Basic engine nomenclature
From Crankshaft Coalition Wiki
(→The "strokes" of an internal combustion 4-stroke engine) |
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| + | ==The "strokes" of an internal combustion 4-stroke engine== | ||
| + | From [http://www.answers.com/topic/internal-combustion-engine#Nomenclature Engine nomenclature]: | ||
| + | 1. Intake stroke: The first stroke of the internal combustion engine is also known as the suction stroke because the piston moves to the maximum volume position (downward direction in the cylinder) which pulls the fuel/air mixture into the cylinder. During this stroke the inlet valve is open, and the vaporized fuel mixture enters the combustion chamber. The inlet valve closes at the end of this stroke. | ||
| + | 2. Compression stroke: In this stroke, both valves are closed and the piston moves upward to the minimum volume position in the cylinder compressing the fuel mixture. During the compression process, pressure, temperature and the density of the fuel mixture increases. | ||
| + | 3. Power stroke: When the piston reaches the minimum volume position at the top of it's stroke the spark plug ignites the fuel mixture and burns pushing the piston down. The power is transmitted to the crank shaft mechanism. | ||
| + | 4. Exhaust stroke: After the power stroke, the exhaust valve opens. During this stroke, the piston starts its movement at the bottom position. As the piston rises the spent exhaust gasses exit through the outlet valve. At the end of this stroke, the exhaust valve closes, the inlet valve opens, and the sequence repeats in the next cycle. Four-stroke engines require two revolutions. | ||
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| + | ==Other terms== | ||
| + | #Cylinder Bore is the Inside Diameter (ID) of the cylinder. | ||
| + | #Stroke is the distance a piston moves between Bottom Dead Center (BDC) and Top Dead Center (TDC). | ||
| + | #Displacement or Swept Volume is the volume swept by the piston when traveling from BDC to TDC. | ||
| + | #Clearance Volume is the volume of the combustion chamber above the piston when it is at TDC. | ||
#Piston deck height. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center. Nominally, with a premium 350 piston and a virgin, uncut block, this dimension will be about 0.025". | #Piston deck height. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center. Nominally, with a premium 350 piston and a virgin, uncut block, this dimension will be about 0.025". | ||
#Squish. This is the dimension from the crown of the piston to the underside of the cylinder head with the piston at top dead center and adding in the thickness of the compressed head gasket. Current thinking is that a squish of 0.035" to 0.045" works best. | #Squish. This is the dimension from the crown of the piston to the underside of the cylinder head with the piston at top dead center and adding in the thickness of the compressed head gasket. Current thinking is that a squish of 0.035" to 0.045" works best. | ||
| − | #Compression height. This is the dimension from the centerline of the piston | + | #Compression height. This is the dimension from the centerline of the piston wrist pin to the top of the piston crown. With a premium piston in a 350 Chevy, this dimension is about 1.560". Lesser quality rebuilder pistons will measure out at around 1.540". This will increase the piston deck height and the squish and make the motor more sensitive to detonation. |
#Stack. This is the combined dimension of the crankshaft radius, rod length and piston compression height. A common stack with a 350 Chevy would be about 9.003". That would be with a crank radius (half the stroke length of 3.480") of 1.74", rod length of 5.703" and piston compression height of 1.560". | #Stack. This is the combined dimension of the crankshaft radius, rod length and piston compression height. A common stack with a 350 Chevy would be about 9.003". That would be with a crank radius (half the stroke length of 3.480") of 1.74", rod length of 5.703" and piston compression height of 1.560". | ||
#Block deck height. Nominally, this dimension would be about 9.025" on a virgin small block Chevy cylinder block. So, when using a stack of parts equalling 9.003", this would result in a piston deck height of about 0.022". Combined with a steel shim head gasket thickness of about 0.018", this would result in a squish dimension of about 0.040", just in the middle of the desired range of 0.035" to 0.045" to help prevent detonation with a reasonable (nominally, about 10.0:1) static compression ratio on pump gas. Alternately, a builder might cut the block decks down to the height of the stack and use a more conventional composition gasket that specs out at around 0.040" compressed thickness. If you had a stack of 9.003", cut the block decks down to 9.003" and used a 0.040" gasket, then the piston deck height would be 0.000" and the squish would be 0.040". | #Block deck height. Nominally, this dimension would be about 9.025" on a virgin small block Chevy cylinder block. So, when using a stack of parts equalling 9.003", this would result in a piston deck height of about 0.022". Combined with a steel shim head gasket thickness of about 0.018", this would result in a squish dimension of about 0.040", just in the middle of the desired range of 0.035" to 0.045" to help prevent detonation with a reasonable (nominally, about 10.0:1) static compression ratio on pump gas. Alternately, a builder might cut the block decks down to the height of the stack and use a more conventional composition gasket that specs out at around 0.040" compressed thickness. If you had a stack of 9.003", cut the block decks down to 9.003" and used a 0.040" gasket, then the piston deck height would be 0.000" and the squish would be 0.040". | ||
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| + | ==Links== | ||
| + | *[http://www.motorera.com/dictionary/index.htm Dictionary of Automotive terms] | ||
| + | *[[How to rebuild an engine]] | ||
| + | *[[Chevrolet engine rebuild guide books and DVDs]] | ||
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| + | [[Category:Engine]] | ||
| + | [[Category:General hotrodding]] | ||
| + | [[Category:Undeveloped Engine articles]] | ||
| + | [[Category:Undeveloped General hotrodding articles]] | ||
| + | [[Category:Undeveloped articles]] | ||
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| + | STACK: The addition of 3 values to arrive at the STACK dimension of parts that you will fit into the cylinder block. PISTON COMPRESSION HEIGHT, rod center to center length and crankshaft RADIUS are added together to arrive at a STACK height. Generally speaking, a builder would want the total STACK dimension to be just short of the BLOCK DECK HEIGHT or exactly the same measurement as the BLOCK DECK HEIGHT, called "zero deck". Some builders have fitted a taller STACK into a block to allow the piston to come up out of the block slightly with the piston at top dead center. This might be done to adjust the squish when using a thicker head gasket, like maybe a 0.050" (fifty thousandths of an inch) thick or 0.060" (sixty thousandths of an inch) thick copper gasket with o-rings for a blower motor. If using domed, or pop-up pistons, the STACK is measured to the piston crown, NOT including the dome. Some pistons are manufactured with a COMPRESSION HEIGHT taller than a standard piston. This additional measurement needs to be taken into consideration when totalling the height of your STACK of parts. | ||
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| + | BLOCK DECK HEIGHT: Measurement from the centerline of the main bearing bore of the block to the flat part of the block deck where the heads bolt on. Blueprint dimension of a Gen I small block Chevy is 9.025". Not to be confused with PISTON DECK HEIGHT, which is the measurement from the piston crown to the block deck with the piston at top dead center. BLOCK DECK HEIGHT is shown here, but is mis-labeled as simply "deck height". It should have been labeled "BLOCK DECK HEIGHT". | ||
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| + | PISTON: Pistons come in 3 flavors, cast aluminum, cast hypereutectic aluminum and forged aluminum. Hypereutectic means that there is a very large amount of silicon in the mix when the manufacturer casts the piston, which gives the piston a different set of operating characteristics over a conventional mix with a standard amount of silicon added to make a conventional cast piston. In addition to the obvious diameter measurement, there is a measurement of the centerline of the wrist pin to the crown of the piston. This measurement is called COMPRESSION HEIGHT.... OR CH for short. | ||
| + | That measurement is one of 3 measurements an engine builder must know to add up the STACK of parts to be used in the cylinder block. Pistons come in many different COMPRESSION HEIGHTS to allow their use in different combinations of stacks. | ||
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| + | CONNECTING ROD: Rods come in 3 flavors, cast steel, forged steel and in the case of aluminum racing rods, extruded. 99% of the rods used by us hot rodders will be forged from one steel mix or another, with the formula varying according to how the manufacturer wants the rod to perform in its lifetime. Rods come in many different center-to-center lengths so that we can custom tailor the measurement of the stack of parts we will use in our motor. | ||
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| + | CRANKSHAFT: Cranks come in 3 different flavors, cast steel, forged steel and billet steel. The vast majority of cranks used in the hot rod hobby will be cast steel. Half the stroke of the crank, or the RADIUS of the crank, will be used to determine your STACK. If a crank stroke is 3.48", then the radius of that crank will be 1.74". In the left part of this diagram, the arrow points to the centerline of the crankshaft main bearing journal. Another arrow points to the crankpin where the big end of the rod bolts on. | ||
| + | The measurement between these two points is the RADIUS of the crankshaft. As stated above, the radius of a 350 crank would be 1.74", or half the 3.48" stroke. A 383 crank, with its 3.75" stroke, would have a RADIUS of 1.875". A 283 crank, with a 3.00" stroke, would have a RADIUS of 1.50". | ||
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| + | PISTON DECK HEIGHT: Not to be confused with block deck height, piston deck height is the measurement from the crown of the piston to the block deck where the heads bolt on, with the piston at top dead center. PLEASE PAY ATTENTION. THERE ARE 2 DIFFERENT DECK HEIGHTS. BLOCK DECK HEIGHT AND PISTON DECK HEIGHT. PLEASE BE SPECIFIC WHEN DISCUSSING "DECK HEIGHT". Piston deck height is labeled incorrectly here as simply "deck height". It should be labeled "Piston Deck Height", not to be confused with block deck height. | ||
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| + | SQUISH: The distance from the piston crown to the underside of the cylinder head with the piston at top dead center and with the head gasket in place and its thickness included in the measurement. If the piston crown were down in the bore by 0.010" (ten thousandths of an inch) with the piston at top dead center and you used a 0.028" (twenty eight thousandths of an inch) gasket thickness, adding the two together would yield a 0.038" squish measurement (thirty eight thousandths of an inch). The closer the piston comes to the underside of the head (without crashing into the head), the better the motor will perform. The action is that the piston comes up very close to the underside of the head and squishes out the mixture in that area, jetting it across the chamber toward the spark plug and creating turbulence to help eliminate rich and lean pockets of mixture in the chamber so that the whole mess burns evenly and offers less chance for the mixture to detonate or pre-ignite. | ||
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| + | QUENCH: The terms quench and squish are often used interchangeably, but they actually have different technical meanings. Quench refers to the passing of heat from the combustion chamber into the surrounding metal, some of which finds its way into the cooling system. The more quench that is in effect, the more heat passes into the cooling system and vise versa. An example would be the close proximity of the piston to the underside of the cylinder head with the piston at top dead center. On one hand, having a quench-type combustion chamber and piston shape and tight quench distance may be looked at as a detriment to power production (heat IS energy, after all). But in the case of the IC engines we are working with, the loss of heat energy is more than offset by the decrease in the tendency to encounter detonation- which will kill power at a much greater rate and amount than the loss of some combustion chamber heat to the quench effect. | ||
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