3.0l 16v turbo carnage
01-29-2009, 06:44 PM
#91
Race Car
Yup..., production date 1991 on the engine, came from a '92 model with 6 speed.
Found crack just starting in the pickup tube, thus my quest to delete it.
I have two compete 968 engines (damaged) less 1 head and a nice '89 2.7 liter block to make 1 last 3.0 NA out of....then I'm all out of 3.0 parts...
Both of the cranks have damage, one in perfect shape except for some blemishes on the #2 journal. I'm debating whether to have it weld repaired and turned back to factory spec or have all the rod journals machined to use the .25mm oversized bearings.
They list for $47 each per half shell so....8 required....
This is just a sideline project that we'll run in a local series class that limits displacement to 3.0 liter, turbos excluded with 1.5 multiple.
The car already competes with a stock 2.5 in PCA and the same local series as an Sp2 and red bracket car respectively.
Chris W. - I sent you an email via the RL member contact page regarding some Wossner pistons....did you get it...?
T
Found crack just starting in the pickup tube, thus my quest to delete it.
I have two compete 968 engines (damaged) less 1 head and a nice '89 2.7 liter block to make 1 last 3.0 NA out of....then I'm all out of 3.0 parts...
Both of the cranks have damage, one in perfect shape except for some blemishes on the #2 journal. I'm debating whether to have it weld repaired and turned back to factory spec or have all the rod journals machined to use the .25mm oversized bearings.
They list for $47 each per half shell so....8 required....
This is just a sideline project that we'll run in a local series class that limits displacement to 3.0 liter, turbos excluded with 1.5 multiple.
The car already competes with a stock
2.5 in PCA and the same local series as an Sp2 and red bracket car respectively.Chris W. - I sent you an email via the RL member contact page regarding some Wossner pistons....did you get it...?
T
01-29-2009, 07:01 PM
#92
Nordschleife Master
Thread Starter
Actually the weight reduction of the aftermarket rods is a big reduction in stress.
Earlier in this thread a very important point was made – the peak stress on a connecting rod has nothing to do with power output, it has to do with engine speed. In fact the more power that you make the less tensile forces your rod will see on the compressive stroke. The combustion forces are actually reducing the peak loading on the rod. On the exhaust stroke there is no combustion force to help counteract the peak forces at TDC. So that is the peak force as seen by the connecting rod regardless of power output. Making the rod (and piston) lighter is a real plus when it comes to lessening those forces.
So, even if the strength of the stock rod and the aftermarket rod are the same the lighter aftermarket rod will be ‘less stressed’ in the same installation (by virtue of reduce loading due to lighter weight).
Ain’t physics dandy?
Earlier in this thread a very important point was made – the peak stress on a connecting rod has nothing to do with power output, it has to do with engine speed. In fact the more power that you make the less tensile forces your rod will see on the compressive stroke. The combustion forces are actually reducing the peak loading on the rod. On the exhaust stroke there is no combustion force to help counteract the peak forces at TDC. So that is the peak force as seen by the connecting rod regardless of power output. Making the rod (and piston) lighter is a real plus when it comes to lessening those forces.
So, even if the strength of the stock rod and the aftermarket rod are the same the lighter aftermarket rod will be ‘less stressed’ in the same installation (by virtue of reduce loading due to lighter weight).
Ain’t physics dandy?
Here's a comparison regarding piston speed:
944 2.5l (78.9 mm stroke) at stock rpm limit (6500 rpm):
3356 fpm (feet per minute)
944/968 3.0l (88 mm stroke) at 7000 rpm:
4042 fpm
Porsche Carrera GT
4186 fpm
CGT is number 22 on the list of production engines with highest piston speed:
http://hondaswap.com/members-lounge/...-speeds-72614/
01-29-2009, 08:46 PM
#93
Three Wheelin'
Join Date: Jul 2008
Location: Dallas / Chicago
Posts: 1,537
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Actually the weight reduction of the aftermarket rods is a big reduction in stress.
Earlier in this thread a very important point was made – the peak stress on a connecting rod has nothing to do with power output, it has to do with engine speed. In fact the more power that you make the less tensile forces your rod will see on the compressive stroke. The combustion forces are actually reducing the peak loading on the rod. On the exhaust stroke there is no combustion force to help counteract the peak forces at TDC. So that is the peak force as seen by the connecting rod regardless of power output. Making the rod (and piston) lighter is a real plus when it comes to lessening those forces.
So, even if the strength of the stock rod and the aftermarket rod are the same the lighter aftermarket rod will be ‘less stressed’ in the same installation (by virtue of reduce loading due to lighter weight).
Ain’t physics dandy?
Earlier in this thread a very important point was made – the peak stress on a connecting rod has nothing to do with power output, it has to do with engine speed. In fact the more power that you make the less tensile forces your rod will see on the compressive stroke. The combustion forces are actually reducing the peak loading on the rod. On the exhaust stroke there is no combustion force to help counteract the peak forces at TDC. So that is the peak force as seen by the connecting rod regardless of power output. Making the rod (and piston) lighter is a real plus when it comes to lessening those forces.
So, even if the strength of the stock rod and the aftermarket rod are the same the lighter aftermarket rod will be ‘less stressed’ in the same installation (by virtue of reduce loading due to lighter weight).
Ain’t physics dandy?
