I have a question about horse power

[FrankWest]

Originally Posted by Tom Wesenberg

When I was in 11th grade, my physics book showed a horse pulling a rope slung over a pulley and lifting a 550 pound weight 1 foot in one second. This was said to be what a normal horse could do for a period of time, and was one horse power.

That is true.. As a boy when I heard a car was 200HP, I imagined a Roman Chariot driven by Carlton Heston being pulled by 200 horses!

[mshmodela]

Originally Posted by 2manycars

The model A engine is 200.5 cubic inches in displacement. It made 40 horse power at 2200 rpm. The model B engine was the same displacement, but with a different cam profile and slightly higher compression, and larger carburetor, and made 50 horse power. The V8 was only 221 cubic inches displacement, but made a claimed 85 horse power. How was that possible? Was the compression of the V8 that much higher? The early ones still had babbit bearings. Was the cam profile that much different? The way they idle so smoothly, one would think it was a pretty tame profile. The valves were still pretty small, and Ford had not yet figured out that intake valves need to be larger than exhaust valves. So why is the horse power so small on a model A engine, and so much higher on the slightly larger V8? Other engines of that period made a lot more power on similar displacement. Any ideas as to why this all is?

Engine horse power is not directly proportional to cylinder displacement.. Today's average el cheapo 4 cylinder cars with less displacement make 150HP... or more... they rev a lot higher with 4 valves and those being over head type...

As for Ford's flat head V8 the crank shaft was pushed from two angles as oppose to one in an inline engine and were pushing at the right sequence to increase power... Think of two 80 lbs kids at play ground spinning one of these below... say standing 60 degrees apart, and timed just right.. as opposed to a single 160 lbs kid from just one point... which could push more kids on the ride? The two working together can produce more torque.

[Kahuna]

It's all about efficiency.
If you take as factual, the HP advertised as 40 hp, just for comparison,
The model A engine is 20% efficient., or 1/5 hp for every cubic inch.
The model B then is 25%, 1/4 hp for every cubic inch.
The 32 V8 then becomes 29%
The last 255 cubic inch Mercs become (depending on what advertising),
about 40% efficient.
Highly modified V8's (flatheads) can be up to 75% efficient and more.
Most of the increased efficiency in the V8s come about from the individual intake ports, more power pulses and increased usable rpm.
The lack of individual intake ports (shared ports) on the model A/B really reduces the engine's efficiency.
A model A/B would be better off using the exhaust for the intakes, which I guess some have tried. That, or the 2 up/2 down crank, which would help some.
Just an observation

[Tom Wesenberg]

I don't see how horsepower per cubic inch can be directly connected with efficiency. I just think of efficiency as how far a given amount of gasoline can move a given weight of car. If an engine was 100% efficient, then it wouldn't need coolant nor a radiator because all the heat of the burning fuel would be converted to mechanical energy moving the car.

[katy]

My original post was in jest,

NOW you tell us

[100IH]

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After all is said and done, efficiency can be boiled down to HP per cubic inch. Refer to post per #43. 1hp / in. is seemingly the upper limit but I have seen almost double that. This may seem like blowing smoke but you only have to think about some of the motorcycles and snowmobiles out there. Are we only talking about the Ford engines that have been mentioned from the early 1930,s or what has come to pass in the recent days of technology. It is all about how much heat you can keep in the combustion chamber without materials failing so long as the valve train and the bottom end don,t go first. Variable valve timing technology is one of the most important tools that have only recently been used to get close to 2HP/ in. Also, variable length intake systems certainly would have a dream in the early days. What a wonderful world, so long "keep it simple stupid".

[Kahuna]

Some newer 4 cylinder engines are capable of more than 100 HP per Liter

[Synchro909]

Originally Posted by Kahuna

Some newer 4 cylinder engines are capable of more than 100 HP per Liter

If the Model A was that efficient, it would develop about 330 bhp.

[Synchro909]

Originally Posted by Kahuna

Pgerhardt
has it correct. More bangs equal more power and smoother

Sorry, I have a different view. If a 200 ci engine burns 200 cubic inches of air fuel mix every 2 revs, it doesn't matter how nay cylinders there are. More cylinders, more but smaller bangs.
The main difference comes down to its easier to fill a small cylinder than a big one.