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under pressure meters

Every year you should make at 2 cylinder engines synchronizing the carburetors or throttle or control. Every time go to the workshop? The ambitious screwdriver makes itself. But how?

The best-known system, two dial gauges. But this has the disadvantage that the same are purely mechanical and inequality is given. Here is aided by the exchange by cross control. Is always kind and the dial also cost a lot of money.

So please a little cheaper. A water level gauge is also a possibility. If the hose is long enough and is filled with a not too thin liquid, it can also lead to hereby synchronization. Here, there are still more BUT.

If due to an error in the vacuum system a much stronger side, it quickly pulls the liquid toward purely motor. Not exactly what you wish for. In addition, the hose must not be too thin so that it does not contract at applied negative pressure. And the hose length does play a role here. So this is not exactly optimal. But very inexpensive.

Since I like both versions not so good, and digital meters used in professional motorcycle repair shops to use (at least in the known to me), so I made myself out my thoughts about it. Subsequently, the result of the deliberations.

Basically, electronic sensors rely on any mechanical components and are therefore subject to no scattering such as a dial gauge. Furthermore, a purely digital processing of the measured values can not be disturbed. And finally, you can build beautiful small electronics.

Principal reasoning was, as I put negative pressure into electrical signals. For this task, there is quite an inexpensive pressure sensors. However, most of this kind of work starting from zero is positive, ie positive pressure, not vacuum. But I have found a sensor that has both measurement capabilities.
Each cylinder such a sensor will be assigned. These sensors are calibrated by the manufacturer using a laser. The difference between them is so low that the desired accuracy for the Sychronisation is far exceeded (by a factor 10).

The negative pressure region of the engine reaches a maximum of 1 bar and thus corresponds perfectly to the sensor. The normal operating range of the sensor goes to 1 bar and in full pressure is the output voltage of the sensor 4.7 volts and can thus be optimally processed further . The error range is a maximum in the temperature range of zero to 85 C at 2.5%.
If one converts the display down to ten points per sensor , you get a normal resolution of 10% of the maximum value . The error value is significantly lower and thus does not play a crucial role and can be neglected . Even with twenty points is the theoretical error without consideration of parallelism with 5 %, well above the component tolerance .
The response time of the sensor is 1 ms . This means that an increase in the pressure values of 10% to 90% appears at the output in 1 ms . Which would result in a theoretical speed of measurable 60,000 rev / min. So plenty of reserve. The warm-up time of the sensor is 20 ms , so it can also be neglected.

It is added as a further contributing factor , the system is constructed dual. If the error increases due to the influence of temperature or other external influences in a sensor , he does it in the very same extent, in the other sensor . The two sensors are an assembled unit. Since the display controls a sensor in the evaluation, the display and the other to negative to positive, here the error is largely compensated by itself

Everything else is now just a little out electronics Tensions to a trimmed analog display . This two level bar are visually side by side. So you can regardless of the crankshaft offset see the absolute level of each intake system. Leaks in the vacuum system can clearly be seen here .

The beauty of this technique is , it can be permanently installed in the motorcycle. So you always have a control facility and / or adjustment . Priced this synchronization aid is about 70 euros for material. That's about half a Messuhranlage . Only with the benefit of higher accuracy.

first attempt

board layout

currently only a novelty. PCB layout is done and the first prototypes of the boards are ordered.

Boards detail