The Pre-history of Hot Air

[JHertzman@domain.elided]

Greg Hermann asks a good question and raises a good point in rebutting my 
comparison of Giuliettas and Giulietta Veloces- "Let us not lose sight of the 
fact that the factory HP ratings upon which you have based your comment were 
based on either the DIN or SAE standards of the day (you do not specifiy 
which ratings you are talking about, and whether you are talking about "net" 
or "gross" HP ratings". Greg goes on to say "_ALL_ of the HP ratings of which 
you could be speaking are based on a testing standard (this is true of any of 
the usual DIN or SAE HP testing standards) which _includes_ a correction to a 
standardized inlet air density and temperature!"

I was talking about the ratings published in Fusi, d'Amico & Tabucchi, and 
factory literature. It used to be commonly assumed that Italian claims of 
power and speed were not necessarily based on the most scrupulous testing; I 
won't take a position pro or con on that calumny. If Greg believes that the 
factory dynamometer laboratory figures in the fifties were rigorously 
corrected to a standardized inlet air density and temperature, I won't argue. 
They are just the best figures I have.

A digression: starting on p.570 in Fusi (the Giulia TI) we get mostly 
un-rounded numbers for horsepower: 106, 92, 112, 78, 98, 82, 109, 89, 118, 
96, 132, 63, 122, 68, 103, 116, with a few exceptions. Going the other way, 
from the Giulia back to 1930, we find 145, 130, 115, 100, 105, 65, 90, 80, 
65, 100, 125, 110, 95, 180, 220, 70, 155, (again, with some exceptions) and 
then it reverts to 46, 84, 76, 54, 44, 48, 71, 61, 56 going back to the 
Merosi era.. A cynic might suspect that there were elements of fashion 
influencing the declared powers.

In the case of both the Giulietta Veloce and the 1900 TI d' Amico & Tabucchi 
refer to pressure but not to temperature: "the long intake manifolds and the 
frontal dynamic air intake designed to create, especially at high speeds, a 
supercharging effect" on the TI,  and "The same partial supercharging effect 
obtained on the 1900 TI was reproduced thanks to the dynamic front air intake 
feeding the carburettors" on the Giulietta Veloce. I will leave it to Greg 
and others to debate the relative importance of the cams (etc) and coolth, 
which should show up in acceleration at moderate speeds, versus the 
"supercharging effect especially at high speeds". As far as I can tell 
virtually all later stock Alfas have taken unheated air from the front; 
although the use of velocity stacks, foam socks, domes, quadraflows etcetera 
breathing heated underhood air seem to be fairly widespread among cognoscenti 
who want to improve their cars.

I would certainly agree with Greg that "a cold air intake  - - - has a 
_distinct_ effect on functional HP in the real world". I suspect that Alfa's 
engineers knew that, and that we should not overestimate the ease with which 
we can greatly improve on their products.

Cordially

John H.
Raleigh, N.C.

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