986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Over-revving: Interesting info

Adam · 05-28-2008, 11:35 AM

I was lurking on the PCA tech site and I learned that not only does the computer log any time an over-rev occurs, it also has different levels depending on how high the revs are. Here is the Q&A.

Question
oil pump shafted breakage/ motor over rev
This occured- accelerated from a traffic light in 1st gear to 4000 rpm, shifted into 2nd gear to 6700rpm then shifted to 3rd gear at 3200 rpm. Noticed a slight shudder in the motor, 5 seconds later display message said take car for service. No red light display. Delivered car to Porsche dealer. Was informed that car had overeved to 9500 rpm, one valve struck one piston head. Motor taken apart, oil pump shaft had sheared off from oil pump gear drive. Parts all over interior of motor.
Trying to tie all these events together. Car was not accidently downshifted at any time at high rpm. I am in agreement that motor overeved (computor log) but am looking for the reason why. Any information assistance would be appreciated. Thanks

Answer
Your description does not indicate a 9500rpm over rev. All 987 and 997 cars utilize a scale for these over revs and a 9500 is a 5 or 6. The over revs are also time stamped by engine hours. The chart below has the different ranges for over revs. There is also a special one called a 10200 that is not shown yet has its own special flag in the VAL or Vehicle Analysis Report that Porsche will run. This is considered by Porsche to be the RPM in which any of their stock engines would be catastrophically damaged.

Range 1: 7300-7500 RPM
Range 2: 7500-7700 RPM
Range 3: 7700-7900 RPM
Range 4: 7900-8400 RPM
Range 5: 8400-9500 RPM
Range 6: 9500-11000 RPM

What you should check is when this category 5 or 6 occurred. It may have been long before this and not had any direct impact on this failure. The pistons have been having issues with breakage and could cause the exact damage that you described even without any over revs.

This type of failure was also common in the older 911 SC pistons in which were cast and not forged.

Scott Slauson - PCA WebSite - 5/20/2008

05-28-2008, 11:35 AM	#1
Adam Registered User Join Date: Nov 2003 Location: Illinois Posts: 3,033	Over-revving: Interesting info I was lurking on the PCA tech site and I learned that not only does the computer log any time an over-rev occurs, it also has different levels depending on how high the revs are. Here is the Q&A. Question oil pump shafted breakage/ motor over rev This occured- accelerated from a traffic light in 1st gear to 4000 rpm, shifted into 2nd gear to 6700rpm then shifted to 3rd gear at 3200 rpm. Noticed a slight shudder in the motor, 5 seconds later display message said take car for service. No red light display. Delivered car to Porsche dealer. Was informed that car had overeved to 9500 rpm, one valve struck one piston head. Motor taken apart, oil pump shaft had sheared off from oil pump gear drive. Parts all over interior of motor. Trying to tie all these events together. Car was not accidently downshifted at any time at high rpm. I am in agreement that motor overeved (computor log) but am looking for the reason why. Any information assistance would be appreciated. Thanks Answer Your description does not indicate a 9500rpm over rev. All 987 and 997 cars utilize a scale for these over revs and a 9500 is a 5 or 6. The over revs are also time stamped by engine hours. The chart below has the different ranges for over revs. There is also a special one called a 10200 that is not shown yet has its own special flag in the VAL or Vehicle Analysis Report that Porsche will run. This is considered by Porsche to be the RPM in which any of their stock engines would be catastrophically damaged. Range 1: 7300-7500 RPM Range 2: 7500-7700 RPM Range 3: 7700-7900 RPM Range 4: 7900-8400 RPM Range 5: 8400-9500 RPM Range 6: 9500-11000 RPM What you should check is when this category 5 or 6 occurred. It may have been long before this and not had any direct impact on this failure. The pistons have been having issues with breakage and could cause the exact damage that you described even without any over revs. This type of failure was also common in the older 911 SC pistons in which were cast and not forged. Scott Slauson - PCA WebSite - 5/20/2008 __________________ '03 3.2L GuardsRed/Blk/Blk---6Spd Options: Litronics, 18" Carrera lights, Bose sound, Painted to match roll bars. http://i100.photobucket.com/albums/m...Mautocross.jpg