dren wrote: ↑28 Mar 2017, 15:11
Tommy Cookers wrote: ↑28 Mar 2017, 11:45
but any element of repetition in surge around this frequency can be even worse than the 'worst-case' - by what we might call resonant amplification
this could occur by any imperfection in co-ordination of a whole lot of actions that need perfect co-ordination (for shifting)
The shifting happens so quick that wouldn't any amplification of the surge you talk about be marginal?
As for the cylinder cut out, Honda's J-series has a noticeable vibration when it changes. The motor mounts are designed to absorb running on fewer cylinders and I think there's noise cancellation to go with the change in vibrations. They'll shift from 6 to 4 to 3 cylinder operation.
The J35 from the Accord 2008-2012 had a notorious oil burning problem because of their cylinder cutting, I've made a lot of money replacing piston rings on these engines. The cylinder cutting would cause the lower oil control ring to sludge up, and somehow force the upper control ring gap to line up with the bottom one, once that happens the engine would start burning massive quantities of oil. That and the factory torque spec for the spark plugs was too low, even the updated 18ft lbs was too low for new plugs with a fresh crush washer. The plug would start backing out and take out the cylinder(probably from cylinder cutting vibrations).
Since then all plugs on Hondas get torqued to 24ft lbs, I know that value is safe because on a spare head I've tested how much the threads will take before they break. 74ft lbs, and it's not the head that gets damaged but the spark plug.