Thread: nos
View Single Post
Old 12-24-2008, 06:21 PM
slipdrive44 slipdrive44 is offline
Motorized Bicycle Member
Join Date: Dec 2008
Location: Tucson
Posts: 34
Default Re: nos

MY BAD! I saw you meant the intake blowers on the Detroit Diesels.

How It Works The DD four exhaust valves and a blower, compared with a four cycle with only two valves and no blower. Each cylinder liner has a row of 14 oblong holes near the bottom. After the compression stroke, the piston travels downward, past this row of holes. This is similar to the way an outboard motor works. Except that once the piston goes below the holes, called scavenging ports, the blower forces air in at high pressure from what is called the air gallery cast into the block. Thus, the DD has not only water jackets, but air galleries cast in the block as well. This one thing that makes DD blocks more complex.

The pressurized air then "scavenges" or forces out the burned gasses up through the four exhaust valves. This enables the engine to make only two revolutions to complete the combustion cycle rather that the four required of the four cycle engine, which relies on a second upward stroke of the piston to exhaust the cylinder of burned gas. In theory, this makes the engine more efficient. In reality, all the friction caused by all those extra moving parts eats up some of the efficiency gain. Why? Because of the drag created by the non-compression stroke, and the power to drive the blower and extra cam shaft. Even so, there is a major power gain through this design.

The blower and turbocharger aspiration system constitutes another major difference. The four cycle engine is aspirated through intake valves next to the exhaust valves; the DD engine has only exhaust valves, but twice as many of them. The DD cylinder heads are very complex and expensive to replace if one gets damaged, such as cracking from overheating. All those extra working parts make for more potential trouble, but also increase efficiency considerably. This why, pound for pound, DD squeezes quite a bit more horsepower out of their engines than CAT does.

Unfortunately, on the China made gasoline engines the design of the piston is meant to hold the fuel/air mixture and compress it in the crankcase to blow into the cylinder, on high quality 2-stroke engines of similar design a one way reed-valve placed between the intake manifold and the cylinder is the only way to maintain and keep a higher compression on the crankcase fuel/air, in which case a turbo might work, but only AFTER the carburetor as it would need to suck air through the carburetor to keep it moving otherwise the high pressure air system would blow the fuel back. This would necessitate a sealed and non-electrical post-fuel-addition boost system.

It is possible. Here is my concept attached.
Attached Images
File Type: jpg boost turbine.jpg (44.3 KB, 41 views)

Specialized Hardrock Sport
80cc Port matched RAW
36T Sprocket
Reply With Quote