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Information on the lower rpm operating range for inverter generators is difficult to find. 

I've done a fair amount of searching and found a forum that had some good info on inverter generators.   I learned that inverter generators run at two speeds only "Eco" mode (low speed) and full load speed.   I was under the impression that inverter generators could regulate engine speed to suit load requirements.  That assumption was wrong.  When the demand on the generator exeeds the power being delivered in Eco mode, the generator opens to max throttle to meet the additional demand.  It was suggested that the lower rpm range is usually half of full load operating rpm.  If that's the case,  the Hyundai continous max. load rpm is 5000 rpm, accordingly lower rpm speed should be 2500 rpm.   I cannot confirm nor dispute this info. however, my rpm measurements tell me otherwise with the Hyundai being either 1700 rpm or 3400 rpm.    

Considering the prominence of electronic fuel injection in many small engines such as those found on late model ATVs, motorcycles etc. one has to question why this technology has not been integrated with inverter generators?  It would simple enough to "map" a sliding scale on the EFI to match engine rpms to generator demand.  Seems like a no-brainer to me.  The efficiency gains would be substantial.      

Would anyone know approximately what the engine rpm operating range would be for an inverter generator?   I know the Hyundai's uppper engine rpm is 5500 at full load.  However, I'm a bit confused with the lower engine no load speed despite measuring it with the Sirometer.   I get strong readings at 1700 and 3400 rpm at no load.   My ears tell me that it's running pretty slow and I'm thinking 1700 rpm.   Would anyone know for sure what the lower no load rpm range is on inverter generators?

I'm back in town now and don't have the figures with me.  If I recall correctly, I measured 8.7 hours run time on close to 4 liters of fuel.  That works out to 2.175 hours per litre wich I rounded off to 2.2 hrs/liter.  Which is approx. 2 hrs. 12 minutes.  

I know I'm pretty much splitting hairs now but I suspect that my measurements are a bit conservative.  During the 8.7 hours, some of it was under 1000 to 1500 watts of load.  Maybe a total of ten minutes or so.  In addition to that, when I refueled I probably squeezed in a few more oz. than normal, which would skew measurements a bit.   I plan to try to be as consistently exact as possible when refueling to get an accurate base line.  However, I'm confident that under my normal light load of 500 watts or less, I should see 2.5 hours per  litre.   Which is considerably better than the 1 litre of diesel fuel per hour  I was burning to run the Kubota powered 6K watt  generator.  

If the Hyundai holds up for five years or more, it will easily pay for itself in fuel savings as well as reducing oil change costs.   I go from using 4.6 litres of oil for the diesel to less than half a litre for the Hyundai and the recommended hourly duration for the Hyundai is the same as the 100 hrs. I was changing the diesel at.  That equates to almost ten oil changes for the Hyundai for each Kubota oil change.   At approx. $30.00 for oil and filter for the diesel oil change, it doesn't take too long for the Hyundai to pay for itself providing it lasts.   Considering that most of it's life will be spent  loafing along at approx 2000 rpm, in a clean environment, I suspect that it should hold up reasonably well with proper maintenance.  

Reducing fuel and oil consumption is also ecologically much more friendly.  I like that.

Overall I'm pretty happy with this little generator.   When we have it running  up at the garage location, it's so quiet that we forget that we've got a generator running.  Very pleasant indeed.  

I did a couple experiments with the Hyundai generator.  Took rpm readings from the plug in location at the garage and hauled it down down for readings at the camp.  No difference in rpm under the same load conditons.  So,  I thought that maybe the six foot exhaust extension I put on it while at the garage location might have compromised engine efficiency by possibly increasing back pressure.  Did tests with and without the extension.  No difference. 

With those possibilities ruled out, I focused on the fuel measurement accuracy.  In the past, I'd fill a  one litre oil bottle to what I thought would be a litre of fuel.  This isn't the best method for real fuel measurement so I bought a one litre funnel calibrated in both metric and imperial measurements.   It's a very functional device with a handle on the side and a valve on the bottom of the funnel to hold the contents until it's time to empty it.  I just clamp the handle in a vice, put a one litre bottle under it and fill it often enough to fill the generator.  Anything left over is re-measured in the funnel. 

Bottom line is that my measurements were off.   Prior to getting the measuring funnel, I was over-filling the litre bottle.  Now with more accurate measuring I can say that I'm getting 2.20 hours to a litre of fuel under light load (500 watts or less). 

Another issue I was having with this generator was oil accumulating at the base.  I opened up the shell looking for an engine leak (i.e. valve cover)  and found everything nice and dry.   I then followed the crank case ventilation tube to the air intake housing for the carb.  Everything was good there until I pulled the air filtre and noticed that the tube terminates at the bottom of the housing and was inserted into a piece of sponge to collect oil residue.  The sponge was fully saturated and the oil was seeping from a seam at the bottom of the air intake housing.  I've concluded that the problem was oil over-fill.   The machine comes with a small oil bottle (.47 litre) that I refilled when I'd do the oil changes.  Problem was that I was over-filling the small bottle thus over-filling the generator.   The volume of the crank case doesn't tolerate much of a variance in oil.  Probably around one oz.   Filling beyond that will cause oil to be forced out the crank case ventilation tube.   When filling the crank case, I was under the impression that a proper fill would be to the top of the threads on the oil fill hole.  That's incorrect.  A proper fill is just to the bottom of the hole. 

Now that I have that figured out, oil seepage has stopped completely and I'm more than pleased with this generator.   It starts and runs great, returns excellent fuel economy and from the garage, I can't hear it.  Only time will tell how long it will hold up.  From what I've seen, it looks to be well built and other than being a bit heavy, is an excellent value for the money.  Walmart sells it for $699.00 CAD regular price and occasionally on sale for much less.   That's half the price of a Honda EU2000 and the Hyundai actually generates 2000 watts continuous, while the Honda generates 1600 watts continuous.   Not saying the Hyundai is in the same class as the Honda or Yamaha.  However, if it holds up half as long, it's a good buy.  Anything beyond that is a bonus.           

Thanks for that.

Being that it's an inverter generator, I'll have to pull out the Sirometer and take some rpm readings at both locations.   It will be interesting to see what the results are. 

Not that I'm too concerned about the difference in fuel consumption.  The generator is extremely efficient for light load applications and the variance is minimal.