Re: Heat crazed mad scientist

[John_Calabrese@ENGELHARD.COM]

"Bruce Plecan" <nacelp@bright.net>@diy-efi.org on 06/05/2000 11:54:51 AM

Please respond to gmecm@diy-efi.org

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To:   <gmecm@diy-efi.org>
cc:
Subject:  Re: Heat crazed mad scientist




> In order to quantify the flow increase, and thus the talk of laminar vs
> turbulent flow, a velocity must be calculated from the area, and cfm flow
> of the engine at different speeds.  Once the velocity and reynolds number
> is calcuated, then you can see whether or not turbulent or laminar flow
is
> present.

>What makes this all fall apart is there is no specific velocity in a
intake
>tract.  The airflow is in pulses.

You can talk about average velocity at the throttle body, this is the
subject I am referring to, not the back of the valve.  The throttle body is
far enough away that it should se and average velocity without BIG
perturbations.



 Either way, in a stock TPI throttle body, there is a abrupt edge
> where the airfoil goes.  Any time there is an abrupt change in direction,
> flow separation will occur, and it will occur easier at higher
velocities.
> Flow separation can be avoided or lessened by smoothing out the abrupt
> changes in the device you are flowing air in, be it a manifold head port,
> or a throttle body.  The airfoils'

>Using the word airfoil really is a stretch

 >job is to fill in a dead spot between
> the two openings, thus making the change in direction less abrupt.  This
> should increase the flow due to the smaller amount of flow separation
from
> the side of the walls.

>So, then using about the same logic here, running with the tailgate open
on
>a pickup should inhance mileage, right?.  Trouble is it don't work that
way
>(>most often).  The air "bubble" formed behind the cab turns out to smooth
.the air flow behind the cab and over the gate then all the turbulence of
>having it open and reducing the size of the "bubble".


Every design has specifics about them.  You cannot compare the throttle
body and the back of a truck.  Stop looking for an argument.


> trying to fill in dead spots in flow that could cause flow separation,
> vortices, and reversion, all which adversly effect flow rates.

>Which matches what I said.


I must've missed that part.

>

> I do have
> to disagree with grumpy on the fusalage being the same as the intake.

>Hang in there you'll get it right eventually.

> Inner flow and outer flow can differ significantly when boundaries and
> finite areas are considered, plus everything on a plane is designed for
> lift and minimal drag....

<>Heard that stuff before, trouble is the engines don't read the same
>material.

.>Just in what you've said, one might be tempted to think the airfoils
would
>have to work wonders, OK, why don't the performance numbers reflect that?.
>I'd suggest reading some of Smokey Yunicks old stuff.


The only way to test this is to flow the throttle body before and after the
installation of a "airfoil".  Performance numbers are the bottom line, but
an increase in flow potential in the intake may be masked by many different
factors in the engine, drivetrain and other associated parts that we take
for geanted as being constants.  You have to isolate the unit, make one
change and test it.  An increase in flow is what the manufacturer is after,
I don't necessarily belive it will make huge improvements in performance.


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