Hi Scott:
Some of the most impressive hp/litre ratios are found in motorcycle
engines. 35 years ago, Honda was producing incredible power from small
engines. They were OHC,four stroke vertical twins. As an example, my
Honda 1963 CB92 - which was introduced in 1959-60 - produced 15-16 hp from
125 cc. This works out to 120 hp/litre. This engine had two valves and a
single carb. It produced this power at 10,500 rpm. A British 125 of this
period was lucky to make 6 hp.
My 1982 Kawasaki 1300 produces the same 120 horsepower from 1300 cc. It
features 3 twin choke carbs, 2 valves, single OHC and is water-cooled.
In the mid to late sixties Honda produced incredible racing engines which
could make 70 to 90 hp from 500cc. They even made a 50cc twin which
produced something over 7 hp at 22,500 rpm. Imagine the size of the
valves. This was a power output of 140 hp/litre.
Today's motorcycle engines regularly exceed 150 hp/litre and are moving in
on 200. I owned a Kawasaki 1979 Z1-R TC 11 - quasi-factory turbo hot rod -
which produced an estimated 155 hp from 1 litre.
Automobiles are now only beginning to approach this kind of specific power
output. It has been 41 years since Chrysler led the industry by producing
the first automobile engine to make 1 hp/cu. in - the 300B with optional
355 hp engine. This was only 61 hp/litre but at a time when the norm was
half of that.
You're right when you say that it has been a long time, and technology
hasn't changed all that dramatically. The first DOHC engines were
introduced before WW1. Four valve engines are old hat and supercharging
has been around "forever".
I believe that the need to develop clean engines both detracted from and
spurred development. At first the need was to clean up what was there
without concern for economy. I have a '73 Eldorado with 500 cu.in. engine.
No power. Less mileage.
Later on, the need for economy dictated smaller, lighter cars with smaller
fuel efficient engines. I have an '82 Cadillac Cimarron with 1.8 litre
engine. No power. Great mileage.
Finally today, the economy/pollution equation has been reduced. Now we are
reaping the side effects - clean, economical powerful engines. It has
taken 25 years but the benefits are going to continue. The only loss has
been - for us LBC lovers - the ability to repair and tinker with our toys.
The future of the automobile-as-appliance is secure. The future of the
automobile-as-artifact is endangered. The future of the automobile-as-toy
is threatened by the future.
John McEwen
> Can anyone tell me what the changes have been in the last hundred
>years that allow a constantly increasing output from a given-size
>engine? I'm not interested in turbocharging or supercharging in this
>discussion. I read about 500 cubic-inch Cadillac engines from
>thirty years ago putting out 145 horsepower, which is the same power
>as my 82 trans-am put out in a 305 c.i., and is about the same
>power some modern cars put out from a 1.8 or 2.0 liter four cylinder.
>Other than four-valve engines and overhead cams, what has been the
>big technology gain that has allowed the big increase in hp/liter? I
>guess this also begs the question "How has fuel flow/hp decreased so
>much in the same amount of time?" I know I've beaten this example to
>death, but my '86 Jetta had a 1.8L in-line four, 8.0:1 CR, with two
>valves per cylinder, just like my 'B', but put out 102 hp at the
>tires versus 95 or so at the flywheel in a 'B', and got about 35-39
>mpg in city driving. The only difference I can think of is the fact
>that it was fuel injected (mechanical FI, though, no
>computer-controlled EFI), and that it had an overhead cam. I can't
>remember what the Jetta weighed, but it certainly wasn't LESS than
>the 'B'.
> I'm kind of amazed that we've been able to steadily wring more and
>more specific power out of engine designs that haven't changed
>radically in almost 100 years. Show a modern engine to someone from
>1920, and after you got past the plumbing on top, he'd recognize most
>of the parts.
>Scott
>
>Scott Gardner
>gardner@lwcomm.com
>www.lwcomm.com/~gardner
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