DIN vs SAE net vs SAE gross and weights

["Mark Battley" <m.battley@domain.elided>]

Richard wrote
> >umm, i may be misremembering, which is why i'm not sending this to the
>entire list, but the US didn't switch from SAE to DIN, it switched from SAE
>Gross to SAE Net. SAE Gross was a much abused system in which engines were
>measured mounted on stands, with no accessory drives (power steering,
>alternator, what have you), without the street exhaust system, and
>sometimes with induction which bordered on forced. SAE Net was a
>rationalization which used the same basic principles as SAE Gross, but
>which required that the motor be measured in a configuration which actually
>left the factory floor for the dealer.
>
>DIN produces slightly different values from SAE Net, whereas SAE Gross
>produces substantially higher numbers than either DIN or SAE Net.
>
You are right Richard, I found the same thing when I got home last night and
looked at a few more books. Some of the road tests are rather vague as to
what standard was actually used, either saying nothing, or perhaps just
gross or net. Some UK advertising for the 2000 cars claimed 150 hp (which
would be SAE gross), but most used the 132 DIN figure.

It appears that Europe switched from SAE gross to DIN, while the USA went to
SAE net. Since SAE is an American institution and DIN German this is not
surprising. I don't know how different DIN is to SAE net, but I believe that
it is similar (Eric??). The only difference that this makes to the figures I
previously posted is that the USA 2000 data is in SAE net, not DIN. The
figures that I gave as SAE are SAE gross.

A quick look in the work library this morning yielded the following:

SAE gross (SAE J1995): the engine is configured "with only the built in
equipment that is required for self sustained operation"

SAE net (SAE J1349): the engine is configured "with those accessories
necessary to perform its intended function"

I couldn't find the relevant DIN standard, but a reference to it in a
generic automotive text stated: "all auxiliary units are absolutely required
for the perfect operation of the engine" and "the output according to SAE
(gross) is [typically] 10-15% higher than DIN. 

The standards give lots of details as to exactly what this means, but
comparing major items::

                        SAE gross       SAE net    DIN
aircleaner               optional         yes      yes
alternator               optional     optional     yes
emissions control        optional         yes      yes
exhaust                  optional         yes      yes
water pump                 yes            yes      yes
cooling fan                 no            yes      yes

The standards of course also specify the exact operating conditions,
temperature etc, which can also differ between standards.

Keith summed it up well in another post:
"Deutchland Invented Number vs. Severely Ambitious Exageration"  I like it!

Emmo wrote:
>Mark Battley posted a comparison chart which included 0-60 and 1/4
>mile times for 1750 vs 2000. Careful here as a 69 GTV probably weighs
>100 lbs. less than a 74. But then talking times like these there are
>so many other variables, such as the driver even if its the same
>driver for each run.

For sure, and that was evident in the data I looked at. I believe that the
in-the-gears times such as 50-70 are much more relevant to real driving than
the 0-60 time. Unfortunately is is not as widely measured or quoted in
tests. The 0-60 time is also a poor comparison for many cars because some
reach it in 2nd gear, others (particularly Italian ones) have to change into
third shortly before. I recently wrote an article for a local classic car
magazine comparing the early MR2 to a later Bertone X19. The MR2 redlines at
61mph in 2nd... helping give it such an impressive 0-60 time. The MR2 is
faster, but not by as much as the 0-60 time might suggest.

As for GTV weights... these are as much of a minefield as performance and
power data. The same numbers get quoted all over the place and you are never
sure what was measured and what was copied off somebody else's data. A
weight of 2292lb/1040kg is quoted in some tests of the Euro and USA 2000 and
1750. The lowest I could find for a Euro 1750 was 2240lb, for a USA 1750
2270lb. Highest I could find was 2335lb for a USA 2000. So perhaps there is
a 50 lb difference 1750 vs 2000, and another 50lbish Euro vs USA?

Mark Battley
Auckland, New Zealand.

1973 Alfa Romeo 2000 GT Veloce

Alfa Romeo 105 series Bertone Coupe home page and register at:
      http://www.geocities.com/MotorCity/1806/105GTV.HTML 

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