#2 Rod bearing failure....why?
03-12-2013, 09:53 PM
#18
1st Gear
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Porsche 944 myths and facts
The information I provide is based on facts. We run 20-25 944's racing and in our driving school. Our average 944 logs in over 100 hours between rod bearing replacement with some cars running over 140 hours.
In December we ran a 1986 Spec 944 in the 25 hours of Thunderhill, finishing after 25 hours of racing and 7 hours of practice with a total of 32 hours on the engine and drive train. We encountered 0 engine or drivetrain problems. Team Raptor. We will be returning this December with a 944 and 924S taking advantage of the NASA rules with more HP and much lighter cars.
The reason #2 rod bearing is the first bearing starved for oil is due to the oil supply to both balance shafts is supplied where #2 rod bearing is supplied oil from the pump.
The causes of the starvation are due from the following:
#1 Driver error, over-revving the engine on up shifting and worse using the engine as a brake downshifting, over-revving the engine. This translates to the transaxle, driveshaft, axles, etc.
#2 Driver error, driving the engine too hard when the oil and water are not up to operating temp. Usually a slow and destructive method damaging rod bearings.
#3 Driver error, failure to properly maintain. Change oil, radiator, water pump, engine overheats.
#4 Distributor rotor failure, usually arching across the top burning out the end of the rotor. The end result is misfiring hammering the pistons, rods and rod bearings.
#5 Oil pump does not properly pump oil due to wear, expansion and contraction of the steel gears and cover to the aluminum housing. This is easily seen when starting a cold engine and the oil takes time to gain pressure or will not gain pressure when cranked unless started. This condition is not catastrophic, it can contribute to bearing failure.
#6 High bank left hand or even right hand corners at high RPM's, the oil pressure gauge will move up and down or lower for a few seconds.
#7 Oil pick up tube cracked and or rubber seal hard and not properly sealing causing air to be sucked into the system under a load.
#8 Main bearings worn out starving the rod bearings.
Street or race the damage can be avoided. All of our cars have hour meters installed and rev limiters, both factory and MSD.
The majority of 944 owners are second, third, fourth, etc. owners. We have no idea how the car was maintained or driven.
All of our 944's have the rod bearings replaced, oil pick up tubes inspected and the 0 ring replaced. All heads are removed, cylinder walls inspected, a rebuilt head and all new gaskets installed. Radiators and hoses are tested and replaced as necessary.
We have installed several sets of coated rod bearings and found little or no wear after as much as 140 plus hours in a race 944. #2 rod bearing showed the coating worn off. To reduce #2 wear we eliminate the balance shaft belts, pulleys and gears. To eliminate the excessive wear on #2, removal and sealing off the balance shaft oil holes is required. This is a process we perform when using a dry sump system allowing a max RPM in the 8-8500 range.
There are hundreds of items we have discovered needing repair, replacement, updating, back dating and at a minimum inspection for possible damage in the 14 years we have been building and racing 944's and 924S's. Every year the 944 was produced there were changes made.
In December we ran a 1986 Spec 944 in the 25 hours of Thunderhill, finishing after 25 hours of racing and 7 hours of practice with a total of 32 hours on the engine and drive train. We encountered 0 engine or drivetrain problems. Team Raptor. We will be returning this December with a 944 and 924S taking advantage of the NASA rules with more HP and much lighter cars.
The reason #2 rod bearing is the first bearing starved for oil is due to the oil supply to both balance shafts is supplied where #2 rod bearing is supplied oil from the pump.
The causes of the starvation are due from the following:
#1 Driver error, over-revving the engine on up shifting and worse using the engine as a brake downshifting, over-revving the engine. This translates to the transaxle, driveshaft, axles, etc.
#2 Driver error, driving the engine too hard when the oil and water are not up to operating temp. Usually a slow and destructive method damaging rod bearings.
#3 Driver error, failure to properly maintain. Change oil, radiator, water pump, engine overheats.
#4 Distributor rotor failure, usually arching across the top burning out the end of the rotor. The end result is misfiring hammering the pistons, rods and rod bearings.
#5 Oil pump does not properly pump oil due to wear, expansion and contraction of the steel gears and cover to the aluminum housing. This is easily seen when starting a cold engine and the oil takes time to gain pressure or will not gain pressure when cranked unless started. This condition is not catastrophic, it can contribute to bearing failure.
#6 High bank left hand or even right hand corners at high RPM's, the oil pressure gauge will move up and down or lower for a few seconds.
#7 Oil pick up tube cracked and or rubber seal hard and not properly sealing causing air to be sucked into the system under a load.
#8 Main bearings worn out starving the rod bearings.
Street or race the damage can be avoided. All of our cars have hour meters installed and rev limiters, both factory and MSD.
The majority of 944 owners are second, third, fourth, etc. owners. We have no idea how the car was maintained or driven.
All of our 944's have the rod bearings replaced, oil pick up tubes inspected and the 0 ring replaced. All heads are removed, cylinder walls inspected, a rebuilt head and all new gaskets installed. Radiators and hoses are tested and replaced as necessary.
We have installed several sets of coated rod bearings and found little or no wear after as much as 140 plus hours in a race 944. #2 rod bearing showed the coating worn off. To reduce #2 wear we eliminate the balance shaft belts, pulleys and gears. To eliminate the excessive wear on #2, removal and sealing off the balance shaft oil holes is required. This is a process we perform when using a dry sump system allowing a max RPM in the 8-8500 range.
There are hundreds of items we have discovered needing repair, replacement, updating, back dating and at a minimum inspection for possible damage in the 14 years we have been building and racing 944's and 924S's. Every year the 944 was produced there were changes made.
03-13-2013, 08:49 AM
#19
Rennlist Member
#2 Bearing
There's a pretty good thread over on the 944 Turbo forum. I think it is worth checking out. Entitled "Elephant in the Room" Currently about 2/3's way down on the 1st page.
After reading all the thread, I would say the single most cost effective thing that all can do for a track day is change out the oil with a foaming resistant racing oil of the proper, higher viscosity (20W-50). Then change it back to your "regular" oil if you are going to use the car as a daily driver. (Racing oil is not meant to be used long term).
I also am dubious that overfilling is a good idea. Higher oil level than Porsche designed for just gets it closer to the crank, which whips more air into the oil.
BTW, someone please educate me on how to copy/paste a link to another forum thread. The URL in my browser bar just says "forums.rennlist.com" which is not a good link to copy. How does one do this?
After reading all the thread, I would say the single most cost effective thing that all can do for a track day is change out the oil with a foaming resistant racing oil of the proper, higher viscosity (20W-50). Then change it back to your "regular" oil if you are going to use the car as a daily driver. (Racing oil is not meant to be used long term).
I also am dubious that overfilling is a good idea. Higher oil level than Porsche designed for just gets it closer to the crank, which whips more air into the oil.
BTW, someone please educate me on how to copy/paste a link to another forum thread. The URL in my browser bar just says "forums.rennlist.com" which is not a good link to copy. How does one do this?
03-13-2013, 09:07 AM
#20
Rennlist Member
BTW, not trying to start an oil thread but I have found that most of the discount autoparts stores in my area carry the Valvoline Racing oil in both dino and full synthetic. As per my post on the Turbo forum, I have been using it and haven't had any bearing failures but this is really a hard case to make as there are so many variables. But being able to buy the Valvoline readily vs ordering something more exotic like Brad Penn or Joe Gibbs can make the difference to doing it vs putting it off. The counter guy at O'Reillys says that he sees the Valvoline go on sale about every 3 months so I plan to watch for that and stock up.
03-13-2013, 05:39 PM
#21
Rennlist Member
Please explain this line. It doesn't make sense the way it is written.
Later on you seem to imply that the balance shafts are robbing oil from #2.
Later on you seem to imply that the balance shafts are robbing oil from #2.
03-13-2013, 06:42 PM
#22
