Horsepower Loss

Horsepower Loss
by Don Terrill (c) -

A large percentage of the energy in each gallon of gas is lost to friction and heat.

So, instead of looking at how to increase power, let's look at what's reducing it.

Frictional Losses
  • Pistons - Optimization of the skirt design for your application can help minimize piston to cylinder wall friction, but if it comes at the expense of lost ring stability and sealing, it may not be worth it.
  • Piston Rings - This area of friction has been beat to death by engine builders. Focus on the oil ring, it has the most room for improvement with the lowest risk. You can also work with the second ring, but you're flirting with disaster if you mess with the top ring.
  • Bearings - First make sure you've got the correct bearing clearance for the oil you're using. Then you can look at risky stuff like journal diameter and bearing width.
For any of these frictional losses, the use of the correct weight synthetic oil will always help.

Heat Losses
  • Combustion - Focus on optimizing your camshaft timing. This will put the heat from combustion to work moving the piston and not just passing out the exhaust system.
Aerodynamic Losses
  • Crankshaft - We've all heard of knife-edging to make the counterweights more aerodynamic, but you can also cut down the counterweight diameter or even thin the counterweights. The use of heavy metal for balancing will allow more latitude for modification.
  • Oiling System - Making items that swing inside the oil pan more aerodynamic may help slightly, but nothing beats just keeping the oil away from the engine components in the first place - A deeper oil pan, a dry-sump system, etc.
Pumping Losses
  • Induction System - Improving the airflow of the induction system not only helps fill the cylinder, it lowers the amount of work required to pull in the air-fuel mixture.
  • Compression - Turn your engine over by hand and you'll get the idea of the amount of work required to compress the air-fuel mixture. You could lower this with static compression and cam timing, but most of the time you'd lose more power than it would be worth.
  • Exhaust System - Improving the efficiency of the exhaust system helps remove non-combustible gases from the chamber, but it also lowers the amount of work required to remove those gases.
Say What?

If you were going to design a rocket to go to the moon, you'd focus on the amount of thrust required to break the Earth's atmosphere, right? But why not look at what's keeping the rocket from going there without any help? Gravity, what if you could turn it off?

What crazy questions should racers be asking?

photo by lorentey

Want to send off a nasty email about how wrong I am? Well, first read this and then write your own article.