De uitlaat had nog een tikkie groter kunnen zijn.
Bij het zien van boven afgebeelde foto zou Herr Maurice een hartaanval krijgen.
Dit is dan ook geen 720 cc motor, zoals Addax, maar de standaard 602 cc motor.
Bij Addax had ik een speciale uitlaat, luchtfilter en sproeiers aangeschaft.
Op de rollerbank is een en ander afgesteld.
Bij Trapper is op de uitlaat na nog alles origineel.
De 2/1 uitlaat kwam bij ons onder het chassis te liggen.
Het nadeel van de 2/1 uitlaat vonden wij toch de herrie.
De boven afgebeelde uitlaat stelt ons in staat om het chassis te voorzien van een vlakke carter beschermingsplaat.
Deze "halve" uitlaat komt uit de 2CV Cross wereld.
Kennelijk is het daar een beproefd concept, dus wie ben ik.
De praktijk zal het gaan uitwijzen.
Voor de liefhebber het volgende: "Stof tot nadenken.".
Dit heb ik even van de site van Herr Maurice gejat. Herr Maurice een beetje kennende heeft hij hier geen bezwaar tegen.
Destroying
a myth.
Some
say that “an engine needs backpressure to work correctly.” Is this
true?
No.
It
would be more correct to say, “a perfectly stock engine
that cannot
adjust
its fuel delivery needs backpressure to work correctly.” This idea
is a
myth. As with all
myths, however, there is a hint of fact with this one. Particularly,
some people equate
backpressure with torque, and others fear that too little
backpressure will lead
to valve burning.
The first reason why
people say “backpressure is good” is because they believe
that increased
backpressure by itself will increase torque, particularly with a stock
exhaust manifold.
Granted, some stock manifolds act somewhat like performance
headers at low RPM,
but these manifolds will exhibit poor performance at higher
RPM. This, however
does not automatically lead to the conclusion that
backpressure produces
more torque. The increase in torque is not due to
backpressure, but to
the effects of changes in fuel/air mixture, which will be
described in more detail
below.
The other reason why
people say “backpressure is good” is because they hear
that cars (or
motorcycles) that have had performance exhaust work done to them
would then go on to
burn exhaust valves. Now, it is true that such valve burning
has occurred as a
result of the exhaust mods, but it isn’t due merely to a lack of
backpressure.
The internal
combustion engine is a complex, dynamic collection of different
systems working
together to convert the stored power in gasoline into mechanical
energy to push a car
down the road. Anytime one of these systems are modified,
that mod will also
indirectly affect the other systems, as well.
Now, valve burning
occurs as a result of a very lean-burning engine. In order to
achieve a theoretical
optimal combustion, an engine needs 14.7 parts of oxygen
by mass to 1 part of
gasoline (again, by mass). This is referred to as a
stochiometric
(chemically correct) mixture, and is commonly referred to as a
14.7:1 mix. If an
engine burns with less oxygen present (13:1, 12:1, etc...), it is
said to run rich.
Conversely, if the engine runs with more oxygen present (16:1,
17:1, etc...), it is
said to run lean. Today’s engines are designed to run at 14.7:1
for normally cruising,
with rich mixtures on acceleration or warm-up, and lean
mixtures while
decelerating.
Getting back to the
discussion, the reason that exhaust valves burn is because
the engine is burning
lean. Normal engines will tolerate lean burning for a little bit,
but not for sustained
periods of time. The reason why the engine is burning lean to
begin with is that the
reduction in backpressure is causing more air to be drawn
into the combustion
chamber than before. Earlier cars (and motorcycles) with
carburetion often
could not adjust because of the way that backpressure caused
air to flow backwards
through the carburetor after the air already got loaded down
with fuel, and caused
the air to receive a second load of fuel. While a bad design,
it was nonetheless
used in a lot of vehicles. Once these vehicles received
performance mods that
reduced backpressure, they no longer had that doubleloading
effect, and then
tended to burn valves because of the resulting over-lean
condition. This,
incidentally, also provides a basis for the “torque increase” seen if
backpressure is
maintained. As the fuel/air mixture becomes leaner, the resultant
combustion will
produce progressively less and less of the force needed to
produce torque.
Adapted
from Thomas V.
What other wannabee
mechanics say:
„What about exhaust
systems? Well, my favorite quote is, "That system
doesn't provide enough
back pressure for good low end power. You need
back pressure for good
low end and mid range on the street.“
Simply put the above
is bullshit and reveals more about the speaker's lack of
knowledge in exhaust
tuning than anything else. He probably gives out lots of
advice like this
because he likes the sound of his voice or loves to see his name in
print on forum boards.
Back pressure (I assume our friend means
restriction/resistance
to flow) does not "help" mid range power.
De discussie gaat nog even door. Een en ander wordt met grafieken "bewezen".
Herr Maurice zet je wel aan het denken.!
Enne, Addax verkeert met z'n trip in Marokko en China nog steeds in een goede "gezondheid".
Voor mij nu zaak om de kleur van de bougies goed in de gaten te houden.
