My
BX2200 has to turn over 10 or 12 times before starting at just +40F. I do plan to put in a block heater. On my old '80 VW Rabbit diesel pickup, the original glow plugs took about 12 sec. according to the manufacturer's specs. Those were replaced by "fast glow" plugs which were specified at 5 sec. The VW mechanics told me that I should wait the specified amount of time for whichever plug I had in as they would not get any hotter after that. I took them at their word, but I surely never ran any tests to see if they were right.
Henro, this is going to seem counter-intuitive, but I have some very hypothetical theories about why the B starts more easily than the BX. There is a difference between temperature and heat. If you leave a heating pad under a pan of water for three hours, it will put a lot of heat into the water, but the temperature of neither the pad nor the water is hot enough to burn you if you touch it. On the other hand, if you light one match and hold it under the pan, it will heat up the water so little that it could only be noticed by the most expensive of devices. However, it you place your finger above that match, it will burn you. The heating pad doesn't burn you, yet the match does. The heat pad warms the water, but the match doesn't. This is because the small amount of heat in the match is highly concentrated in a small area over a short amount of time. The heating pad gives off more total heat, but it is over a larger area and a longer period of time. Though the heat pad gives off more total calories or therms of total heat, it is diffuse and therefore has a lower temperature. Though the match gives off fewer therms or calories, they are concentrated and are therefore at a higher temperature. Heat pumps, air conditioners, and diesel pistons all work on the principle of taking an existing amount of heat in a given volume of gas, compressing the volume of the gas, and thereby compressing the same amount of total heat into a smaller volume and thus concentrating it to a higher temperature. If you let the sun shine through a magnifying glass onto the ground, that spot in the center has a temperature rise while the shadowed area has a temperature loss, yet the total amount of heat within the entire area is still the same.
Though that match is hotter than the pan of water, it cools far more quickly. That is due to the thermal mass of the water and the ability of water to absorb huge amounts of heat. Water absorbs heat slowly and surrenders it slowly due to the fact that it takes a tremendous amount of heat to change the temperature of water compared to other substances. Metal will not hold as much heat; it heats and cools more rapidly and it conducts heat much more quickly.
Heat is transmitted in a couple of ways. Infrared radiation and conduction are the primary ways. If the heat is conducted into a liquid which can absorb some of the heat then evaporate, we have a synergistic effect. If a fluid (gas or liquid) is flowing across a surface, convection occurs (like air across your radiator) and there is a synergistic effect. If you have both evaporation and convection simultaneously, the effects are even more greatly compounded. This is why you wash your hands at McDonalds, place your wet hands under the hot blow dryer, yet your hands feel cold. The convection and evaporation together are absorbing so much heat that hot air actually feels cold.
The engines in the B and BX most likely differ in size, weight, shape, cylinder wall thickness, and alloy composition. Though the two engines may be brought to the same temperature by block heaters, it is possible that the BX engine has less total heat in the block. The cylinder walls may be thinner. Either or both of these factors could result in the loss of temperature within the cylinder on the compression stroke. As the piston compresses the air in the cylinder, a specific amount of heat is concentrated to a higher temperature within a smaller volume. As that compression occurs and the temperature simultaneously rises, several things could occur. A different alloy could allow the heat to be conducted away faster. Thinner cylinder walls, a lower block total mass (which means less total heat within that mass), the shape of the block, the amount of other stuff around the block which could insulate or even absorb heat, any or all of these can affect the amount of heat which radiates away as infrared radiation as the piston compresses the air. The engine in the B could have a higher compression ratio which would lead to a higher temperature. Even the distance of the tractor from a wall and the temperature of that wall as well as the tendency of that wall to insulate or absorb infrared flow could have a small affect on how much heat is retained in the gas between the cylinder and head. At that moment of maximum compression and injection, both the air and the diesel mist have to be at a critical temperature and pressure for combustion to occur.
Another possibility could be the amount of heat which makes its way from the block heater to the injectors. If enough heat conducts its way through the block and into the injectors, then that very first shot of fuel should be warm. If no or little heat is conducted from the block heater through the block to the injectors, then those first shots of fuel will be colder when they mix with the air. I would suppose that the first one or two shots of fuel would be warmer than subsequent injections, as those will be from fuel entering from further down the line. This could explain why an engine sometimes almost gets combustion on early revolutions then doesn't on following revs. The warmer fuel is gone and sheer friction has to warm everything for a few revs until it can sputter again. Once combustion occurs, the burning fuel brings the temperature on up and she's off.
Well, these are just some thoughts, theory applied to situation. I've never tested any of it so I'm not saying I know for sure. Replies with differing opinions are welcomed.
