All right guys, this whole TB spacer/velocity/restriction question has
raised my eyebrows several times and it's time to lay down the
(aerodynamic) law.
1.I was thinking of the ram air effect. If the air has more time to
increase velocity, then the air would be moving at a faster pace when it
is needed.
--->More time to increase velocity? Why? Velocity change over a
differing cross section is almost instantaneous - in fact, it's small
enough that airflow calculations don't even account for it (unless you
work for Lockheed skunkworks or something)
2. I know, I know, 1.25" doesn't seem like alot, but try that on another
vehicle. That is how the Edelbrock intake for the slow.0 (aka 5.0)
mustang works. The runners are a little larger, yes, but they are also
about 1.5" longer in length.
--> Runner length has an effect on air velocity, but only as a function
of restriction. Here is our starting point: a motor of a given
displacement will draw in a volume of air equal to half of it's
displacement on each revolution of the crankshaft. The last thing that
the air does is pass through the intake valve, which remains of a
constant cross sectional area, if you haven't changed valve size or
camshaft profile. These two things together mean that the air passes
through the valve and into the cylinder at exactly the same speed
regardless of anything you have done before this point (intake manifold,
cold air setup, rotated your tires, etc). Isn't this velocity the one
we're truly concerned with?
3.With the Dakota having a single plane intake, this would effectively
add to the length of the runners. Thus increasing air velocity, and air
flow past the valves while they are opening since the air is moving at
an increased speed.
--->The air is not going faster, so no, it is not presenting the intake
valve with faster air and thus increasing flow.
4. Another option we thought of today was to enlarge the outer
> part of the plate, drill and tap, and set it up to be water cooled from an
> exterior source. In other words, add a seperate electric water pump(a small
> one) and use it to cool the incoming air. Anyway, just thought I would give
> you the reason behind the insanity.
---> OK, but I am sure gains will be minimal as the air spends very
little time in a 1.25" long air channel.
Having said all that, it's probable all BS since my arguments are based
on steady-state conditions, not the stop-and-go flow that occurs in the
intake runners. The harmonics of this kind of flow are what intake
runner tuning are all about, not velocity. Bernd mentioned tunnel rams,
and another great example of this is the Hemi's cross-ram intakes. This
length also has a great effect on power across the RPM range - check out
a Jeg's or Summit catalog to see how very different manifolds will
perform at different RPM's.
The one thing to remember is that air velocity depends chiefly on two
things - air volume and the cross sectional area that it is passing
through.
My apologies to Will if I sound like I flamed you, but what you wrote
doesn't make sense to me. Everyone please feel free to respond to this
thread!
Cale Bargen
98cc318sporty
> Will
> 96 Dakota ext. cab
> Cylindrically Challenged V-6
> soon to be sprayed d:o)
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