Before and After

LIM Technology approached the development of its third proof of concept prototype with some hard learned lessons and very specific goals. Following careful consideration, it was decided that a four-stroke, single cylinder Diesel could for reasonable cost and effort, be modified to our system, and that tests could then be performed to establish the value of building larger engines.

There is no new physics or chemistry in our system; the effort comprises our attempt to demonstrate the value of our patented mechanical arrangement. We tested both versions of the engine using the same equipment.

The base engine is a mass produced commercially available conventional four-stroke, single cylinder Diesel. We purchased two of these, and modified one. The one we modified was literally taken all apart. Many of its major parts were completely replaced, but the modifications were kept to the minimum which would be compatible with our theoretical system and our intended experiments.

The renovations included replacement of the head, manifold, piston and connecting rod, and a new cylinder and exhaust manifold. All of the original valves and push rods, rocker arms and valve springs were set aside along with the parts we replaced. Once the extensive remodeling of the engine was done, our project passed from theoretical to experimental.

In the "Before" photo, the crankshaft (smaller gear) drives the camshaft (larger gear) at half the rate of crank rotation. The camshaft (not shown) has lobes which manage the timing of the intake valve and exhaust valve, and allow them both to remain closed during Compression and Power. In the "After" photo, the gears are of equal size. The camshaft remains just to time the fuel injection event which happens during each revolution of the engine. There is no longer any need for the camshaft to manage the intake and exhaust.

The original engine had an intake valve and an exhaust valve. We experimented with many different sizes and numbers of valves, and eventually found that we could improve the performance of the engine to a greater extent with a larger valve area and smaller individual valve mass. This led to a six valve configuration, but a four valve head with larger valves seems to be more powerful.

All of the valves in our experimental engine are for intake. All of the exhaust leaves via ports disposed about the circumference of the cylinder, which is one reason we needed a new and longer cylinder. A benefit of this system is the lack of exhaust valves, which are one of the most notorious potential trouble spots in a conventional four-stroke engine.

The standard engine is claimed by its maker to produce up to 4.7 hp (hp) @ 4000 rpm for short periods, and to be able to produce 4.2 hp @ 3600 for sustained periods. Our tests confirmed these claims, but also revealed that above about 3.0 hp the exhaust is smokey.

Our experimental variant is also smokey above 3.0 hp, but its maximum hp is about 6.0 at only 2250 rpm. The original makes torque of about 8 lbs.; the variant makes about 15 lbs. Stroke, bore, and therefore displacement, are the same.

Our next prototype, number 6, will be a conversion of a Mercedes 5 cylinder four-stroke automotive Diesel. This may be installed in a test vehicle in Autumn, 2002.