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Grunderna
för "V" motorer
V-motorer använder 2
cylindrar till varje vevaxel. Det är bra eftersom man då kan
använda en kortare vevaxel. Cylindrarna i en V-motor kan sitta i
olika vinklar (60, 90, 180) beroende på olika faktorer. Den
största faktoren är det totala antalet cylindrar i motorn. Den
vanligaste vinkeln på cylindrarna på en v8 motor är 90 grader. Om
en v6a har 90 graders cylinderlutning krävs en balansaxel som
snurrar dubbelt så fort som vevaxeln för att undkomma vibrationer
från motorn.
Det här är viktigt att förstå eftersom de flesta nya
V-dieselmotorerna har 8 cylindrar så är de bättre balanserade.
Det gör att motorerna får sitt maximala vridmoment vid ett högre
varvtal utan att motorn tar skada av stora "torsional"
påfrestningar.
Grunderna
för "raka" motorer
"Raka"
motorer har alla cylindrar i en rad och använder därför en
längre vevaxel jämfört med en v-motor. Raka 6-cylindriga motorer
erbjuder en mjuk prestandakurva, men så är inte fallet med raka
4-cylindriga motorer, de saknar "1st
order balance".
Eftersom de raka motorerna redan är längre än "V"
motorerna så
in effort to maintain adequate volumetric displacement
används oftast
längre slaglängd istället för större cylindervolym. Tack vare
detta ger de "Raka" motorerna en trevlig prestandakurva
på låga varv. För stor cylindervolym kan orsaka poor “flame front traveling” combustion
issues that are difficult to manage along with yielding less than desireable
emmission levels Relating to these mid-range marine
applications; among
several performance drawbacks of the inline engine configuration is that due to
the longer stroke and longer crankshaft, achieving higher rpm levels is much
more difficult than with that of the “V” configured engines. It is much more
difficult to package equivalent “inline” engine displacements versus that of the
“V” configuration as the overall engine length and height quickly grow to
unacceptable proportions. This being the case you can normally group the inline
engines into two categories; 1) Highly boosted small displacement. 2) Similar
displacement but larger, heavier, low rpm products that yield excessively high
idle speeds.
In the typical mid-range marine application when replacing
250 - 400 Hp small or large V8 gas engines, the majority of inline diesel
offerings will be approximately 30% smaller in displacement and therefore have
to be highly boosted to make up for this shortfall.
Användningsområden
för MDs "V" motorer
En
"V" motor tar mindre plats än en "rak" motor
med samma antal cylindrar. Därför har MD valt att använda v8
motorer.
bla bla bla bla bla............................
Basics of the “V” Engine
Engines classified as “V” type
utilize 2 seperate banks of cylinders connected to a single crankshaft. This is
beneficial in that a more desireable, shorter crankshaft can be utilized. The
cylinder banks of a “V” engine can be at different angles (60, 90, 180)
depending on several factors. Of these factors the overall number of cylinders
plays an important role of which the smoothness and or vibration of an engine
results. For example 90 degrees is a common bank angle for V8 engines, and V6
alike, however the 90 degree V6 is inherently subjected to 2nd order vibration
and typically requires a balance shaft spinning twice the crankshaft rpm to
cancel this out.
This is important to understand for the reason that
most of the new “V” configured diesel engines emerging on the automotive markets
are 8 cylinder and therefore inherantly balanced. This allows these engines to
turn at a higher rpm without experiencing failures resulting from excessive
torsional stresses.
Basics of the
“Inline” Engine
Engines classified as
“inline” are configured such that the cylinders are inline on a single bank and
therefore typically utilize a longer crankshaft versus that of the “V” engine.
Inline 6 cylinder engines typically offer smooth power delivery, however this is
not case with the 4 cylinder counterparts as they are inherantly out of 1st
order balance.
Since inline engines are already longer than “V” engines,
in effort to maintain adequate volumetric displacement they typically utilize
longer strokes rather than larger piston bore diameters. Due to this length of
stroke the inline engines typically yield nice low rpm torque production however
become quite tall in overall height. Regarding large bores versus longer stroke,
too large of a bore diameter can create poor “flame front traveling” combustion
issues that are difficult to manage along with yielding less than desireable
emmission levels.
Relating to these mid-range marine applications; among
several performance drawbacks of the inline engine configuration is that due to
the longer stroke and longer crankshaft, achieving higher rpm levels is much
more difficult than with that of the “V” configured engines. It is much more
difficult to package equivalent “inline” engine displacements versus that of the
“V” configuration as the overall engine length and height quickly grow to
unacceptable proportions. This being the case you can normally group the inline
engines into two categories; 1) Highly boosted small displacement. 2) Similar
displacement but larger, heavier, low rpm products that yield excessively high
idle speeds.
In the typical mid-range marine application when replacing
250 - 400 Hp small or large V8 gas engines, the majority of inline diesel
offerings will be approximately 30% smaller in displacement and therefore have
to be highly boosted to make up for this shortfall.
Benefits of
MarineDiesel’s “V” Engine
The following points
we would like to illustrate relate to the marine market and mid range (5,000 -
30,000 Lb) boats. The larger, heavier commercial type vessels have completely
different torque, power and rpm requirements. There are countless boats from
years past that were powered by small and big block V8 gas engines; the
MarineDiesel product offers numerous fundamental product advantages of which
many are of the same reasons the automotive industry is moving towards the
higher revving “V” configured diesel engines.
Packaging: Overall a
V8 diesel product will package it’s displacement better than an inline engine of
the same displacement. Inline 4 & 6 cylinder engines cannot offer these same
packaging benefits as they are inherantly longer. MarineDiesel built on this
concept by teaming with AM General and their Optimizer 6500 block in developing
the only direct replacement marine diesel engine. The 6500 block
matches the engine mounting position, bell housing, flywheel, height, width and
weight of GM big block V8 engines. MarineDiesel continued this direction when
developing the center-rise exhaust that matches up with nearly all GM based
small and big block V8 gas engine systems. The bottom line is that the
MarineDiesel product will drop directly into the same place a big block gas V8
is being removed without any major boat hull modifications. No inline based
engine product can offer this. This packaging benefit also allows MarineDiesel
to offer the marine industry’s only Tow
Sport
specific diesel engine.
Displacement: With the packaging problem
at hand, inline engines cannot offer as much overall engine displacement without
becoming excessively long and heavy. MarineDiesel offers as much as 30% more
displacement for the same power level when looking at our competitors. Small
displacement, excessively boosted engines do not yield the best durability as
the only way they can try to offset the smaller engine displacement is by
increasing fuel and turbo boost, and consequently cylinder pressures. Inline
engines that do match the displacement of a “V” engine will be much heavier due
to the stroke, size and length of the required crankshaft.
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