Overrev Report
10-09-2009, 09:23 PM
#16
Nordschleife Master
Not all spins are the same. In some cases (keeping your foot on the gas), you can light up the rear tires in the fwd direction even with the car pointed backwards relative to the track (especially when in the grass/dirt/gravel/wet).
Other times (foot off the gas and car stays on the dry tarmac), you can have the wheels spinning backwards (and the engine too if you don't press the clutch pedal). Believe me, it has happened many times to many people...
Overrevving in reverse direction is not the fear (that is virtually impossible), it's counter-rotating the motor that is bad (timing chains and other parts don't like that on some models).
Other times (foot off the gas and car stays on the dry tarmac), you can have the wheels spinning backwards (and the engine too if you don't press the clutch pedal). Believe me, it has happened many times to many people...
Overrevving in reverse direction is not the fear (that is virtually impossible), it's counter-rotating the motor that is bad (timing chains and other parts don't like that on some models).
10-11-2009, 01:16 PM
#17
Addict
Rennlist Member
Rennlist Member
In a 911, the motor spins clockwise as viewed from behind the car - it could be made to spin counterclockwise in the scenario I mentioned above.
Yes, this would happen due to the wheels (half-shafts) spinning backwards through tires with lots of grip, causing the motor to reverse directions (if the clutch pedal is not pressed).
When rotating the engine for a valve adjustment (air-cooled 911's), it is said that you can damage the engine even by counter-rotating the engine with your wrench by hand (less than 1 rpm). So, it doesn't take much counter-rotating to screw things up (no need to reverse the engine at high revs to hurt it).
Last edited by GrantG; 10-11-2009 at 03:24 PM.
