986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post

mjw930 · 09-17-2005, 02:33 PM

Brucelee,

I'm not blind to them either

I love Porsche cars, I bought my first one in 1977. I also know that they aren't perfect BUT, nothing else out there is either.

Oil issues on the car and motorcycle boards are almost like talking about religion, always heated and always many different opinions. No one wins in these discussions, trust me.

As for the computerized dyno break in, I'm referring to a computer controlled dyno. The Porsche engine dynos have some of the most rigorous and torturous models on the planet. They can do things to motors that we would never think of in the real world. They aren't the only manufacturer to have this level of sophistication but theye are the only one I have some first hand knowledge about. They have one model called the Stuttgart to Dusseldorf ( I think ) run. It's been known to break motors in less than 10 hours. For a motor's design to pass muster it must be able to be run in that simulation for over 500 hours none stop without failure.

Anyway, back to how you can break a motor in in 5 minutes. With modern metalurgy the only thing that really has to seat are the rings. There's no "wearing" of parts to match each other any more. Rings don't wear to the cyclinder walls, rod and crank journals don't wear the bearing surfaces and valves don't wear their seats as part of the break in (of course those parts wear but not as a function of break in). All that really occurs is the rings wear to match the ring lands in the pistons (i.e. seating the rings). This is required so they don't bind but still seal properly (hot exhaust gasses actually must pass over the top of the ring and into the land to push the ring tight up against the cylinder). If the ring is not properly seated in the land that process can't occur and you end up with all kinds of problems, the most notable ones being blow by and oil consumption. The single biggest thing that does damage during an engine's break in is heat. The maximum heat, heat cycles and average heat must be maintained within a certain range to prevent damage and allow the rings to seat properly. In addition, the force applied to the rings must be a combination of accleration (high top side pressure) and deceleration (high bottom side pressure) for them to work their way around in the land and seat properly. The break in and testing models that Porsche (and many other professional engine builders) use takes all of that into account. The first 5 minutes will make or break a motor, after that most of the dyno time is spent dialing in the fuel injection or carburation.

Don't trust me, go find a world class engine builder (not someone who rebuilds motors in the back of their shop, someone who builds competition motors in the top tier of their sport) and ask them if I'm right or wrong.

Now, when do I change my oil...... Since my P-Cars aren't typically daily drivers (anymore) and when they do get out they are driven fairly hard I follow a 5000 mile or 6 month interval schedule. The initial change is done at 5000 or 6 months also. If they were daily drivers I would still follow the 6 month rule but up the mileage to 7500. (so much for me following what Porsche says

)

09-17-2005, 02:33 PM	#6
mjw930 Registered User Join Date: Aug 2005 Location: Central Florida Posts: 182	Brucelee, I'm not blind to them either I love Porsche cars, I bought my first one in 1977. I also know that they aren't perfect BUT, nothing else out there is either. Oil issues on the car and motorcycle boards are almost like talking about religion, always heated and always many different opinions. No one wins in these discussions, trust me. As for the computerized dyno break in, I'm referring to a computer controlled dyno. The Porsche engine dynos have some of the most rigorous and torturous models on the planet. They can do things to motors that we would never think of in the real world. They aren't the only manufacturer to have this level of sophistication but theye are the only one I have some first hand knowledge about. They have one model called the Stuttgart to Dusseldorf ( I think ) run. It's been known to break motors in less than 10 hours. For a motor's design to pass muster it must be able to be run in that simulation for over 500 hours none stop without failure. Anyway, back to how you can break a motor in in 5 minutes. With modern metalurgy the only thing that really has to seat are the rings. There's no "wearing" of parts to match each other any more. Rings don't wear to the cyclinder walls, rod and crank journals don't wear the bearing surfaces and valves don't wear their seats as part of the break in (of course those parts wear but not as a function of break in). All that really occurs is the rings wear to match the ring lands in the pistons (i.e. seating the rings). This is required so they don't bind but still seal properly (hot exhaust gasses actually must pass over the top of the ring and into the land to push the ring tight up against the cylinder). If the ring is not properly seated in the land that process can't occur and you end up with all kinds of problems, the most notable ones being blow by and oil consumption. The single biggest thing that does damage during an engine's break in is heat. The maximum heat, heat cycles and average heat must be maintained within a certain range to prevent damage and allow the rings to seat properly. In addition, the force applied to the rings must be a combination of accleration (high top side pressure) and deceleration (high bottom side pressure) for them to work their way around in the land and seat properly. The break in and testing models that Porsche (and many other professional engine builders) use takes all of that into account. The first 5 minutes will make or break a motor, after that most of the dyno time is spent dialing in the fuel injection or carburation. Don't trust me, go find a world class engine builder (not someone who rebuilds motors in the back of their shop, someone who builds competition motors in the top tier of their sport) and ask them if I'm right or wrong. Now, when do I change my oil...... Since my P-Cars aren't typically daily drivers (anymore) and when they do get out they are driven fairly hard I follow a 5000 mile or 6 month interval schedule. The initial change is done at 5000 or 6 months also. If they were daily drivers I would still follow the 6 month rule but up the mileage to 7500. (so much for me following what Porsche says )