jackh@zehntel.UUCP (jack hagerty) (10/24/84)
In the interest of ending this discussion so we can get on to bigger and
better subjects, I'm going to make a qualified concession.
As Jeff has made abundantly clear to me (both on the net and in personal
mail) he did not make up the 2.6 second time and that he had achieved it
himself in his own car. The difference lies in the definition of "stock".
I say that you walk into a dealer, lay down your Samolians and drive away;
that's *stock*.
Jeff's definition, as I understand it, is that as long as something is
available from the factory, even as a special order and as long as you
don't add any after market performance pieces then it's still stock. This
leaves you free to fiddle with the engine settings, exhaust system, etc.
You can take things off (exhaust pipes, air cleaner, etc.), but as long as
you don't add them, it's still stock.
Then there are the tires. Checking with some ex-drag racing friends of
mine, as well as with some Corvette owners who are following this
discussion with keen interest; they say that on such a short run, racing
rubber should account for a 20 to 25% improvement in ET, not 10% as I
had assumed. A point to Jeff.
Given this rather broad definition of "stock" I will concede that a "stock"
1965 Corvette could accelerate from 0 to 55 mph in 3 seconds (changing the
tires, of course).
I still maintain, however, that while that may be what you meant,
It-Ain't-What-You-Said!
Jeff's right that I'm not that well steeped in Corvette lore. I come from
the other end of the spectrum: I'm currently in my tenth year of ownership
of my '74 Alfa GTV. Before that I had an Austin Healey Sprite Mk IV. For
a family car we have a Saab 900. Finally, there's a VW Beetle that I've
been vainly trying to change into a prewar Alfa GP replica for the past
few years. I'm sure all of the above fall into Jeff's definition of "putt-
putt cars", even though both the Alfa and the Saab manage 1 HP per cu in;
a figure held sacred by Chevy enthusiasts ever since the 283 managed it
in 1956.
In closing I'd like to say that I still don't understand the apples and
oranges comment. Maybe the apple is stock as defined by Jeff Buchanan
and the orange is stock as defined by everyone else ;-)
If you still want to continue this discussion, maybe we should meet on
net.religion, since neither of us is going to convert the other!
Jack Hagerty, Zehntel Inc.
...!ihnp4!zehntel!jackh
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BOREDOM WARNING BOREDOM WARNING BOREDOM WARNING
The following addendum is provided for those of you with a technical/
mechanical bend. Those with a low boredom tolerance (actually you've done
pretty well to get this far) should just "q" on to the next article.
===========================================================================
The following variables are used:
a = acceleration in ft/sec^2 v = velocity in ft/sec d = distance in ft
m = mass in slugs (which are lb-sec^2/ft) CdA = drag form factor in ft^2
F = force in lbs P = power in ft-lb/sec HP = horsepower which = P/550
T = torque in lb-ft t = time in sec
The following constant is used:
rho = air density = .00238 slugs/ft^3 at STP (that's Standard Temperature
and Pressure, not the oil additive!)
Basic Data:
Vehicle Mass m = 105 slugs (3380 lbs) - test weight from 11/65 C/D test
Rolling Radius (distance from axle hub to ground) r = 1 ft.
Frontal Area A = 19.6 ft^2 (from 8/65 R&T test)
==============================================================================
Acceleration from rest to 81 ft/sec (55 mph) in 3 seconds
ave rate: a = v/t = 27 ft/sec^2
distance traveled: d = .5 at^2 = 121 ft
force required: F = ma = 2835 lbs
Power required: P = Fd/t = 114,345 ft-lb/sec = *208 HP* AT THE TIRE PATCH
Torque required: T = Fr = 2835 lb-ft
divided by the 5.13:1 rer and 2.52:1 low
T = *220 lb-ft*
The above makes several simplifying assumptions: constant power available,
no tire slip, perfect drivetrain, etc. By the time you get into the real
world several irregularities have cropped up: the engine doesn't make that
power at a standstill, imperfect drivers, tires do slip, drivelines absorb
power, time out for shifting (1st gear at 55 mph is 9950 rpm) and so on.
All of these conspire to raise the power and torque required by at least a
third.
===============================================================================
Steady state at 257 ft/sec (175 mph)
With a 3.08:1 rer and 1:1 top gear engine speed = 7550 rpm. High, but OK.
Drag form factor:
Total drag at 88 ft/sec (60 mph) F = 125 lbs (R&T Tapley data, 8/65)
We'll be generous and subtract 15 for mechanical/tire losses (the
rest is aero losses).
CdA = 2F/(rho v^2) = 12 ft^2
Power/Torque required at 257 ft/sec
F = .5 rho v^2 CdA = 943 lbs + 15 mech/tire losses = 958 lbs
HP = Fv/550 = *448 HP*
T = Fr = 958 lb-ft
divided by above drivetrain, T = *311 lb-ft*
============================================================================
Summary
The acceleration claim appears marginally achievable given ideal conditions
and a very very good driver.
The top speed claim? Sorry, uh-uh, no way. Of course, Jeff has already
conceded that point. I'd believe maybe 155 mph as a realistic top speed.
JJH