Jim Muller wrote:
>
> So it's a matter of tradeoffs - you gain a price advantage in a
> highly competitive "bottom-feeder" market, but you lose a little bit in
> optimized timing at part-throttle.
Certainly could be. I've always found it difficult to follow car
maker's thinking, and S-T is no exception. I sometimes think that
'corporate wisdom' is an oxymoron.
> The historical fact is that the later (at least) Spitfires never had vacuum
> advance, though they did have the vacuum retard at idle.
My Haynes only covers to 1974, but it says that only USA models lacked
vacuum advance.
> By comparison, the TR6 had both.
I believe the TR6 vacuum advance was deleted in mid-1970, again only for
USA models.
> Also the Spitfire *did* use EGR to lower NOx, and air-
> injection with catalyst to reduce CO and unburned C.
Well, I did say the _US_ makers figured it out <g> Actually, AFAIK
there were very few US-made cars that lacked vacuum advance, it seems
to've been common only on European cars of the period. However, at
least at some point, California emissions retrofit required disabling
it, so it may be simply that it was required in CA, and only the US
makers were willing to do special models (at extra cost) for the CA
market.
One rather striking example (to me) was the 1970 Audi 100LS I owned,
versus the 1970 Peugeot 504 my Dad owned. The Audi had a slightly
smaller displacement engine, with both vacuum retard and vacuum advance,
while the Peugeot had no vacuum spark controls at all. Both were 4-sp
trannys, similar car weight and size, both 4-door sedans. But, the Audi
would run circles around the Peugeot, both in acceleration and in fuel
mileage. I always got between 30 and 35 mpg on the highway (depending
on how recently the points had been changed), while Dad never got better
than 25 ! 0-60 for the Audi was about 10 seconds, the Peugeot was more
like 15.
> One final point, as far as I know (though my memory is fuzzy and I'm
> certainly not an expert at the Feds' air regs), the regs didn't worry much
> back then about running conditions. Rather, they concentrated on idle since
> the air in big cities was the problem and most cars spend a majority of
> their urban time idling at stoplights.
I've never seen the regs themselves, but the articles I did read about
modifications made always included substantial changes for cruise
conditions. They just weren't as obvious as the idle mods, since they
were mostly things like recalibrated mixture, advance, and valve
timing. Later of course, they included things like EGR and catalyst,
both of which are not especially effective at idle.
Cheers
Randall
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