Alcor EGT

[Wayne Pearce]

I have solved problem with Tacho's interestingly they were reading 80 RPM low explains why I was running 3 litres per hour richer than normal.

Last problem to fix is EGT calibrating knobs, I have one calibrating knob that does'nt adjust needle or appears to slip with only very small movement on needle. The probes etc. are new so ti is only the knob that I need to fix. Can any one tell me if there is an easy way to remove guage face and what will I find if I can do this ie. is this a simple fix or am I dreaming

Regards ........ Wayne

[Bob Cook]

Wayne

Think you are "snookered". There is no easy fix unless you send it out for overhaul and calibration. I don't think it is legal <G> to play with them.

I have an alcor guage that I can send you to either compare with you current guage or you can buy it. Probably cheaper than calibration. Email if you are interested. I replaced mine with a JPI 760C. It was functioning fine when it was removed.

Bob

[Wayne Pearce]

thanks Bob but I spose it may not be worth the effort as the odd one is still reading half scale at peak EGT and I tend to lean to 100 deg rich so I get a cruise reading of about 1/3 scale ....... I'll stew on it and maybe see if I can get an exploded parts drawing or similar.

Regards ......... Wayne

[Bob Cook]

Wayne

There is no electronics or amplifiers involved with this guage.

If I remember correctly; I don't remember the peak reading being much above 1/2 to 2/3rd full scale.

maybe someone else on the board can verify the readings.

The Front adjustment was meant to "balance" the readings at peak so it is a little easier to remember "normal" settings.

you can check the calibration by carefully using a flame and measuring the peak temp of the flame. Both reading should be similiar in no wind conditions. just be careful using an open flame from a small propane torch.

Bob

[Wayne Pearce]

I always thought rear EGT needle was also adjustable, are you saying that only the front needle is meant to be adjustable so that you match both needles huh?

Cause thats what I've got when I match the front (adjustable) to the rear peak is about half scale with new probes just fitted, new probes cost me A$300.00 each wow!

Regards ..... Wayne

[Bob Cook]

Wayne

per manual pg 14-19. Btw this is an optional guage and is not part of the mel.

1) make sure front adjument screws are in mid position. Adjustment bars are in mid position

2) partially remove instrument and test fly.

3) set power to 75% and lean for peak egt. Adjust rear screws so instrument reads 4/5 full scale. Both should read the same.

4) reinstall. The instrument will drift a little after use and the front screws can be used to readjust in (3).

Probably you tried to peak at less than 75% power and the egt is not hot enough to get to the 4/5 th's of full scale.

on the P337 the say to enrich to +50 degrees and should require 9 +/- 3 pph on the fuel flow guages.

The pointers should agree to within 1/2 increment of each others at PEAK EGT. again 75% PWR.

BTW your tack issue. There are some very accurate hand held tacks for less than 150 dollars that can be used inside the cockpit to keep accurate. The alternative is the small JPI tack that uses the P lead and install on one engine. You then need not worry too much about calibration of the very inaccurate, sloppy, bouncy, crappy tacks on the aircraft.........


bet this will help

Bob

[Tony Giantonio]

I have just one word of caution. When ever i check probes for accuracy i use heated oil with a candy thermometer for a guide. its much more safe than an open flame method. I do believe you can not open the insturment to adjust it with out having the correct equipment to calibrate it and then put it back in the airplane. If you want to just see how it ticks fine, but don't do it and put it back in the airplane. Just my thoughts.

Tony G.

[Sten]

Hi,

The EGT is essentially just a mV meter and can easily be checked an calibrated with a simple millivolt source. The probe is a thermocouple that generates a very small voltage when heated.

You need an adjustable voltage source like the one found at http://www.5bears.com/circuits.htm. Forget one turn potentiometers, you need a ten turn, knob- (expensive) or trim- (cheap) pot.

You also need a temperature – voltage table such as http://www.carl-fh.com/carl/referenc...-ni-codes.php.

Finally, you need a DVM capable of reading with a resolution of at least one millivolt.

Remember, other than certified instrument shops cannot do work on normal category aircraft!!

Good luck!

/Sten S