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S-Series Combine with the Isochronous Governor

Cross Implement Inc

An important new feature on the S-Series Combines, called isochronous governor allows cleaning shoe drives to operate at a constant speed, enhancing the system’s overall capacity and efficiency. Isochronous governor electronically controls the drive speeds via the engine control unit (ECU) as opposed to a mechanical governor.

Although most customers are familiar with isochronous governor technology (such as FieldCruise™ in John Deere row-crop tractor applications), it is a new concept to combines, and this feature will change how a customer will monitor S-Series Combine performance.
This bulletin is intended to provide additional information on how the isochronous governor plays into the overall operation of S-Series Combines.
Regardless of the engine emission compliance (tier) level, the isochronous governor works as follows:
  • When the separator or unloading auger is NOT engaged and the engine is running at high idle, the engine will run on a typical engine speed droop curve, which is similar to a mechanical governor
    • The S550 high engine idle, no load speed will be approximately 2550 rpm
    • The S660/S670 high engine idle, no load speed will be approximately 2340 rpm
    • The S680/S690 high engine idle, no load speed will be approximately 2240 rpm
    • As engine load increases, engine speed will slow down and power will rise to the point of peak power
  • When the separator or unloading auger is engaged, the engine will follow an isochronous or constant engine speed curve
    • The S550 engine speed will drop to a unique isochronous speed of 2400 rpm
    • The S660/S670 engine speed will drop to a unique isochronous speed of 2200 rpm
    • The S680/S690 engine speed will drop to a unique isochronous speed 2100 rpm
    • As engine load increases, the engine speed will remain constant until rated or 100 percent engine load is achieved. 
Varying engine loads will only change the engine speed within a range of  +/- 20 to 30 rpm. This small range of engine rpm fluctuation results in constant drive speeds for enhanced performance. If the engine load continues to increase beyond rated or 100 percent power, the engine will fall off the isochronous or constant speed curve and the engine speed will decrease resulting in reduced cleaning system performance.
In the past, combine operators utilized the following parameters (among others) to run combines during harvest:
  • Monitored the calibrated loss monitor
  • Monitored tailings monitor
  • Monitored engine rpm on the corner post.
  • Monitored engine rpm by listening to the engine sound fluctuations from yield changes and/or slug feeding
S-Series Combine operators will no longer be able to view or hear engine rpm fluctuate while harvesting due to:
  • S-Series cab being much quieter than the 70 Series STS™ cab
  • Engine exhaust exits the rear of the combine
  • When engine is at high idle, the engine rpm will be at an isochronous or constant speed when the separator or unloading auger is engaged
  • Slug feeding reduced due to uniform feeding in soybeans and small grains with the 600FD HydraFlex™ Draper Platforms
Depending on crop conditions, the capacity of the S-Series Combine may be limited in one or more areas. The combine operator will need to utilize the following monitors (among other parameters) to determine the limiting factor and operate the combine at maximum capacity.
  • Monitor the calibrated loss monitor
  • Monitor the tailings monitor
  • Monitor the engine power meter
  • The display bars in the green indicate the current engine power up to rated or 100 percent power. Bars displayed in this region also represent the power when the engine is running at isochronous engine speed for peak cleaning system performance
  • The display bars in the yellow represent the engine bulge power or power beyond rated.  Bulge power is available to power through tough conditions and slugs. Engine speed will decrease as the load increases when operating in this region
  • The display bars in red indicate peak power. There is no reserve power at this point to power through tough conditions and slugs, and engine speed will continue to decrease
  • To maximize machine performance and engine economy, operate the combine at the top of the green power-meter display bars
  • For example, if operators choose to run at 50 percent, 60 percent, and/or 70 percent of the green power-meter display bars, the combine is not running at capacity and their cost per bushel can increase
  • Operating the machine with the power meter in the yellow or red region will result in reduced engine and cleaning system speed and reduced performance. Additionally, operating the combine with the power meter in the yellow will reduce the bulge power available for tough conditions or slugs. When the combine is operated with the power meter in the red, there will be no bulge power left for tough slugs and the low-speed alarm will activate
Reference feature story Isochronous engine governor enhances overall capacity and efficiency for additional information.
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