Another reason I love cooler temperatures... I just love the way my MINI drives when it's cold outside! Won't gas mileage go up also during the autumn/winter, or is that just a myth?

 

The more fuel (o2 and gas) you can jam into a container, the more power you're going to generate. Cold air is more dense than hot air (there is more o2 content for the same area) which means you can get more o2 and gas into the same cylinder than you could on a hot day.

Water injection is another story. Newton says Force is F = M * A. Water has greater mass than regular air alone. Injecting water increases M, which in turn increases F. This is also why it works in jet engines Thrust = M * A also.

Someone mentioned earlier about maximum aircraft altitude. In piston engines, its true that you would eventually run out of performance at a given altitude due to the lowering density of the air. This is why they have SC piston engines. Jet aircraft actually become more efficient the higher they go (to an extent). A jet aircraft's maximum altitude is more a function of airfoil design than engine power. The ends of the aerodynamic envelope start to close in on you at high altitudes. The true maximum altitude of jet aircraft is where the airfoil stall speed is equal to the speed that the airfoil starts to see mach buffet.

How was that for thread hijack?

 

Can't answer this until we know the average temperature coming from the East and coming from the West. As we all know an MCS goes faster in cold weather.

 

hehe, if you think cold air in a MCS is golden, sit in the seat of a M3 and fell the difference.

 

I am no expert, but... my bet is that F=M*A is not the appropriate formula for determining how water injection affects HP. An internal combustion engine doesn't work by mass ejection (throwing water out the back to push you forward). Throwing water out of the cylinders is not responsible for HP gains. Actually, even in a situation where it would be appropriate to use F=MA, increasing the mass wouldn't necessarily increase the force, it may lower the acceleration and keep F constant.

 

You're right, it's not throwing mass out the back, which is why I didn't use "thrust" there. Force is what is being applied against the piston head to drive it downwards though.

I am not a car expert either. Just trying to adapt what I know about jet engines to car engines.

 

I understand, but the expansion during combustion doesn't push the cylinder any harder because of the higher mass of the water molecules. It takes more energy to get the higher-mass water molecules moving.

 

Same goes for my STi. However the tires performance drops at the same time. 3rd gear wheelspin is fun.