Diesel Bombers - Lowering EGT's

Quote:

Originally Posted by AndyMan (Post 47817)

On the bigger inector cooling the cylinder deal... The extra fuel that can't be burned in the cylinder gets burned in the exhaust. That's where your black smoke comes from. To get enough of that unburned fuel in the combustion chamber to cool it, you're either going to "put the fire out", or you're going to create so much smoke that the truck would be undriveable.

There's two things that can cause black smoke:

First of all, you might be using all of the air in the combustion chamber, and you only have fuel left over. In that case, the fuel particles do act as coolant by absorbing heat but not burning- the same reason water vapor acts like coolant. However, it is possible to dump in so much fuel that you get too much cylinder cooling and "put the fire out", or reduce temperature to the point that the Diesel that does have enough air to burn doesn't want to burn.

The second way to get black smoke is if there is enough air to totally burn the fuel, but due to retarded timing or inefficient atomization, there isn't enough time in the cylinder for the combustion to take place. In that case the fuel and air continues to burn even after leaving the valves. If you had a NASCAR with short exhaust pipes, this is when they start shooting flames. On a turbo Diesel you don't see the flames because they're busy roasting the turbocharger instead of flying out the tail pipe.

So extra fuel raises temperatures if you aren't using all your air, and it lowers temperatures if you are. I'm willing to bet that fellow-Phoenician Sharx's exhaust is a pretty rich mixture and that if he was going to get any afterburning, he'd have it already.

None of that is meant to imply that he doesn't need a much bigger turbocharger, or twins, or water injection.