General setup:

Take spark plugs out, replace with diesel injectors and time diesel injection pump to inject very hot diesel fuel at TDC. Autoignition of hot fuel causes the ignition source.

In my previous post, I've made several conclusions.

1: Piston and cylinder might melt or polish the oil off the cylinder wall due to diesel injector spray pattern in spark plug hole.

2:Incomplete combustion due to short stroke length and colder uncompressed air than a diesel engine. Which may lead to coking of the piston rings, valves, injector and less fuel economy/emissions.

To solve problem no.1 use a short prechamber screwed into spark plug hole with mounted injector to inject fuel causing ignition which spreads to cylinder without causing thermal damage in cylinder. (will cause thermal loss)

To solve problem no.2 use gasoline port injectors to inject majority of fuel but preheat it for greater atomization

and only maybe you could alter pump timing to inject fuel before TDC to allow combustion pressure to build.

I did learn that the extra torque generated by diesel fuel is not because of extra btu's but because of cylinder compression and fuel injection duration down the power stroke. So, no doubt it will burn but will it burn to the point of no carbon soot or deposits form in the engine?

The "smart plug" spark plug causes ignition to occur in constant speed, constant load engines (think generator) by lowering the activation energy by chemically altering the fuel through heat & a catalyst to cause diesel ignition in a gasoline engine. This removes requirement for high compression.

The "smart plug" drawback is when the engine's speed and load changes, timing is not consistent. So if you have mechanical pump ignition timing, why wouldn't this work?

Propane aspirated conversion kits for diesel engines use the same ignition system but the high compression is used as the main energy source.
-- danheathmoore, Nov 02 2007

http://hyperphysics.../thermo/diesel.html [the dog's breakfast, Nov 03 2007]

Remember diesel is almost twice the fuel efficiency as gasoline, so the lack of compression and short-stroke may just lower the fuel efficiency down to gasoline levels. Hopefully uncomplete combustion byproducts will not destroy the engine!
-- danheathmoore, Nov 02 2007


Hmmm, I belive this is viable. But wouldn't it be a bit expensive? I mean, there are several kits available for cars that can add benefits (exhaust filters, cylinder cleaners, ect.) The only thing stopping people from using them is time and money. This wouldn't do so well on the markets. Just buying a diesel car makes more sense to the average consumer.
-- Shadow Phoenix, Nov 02 2007


Expensive maybe, Biodiesel conversions instead would make it more attractive. I think there is a huge demand for people to drive their cars and SUV's on biodiesel.
-- danheathmoore, Nov 03 2007


The most expense would be to connect the diesel injection pump to the engine. I suggest you use an electric motor to operate and synchronize the pump with IC engine. So when the throttle opens on the engine, more biodiesel is misted into the intake, the engine shaft speed sensor signals the electric motor control to increase in speed accordingly.
-- danheathmoore, Nov 03 2007


Huh.

Okay, so instead of relying exclusively on high pressures for temp rise to autoignition, you're saying use high temperatures to start with, and get the rest of the way on compression. You'll probably have to preheat the incoming air, too.

Sounds like you've re-invented the old gasoline-start diesel tractors, but I like it so far.

I'm guessing there would be a radical reduction of power compared to the same engine under gasoline, but an even more radical reduction of fuel consumption. I have no math to back this up, it's just a hunch. Supercharging would go a long way toward getting some of the power back.
-- elhigh, Nov 05 2007


[+] Bun for its half-bakedness. But this has been already baked..somewhat. In the mid-80's General Motors had diesel V8 engines that were nothing more than a standard small-block gasoline engines with heads and a manifold designed to accomodate diesel fuel.
-- Jscotty, Nov 05 2007



random, halfbakery