<VV> was: testing Tom's cooling system, now: fuel economy
NicolCS at aol.com
NicolCS at aol.com
Thu Aug 11 01:11:26 EDT 2005
<snitp>I'm a big fan of the 140PG engine. It definitely has significant
torque down low and would be ideal for pulling a steep gearset like you have.
BUT it's "all in" by 5000 rpm (even with a less restrictive exhaust) and is
almost 20% weaker at the top end. I don't think EFI would change that much.
Bill Elliott <unsnip>
Here's my thinking, Bill: The idea is to combine strategies that improve
low-end torque. What happens at 5000 rpm isn't relevant to the goal. EFI and
the 140PG cam both improve low-wnd torque. Why do we want to improve low end
torque? The most significant factors in fuel economy are engine friction
(proportional to rpm, so lower rpm is better) and (you can say this ten ways...)
reduced production of unnecessary engine vacuum (vacuum indicates incomplete
cylinder filling - we don't want a 164 cubic inch vacuum pump - that consumes
power). Increasing the low-end torque capabilities allows you to accelerate
briskly with lower and lower rpm. The condition of the engine at 5000 rpm
is completely irrelevant when you are shifting at 2000 or 2500. The
combination of tall gearing for reduced rpm and lower engine vacuum in combination
with EFI for more efficient use of fuel is the "magic" that causes modern cars
to get double or better fuel economy while making the same hp as an older
engine.
BTW, I have a carbureted version (140 with retarded 95 cam ala PG140)
driving a wide-ratio trans (keeps a normal 11.2 first-gear ratio). This combo is
more responsive than a "normal" 140 in all regular driving and displays
unusual "impact" when the secondaries kick-in. I think that if I added EFI, the
raising of the low end torque that is a byproduct of EFI would make the combo
even more FTD. That part is speculative though.
Craig Nicol
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