Now admittedly this idea will sound a bit crazy:

We know that propane can act as a refrigerant in automotive AC systems. Safe, maybe not, but it does work.

Now here's my idea:
Direct cylinder injection, of LIQUID propane, in a 4 cycle internal combustion engine, when the piston is at or a little after BDC, starting the compression stroke, right after the intake valve closes. The propane would cool the air in the cylinder as it transformed from a liquid to a gas, lowering the amount of force needed to compress the mixture, thereby increasing engine output and efficiency. Then it would be ignited conventionally by a spark plug slightly before TDC.

Thoughts? Just something that popped into my head this morning.

 

In short: silly.

When a liquid turns into gas, that will increase the pressure, so even if your mixture nay become a few degrees cooler there will be more gas which will more than make up for that little drop in temperature.

 

Although if you could properly meter it, you could inject liquid propane to the intake manifold, let the expansion of the fuel cool the intake charge and pack a denser air/fuel mix into the cylinder. IF you could properly meter it.

 

Oh that's right! It would expand wouldn't it. Oh well, at least I'm thinking!

 

At least you admit that you made a mistake and won't argue about it!

Intercoolers do make sense with turbo or superchargers where the air heats up somewhat. You can get more power out by using a cooler mixture, but how would that effect efficiency, I do not know. More power doesn't necessarily mean more efficient operation.

 

Problem: You cooling the air charge AFTER it's in the combustion chamber, then compressing it AGAIN, then igniting it. The fuel you're using is actually cutting the power you can get out of your engine.

Gunner15a

 

I believe Chrysler played around with liquid propane injection. Don't know what came of it, but I don't think it's in wide use anywhere.

 

If something is good and useful, or at least with some 'perceived benefits' usually make it to market in some way. Things with no benefits or marginal benefits usually do not, unless mandated. Of course, this doesn't include smaller entities or people peddling 'snake-oil' type items.

 

Liquid propane injection is already commercially available both in the USA and in Europe. The only way for automotive LPG conversions to meet current EPA regulations is with port injection and vapor injection is more commonly used than liquid injection.

Generally, conversions are done for economic reasons rather than for 1/4 mile drag racing performance. Actually, it is not the fuel that governs the performance of an engine but rather the amount of air that it can ingest. Propane's effect on full-throttle performance is that the propane vapor displaces more air in the intake manifold than atomized liquid gasoline. Once in the combustion chamber, all fuels must be vaporized before they can burn.

 

Look at the BTU numbers on propane vs other fuels.

In 1,000 BTU's

diesel 139.2

gasoline 125

LPG 95.4

propane 91.5

ethanol 84.4

methanol 62.8

hydrogen 51.9

.....=o&o>.....