Timing Belt Tension Data

The disparity of the runs off of the tensioner pullies to the crank cog (?) are amazing ............. AND SCARY !!!!

WoW !!!!!

 

Your data only has meaning if you also give the positions of the cams -- i.e., at any particular static position, the valve spring actions put a different net moment on each cam, which puts additional forces, acting in potentially different directions, into the belts, so the tension in seemingly identical runs of the two belts can actually be different at a particular position. Note that on the 1-4 bank, the tension in the "long" run from the drive sprocket to the exhaust cam is lower than in the run from the tensioner pulley to the drive sprocket, yet, on the 5-8 bank, the tension in the "long" run from the drive sprocket to the intake cam is higher than in the run from the tensioner pulley to the drive sprocket. At some other engine position, both those conditions will be reversed.

Also, I'd add that that equation assumes: 1) perfectly rigid and precisely located end terminations for the span, and 2) a string having mass, but no bending stiffness -- both of those assumptions aren't quite true so the measurements in the longer belt runs will be more accurate than in the shortest run between the two cams (i.e., the longer the span, the less error introduced from not having the "perfect" conditons assumed in the derivation of the equation).

So give the corresponding "postion" of the cams (e.g., crankshaft at PM1-4 and cyl #1 at end of compression stroke ready to fire, or whatever it is) and also the condition of the belts (e.g., new, just installed, or whatever it is). Although they do everything possible to prevent the belts from stretching, it would be interesting to see your data when new (in a certain position) and then after some use (in that same position) to see how much it's changed.