8 cylinder to 4 cylinder in new DC V8's

Matt Whiting · Apr 19, 2004

Joe, cat got your tongue?

Matt

Matthew S. Whiting wrote:

I guess insults are the best you can offer when you don't have any facts.

Yes. The forumla for a cylindrical shell's volume is: V = 2*pi*r*h*w,
where r is the radius of centroid of the revolved rectangle, h is the
height of the shell and w is the thickness of the shell. I checked a
few places and found typical piston/cylinder clearances of 0.0005 -
0.002". Let's use the large value which is the w in the above formula.
A 4" bore isn't all that uncommon so we'll use that which gives an r of
2". I didn't find any listings for distance from the piston groove to
the top of the piston, but pistons I've seen in the past were probably
around 0.25" so I'll use that for h. This gives a volume of 6.28 x
10^-4 cubic inches which is miniscule in my book.

Makes little difference. Let's assume the above cylinder has a stroke
of 3.5". The volume swept by the piston is therefore: pi*r^2*h or 44
cubic inches if I punched the calculators buttons correctly. If the
compression ratio is about 10:1, that gives a cylinder volume of
approximately 5 cubic inches. This means that the volume of cylindrical
shell above the top ring amounts to ~0.001%. So even doubling or
halving the diameter of the engine bore will make diddly squat
difference and wouldn't contribute enough to exhaust emissions to be
even measureable.

Have you been embarrassed enough yet? Can you find any flaws in my
assumptions or calculations or, better yet, provide some calculations of
your own that support your theory about this contribution to engine
emissions?

And the above percentage is assuming that the entire volume of gases
trapped in this annulus is exhausted unburned on each cycle. Anyone
with a modicum of knowledge of fluid mechanics knows that you'll have a
very hard time moving the air/fuel mixture into and out of this
cylindrical shell that is only 0.002" thick or less. So the effective
percentage above is probably more like 0.00001%.

Matt
Click to expand...

Dori A Schmetterling · May 11, 2004

In this newsgroup everybody needs at least 350 HP to win the Traffic Lights
Grand Prix...

DAS

8 cylinder to 4 cylinder in new DC V8's

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8 cylinder to 4 cylinder in new DC V8's

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