Hi Mike

I'm not knocking TJT here, but when your doing your thrust measurements, you have to take into account air temperature and adjust your numbers back to STP(Standard Temperature and Pressure: 15C at Sea Level).

Earlier you posted that you were getting 27lbs at 126K and I'd guess that the temperature was about 60F(15C). Your now getting 30-31lbs at 40F(5C). The colder the air charge, the denser the air, the better your combustion, the more thrust you get. For turbine engines, regardless of size)there is approximately a 1% change in thrust for every degree celcius difference above or below 15C(60F). If I use your 27lb measurement from earlier on and make the assumption that that was measured at 60F(15C). Your new measurements at 40F(4.5C) of 30-31lbs fall into the 1% thrust per degree celcius change formula within +/- .5 lb. If you extropolate that to say 75F(24C) you'll only get about 24.5-25 lbs thrust.

Again, this is not a knock on TJT . What I have stated above affects every turbine manufacturer, Big AND Small.

SimJet turbines are affected in the same way. For example we(GNM) rate the 3000AES at 28lbs at 25C(77F) or 31lb at 15C(60F). At the moment, they are putting out 33.5lbs at 5C(41F). All the thrust numbers are within +/- .5 lbs.

I hope I have added some insight into the different thrust levels you are seeing. If you have any questions, please contact me off line.

Ed