How is Acetone supposed to work?

[dkjones96]

Beyond the first few days? A friend of mine says it's supposed to work because the acetone evaporates better and is supposed to make the fuel vaporize better so I asked him how that works when the acetone evaporates out of the fuel? He called me stupid for thinking that the acetone, once dissolved in gasoline, would evaporate any faster(wasn't that the point of it?).

So I did a little test and I took 3 identical glasses and put 1/2 oz of water in two of them and 1/2 oz acetone in the other. I then put 1/2 oz of acetone in one of the water glasses and stirred it to make sure it'd dissipated.

After a day, the water levels were equal and the acetone glass was dry. So how does acetone work beyond a couple of days(my tests show no gains but i'm curious)? Especially in cars where the evaporative emissions system is working properly?

[bobc455]

My understanding of the theory behind acetone was that it affects the surface tension of the liquid. This would allow the gasoline to break into smaller droplets after injection, giving a more efficient combustion.

Maybe I'm wrong...

-Bob C.

[bones33]

I think bobdc455 has it right.

Just for grins, fill two glasses with the same amount of gasoline, stir in acetone in one and re-test. Mark fuel level in the one without the acetone. I wonder if it's mix with gasoline will inhibit evaporation at room temp/pressure.

Anyway it seems the consensus is that it has a placebo effect. In using it people drive easier using mild hypermiling techniques and that is where the gain really is. I personally haven't seen any repeatable A-B-A or long term testing accounting for other variables that back the acetone gain claim.

But, I may be wrong.

[dkjones96]

I should go get a fuel injector from the junkyard with a regulator and pump and see if I can photograph a difference. If the gasoline injects at smaller droplets I should be able to capture that.

I've been wanting to see what the spray pattern is anyways so I could compare mine to others like these. I want the spray pattern second from the right.

[1bolt]

Acetone has been debunked it cleans out your injectors if they are varnished up. after that it is a waste of time and money.

The injector pic is interesting but the two injectors that have the best spray pattern (Bosch design 3 and either Denso or Bosch design 2) are also just about the only designs used (or copied) in the last 20 years. If you own a car built after the mid 90's chances are very good it already has the second on the right (Bosch design 3's)

[GasSavers_Gollum]

I've actually been wanting to get a test bench setup like that, so I can measure flow on my injectors at various pressures.

I love how the well the classic pintle works (farthest on the right), even compared to some of those other ones trying to be more "modern". My injectors are similar to the farthest right, with a slightly longer needle still. The nice thing about pintle types is that they're very unlikely to clog, and overall a bit more reliable, and usually offer more consistant flow/pressure ratio.

For all out economy the multi point Bosch clearly wins.

As for myself... I'll just put my injectors another inch up stream...

[1bolt]

the problem with moving injectors away from the intake port is fuel metering issues... It's an excellent way to maximize horsepower by allowing the air charge to mix more thoroughly with the fuel, but for economy (and emissions if you care) you end up with more fuel slamming into a closed intake valve, backing up the intake port and runner.

This means that other cylinders will have an opportunity to pull from this part of the charge (see inertial ramming or Helmholtz effect commonplace in modern EFI intake manifold designs), this can lead to overly rich mixtures in some cylinders. Odd fuel distribution is never good for economy.

It also leads to fuel being pulled out the exhaust when the intake valve opens back up, during overlap (intake opens while the exhaust valve is still closing). This last one is one reason why carburetors are generally less fuel efficient than multi point injection.

The OEM's put injectors right at the intake port for these reasons, best compromise of fuel metering, emissions and power.

if you're Drag racing (or if I am for that matter) we don't care so much about precision as cramming as much of it in as well mixed as possible

[GasSavers_RoadWarrior]

Another problem with moving injectors away is that at light load most multipoint systems are designed to spray against a closed valve, into a hot intake port that will evaporate the fuel off the walls. So if you have them sitting back a ways, the fuel will fall short into the cooler manifold.

[dkjones96]

The engines pulling fuel from another runner is strictly dependent on how the engine is configured. The runners on my stock manifold are about 18" in length. I could easily move the injectors upstream a bit and it wouldn't be an issue.