Hey guys -

I just started hopping some rides in a Piper Saratoga II HP and I've got a question mainly focused on a digital EGT gauge that is installed.

First off, I'm trying to identify it. It looks just like a J.P Instruments digital CHT gauge, with the yellow calculator-like bar graphs, but it's not the EDM-700. There are a few differences. First, at the top of the instrument, the left side says "EGT" and the right side says "CHT". Then, on the right side, instead of having "% Max" it has a temperature scale that tops at 500 degrees. The left side of the gauge just has some hash scale marks. There is a single button on the bottom left (which I have NO idea what it does, except for make the bar graphs flash every now and then.)

So first, does anyone recognize this gauge? I can't find any manufacturer on it, and I don't have a picture handy.

Secondly, the yellow bar graphs for each cylinder always have a blank bar, similar to the EDM-700. What does that black spot indicate? EGT or CHT?

Thirdly, how can I best use this instrument? Are there ranges I should shoot for? Is there a way it can help me lean? I really want to figure out the best/safest way to run this IO-300 engine (any additional information on THIS would be great too...)

Thanks!
Saint

 

Sounds like a pretty standard CHT/EGT instrument. The top of the bar is likely EGT, and the "missing" bar (blank bar) indicates the CHT (which is always cooler than EGT, it's a way to have both temperatures read on one graph). The mystery button is likely a leanfinder, it will make each cylinder's EGT flash when the temperature starts decreasing (IE, peak EGT). You'd press it, slowly lean the mixture until the first bar starts flashing, then go back rich a certain amount of degrees (usually 50-70) for best power. Or, press it, lean until the last bar flashes, then keep going lean until you are a certain amount of degrees (usually 30-50) lean of peak for best economy. PM me if you have any other questions.

 

Forgot to mention- the best info for operating the engine is obviously the POH. Some may be missing the supplement for that particular instrument, but the POH will tell you, for example, how many degrees rich of peak or lean of peak to lean the mixture to.

 

He's right, the bright lines will be EGT's, the blanked out are CHT's. Most of these instruments don't have actual values attached to them, so you're just going off of what you see. The good news is that since it's not turbo-charged, you really don't have to worry about cooking some cylinders by learning the system. Just play around with a variety of mixture settings, I do them by sound/feel first, then start modifying the mixture and watching the guages. You'll eventually see a pattern. Also watch the values on climb vs. descent, that will really highlight the CHT values for you.

 

If you can get the documents for the airplane you may be able to find out model and make the instrument is, then you can surf up an operating manual for it at the manufacturers website. Just a suggestion.