Since the time I set mine up I've had many TRX owners put their probe in the same location with comparable results. These silly-semi-supercharged two strokes spit so much fresh, cool mixture out the exhaust during the pipes suction phase it cools the probes - to the tune of about fifty to seventy five degrees for every inch it is placed closer to the piston.
There seems to be a kind of "sweet spot" that can be noticed if attention is paid to the color of the exhaust pipe s. Sometimes there's an area on the head pipe where it shows some discoloration from the engines exhaust heat - where that starts would be a bit too far down the pipe to locate the probe. An EGT gauge is a tool. By itself it adds no power. This curve would show that the EGT rises to a peak and then starts to decline.
On the left side of the peak, we are richer than stoichiometric, and on the right side of the peak, we are leaner. The combustion of gasoline is a chemical reaction that, like any other chemical reaction, has a specific a stoichiometric ratio. Remember Chemistry , probably not, but you were told that stoichiometric when referring to combustion is the ratio of air to fuel at point where the combustion reaction is the most efficient.
That requires a little richer mixture ratio of about We need to control where the engine runs by controlling the jetting so that we are on the left side of peak, near the richer ratio of First of all you could, and it would work fine. Sensors tend to deteriorate due to the higher oil content of a two-stroke exhaust. EGT should rise rapidly with the RPM as you accelerate and should come to a point and stay there the time you are at full throttle and a constant load. If your EGT rises to a peak and then starts to fall as you maintain full throttle, you are now on the right which is the wrong side of the curve and lean.
Normal reading will vary slightly from machine to machine, due to slightly different probe positions and engine characteristics. So they are relative to a certain degree. We want to run on the upside of the curve at about At this setting your plug and piston reading should show you a great burn pattern and color. What now coach?
Then richen it back up a tad so you see a small temp drop, then you will have a real number to look for. Using the specified sensor location will at least have you seeing things in the expected range to start with ;. Kind of helps set up your base and when you have to ask questions, other results are similar.
Thanks to anand for the deeper explanation too as others have said the peak temp isn't the issue as much as the 'drop off' when going full throttle. Jetting from the bottom to the top! To properly jet your carburetor the carb must be clean and with sound gaskets, seals and o-rings. Vent tubes must be clean and free flowing.
Disassemble and clean the carb and all the passageways with carb cleaner and compressed air. The engine must be in sound mechanical and electrical condition with no air leaks. A new spark plug with the correct gap and properly set ignition timing is also helpful. You can tune till you're blue in the face, if you don't have a clean carb, with a mechanically sound engine as a baseline.
A properly set float level is critical to all circuits in the carburetor and it must be set first. Continue to tilt the carb to the point where the spring just barely touches, and then look at the float casting marks found on most floats. With a properly set float the marks will typically be parallel to the body of the carburetor. Please remember that we tune each of the carburetor circuits based on throttle position and not RPM. This is one of the major reasons that you jet from the bottom to the top.
Note how each circuit overlaps! Then an adjustment would have to be made on either side to make the transition smooth. Then as you roll off the throttle you'll have a smooth transition back down the range also. This is just as important! A lot of two stroke engines start to seize shortly after you come out of the throttle, not when you are WOT! Most MX style carburetors have the adjusting screw on the air cleaner side, so it controls the airflow. Warm up the engine to a normal operating temperature.
Adjust the idle speed adjusting screw so that you are about RPM higher than your normal idle speed. Go slowly and let the RPM stabilize. Go back and forth a couple of times so that you get it spot on. Note how many turns it took on the adjusting screw to get your best idle speed. Using this method allows you to make minor air adjustments to compensate for small changes in weather conditions at the track and still be in the working range of the air screw taper and spring.
Slides are numbered in millimeters of cut away at the closed throttle position. A number 6 slide has a 6 MM cut away and a richer number 5 has a 5 MM cut away. Accelerate out of a slow, first gear corner to give it a good test. The slide works in close conjunction with the pilot circuit to allow you to transition to the next tunable area, which is the jet needle and needle jet. We want a smooth transition from the throttle slide to the main jet.
This transition is controlled by the needle jet and jet needle. The needle is tapered, and has groves cut in one end, to hold a clip. This clip allows you to change the length of the needle. There are also small, thin spacers available, that will let you set the needle length even more precisely, by placing them under the clip. Needle jets come in a couple of different styles and of course numerous jet sizes. The provide additional avenue to fine tune your mid range.
Some tuners find it more convenient to replace the needle jet with one size richer instead of raising the needle. This way your needle will stay in middle clip setting all the time. Different strokes for different folks! Keihin and Mikuni use a different system for numbering their needles and you need to become familiar with whichever carb you are running. You can get the mid range perfect if you take your time and have a selection of needles and needle jets, which by the way, is sometimes called an emulsion tube.
The needle diameter controls the lower end of the mid range jetting The setting of the needle diameter is critical to the engines lower mid range power and drivability. It should be noted that either one of these situations can be caused by your fuel delivery system or by clogged vent tubes. Moving on now to the overall length of the needle. On most needles there are 5 clip positions.
To richen the circuit you have to raise the needle by lowering the clip.
On high output diesel or forced induction applications, there are few gauges that are more critical. Advanced Search. Product Shipping in 2 business days. Description: Watching your precise exhaust temperature can mean the difference between maximum performance and catastrophic engine damage. Skip to the end of the images gallery. Skip to the beginning of the images gallery.
Additional Notes. Add to Cart. The included Type K thermocouple assures maximum accuracy and minimum response time. There is, quite simply, not a better measurement of your exact exhaust gas temperature available anywhere, for any price.
A variety of included installation options and direct plug in harness simplify installation on any application. Hi, This pyrometer does require a 12 volt power source to operate. Thank you for your question. Stepper Motor refers to the type of meter movement this gauge uses. I have a Pyrometer and the probe harness does not plug in it has two studs to connect the probe red and yellow.
Thank you for your inquiry. Water temp and pyrometer not working. So far I am running stock ports and ignition. Thanks for the info on the 2 ignitions. I will check them out. As for the piston top it looked great after Sep but I have not pulled the head since the last runs in Oct.
Busy making a living. As for the AFR vs EGT I am looking for something to watch on the fly to help predict imminent disaster and thus warn to abort the run and make a change rather than seizing. Jarl, You are in a very good place to be, better to start with a stock motor than a mussed-up one. I don't have any information about this, I recall having conversations with some tuners who were experimenting with microphone pickups on the dyno to detect detonation and or bearing failure before it let go.
You might try searching it out. Happy Holidays, John. All our 2stroke sleds out here in mountain land have the pyro no more than 1" out from the port. A lot easier to keep tabs on than a needle or didgets. Jessechop Guest. The further you get away from the port the cooler the temperatures. The AFR sensor won't last long enough to get a reading. Running a two stroke wide open is an easier tuning challenge then a roadracing setup. The easy way is to lean it out until it melts then back off a little.
All sensors are relatively slow to react. You can melt it before the reading stabilizes. You are approaching the melting point of the piston past that. I also run a head temperature sensor. The EGT shows rapid changes. The head temperature shows a more stable reading. At some point the EGT will hit maximum and then drop as you continue to lean it out. If you end up rare in that condition you will melt it before you figure it out. Plug readings and piston inspection are mandatory.
The piston and head have to be spotless. Any carbon creates a hot spot. At the end of the run kill the engine. If you run it back to the pits the plug reading is worthless. Well, it used to be Los Angeles. Just remember. It isn't life or death. It's bigger than life or death!