William. I guess there are two "types" of Imperials here. The big blocks like
my 68's and the small blocks like your 83. So, I will try to answer for both
cases.
Big blocks. Even the relatively weaker 413's have way too much power to be able
to accelerate them in traffic at WOT on a regular basis. But even if you
could, the fuel economy would not improve. This is not an easy answer, as
there are conflicting factors. The heavier the load, the more efficient an IC
engine typically is (IC=internal combustion). However, in the case of spark
ignition, when you are WOT, you are also on a rather rich mixture. Second, the
heavier the acceleration, the more the torque converter slippage, and this
translates into a direct energy loss. At the end, it turns out that our cars
will suck the gas no matter what. So, there is nothing wrong with accelerating
hard every now and then. But accelerating hard will not save you gas money.
Small blocks. Even though I have never driven an 80's Imp, from the specs it
looks like a relatively big car with a relatively detuned engine, geared very
high. In a car like that, it appears that it is more feasible to operate near
WOT, even in traffic conditions. However, in this case the enrichment at WOT
may hurt fuel economy even more, because the EFI will control the mixture close
to stoichiometric a lot better than the older carbureted cars. The converter
slippage may be an issue too, as the car may stay on high slippage conditions
longer, since it takes longer to accelerate. Also, if the 81-83's have lock up
converters, these lock only at light acceleration, giving another reason to not
accelerate hard if you are trying to save money. Still, even for the 80's
cars, driving the car hard every now and then can be good for it.
Quoting Phil Patterson <hilljack7@xxxxxxxxxxxxx>:
> . I can't see where sticking your foot in down in the throttle would be good
> for gas mileage, except maybe for a very light high horsepower car, where it
> could brought up to speed quickly then allowed to coast.
Even for a small car, getting too small an engine does not always help with fuel
economy. Sometimes, if the engine is too small, it goes over rich operation
way too often, braking even on fuel economy over the slightly larger engine
option. Unless of course you have a hybrid electric, where the electric motor
will help the anemic engine in the heaviest accelerations.
D^2
Quoting William <mopar@xxxxxxxxxxxxxxxxxx>:
> Hi All,
> This may be a bit of a stretch as far as Imperial content, but since they
> are big cars, and do use a fair bit of fuel, I hope this isn't too far off
> topic. I have a question regarding fuel economy and acceleration. Not based
> on my practical desire to conserve fuel as much as the theorietical optimum
> (read: settle an argument!). I am not interested in cruising economy, as
> that is pretty straightforward.
> Regarding acceleration, as I see it, there are two variables; throttle
> setting and shift point. What combination will provide the most economic run
> to cruising speed X? Is it wide open throttle and high shift points over a
> short distance, low throttle and low shift points over a long distance, or
> something in between? I remember reading about the Mobil Economy Run, where
> in certain cases it was optimal to use WOT (or near) to accelerate to
> cruising speed, but conventional wisdom usually states slow acceleration is
> best.
> One side is that it is better to accelerate quickly to cruise speed. The
> counterpoint being that earlier you shift, and the less throttle you use,
> the better. Which is correct? Thanks for the input on this one. I will
> reveal later which side I was on...
> William
> 83 EFi
> Edmonton, Canada
>
>
>
>
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