Message text written by pbrandsema
>Well, after a long winter, I can finally start looking foward to the
driving
months. I have decided that the driving experience would be more enjoyable
with a little more horsepower (a lot more would be nice also). I'm looking
for suggesting on quick and easy mods, to produce a few more ponies. I've
been reading up on polishing the inside of the intake manifold, to allow
more air and fuel to get into the engine. I've also heard that it would
not
be advisable to smooth out any rough areas in the TR4 manifold. The reason
for this was stated that by polishing the intake, the fuel would tend to
accumulate on the walls of the intake. The main reason stated for this was
that the rough areas served to swirl the air and fuel mix together. So,
the
conclusion was that a loss of power would occur instead of an increase.
Anyone have an opinion?
<
Well, yeah. But a reasoned response would be better.
But lacking that, here's my opinion.
I heard the same thing many years ago so I've had many years to ponder this
(not that it has been uppermost in my mind) and here's my take:
A rough surface in the intake wall will create turbulence which may
decrease the tendency of gasoline to precipitate out of the mixture onto
the inner wall of the manifold. However, at wide-open-throttle (which is
what you do when you want to make horsepower) the air moves through the
manifold so quickly that there is little opportunity for the petrol to
condense on the manifold walls. Gasoline precipitation is only an issue at
very low intake mixture velocities (idle) and this is why they added
manifold heat (engine coolant passage) to the manifolds of later model
cars. The warming of the manifold will cause the fuel to remain in
suspension at idle conditions but the airflow through the mainfold at
serious throttle positions will be high enough that the mixture will not
pick up any heat on its way to the cylinder.
So, the trade off is WOT horsepower vs a minor (if noticeable) improvement
in idle quality.
But the real reason they didn't polish the intake manifolds at the factory
is for cost reasons.
And that's my opinion. Go for it.
Cheers
Dave
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