment and rmp maybe not sure here not really my area

[xpensive]

Auxilliary losses should be neglectable in the context flyn, any ideas on F1 starter-power and Rpm?

[flynfrog]

Auxilliary losses should be neglectable in the context flyn, any ideas on F1 starter-power and Rpm?

Not a clue http://www.f1technical.net/features/2267

you could make a rough guess by looking at the wire gauge and you know it is 24 volts. but at this point I could use a dart board and get about the same quality of guessing.

also the starter is turing the oil pump and they alternator as well.

Interesting problem you have there let me think on it.

[F1_eng]

As has been said, the suggested starter motor method won't really do it. You don't get the same oil pressures and oil film thicknesses as you do during normal running. Both the oil film thicknesses and friction coefficient are included in determining the friction generated by every single component.
Also as said, some components of friction increase with the square of the speed and some don't so you couldn't even attempt to extrapolate the cranking friction up to 18000rpm as you don't know what component of the power loss is dependant on this relationship.

How would I put an image up? I will put up a graph of FMEP for a 1600cc engine through its opperating range for some people to get some idea of frictional power losses, I won't tell you the engine.
If its straight-forward I will put it up if you want xpensive?

[xpensive]

As much as I appreciate the analysis, as is obvious from my original post, all I really ask for is a credible ball-park number for internal friction-loses of a 2.4L V8 on full song?

[flynfrog]

As has been said, the suggested starter motor method won't really do it. You don't get the same oil pressures and oil film thicknesses as you do during normal running. Both the oil film thicknesses and friction coefficient are included in determining the friction generated by every single component.
Also as said, some components of friction increase with the square of the speed and some don't so you couldn't even attempt to extrapolate the cranking friction up to 18000rpm as you don't know what component of the power loss is dependant on this relationship.

How would I put an image up? I will put up a graph of FMEP for a 1600cc engine through its opperating range for some people to get some idea of frictional power losses, I won't tell you the engine.
If its straight-forward I will put it up if you want xpensive?

you are correct there would be alot of estimating to use the starter. But one could assume it happens at a simaler rate to other engines.

to post a picture you first need to host it then put the url between img tags or use the img button

Code: Select all

[img]www.mypicturehere.com/mypicture.jpg[/img]

[flynfrog]

also the starter will be sized to overcome static friction not dynamic. back to the old board.

[xpensive]

Just thinking out loud here, F1_Eng.

As viscous resistance-force is proportional to speed and power is force times speed, all viscous power-losses in any oil-film will be related to the square of the speed.

Which components of friction power-loss do you suggest are directly proportional to speed then?

If beginning with the squared assumption, if the starter is 1 kW at 1000 Rpm, power-loss at 18k would be 320 kW or 440 Hp, would that be reasonable?

[machin]

If beginning with the squared assumption, if the starter is 1 kW at 1000 Rpm, power-loss at 18k would be 320 kW or 440 Hp, would that be reasonable?

As stated above the problem is the starter has to overcome static friction.... I don't have figures for oil lubricated bearings, but for composite water lubricated bearings* on bronze liners the coefficient of friction drop-off with speed is pretty large:-

RPM Coeff of friction
0 = 0.6
5 = 0.36
10 = 0.2
15 = 0.12
20 = 0.085
30 = 0.05
40 = 0.03
50 = 0.022
60 = 0.018
70 = 0.015
80 = 0.012
90 = 0.01
100 = 0.01

(*I design boat propulsion systems!)

[F1_eng]

None are directly proportional to speed. This is why I was saying that you discover interesting occurances when simulating systems and looking at dyno results or friction rig results.

Power loss would be force * speed yes, but the force in question is constantly changing. So if the speed goes up, you must also bear in mind what happens to the force. The force involved is the force excerted in the con-rod, be it tension of compression, this then acts on the cylinder wall at an angle dependant on crank angle and engine geometry.

Build up a simple model to show piston acceleration through the opperating cycle. You will then observe that the areas of positive and negative acceleration are not the same.

I won't go in to it any further as it would appear you don't want to.

I am not going to disclose figures about the engines unfortunately but what I can tell you is, 320kW is not close.