Negative Boost
If you have written the 'eliminating the negative
boost' series of articles, I would like to let you know that as you describe it
you only measure the static pressure with the tubes connected at the side of the
passages. As the inlet air speed is increased (when passing in smaller diameter
passage or other airflow meter etc) the dynamic pressure having the direction of
the moving air mass is actually increased. It is proportional to the square of
the inlet speed and density. So as the static pressure measured from the side is
lowered, the dynamic pressure pushing the air is increased, so up to a point
(connected with the mach index of the incoming mass) these are actually helping
the inlet pressure (and mixture). This is why multiple technologies exist to
narrow/(close by flaps) or make longer intake passages at lower speeds. This is
done to increase the air speed and the dynamic pressure which helps a lot in
these conditions.
So as in the articles if you measure the
dynamic pressure you would see it is higher at the locations described. To
measure it the best way is to use the static/dynamic pressure differential via
some tubes one of which is placed in direction of the moving air, as any moving
gas has a direction of movement and at that direction there is a pressure acting
coming from the movement. As a garden hose when squeezed squirts further away as
the force in that direction is increased when the speed of the water is
increased as a result of the narrower outcome area.
I hope this
information would help you when some mods are suggested in the articles. For
example if some of these engineered restrictions are removed, the effect would
be that at lower rpm the inlet air speed would just drop, the dynamic pressure
would decrease and the net effect be opposite as suggested in the article. And
please see the decrease is not linear but quadratic (^2) with speed of the
air.
Some systems like BMW DISA and many others use it with good results.
Also it is even used in static manifolds, intake runner length-diameters. (Like
BMW M52/M50 intake manifold design differences, etc).
Lubomir
Putting Pitot tubes in at each measuring point
would be better than measuring just static wall pressure, but that’s a pretty
well impossible approach. The quoted technique works very well in practice,
whatever its theoretical shortcomings.
The Loremo
If you haven't come across it yet, the Loremo,
a very economical car, may be worth an article: http://www.loremo.com/index_en.php
Edwin
Australia
See
The Loremo!.
Subs
I'm a stooge and have been reading the
beginning of your articles for a few years now (no subscription) and now I'm
excited say that I'm no longer missing out and wish to thank you for sharing
your full articles with us non subscribers. I believe if you continue to do this
and also continue to keep the standard of your articles high you will not fall
short but instead your following will grow and your advertising revenue
will quickly surpass your subscription fees. Keep up the fantastic work!!! By
the way, have you considered a composite construction HPV. You'd be saving
weight and designing something more easily mass produced for consumers.
Geoff
Australia
As you have noted, we are moving towards a non
subscription model. Re an HPV made from composites: such a design is of course
possible but it does not lend itself very well to prototypes.
Closed Loop Monitor
I decided to try
out your "Closed Loop Monitor" Project. Bought the parts, soldered them to the
board, checked for unexpected shorts and cold solder joints with an ohm-meter,
and went on to try it on my car. It's been a whole day trying to figure out what
I did wrong. Double, triple and quadruple checked the drawings, inside and out,
top view and bottom view. It stays either completely lit or completely off, no
matter idling or under load. Measured the output of my oxy sensor with a
voltmeter – perfectly fluctuating between 0,2 and 0,6 V at idle, going up to
0,8V at load. Are you sure the pot has to be wired in this way? If the LM311 has
to compare between the oxy output and a corresponding reference, I think
the pot has to be a voltage divider with a coefficient of 20 to create a
reference voltage of 0,6V from the 12V supply. Can you please help me solve this
dilemma?
Stanislav Randjev
Bulgaria
The circuit is the simplest possible and so it is
not protected against voltage spikes, etc. If you are continually having
problems we suggest that you instead build the Smart Mixture Meter
Smart Mixture Meter, Part 1 and if required mount just
one of the orange display LEDs on the dashboard.
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