How does Gasoline "Cool" the engine?

[Michael Savage]

I've read this several places, but what's the point of dumping gas out of the exhaust and how does it cool the engine by any means in the split second it travels out the exhaust valve?

[RobertISaar]

same reason blowing air over wet skin feels cold, even if the air is the same temp as ambient air: the liquid converts to a gas and takes heat with it.

 

it isn't super effective with an engine, since the heat just ends up somewhere else(tends to get picked up by the exhaust valve, through the exhaust ports in the head, the manifold, O2 sensor, cat, etc...), but it can take an engine that is experiencing or on the verge of detonation/pre-ignition into a safer range of operation.

[pitzel]

Its a thermodynamic thing.

 

This article, in the context of piston aircraft engines, might be useful:

 

http://www.experimentalaircraft.info/articles/aircraft-engines-leaning.php

 

The aim of the ECU in the car is to lean out as soon as parameters for closed-loop operation are achieved.

[Michael Savage]

I've seen hundreds of vehicles, lawn mowers and stuff only running off flammable vapor since it combusts faster and creates less heat in doing so running fine for extended amounts of time. 1 guy has been running his car like that since 07 and hasn't had any issues. Pretty much turning a Throttle Body into a vapor carborator lol

[Garrett Powered]

you mean different AFR's than what reg gas uses? runs on leaner than 14.7/1 or sum?

[skitchin]

One reason E85 or even pure ethanol makes engines run cooler is because alcohol's stoichiometric ratio is much lower, requiring more fuel to achieve target ranges. I'm guessing the fuel absorbs cylinder heat during the compression stroke, so the more fuel you flow the more heat is removed.

 

[TABLE=width: 157]

[TR]

[TD]Gasoline stoichiometric[/TD]

[TD]14.7[/TD]

[/TR]

[TR]

[TD]Gasoline max power rich[/TD]

[TD]12.5[/TD]

[/TR]

[TR]

[TD]Gasoline max power lean[/TD]

[TD]13.2[/TD]

[/TR]

[TR]

[TD]E85 stoichiometric[/TD]

[TD]9.77[/TD]

[/TR]

[TR]

[TD]E85 max power rich[/TD]

[TD]6.98[/TD]

[/TR]

[TR]

[TD]E85 max power lean[/TD]

[TD]8.47[/TD]

[/TR]

[/TABLE]

 

 

Even with such widely different target stoich values, E85 generally requires about 30% more fuel over regular gas, so the difference would be quite noticeable if converting between the two fuels. Now with all of this in mind, running slightly more rich probably isn't going to make much of a measurable difference, but as Saar said it might make the difference of detonation if you're pushing the timing. I don't know if it would heat the exhaust per-se especially if you go near or past rich stoich, because that's exactly what the computer does for COT(cat over temp) protection.

[Michael Savage]

Not exactly what I'm talking about is instead of the cylinders turning gas from a liquid to a gas then burning I want to only use gas instead of liquid. Which we've made work on a 5.9l Dodge and we're working on applying it to anything but there's this rumor the reason the engine dumps 60 to 90% of the gas liquid input out the exhaust is to cool it. Which so far with testing it doesn't make a difference running gas in gas form or liquid form and actually gas form shows dropping exhaust manifold temps by 30*F so far.

[Schurkey]

there's this rumor the reason the engine dumps 60 to 90% of the gas liquid input out the exhaust is to cool it.

Total, complete and irresponsible bullshit. Gasoline is a hydrocarbon (HC). HC emissions are regulated by Federal (and state) laws. Fifteen minutes of searching for Federal HC emission levels would dispel this "myth". What do you suppose would happen to a catalytic converter forced to deal with that much HC emission? What are the permissible HC levels of a pre-catalyst vehicle? What happens to carbon monoxide (CO) emissions when a fuel mixture goes rich? What are permissible CO emissions for pre-catalyst vehicles?

 

Which so far with testing it doesn't make a difference running gas in gas form or liquid form and actually gas form shows dropping exhaust manifold temps by 30*F so far.

1. HOW are you measuring exhaust manifold temp?

2. Is the Air/Fuel ratio IDENTICAL for normal atomized-liquid gasoline induction vs. gasoline in gas form? How are you checking air/fuel ratio?

3. You can pretty much expect to reduce power level when you use gaseous gasoline. It's no surprise that reducing available power will result in lower exhaust temperature. You're traveling ground already covered by Smokey Yunick; he used a turbo to add a pound or three of intake pressure to make up for the loss. Gasoline in liquid form takes up less space than gasoline in gas form. Therefore, if you try to induct gasoline in gas form, there's less room for the air. Adding intake pressure restores the full air/fuel charge, but sucks in terms of expense and complexity. For virtually all "normal" uses, the best possible induction provides (atomized) liquid gasoline past the intake valve, but in droplets sized small enough to completely vaporize from the heat of compression just as the spark jumps the gap. Even then, whatever isn't vaporized at the time of the ignition spark, still has a chance to vaporize as the heat of combustion begins. Controlling the gasoline in liquid form is the big challenge; it wants to separate out of the air stream and run like a river in the bottom of the intake manifold and intake port.

 

 

Aircraft run (or at least USED to run) rich mixture to "fuel-cool" the engine, but it's along the line of using a "power" mixture when the engine is in "cruise" conditions. (10:1 or 12:1 rather than 13:1 or 15:1) We are NOT talking about "60 to 90 percent" of the gasoline going out the exhaust. At least that's what I understand from reading a couple of books about WWII aircraft engines. They were real proud of achieving .5 pounds of fuel per horsepower per hour. This would not be so bad, except that they were talking about cruise-power instead of full-power; and modern race engines are using less fuel than that for full-power.

Edited June 27, 2014 by Schurkey

[Michael Savage]

Laser Temperature Gauge

And the way I'm applying it you can do a dual application for MPG and Performance takes about 5 minutes to switch between the 2 so you can have both applications. I did notice running that way (with the retarded rig we made) it did loose a bit of power but it didn't use any gas so we were like this is awesome. For everyday driving it's wonderful and it takes like 5 minutes to get your performance back.