Re: cooling fan HP, The Vandenberg Papers, etc.

[Scott Fisher <sfisher71@domain.elided>]

--- John Hertzman <johnhertzman@domain.elided> wrote:
> 
> Yes, but - was this contrast (weaker cam/stronger
> cam) ever suggested?

I raised the question after reading the cam data
published in Centerline's current catalog (#12) and
after looking over historical data for various flavors
of Alfa Spider from contemporary road tests.

The 10502 cams are called out in the Centerline
catalog as used in "1600 late 105 series, 1300 105
series, Early 1750 Euro, and 1750 FI"); the 10548 cams
are described as "Late 1750 Euro, 2000 Euro;" the
10520 -- ah, and here's the rub, there are six
separate applications for the 10520 cams with
different valve timing and, in the case of the later
cars, different duration, overlap and lobe centers. 
Centerline list the following data for the three cams
you mention (I'll use only the first five digits and
limit specs to lift in MM, duration and overlap to
make the table narrower):

Cam #  Lift   Duration    Overlap    Lobe center

10502  9.5    278i/264e   67         102i/102e
10548  10.1   281i/269e   76         99.5i/99.5e
10520  9.6    272i/258e   49         114i/102e

Those 10520 figures are only for 1972-74; from 1975
through 1985 (the latest year listed in the table I am
excerpting), Alfa played with overlap and lobe
centers, presumably to find the best balance between
power and emissions.

Interestingly enough, the post-VVT cams have much more
aggressive duration figures, 286 degrees for intake
and 272 for exhaust; the VVT mechamism adjusts the
overlap (and lobe centers) to reduce overlap and
retard timing (to 118 degrees ATDC) below 1650 RPM,
and increases overlap and advances timing (to 98
degres ATDC) above that figure.

> I don't believe it was ever
> claimed that the Spica 2000 with the 105.20 cams
> produced the same power as
> the carbureted 2000 with the 105.48 cams.


I raised the question, based on what I've been able to
piece together: were they perhaps closer than has been
credited in the popular conception?

I have not yet been able to locate a published
horsepower claim for the U.S.-market Spica/105.20 cars
(prior to 1977), which is itself interesting;
unattributed oral tradition claims that the stated
horsepower for 1972-74 2L Alfa engines in U.S. trim
was "about 125."  My question, and it was (or was
meant to be) a question rather than an assertion,
centered around the net/gross differences which have
caused enthusiasts so much confusion over the past 30
years; the details of these differences are also not
widely documented.  In the absence of definitive
statements (should such statements be found, and found
to be trustworthy, which would appear to be two
distict tasks, probably of comparable magnitude), I
located published data which indicate that net power
(expressed in KW -- 112KW gross and 95KW net) is
approximately 84% that of gross power.  That, of
course, is net and gross by an unstated standard
(DIN?).

I *was* able, from several international sources
(reprinted in the Gold Portfolio), to locate published
figures of European-spec 2-liter engines (hence,
presumably, using the 105.48 cams), at a stated 150
SAE gross bhp -- equating to 112 KW in the same table.
 Applying the 84% correction factor (hypothetical at
this point) to this gives us 127 bhp as an equivalent
net horsepower rating for Euro cars.

This raises several questions:

1.  What is the stated U.S.-spec horsepower (net or
gross) of 1972-74 2-liters using the 10520 camshafts?

2.  Is there a more palatable, acceptable, or
agreed-on standard conversion factor for calculating
the net/gross difference from contemporary reports
(thereby introducing, perhaps, the term "CHP" for
"calculator horse power")?

3.  Why should anybody care, today, whether there
really WAS any difference between Euro BHP and US BHP
thirty years ago?

I can at least suggest two possible answers to the
open-ended question #3 -- first, to suggest, perhaps,
that Alfa's U.S. efforts were more carefully thought
out and more effective than many detractors give them
credit for; and second, to consider that converting a
U.S. Alfa to "European" spec may not necessarily give
the immediate 25 bhp increase that a casual reading of
old documents might suggest.  I'm sure there are more
possible answers.

> Vandenberg was
> checking the improvements several variables offered
> against the 1976 Spica
> engine, which was probably the most strangled
> version of any, and against the
> 1979 version, which was considerably better,
> certainly the best of the late
> Spica engines.

Contemporary reports, coupled with the cam
specifications, support John with the how and why. 
R&T's 1978 test of a 1979-market Spider stated that
the use of a less restrictive catalyst (2 liters
rather than 1.5 liters) not only helped with
breathing, but also allowed Alfa to change the cam
timing (among other things, presumably; it is not
stated) for a claimed 8 bhp improvement; Centerline
concurs on the cam timing, noting a jump in overlap
from 37 degrees in 1975-76 cars to 61 degrees for
1977-79. 

> he recorded six hp gains at 4500, 5000, and
> 5500, up from one hp at 3000 and 3500 and 4 
> hp at 4000.

Thanks for reprinting that, John -- some years ago you
cited those same numbers to me in private
correspondence which, I fear, was lost several
computers ago.  I remembered the "up to six" figure,
but couldn't recall the provenance or the curve.

> It could be the gains progressed to 7, 8, 10
> at 7000, or it could be it flatlined, but the
> reading at 7000 is a guess either way.

Eric Storhok's calculation (in later email) based on
the engineering formulae for calculating pumping
losses certainly seems authoritative, but probably
unnecessary -- a 6-bhp increase at 5500 RPM is
significant enough to merit investigation.

> At 3000 and 5500 his 105.48
> Euro cam was producing one more hp than both of the
> US cams (71, 70, 70 at 3000; 105, 104, 104 at 5500.)


Again, this -- while hardly conclusive -- suggests
that the difference between the calculated 127 bhp
(that is, .84 times the stated 150 SAE gross
horsepower) for Euro 2Ls is not vastly superior to the
unattributed oral tradition of "about 125 bhp" for
early U.S. cars.

> Above 5500 all three cams were on the downslope,
> with the 105.02 (2000 FI)

Minor clarification -- did you mean to type 105.20
(2000 FI) or 105.02 (1750 FI) cam?

> The conclusion of the article was that the best
> combination of the variables
> they tested for a normally aspirated 2-liter Alfa
> motor produced a 12 percent
> increase in horsepower compared to the 1976 motor
> and a 6 percent increase
> compared to the 1979 motor, and "This increase in
> power is small in both
> comparisons, showing the efficiency of the stock
> Alfa motor to be relatively
> high for the street". It is interesting reading, but
> not too encouraging for
> those who want to buy useful gobs of added power.

But very encouraging for those who don't particularly
want to spend the money.  Thanks, John.

> I will also mention that Fusi publishes a number of
> comparative power-curve charts which some may find 
> worth looking at. [...] The two Alfetta curves
> offer a nice comparison; with
> the same cams both the 1779 and the 1962 cc engines
> peak with 140 hp SAE at
> 5500, 

This figure would appear to be gross SAE bhp, for
those wishing to compare apples to apples.

Thanks,

--Scott Fisher
  Tualatin, Oregon
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