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Only if you make some other modifications Posted by Ari [Email] ![]() ![]() In Reply to: poor man's intake hydration (increases gas milage), MS, Sun, 24 Apr 2005 11:29:14 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Yes, a more dense combustion charge gives more power. As I understand it, that's what the turbo is for.
But humid air is LESS DENSE than dry air. A water molecule has two hydrogen atoms and one oxygen atom. Hydrogen is about as light as you can get, mass wise. Air is about 80% nitrogen, 20% air. So water molecules take up space that oxygen and nitrogen molecules would, and since water vapor is lighter than air, it is less dense. Don't beleive me, check out http://www.usatoday.com/weather/wdensity.htm
But that has really nothing to do with fuel mileage. The engine control is going to adjust fuel to meet the stochiometric ratio of the amount of air going in. And bubbling air through the water does nothing - first, air is only 20% oxygen, and second, the water vapor is already vaporized - it contains no additional oxygen.
Why water injection? Because it cools down the combustion chamber, and that can be a good thing. It can also be a bad thing. It can be bad because if done incorrectly, it pulls heat away and prevents complete burning of the intake charge. Very bad. When is it good? It's good when you take an engine and crank up the compression ratio, which tends to cause knock. The additional water helps keep the charge cool and prevent knock. It's not there for fuel economy - it's a way to pull a little more heat away when you've got an engine running at it's limits.
OK, why are turbos happier on cool, wet days? Actually, they're happiest on cool, DRY days. The cool air is nice and dense, and contains the most oxygen. And after the turbo compresses and heats the intake charge, the Cool air over the intercooler sucks that heat away. On a cool, wet day the moisture in the air may also help to make the intercooler more efficient. But the intake charge is less dense to begin with.
If this water infusion idea was true, cars would be happier on warm, wet days than on warm, dry days. I haven't noticed that.
The only way I'd see this working is if you were to intentionally lean out your mixture, and then keep the combustion chamber temps down with water. You'd suffer some performance, but may get an incremental fuel milage increase. Assuming it didn't screw up and melt the pistons.
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