> IMHO low rpm power should be nearly identical for both fuel systems.
> The 2.5 PI generated most of the power increases through higher compression
> and a longer duration cam.
You'd think that wouldn't you... but as it turns out there's a major advantage
for PI (especially with modern EFI/TPI) in low end torque. Carb's, you see,
require a vacum "signal" to meter fuel properly. So when you plonk a big set of
Weber 45's on your 1100 Spit you get no bottom end because the carbs are too
big to generate a vac signal at the venturi's. PI doesn't rely on vac signal to
meter so you can run a huge cam on the street and not loose the bottom end. You
can run long, long, long intake runners that accentuate the "ram effect" and
bolster low-mid-range torque. You can even boost compression (which is a major
contributor to torque at all RPM's) without pinking because the mixture is far
more even across each cylinder! Cooler, denser mixture! No puddling of fuel! Go
farther on every gallon and make more power while you're doing it....
Man, you got me going now!
But while you're at it, don't bother with mechanical PI. It's like using a
abacus to do your taxes (or quantum physics) - easier than your fingers but a
calculator wins every time.... and a computer can actually adjust on the fly to
suit conditions - like Turbo Tax or Mathematica!
Mechanical PI has one mixture curve (and maybe one temperature sensor to vary
it.) It might be pretty close when its rebuilt and calibrated but it's
forever going away and getting less accurate as its many moving parts wear
- even the abacus is better in this regard... or an HS6! (fewer moving parts)
Go ahead and use the TR PI manifolds and throttle bodies, but throw
an Electromotive TEC II EFI/direct ignition on there and then you'll make big
torque and pass emmissions... A TPI set up like Total Advance's would make
even more torque.
Too complex? Nahh, much, much simpler. (I've worked on one too many Alfa's with
SPICA's)
I like my HS6's better, though.....
Chris Lillja
Spit MKIV
Norton Commando
TR4A
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