I thought propane cooled the intake charge as well?


1999 TTA #1of2
Mar 25, 2002
ok when propane first came out, it was said to cool the intake charge, by means of a phase change as the gas comes out of the nossle to hit air.

reading some threads here people say that propane does not cool the Intake charge, is that becasue their not injectiong close to the throttle body or is it tha it doesnot signifcanly cool?
Due to a phase change, it will cool the intake charge but with the relative low pressure and low volume of propane being used, it doesn't amount to more than a couple degrees. Basically the amount that it does cool the intake charge is negligable and all of it's benefits are occuring inside the combustion chamber.
Seriosly, I thought this was supposed to dramatically reduce the intake temp. I read on the site that it came out of the bottle at minus 60 deg.
It will give up it's heat (become cool) at the initial point of pressure drop - the solenoid - which is 15 feet from the up-pipe. Whether or not it remains cool at the actual point of injection is debatable...
Originally posted by smokinHawk
the benifits as a high octane source then? or is it something else.

Here we go again..............LOL

OK, since it is a gas with an octane of 108~ it mixes with the air much better than the gasoline. Therefore any lean spots in the cylinder (which will naturally burn faster than rich mixtures) will have a higher average octane rating reducing the chance of detonation.

well said.....but does it raise octane level? or just reduce lean spots in the cylinder?

Originally posted by -=TWITCH=-

well said.....but does it raise octane level? or just reduce lean spots in the cylinder?

Both, but doing the math tells me the average octane when running 91 pump gas and 108 propane will only amount to about 94 octane. That would make me think that the overall increase isn't what helps the most.
There are at least two ways you can run a propane system one would be to push liquid propane up to the engine and perform the phase change right at the engine.

Most systems I have seen are actually moving just gas (and a tiny amount of liquid) up to the engine. The gas is low pressure and therefore does not cause hardly any phase change. Infact all automotive systems I have seen have a regulator right on the tank, just like a grill. As soon as the propane goes through the regulator its in gas form.

To get liquid you would need either a pump (piston, scroll) or something like nitrogen to push the liquid. I have only seen a few commercial systems (as in heavy equipment) that partially do this. Its very hard to maintain the propane in liquid form.

I hate to jock your flow as far as the liquid comment goes, but getting liquid is easy. You just need the right type of cylinder to do it is all. The liquid's in the bottom, so all you need to do is have a tank with a tube that runs to the bottom (I'd reccomend either a forklift tank, a tank off of a camper if it's got a liquid tap or a buffer tank if you can find one with a liquid tap) The buffer tank would probably be best for the track, the forklift tank or the camper tank would be best for daily drivability. The forklift and buffer tanks also come in alluminum so they're lighter as well. The tanks can be laid either horizontally or stood up vertically, so clearance isn't as much of a concern. The gas pressure pushes the liquid out without a pump or anything like that. Keep in mind that one volume of liquid in such a setup is equal to 272 times the volume of vapor, so you're getting a lot more fuel then you would otherwise. There are a few issues with LPG in my book though, a biggie being how to keep the pressure constant. Using liquid would alleviate some of these issues since the boiling of LPG is a cooling action, the pressure decreases as you draw off the vapor. Far as using it goes, I'd lean out the gasoline as much as possible replacing it with LPG vapor, or just run more boost with the liquid because the more liquid you dump in the higher the cooling action. Another thing to keep in mind is that LPG gives you LESS fuel per set energy volume, so for every gallon of gasoline you need about 1.35 gallons of propane liquid. There's special hosing required for liquid versus vapor, as well as special solenoids (find a place that does bulk trucks or an LPG plant to get the solenoids, hoses and that stuff for you) I've got a project I'm working on, I'm planning on a 3 stage system using a nitrous fogger nozzle (cheap easy to get jets) along with a homebrew electronic controller for it. What I'm thinking about right now is having it set up to displace about 50 hp worth of fuel, then it'll switch to a 100 hp nozzle then it'll open both of them.