I put Steve's drag figure (0.596) in a model I built about a year back using
MS Excel. (No reason to do it except it was there). The result looks
reasonable-optimistic for a 1992 plus 4
0-60 7.4s OK
30-50 4s Optimistic
50-80 7s just a bit optimistic
Top speed 110-115 ( if you can wait about long enough)
This leaves just 3 theoretical inaccuracies with the model
First engine power and torque (I built a guestimate based on peak torque
and peak power figures and the normal power to torque to speed relationship
which is not too bad for this engine as peak torque is at 4500rpm and peak
power at 6000rpm and the variation is quite tight constrained by those)
Second transmission loss (I used a linear 15% of throughput power.)
Finally its a piecewise model based on 200rpm and 5mph steps which probably
compensates for the time to change gear effects.
I am kind of happy with the engine end of things (short of hiring a
dynamometer) and the steps could be made as small as I wish (subject to
memory in the PC and processing time) but does anyone have any data on
transmission loss. Roughly how big would you expect it to be? How does it
vary with torque/power/revs?
There is clearly no rush for an answer as the weather is good and
theoretical analysis is no substitute for the real thing!!
Incidentally how would one fit a nice V8 (or even a grotty Rover in line 4
like mine) in a barn door/pile of bricks for the purposes of the comparison
Steve suggested below?
Dave Vodden
Plus 4 4 Seater
Hampshire UK
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From: morgans-owner
To: morgans
Subject: Drag
Date: 20 April 1997 06:00
Many months back there was some question as to the drag coefficient. While
reading the May issue of Road & Track, I noticed Engineering Editor for R&T
and fellow Morgan owner Dennis Simanaitis had written an article titled "My
PC Morgan."
Dennis was writing a review of a piece of software that calculates various
auto performance data. As a test he uses his 1965 Morgan Plus 4 four
seater. One of the more interesting items is that with collected data
about the car, the software was able to come up with the coefficient of
drag, .596. This was done top down.
This begs the next question, drag wise, where does a Morgan fall in
relation to barn doors and pile of bricks? Then again, in the world of
Morgans, who really cares as long as its a nice Spring day and there is a
nice bit of road out there.
Steve Bauserman
67 Morgan 4/4
83 Mercedes 300SD
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