Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Normal
Hi Larry Yes indeed, I believe it could happen (I’m about 85% sure) but the cams would have to be in an exact position and the speed of the car and/or slope would probably have to be radical. There is a cam position where the rear exhaust cam is sprung so that it wants to rotate counterclockwise such that there is some relative slack in the t-belt between the rear exhaust cam pulley and the crankshaft pulley. Next time you’re doing a t-belt, watch the tension in the belt in this position as you rotate the crankshaft and notice the tension variation—it varies quite a bit at this spot. Side: there’s something specially related to that 9th tooth (on the crankshaft pulley) past TDC mark and either max tension or min tension on the belt at the tensioner (see SM pg. 6-22 step 5)—wonder what exactly is happening there? Anyway, the tension varies between the pulleys at different times depending on the direction and orientation of the spring force on all four cam pulleys. From personal experience in trying to remove my crankshaft pulley bolt, there are certain cam positions that will certainly skip a tooth on the crankshaft pulley without too much counterclockwise torque on the wrench (under 200 lb ft, probably less than 100 lb ft), so it shouldn’t take too much force at the wheels to make enough torque at the crank to skip teeth.One question I have: can the engine naturally shut off in such a way that the belt is in this “loose” combination or will it always shut off so that this portion of the belt is tight. If this portion is naturally tight when the engine shuts off then it would probably take a pretty severe act to skip the belt…like trying to stop your car from rolling down the hill backwards at 25mph (when the ignition is off) by putting it in first and popping the clutch. .01DanO
Hi Larry
Yes indeed, I believe it could happen (I’m about 85% sure) but the cams would have to be in an exact position and the speed of the car and/or slope would probably have to be radical. There is a cam position where the rear exhaust cam is sprung so that it wants to rotate counterclockwise such that there is some relative slack in the t-belt between the rear exhaust cam pulley and the crankshaft pulley. Next time you’re doing a t-belt, watch the tension in the belt in this position as you rotate the crankshaft and notice the tension variation—it varies quite a bit at this spot. Side: there’s something specially related to that 9th tooth (on the crankshaft pulley) past TDC mark and either max tension or min tension on the belt at the tensioner (see SM pg. 6-22 step 5)—wonder what exactly is happening there? Anyway, the tension varies between the pulleys at different times depending on the direction and orientation of the spring force on all four cam pulleys.
From personal experience in trying to remove my crankshaft pulley bolt, there are certain cam positions that will certainly skip a tooth on the crankshaft pulley without too much counterclockwise torque on the wrench (under 200 lb ft, probably less than 100 lb ft), so it shouldn’t take too much force at the wheels to make enough torque at the crank to skip teeth.
One question I have: can the engine naturally shut off in such a way that the belt is in this “loose” combination or will it always shut off so that this portion of the belt is tight. If this portion is naturally tight when the engine shuts off then it would probably take a pretty severe act to skip the belt…like trying to stop your car from rolling down the hill backwards at 25mph (when the ignition is off) by putting it in first and popping the clutch.
.01
DanO
