What gives an engine more HP

[kermit911]

I own a hovercraft, and I was looking at engines to try and increase the speed. There is an engine that weighs 85 lbs and has 35 HP, then there is an engine the weighs 85 lbs and had 90 HP. I'm not understanding how that worked. Same weight more power. Could someone explain. Thanx a lot

Dave

[Clanad]

Could be a number of things that really have minimal affect on the weight of the engine... such as compression ratio, size of intake manifold, number of intake and exhaust valves or perhaps it has to do with the horsepower versus RPM ratio being higher on one engine producing a peak horsepower at a deceptively higher and often unobtainable RPM. A quick look at the specifications for each engine from the owner/operator's manual should tell you the pertinent differences...

[Toureman]

A normal car engine produces say 120 bhp and costs around �1500.

An engine fitted to a Formula 1 car probably weighs the same but produces 900 bhp and costs at least �250,000. at a guess.

This cost is because of development, high tech parts, months of tuning etc.

Thats how you get more power from the same weight of any engine.

[Space]

engine displacement, rather than weight, is one of the basic characteristics of an engine that influences power. It's the volume of the cylinders.

[craig5470]

It is down to the power produced in the combustion cycle i.e induction ,compression ,ignition,exhaust, so the compression cycle creates the hp in the combustion chamber therefore having the cylinder head skimmed by a few mm will produce more power but be carefull not to take off too much or the inlet and exhaust valves will bend

[mini23]

Its down to how much fuel and air is burnt at the correct mixture.
A higly tuned engine will have larger cylinder head valves and a longer camshaft duration (the inlet valves are open for longer duration) this allows a greater volume of fuel/air mixture into the engine creating more power and normally making the engine less efficient.
Alternativly use a turbocharger or supercharger to force even larger amounts of fuel/air mix into the cylinder by putting it there under pressure.
For something really extreme, use nitrous, wet system is far superior to dry because you mix nitrous with extra fuel (the nitrous being 33% oxygen allows the burning of the extra fuel)