Monday, March 25, 2013

EGT and engine load..

We received our Mail Drop today, and in it was an EGT probe for the Kubota!   A little drilling, reaming, and a 1/8" MPT tap was all it took to get the probe installed:

EGT in its place.
(I positioned it about 6" from the exhaust port, and in such
a way that it does not interfere with the exhaust insulation sleeve.)

And the controller board all installed and wired up.
(Less box cover)

Using a watt cap of 1700w, and while turning around 2500rpms (2650 under no load), the EGT stabilized at 890f.  And at this level of work the engine is preforming well, no indication of overload (black exhaust), and the engine responded well to small changes in the governor level position.  Alternator output was for example 133A at 12.9v  (batteries placed under heavy load for the test)

I then made a run with the system configured for 2100w.   This time the alternator produced 155A (at 13.42v) and the EGT raised to 1020f, and there was obvious signs of overloading in the exhaust stream.   And there was no engine response to governor changes.   Plus the RPMs had dropped to 2400 rpms under load.

Clearly 2100w is too much to draw out at 2400 RPMs.  At 2400 RPMs the engine is rated at 5.2hp continuous   (5.4hp for 2500 rpms).  IF we assume 1700w at 2500 is a good max continuous load, then that turns into 42% efficiency (1700/(5.4*746))

A key question for me is:  At what EGT should I run?  It seems 900f is a good target, and clearly 1000+ is too much.  Could it be I have already hit the correct target value, and there is no room to grow (without increasing RPMs)?  What is the chance of that.....

This has also given me an idea for yet another fault check:  The max RPMs demonstrated under no load is measured during the RAMP phase.  If the RPMs fall under a definable % of that max (while in Full Throttle mode), then it would be safe to assume the engine is lugging.  For example, in the 1700w case the engine dropped 175RPMs from no load to full load, while in the overload condition the drop was 240RPMs.  Maybe a trap at 200 RPMs would be appropriate in this case.

And here is a question:  The above leads me to believe that 900f is a rather good target to shoot for on EGT.  But I can find NO basis for these small engines (lots of EGT talk around diesel Pickups..) to confirm that.   Does anyone have any insight into what to expect for EGT on these small Diesels?

1 comment:

  1. Hello.

    This project can be used on any engine type, small diesels, and likely small gas engines. It is not restricted to only 'Kubota' engines, though that is what I have.

    ED NOTE: Original comment has been removed due to embedded SPAM hyperlink, but I thought the question was a good one. Here is the original post w/o the link:

    J. Johnson asked: "Is this equipment works on all types of Kubota engine."