Dick:
Thinking about the seemingly low HP gains, I would think that
for 6 lbs of boost the final HP would be ((6lbs + 14.7lbs)/14.7lbs) *
105 HP = 148 HP
That comes out to be 43 additional HP on our motors. This
formula assumes that the compression is adiabatic, which it is not.
Allowing for some heating of the incoming air/fuel charge, 39 HP seems
very reasonable indeed. In fact, I am surprised that only 4 HP is lost
between the parasitic drag and the inevitable heating of the incoming
air. There must be some additional HP gained somewhere, perhaps from the
use of the Holley carburetor, otherwise that would be the most efficient
supercharger I have ever heard of.
The HP gain is not a fixed multiple of the boost pressure, it is
a proportionate gain on the original power of the motor. The rule of
thumb you cite must (?) be derived from a recognized standard mule
engine or some such, and could not be applied to any other motor without
additional correction. At least, that is what it seems like to me (which
is always questionable).
As was previously noted, that amount of HP (39HP) can be gained
from less expensive, simpler modifications. On the other hand, a simple
pulley swap on the supercharged motor and suddenly you are running 180
HP with no loss of drivability. Try doing that with a naturally
aspirated TR6 engine.
$90/HP includes the engineering costs, plus their profit. Given
the limited market for the supercharger kit, this seems a reasonable
price. Moss is to be commended for their commitment to our cars. BTW, I
saw one of their kits on an MGB, and it looked top drawer. Very neat,
and the "equipment envy" from the onlookers was very apparent. Just
remember "Size doesn't matter", at least that is what I kept telling
myself. =:-o
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Sally or Dick Taylor
Sent: June 19, 2006 10:27 AM
To: 6pack@autox.team.net
Subject: Re: Moss supercharger
Stan, and interested parties---I don't know why the 6 lb. of boost would
only yield 39 additional hp on the Moss setup. I wouldn't think the SC's
belt drive should cause this much parasitic drag at the crank.
Typically, one can expect about 10 additional hp per lb. of boost, up to
where air density is compromised at higher boost pressures. (At least
this is true with turbocharging.)
<snip>
Dick
From:
stan.foster@hp.com(Foster, Stan)
I did wonder about the cost/benefit and if that was a good route to
take. For the TR6 they claim an extra 39HP for $3500, so close to $90
per HP. I guess one advantage is that it just bolts on more or less.
Really appreciate Moss's innovation and investment though.
Stan
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