Quoting FltSgt@xxxxxxx:
> Rob
>
> When I called MoPar Performance to see what the difference was over my OEM
> Imperial dual exhaust they stated the TNT etc manifolds are five to eight HP
> more depending on your total system.
Do they sell these like Year One does? If yes, may be the real number is closer
to the "five" as opposed to the "eight". The 5 hp represents about 1.6%
improvement, which is rather negligible, compared to the effort to replace the
manifolds (changing the pipe may be the toughest part), and the cost to buy
them.
Also, as you know, the performance benefiits of improvements in exhaust
(especially a minor improvement such as a bit higher rise in the manifold)
occur as the air flow is increasing. That means, that at WOT, the higher the
rpm, the higher air flow, and thus the higher the potential benefit. So, my
guess is that the larger benefit of the upper end of the quoted range (5-8 hp)
occurs probably over the peak power, like at 5500 or 5800 rpm, so that's manly
of interest to muscle cars that tend to have low gears and over-rev their
engines (Rob P?!). Also, for them, that can be important, because even a small
hp advantage could mean winning or losing against a fellow racer. For the rest
of us, this benefit is trivial. Even I, do not rev my 440 more than 5000 rpm
(that's a bit over 100 in second gear). So, even for me the benefit would be
small.
> on the 1959 to 1966 Imperials. But if you happen to have a '67 or newer
> Imperial w/o the TNT and etc exhaust system, it will aide in the hill
> climbing ability or Interstate mpg figures.
Rodger, in the very rare ocasion I challenge the hill climbing ability of my
Imperials (they are both fairly powerful), it usually happens at medium rpm and
high gear, like 1500-2000 rpm. These are the ocasions where you are trying to
postpone downshifting (in the LeBaron with lockup converter, sometimes I can
dig down in the 1300 rpm low end torque). At these low rpm cases (secondaries
are usually closed), the air flow through the engine is very small compared to
WOD/5500 rpm, so the benefits of the manifols are about zero. As for gas
mileage, this is also a part load case, so even then the benefit will be
marginal.
Again, we need to remember how these muscle car engines were marketed. Usually,
some young fellow that knew little about engines, but wanted to impress their
friends would buy a 440 cuda or Charger or whatever with the "TNT" or "super
comando" or whatever gimic name was used. 440's were fairly common on C-body
cars, so these guys wanted to have something "different". As the only
difference between the HP and non-HP engines (both very capable by those 60's
standards)was in the cam which was non-visible, they wanted to have something
visible to identify their hot engine and show off. The weird looking exh.
manifold offered exactly that.
D^2, 2x68
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