Allan74
01-23-2010, 12:41 AM
Rod/Stroke ratio
The rod/stroke ratio is the ratio of the length of the connecting rod to the length of the piston stroke. A longer rod will reduce the sidewise pressure of the piston on the cylinder wall and stress forces increasing engine life. It also increases cost and engine hight. A "square engine" is an engine with a bore diameter equal to its stroke length. aA engine with a bore diameter that is smaller than its stroke length is known as an undersquare engine. An engine where the bore diameter commonly known as an oversquare engine, conversely, an engine with a bore diameter that is smaller than its stroke length is known as an undersquare engine.
Most engine builders shoot for a ratio between 1.5:1 and 1.8:1, which shows that the RB26DETT designers made this a key consideration during it's design due to the fact that it ends up EXACTLY in the middle with a ratio of 1.65:1 (1.5:1, 1.8:1, +/- 0.15:1 either way) and an odball stroke (73.7mm) as the result.
ROD LENGTH/STROKE = RATIO:1 (Rod Length devided by Stroke equals Ratio, to 1).
-----------------------------------------------------------------
Common Rod/Stroke Ratio Examples.
---------------------------------------
1.49 B20A
1.54 B18B
1.58 GSR
1.74 B16A
1.78 B16B
1.99 VW Air-Cooled Type I
1.90 Chevy 283 CID SB
1.75 Chevy 327 CID SB
1.64 Chevy 350 CID SB
1.53 Chevy 454 CID BB
1.65 RB26DETT (73.7mm Stroke, 121.5mm Rod)
1.54 RB26 Stroker (77.7mm Stroke, 119.5mm Rod)
1.77 RB30DE (86mm Stroke, 152.5mm Rod)
+++++++++++++++++++++++++
+ RB26DETT Variants Explained +
+++++++++++++++++++++++++
** CH/PH = Compression Height/Pin Height.
(Stock Config "Overaquare/Short Stroke" 86mm x 73.7mm & 121.5mm):
OEM RB26DETT Configuration/Stroke.
121.5mm Rod Length & 73.7mm Stroke = 1.65:1 (1.64857530529)
30mm CH/PH Piston Used (Standard).
-----------------------------------------------------------------
(Stroker Short Rod Config "Overaquare/Short Stroke" 86mm x 77.7mm x 119.5mm):
(Nismo GT Spec 1, Tomei, HKS, Generic 'JDM' Stroker) +4mm Stroke Increase.
119.5mm Rod Length & 77.7mm Stroke = 1.54:1 (1.5379665379)
30mm CH/PH Piston Used (Standard).
-----------------------------------------------------------------
(Stroker Long Rod Config "Overaquare/Short Stroke" 86mm x 77.7mm x 121.5mm):
(Nismo GT Spec 2) +4mm Stroke Increase.
121.5mm Rod Length & 77.7mm Stroke = 1.56:1 (1.5637065637)
28mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
(Stroker BRIAN CROWER Config "Overaquare/Short Stroke" 86mm x 79.0mm x 121.5mm):
USDM Product, Longest Off The Shelf RB26 Stroked Crankshaft, + 5.3mm Stroke Increase.
121.5mm Rod Length & 79.0mm Stroke = 1.54:1 (1.5379746835)
27.35mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
(Stroker JUN Config "Overaquare/Short Stroke" 86mm x 75.7mm x 121.5mm):
JDM Product, Shortest Off The Shelf RB26 Stroked Crankshaft, +2mm Stroke Increase.
121.5mm Rod Length & 75.7mm Stroke = 1.61:1 (1.6050198150)
29mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
The above information is based on the useage of a STANDARD Deck Height RB26 Engine Block. No Block 'Extensions' etc.
Please feel free to add Info on other RB motors such as Stroke, Piston CH and Rod Length....and I will add them to the above list to be used as a reference.
Cheers,
Allan
The rod/stroke ratio is the ratio of the length of the connecting rod to the length of the piston stroke. A longer rod will reduce the sidewise pressure of the piston on the cylinder wall and stress forces increasing engine life. It also increases cost and engine hight. A "square engine" is an engine with a bore diameter equal to its stroke length. aA engine with a bore diameter that is smaller than its stroke length is known as an undersquare engine. An engine where the bore diameter commonly known as an oversquare engine, conversely, an engine with a bore diameter that is smaller than its stroke length is known as an undersquare engine.
Most engine builders shoot for a ratio between 1.5:1 and 1.8:1, which shows that the RB26DETT designers made this a key consideration during it's design due to the fact that it ends up EXACTLY in the middle with a ratio of 1.65:1 (1.5:1, 1.8:1, +/- 0.15:1 either way) and an odball stroke (73.7mm) as the result.
ROD LENGTH/STROKE = RATIO:1 (Rod Length devided by Stroke equals Ratio, to 1).
-----------------------------------------------------------------
Common Rod/Stroke Ratio Examples.
---------------------------------------
1.49 B20A
1.54 B18B
1.58 GSR
1.74 B16A
1.78 B16B
1.99 VW Air-Cooled Type I
1.90 Chevy 283 CID SB
1.75 Chevy 327 CID SB
1.64 Chevy 350 CID SB
1.53 Chevy 454 CID BB
1.65 RB26DETT (73.7mm Stroke, 121.5mm Rod)
1.54 RB26 Stroker (77.7mm Stroke, 119.5mm Rod)
1.77 RB30DE (86mm Stroke, 152.5mm Rod)
+++++++++++++++++++++++++
+ RB26DETT Variants Explained +
+++++++++++++++++++++++++
** CH/PH = Compression Height/Pin Height.
(Stock Config "Overaquare/Short Stroke" 86mm x 73.7mm & 121.5mm):
OEM RB26DETT Configuration/Stroke.
121.5mm Rod Length & 73.7mm Stroke = 1.65:1 (1.64857530529)
30mm CH/PH Piston Used (Standard).
-----------------------------------------------------------------
(Stroker Short Rod Config "Overaquare/Short Stroke" 86mm x 77.7mm x 119.5mm):
(Nismo GT Spec 1, Tomei, HKS, Generic 'JDM' Stroker) +4mm Stroke Increase.
119.5mm Rod Length & 77.7mm Stroke = 1.54:1 (1.5379665379)
30mm CH/PH Piston Used (Standard).
-----------------------------------------------------------------
(Stroker Long Rod Config "Overaquare/Short Stroke" 86mm x 77.7mm x 121.5mm):
(Nismo GT Spec 2) +4mm Stroke Increase.
121.5mm Rod Length & 77.7mm Stroke = 1.56:1 (1.5637065637)
28mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
(Stroker BRIAN CROWER Config "Overaquare/Short Stroke" 86mm x 79.0mm x 121.5mm):
USDM Product, Longest Off The Shelf RB26 Stroked Crankshaft, + 5.3mm Stroke Increase.
121.5mm Rod Length & 79.0mm Stroke = 1.54:1 (1.5379746835)
27.35mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
(Stroker JUN Config "Overaquare/Short Stroke" 86mm x 75.7mm x 121.5mm):
JDM Product, Shortest Off The Shelf RB26 Stroked Crankshaft, +2mm Stroke Increase.
121.5mm Rod Length & 75.7mm Stroke = 1.61:1 (1.6050198150)
29mm CH/PH Piston Used (Custom).
-----------------------------------------------------------------
The above information is based on the useage of a STANDARD Deck Height RB26 Engine Block. No Block 'Extensions' etc.
Please feel free to add Info on other RB motors such as Stroke, Piston CH and Rod Length....and I will add them to the above list to be used as a reference.
Cheers,
Allan