Digital engine temperature indicator for motor vehicles
The article presents equipment for snowmobiles and other vehicles with air engine. digital engine temperature indicators CITD of Russian development. Their characteristics and device are described, in particular the patented system of protection of DITD power supply from impulse noise in the onboard network.
Causes of overheating of air-cooled engines
Snowmobile, ATV, speedboat and other motor vehicles. most of these vehicles use air-cooled engine, and their owners have to deal with the problem caused by this circumstance. Unlike liquid-cooled engines, air-cooled engines require air flow, which takes heat away from the cylinders, which means that if you stop without turning off the engine, its temperature will begin to rise quickly enough, which can put it out of operation.
A device that signals cylinder overheating can save the situation. We are very pleased that such a device was developed, produced and put on the market by our company. Termiko Company, Moscow. The indicator was created on the basis of the company’s own developments and is highly appreciated by the owners of “air vehicles” and enjoys well-deserved popularity for a long time.
Digital engine temperature indicator (DITD)
Digital engine temperature gauges, or DITD, have been around for about 20 years and are most commonly purchased for snowmobiles. During this time there were several modifications of the device, some of which are obsolete and have been removed from production. Thermiko company produces three models: CITD-3, CITD-5 and CITD-6. The main purpose of any CITD model is to measure and display the engine temperature, as well as alert the owner of the vehicle that the temperature of the cylinders (or one of the cylinders) is approaching a dangerous limit. The critical temperature is preset at the factory to 195 °C, which is logical, since the destruction of the cylinder-piston group in some engines begins at 200 °C. However, this installation can be changed if desired.
The alarm for overheating in CITD models is visual: when the temperature reaches 195°C, the CITD temperature scale starts flashing, after which the driver must take some action to cool the engine. Optionally, you can connect an external audible alarm. The brightness of a scale of indication the owner of a vehicle has an opportunity to adjust, proceeding from a situation (for example, depending on time of the day).
Besides the specialists of “Termiko” have developed and patented the solution for the protection of DITD from the impulse interferences which appear in an onboard power line of a snowmobile and thus have essentially increased reliability of its work.
This basic functionality can be supplemented by a number of other functions, as will be written below. in the sections on CITD-5 and CITD-6. Also, all the basic functions of the three CITD models are listed in the summary table at the beginning of this article.
A DTC consists of an electronic digital display unit, also called a meter unit, which is mounted on the dashboard, and three sensors, two for measuring right and left cylinder temperatures and one for ambient air. Sensors transmit signals, which are read by measuring unit, converted and displayed digitally. The default setting is always to show the engine cylinder temperature. If you want to see the air temperature, you need to press the button to change the mode, located on the front panel of the measuring unit. After a few seconds, the CITD automatically returns to the cylinder temperature display mode.
The connection cable included in the delivery set is used to connect the sensors to the measuring unit. On one side of the cable is wired for three sensors. Wires of different length: the shortest one is for air sensor, the middle one is for left cylinder sensor, the longest one is for right cylinder sensor. The other side of the cable has a connector for the measuring unit. Sensors are installed under the plugs or in the engine head, the measuring unit is in the dashboard.
It is necessary to separately mention temperature sensors TPT-3-6x, which are part of DTC. They are made on the basis of the same sensors as platinum thermometers TPT. which, by the way, are the main products of Termiko. Thermometers TPT provide the highest reliability and metrological characteristics. They are widely used in many industries in Russia, as well as in two dozen other countries. Platinum thermometers TPT “Termiko” have the highest accuracy class. AA, are resistant to mechanical impacts and reliably serve in places exposed to vibrations, keeping metrological parameters within the norm for many years.
Table 1 . Main characteristics of CITD-3, CITD-5 and CITD-6
Sensor Mounting Recommendations
When installing the device housing into the snowmobile dashboard take into account: the place of installation should be always in front of your eyes, without interference of visibility, with insignificant influence of air whirls. when driving the snowmobile it lifts snow dust, which in different parts of the snowmobile does not settle in the same way. When cutting out a place for the housing in the snowmobile dashboard, remember the proverb “Measure twice and cut once”. Wires should be lead with a frequent anchoring or the leads should be placed in an additional protection, such as a clamping sleeve. Wires insulation is negligible, the vibration causes friction, which leads to short circuit. When you lengthen the sensor cables (if necessary), it is necessary to take into account that the temperature sensor is polar and make the connection according to polarity. Places of connections should be soldered, insulated and wires should not be mounted on stranded joints. It is possible to do without soldering, using el. car type connectors. In the future, such a connection is more convenient for repair work, as it allows to make the components of the device easily removable. Note! sensor wires are heat-resistant. they can withstand the operating temperature of the engine, but not the exhaust manifold. They can be extended with any wire, not exceeding the resistance of each wire of 5 ohms. The sensor itself is a kit sealed, and can be used to control the temperature of the engine by the oil or coolant temperature, or to measure the ambient air temperature, like an outdoor thermometer.
no matter how you mount the sensors, they must be isolated from the oncoming air stream. otherwise the readings will be understated, since part of the temperature will be blown away by the cooling stream. The sensor or adapter tube can be insulated with heat shrink tubing, kemnik, xlib tape, auto sealant.
Voltage supply. temperature sensor connection must be carried out according to the kit’s installation manual. Do not connect power supply to the wires, on the “at random”. Check the voltage at the place of the planned connection with a special tool at different engine speeds. Please note that the unit is not designed to be connected directly to the engine’s magneto without a voltage regulator. Also it should not be connected to the old type of rectifier devices of the VU type.
The average operating temperature of an engine in good working order, under light and medium operating conditions is 140 to 150 degrees Celsius. Difference in temperature readings of the left and right cylinder, on new. serviceable engines, at different loads, ranges from 2 to 25 ° C. In normal operation 8.12°С. Variation in temperature between cylinders, can vary depending on the speed. If the temperature spread across the cylinders is close to 30°C, it usually indicates a running technical condition of the engine. Be sure to check: the condition of the spark plugs and the setting of the ignition system, fuel supply, engine leaks, cooling system.
Installation of sensors under the spark plug has undoubted advantages which include: if the engine is under warranty, such installation will not lead to the loss of warranty (requires clarification at the dealer); method of installation is less time-consuming; a certain accuracy of readings. the sensor is in the vicinity of the epicenter of combustion, it is not affected by heat dispersion in different engine parts. at such installation, when taking readings, you can rely on the generally accepted pattern 180. 200 degrees (according to the Operating Instructions).
Principle of sensor work is the same as in many devices, which were used in soviet-made snowmobiles. The device is located under the spark plug and is a ring, the design of which includes a thermocouple.
The element, determining the temperature, sends a signal to the device that monitors this indicator.
In some models, there are no holes to install sensors, so you can drill it out if necessary.
With the help of a digital temperature sensor, it is possible to measure not only the temperature indicators of the running engine, but also to determine:
The latter can be found out by analyzing the temperature difference between cylinders. Also the sensor is able to indicate engine overload and air leakage into the system. It is noteworthy that it is high temperature that causes many malfunctions. Therefore, the owner of a snowmobile should take this point into account.
The characteristics of the temperature sensor:
- The operating range is from 50 to 250 degrees Celsius;
- The error is 2 degrees this way and that way;
- Possibility of use. on snowmobiles with and without battery;
- The dimensions of the housing are on average 45×90 cm.
Some models have additional elements that provide more reliable operation of the device.
The sensors are controlled with a multi-function button.
During the operation, the sensor lights up in the standard color, as declared by the manufacturer. In case of a sudden change of color the owner of the equipment should take measures, as the sensor reports the approaching critical temperature.
Repair and adjustment of ignition of dm1k engine
The ignition system of the four-stroke engine of domestic production DM1K is electronic with contactless magneto. The model MB-2K with 6,5 hp and 7,5 hp engines are equipped with such engine.
If the ignition does not work, do the following:
- if the spark plug is faulty during the spark test, it should be replaced with a new one;
- Check the spark plug and the wire to it;
- check the ignition button and the integrity of the wiring;
- If all the above mentioned is done and the system doesn’t work, it is likely that the ignition itself is defective and should be replaced.
How it works
Back in the 80’s it was popular to install various aviation devices on “Burans” and “Icars.
They read the temperature through a ring with a built-in thermocouple under the spark plug.
The same principle is used by many of the modern temperature sensors offered for snowmobiles.
On Lynxes, the cylinder head has an unoccupied threaded technological hole. They used to have temperature sensors that wrapped around this hole, but due to the discontinuation of snowmobile production, they are quite difficult to find.
Other snowmobiles, on the other hand, would require drilling the cylinder head. For new equipment under warranty, not much is acceptable.
For water-cooled snowmobiles without a regular coolant temperature indicator, there’s a suggestion from Koso and its Chinese clones.
Сдох датчик температуры на Т40. Ищем замену/Died temperature sensor
It is a small metal tube, in the middle of which there is a thread for a sensor, is inserted into a cut hose of the cooling system.
As mentioned above, the main problem with 2-stroke engines is piston burnout with a lean mixture.
Exhaust temperature sensors give a good indication of mixture composition.
For example, such a device is not only standard on the Rybinsk TAYGA Varyag 550, but is also recommended for use on all TAYGA snowmobiles.
Some manufacturers of similar devices are trying to broaden their functionality by combining temperature indicator with tachometer.
This practically does not complicate the device installation, as RPM sensor is just a few coils of wire, which are wound on a high-voltage wire.
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