Irritable Throttle Syndrome

[mad1150]

They are in sync but here's what they are doing at idle:

On Rob's manometer - It cycles between an equal but more movement of water to an equal but less movement of water.

...or on a TwinMax - It cycles between wider needle movements to narrower needle movements.


It does it about every 8-10 seconds and repeats, it does seem very smooth at operating speeds.


Is this a "they all do that" or is another adjustment needed?

[boxermania]

mad1150

Your observation is very keen and you are witnessing when the accuracy of the measuring instrument is approaching the repeatability of events taking place inside an internal combustion engine. Mechanical components need clearances/lubrication to operate and electrical components are designed with a level of accuracy and repeatability sufficient to meet the intended purpose.

What I'm trying to say is that the movement of the columns of water or the Delta in the TwinMax depend on many events; opening/closing of the valves, the slack on the timing chain, the position of the piston in the cylinder, the amount of fuel dispensed by the injector, the timing of the injection along with the nuances of the measurement devices as an example. These events are not repeatable themselves to the nth degree, hence your observation.

To me, because the engine is an opposed design with fairly large pistons (rotational mass) the best gains to be made, everything else being equal is the Sync of the TB's as it insures the equal contribution of the cylinders to the power stroke.