Topic: Infrared thermometer for tuning

[Prospect]

I'd like to use an infrared thermometer to measure either the exhaust gas temperature or the pipes themselves as a tuning method.  I've flow vintage airplanes for a living and many of them have an EGT (exhaust gas temp) gauge allowing the pilot to control the mixture (gas and air) to reach peak EGT and then enrichen it a bit (add gas and lower EGT) to achieve optimal running conditions for the engine.  I'd like to use this method to make sure all temps are the same in four pipes as a tuning method. 

Anyone see a problem with my reasoning?

[Kickstart]

I think your reasoning is sound, but I'm not sure how straight forward it will be to use the infrared thermometer on chromed pipes (assuming yours are chromed.) 

My friend works for the Navy (civilian engineer), and he has one that he was going to let me borrow a while back.  He made a comment that it's hard to get an accurate reading off of reflective surfaces.

I don't have any experience to confirm it, but I would recommend doing some research on this before buying one.

Good luck

[Bob Wessner]

Interesting point about the reflectivity of the surface to be measured. Hadn't thought about that, this supports what you were told.

http://www.omega.com/prodinfo/infraredthermometer.html

[K5owner]

+1 with Kickstart. We used infrared thermometers for checking hot spots in electrical panels & substations. I believe the scientific term is "emissivity"for differences in surfaces & material. You're thinking is correct, and if you have the same surface and same distance; I think you'll be okay. When I sync my carbs next spring I'll take exhaust readings too and see what the correlation is.

Good idea. Thanks!
-Ray

[Prospect]

looks like the best idea would be to directly measure the exhaust as it's coming out the baffles or use black water based paint to temporarily paint a small section of the headers for a more accurate reading.

[K5owner]

I like your thinking. Yes, on both suggestions.

[72500john]

i have not worked on piston aircraft engines for many years now. but wasnt the probe for cylinder temp located under the spark plug. so why not read your temp at the head?
or better yet get/buy/borow a multimeter that has a temp reading function and test at each pipe.

[steam-powered man]

i have an infared temp sensor and could not get consistant readings on the headers because of the point previously mentioned.  best results for me occured when i managed to get temp off the exhaust collars.  it was more of a curiosity thing;  all four pipes had felt evenly hot to my uncalibrated fingers and the plugs looked tan after plug chops at various rpm's.  called it good enough.     

but to consider your question. 

before i would tweak the idle, needle and main jetting only based on exhaust temp, i'd confirm across each carb:  equal cyl compression, airflow thru the head pathway from carb to exhaust, spark quality, spark timing, valve and seat condition, valve adjustment, valve guide condition, equal flow thru each carb circuit (idle, needle and main jets), carb settings and zero vacuum leaks.       

[Prospect]

i have not worked on piston aircraft engines for many years now. but wasnt the probe for cylinder temp located under the spark plug. so why not read your temp at the head?
or better yet get/buy/borow a multimeter that has a temp reading function and test at each pipe.

If I remember correctly the EGT probe was drilled into the exhaust near the head.  Could be different on some aircraft.  I'll look into a multimeter with a temp function.  Wasn't aware they existed.

before i would tweak the idle, needle and main jetting only based on exhaust temp, i'd confirm across each carb:  equal cyl compression, airflow thru the head pathway from carb to exhaust, spark quality, spark timing, valve and seat condition, valve adjustment, valve guide condition, equal flow thru each carb circuit (idle, needle and main jets), carb settings and zero vacuum leaks.       

I'm doing a complete top and bottom end rebuild so this thermometer test would be a last step of many. 

[steam-powered man]

very cool (sorry!).  and good luck with your build!

[marknpb]

I just picked up a Sears Multimeter for $48 that came with a thermocouple. It reads up to 700 degrees Fahrenheit, though if i were using it to tune, I may pick up three more thermocouples so I can use a separate one for each cylinder. That way if one cylinder is running much hotter, I don't have to wait as long for the probe to stabilize to the new temp. I can have one on each exhaust pipe, and since they use a contact wire, there's no issue with getting a reading off a chrome pipe (mine are black).  They sell for $11.89 each at Sears.

>>>>If I remember correctly the EGT probe was drilled into the exhaust near the head.  Could be different on some aircraft.  I'll look into a multimeter with a temp function.  Wasn't aware >>>>they existed.

[dave500]

i think its a good idea,if somewhat fussy,,airplane engines have to cope with widely varying air temps and density from ground level to what ever the ceiling hieght is,and have provision to manually adjust "on the fly",tuning a stationary bike you might find the two inboard cylinders run hotter?

[Scott S]

 I've had one for years. I think it's a good tool to have in your arsenal.

[bollingball]

markmpb just for you

http://www.harborfreight.com/lcd-automotive-multimeter-with-tachometer-kit-95670.html

                                           Ken

[Prospect]

http://www.knfilters.com/airfuelmonitors.htm

This might do the trick.  Air/fuel monitor made by K&N.  Saw it on another forum. 

[TwoTired]

In the airplane you are tuning EGT under load, and fuel requirements vary with the load, even if operating at the same RPM.

Many of the stock Head pipes are double wall, and outside surface temps vary with how close the inner pipe is to the outer pipe at the section you are measuring.

Also note that the measurement spot size (sample size) varies with the distance from the detector and that the laser pointer is simply a pointing aid and NOT the spot size of the measurement sample.

An inserted probe in the exhaust stream is quite accurate feedback for an operator.  However, if you are drilling holes in your exhaust, you might prefer a lambda sensor, which measures the oxygen (O2) in the exhaust.  It's what modern vehicles use for mixture control feedback, and accounts for load variance.

Cheers,

[Don R]

I was at a chopper company for the first start of a new build. they choked it, then started it and shut it off several times. I asked why. The reply was to build carbon inside the pipe so the chrome doesn't turn blue. I wonder if differing thicknesses of carbon would skew the temps. I haven't had much luck with a heat gun myself except for a dead plug or something radical like that.
 I have an O2 sensor in my race car, just on one cyl. I record the air/fuel ratio. It makes the exh. temp too high if I tune by it alone.