Anonim

CLUB OF CAR FANS

"KETTLE" NOTICE

COLD START

We know that starting the engine in cold weather can cause problems. But experience comes with time, but what about the one for whom this winter is the first automobile?

Victor SLESAREV

Let's start the conversation about the features of a cold start with common truths. Namely: what conditions the engine needs so that the treasured process in its cylinders goes smoothly …

Equally important are the power, ignition and starter systems that can stir up a frozen engine.

First about nutrition. What does the engine “eat”? It is fuel (in our example, gasoline) and an oxidizing agent (atmospheric oxygen). If one or the other is too small (or too much), then the combustion will be sluggish or will not take place at all. Remember how a pool of gasoline burns: a dark flame, soot … and relatively little heat. Why so? After the first outbreak, gasoline in a pool, heating up, begins to evaporate more intensively, making it difficult for air to reach the core of the flame. The mixture, as they say, is extremely rich (that is, with an excess of fuel). But the wind blew - immediately the flame was brighter, hotter! The wind added the missing oxidizer.

Ideally, for the complete combustion of gasoline, its weight ratio with air should be about 1:15. This is strictly monitored by the corresponding devices in any working blowtorch, gas burner, primus, providing a transparent, bluish, hot flame. A carburetor, which should prepare a gasoline mixture for various operating modes, is more complicated than a primus. But one of his tasks is the same - to keep the ratio of fuel and oxidizer in a "combustible" framework.

When the engine has already warmed up - it's easy. Much harder than a cold winter start! Frozen air in the diffusers of the carburetor is cooled even more, and droplets of gasoline, mixed with this stream, evaporate reluctantly. And for an outbreak, an optimal mixture is needed - a liquid drop of a combustible spark will not ignite. The matter is complicated by the fact that part of the gasoline vapors, which nevertheless formed during carburation, condenses again on the way to the cylinder in contact with the cold collector, and the candle again has one air - and, alas, it does not burn.

A way out of this difficult situation was found long ago - any carburetor is equipped with one or another starting device that dramatically increases the supply of gas so that the saturation of its vapor near the candle becomes sufficient for a flash.

Unfortunately, for many inexperienced motorists, carburetors are far from perfect. And especially - their starting devices. The simplest “semi-automatic” seems too tricky - although in fact, any thoughtful student can study and debug it.

Another factor in a successful start is the condition of the engine. During the compression stroke, the “charge” of the mixture in the cylinder is heated, contributing to the evaporation of gasoline. A worn out motor that normally starts in the summer can be capricious in the winter! We hope that your part is in perfect working order, otherwise it would be better to postpone the trouble with starting it up until warm days.

The next important system is ignition. Is the spark power between the electrodes really important, if a weak one successfully ignites a charge! Indeed, in light conditions (summer, a working engine, a normally working carburetor …), a super-powerful spark is not needed. That is why for the time being we neglect obvious defects in the ignition (for example, there is almost no gap between the contacts of the chopper). The cold start conditions are another matter!

A powerful, biting spark, heating droplets of gasoline, contributes to their ignition. A weak one is not capable of it. In addition, it is important that the spark between the electrodes jumps in time - at the end of the compression stroke, before the piston is at top dead center. This is the so-called ignition timing or the ignition timing, for each engine its own, regulated.

What determines the power of the spark? In a conventional contact ignition system, for example, from the operation of a chopper. The longer his contacts are closed, the better. But the gap between them, which determines the reliability and opening speed, should not be too small. The normalized parameter here is the angle of the closed state of contacts (UZSK), which is usually controlled by the size of the gap in the breaker. Of course, for each model of the engine he has his own.

But the power of a spark often depends on simpler things. First of all, from the voltage in the on-board network. And while the engine is not running - from the state of the battery.

… Reader A. arrived with a story about "miracles." One of the cans of the battery turned out to be closed, and that one, now 10-volt, turned the engine quite vividly, but without flashes. At the same time, it was at the moment the starter was turned off that the engine suddenly started!

There is no miracle here. When the starter was turned on, it “fed up” the voltage to almost 7 volts, but this is not enough with a conventional contact ignition system. It was worth turning off the starter - the voltage jumped, and with the "untwisted" crankshaft with a flywheel, the motor began to work.

Now we come to the starter. Its task is to turn the engine, and quickly, so that the carburetor has enough rarefaction, and compression in the cylinders warms up each charge well. The slower the crankshaft rotates, the more difficult it is to start the engine.