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RPM

Old 08-28-2007, 04:06 AM
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Default RPM

I have a J600 which was converted up to J600R at its last service. Is the max rpm 160k or 163k? I have a vague memory of seeing the figure of 163k somewhere.

Why doesn’t the TEMS manage the rpm? My model was way down on thrust this weekend, I found the engine was peaking at about 148k rpm. The max rpm is set to 160k. What’s the point of having a TEMS if it can’t think for itself to alter the pump power to whatever is required to reach 160k rpm? Does it simply work on running the pump at a fixed power level and not actively manage the pump power to achieve a particular rpm?

I ran the autocalibrate function which mostly sorted the problem. I say mostly because the engine now peaks at a steady 159k though 160k is what the max rpm is set to. Why doesn’t it actually achieve the 160k that is in the settings? Am I supposed to increase the setting say to 161k or whatever is required in the settings until the engine actually achieves 160k (or 163k?)? The engine runs fine and is perfectly smooth at 159k so there is nothing fundamentally wrong in the engine itself, any changes that caused the drop in rpm must have been in the pump.

I had to fit a new pump a few months ago and ran the autocalibrate function then. Presumably the pump has run in now hence the change in the power values it requires, but why can’t the TEMS simply alter the power in order to manage the rpm, rather than require autocalibrate to be run again? How often should autocalibrate be run? Is the fact that rpm had fallen so much over the last few months an indication that there is a problem somewhere e.g the pump becoming sticky.

TIA for any advice,

Harry
Old 08-29-2007, 11:26 PM
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Default RE: RPM

Hi Harry,

The TEMS is designed to control a commanded rpm. One factor contributing to lower rpm reading is the sampling rates within the GDT. This means that the turbine is actually spinning at 160K but the GDT may read 159K or lower. The rpm, however, can be adjusted to read the max rpm while the engine is running. Your GDT probably have the V2.24 or older software. GDT with new V2.26 software has improved rpm sampling rates and the reading is more accurate. The J600R is safe to operate upto 163K so raising the max rpm to 161K will not be a problem.

I agree that the TEMS should control the rpm and command the fuel pump to do just that. However, if we look from safety perspectives, the current design has an important point. If there are malfunctions or changes in the system setting/installation since last calibration that require significant different pump voltages, the TEMS will not allow the variant to be so large. This is when you will notice abnormality in the rpm output and you should check the system and recalibrate. Recalibration doesn't hurt the system and takes only a few seconds. Calibration is also suggested after long storage or when you have changes in your fuel plumbing.

If you have further suggestions or questions, please feel free to contact us direct at [email protected]

Regards,
Kraivuth S.
PST Jets
Old 08-30-2007, 03:06 AM
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Default RE: RPM

Thanks Kraivuth.

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