An acetone success

Discussion in '2-Stroke Engines' started by Flapdoodle, Nov 20, 2008.

  1. Flapdoodle

    Flapdoodle Member

    I had tried acetone on my car without any real increase in either performance or economy, but wanted to see if it would make any difference on my HT 80.

    Proponents of acetone recommend 3-4 ounces per 10 gallons of gasoline. For the 1/2 gallon tank on my bike this works out to about .2 ounces.

    I got the engine running on the fuel that was already in the float bowl, got it cruising about 15 MPH. It had the familiar 4 cycling sound.

    When the acetone mix reached the carburetor, there was a noticeable difference in sound with it 2 cycling in spurts a few times with an accompanying feel of acceleration. Then it settled to 2 cycling at a somewhat greater speed. I took it to town and around town. It was much smoother for the entire tank of gas, with easier starts. (my engine is not great on starting). Cold starting on successive days was also encouraging.

    I know from working with cars that what works on one may not work on another seemingly identical engine. Also, I am NOT recommending acetone since I do not yet know the long term affects on plastic, fuel line items, and gaskets. I have two spare carbs so I am not taking any great chances trying this. Besides, .2 ounces per tank does not seem like a great amount of dilution.

    As I learn more I will update it here.


  2. bluegoatwoods

    bluegoatwoods Well-Known Member

    Yes, please keep us posted. It sounds interesting.
  3. BSA

    BSA Guest

    I would hazard a guess that the flamability of acetone reduces the octane of the fuel to a level more suitable for HT engines.

  4. fetor56

    fetor56 Guest

  5. DIYMark

    DIYMark Member

    Acetone breaks the surface tension of the petrol so that it vaporizes better. This then reduces combustion time of a cylinder of fuel/air mix. So it basically speeds up the power stroke.

    This will mean that your engine should rev higher and smoother (smoother ride and better top speed) as the combustion is taking less time.

    Also because of this your torque (bottom end) dies. This is because having a "longer" combustion time favours the low RPMs. So with acetone the power stroke is short and sharp which at low RPMs causes negative outcomes.

    Ill gladly try acetone next time I can get some! My HT 80 (as it currently is tuned) creates monster torque. Its like a tractor, my highway speed and uphill speed is the same (needs gears) you can even do wheelies on my bike :biggrin:

    So I want to double check what I said and see if in fact my torque does die at low RPM.
  6. Flapdoodle

    Flapdoodle Member

    You beat me to it. I was about to post almost the same thing. Theory is acetone breaks the surface tension in a manner similar to soap on an oil slick. It takes only a very small amount to accomplish this. I wonder if having all that synthetic oil mixed in my gas tends to make it harder to vaporize.

    Proponents of acetone claim you must have 100% and most sources are not that pure. They say to buy from Sally's Beauty Supply common in most cities. Mine came from Ace Hardware in the paint section. If I remember it was about $7 for a pint.

    The .2 ounces I mentioned is about 1 and 1/2 teaspoons per 1/2 gallon tank. I could get 80 tank fulls (or is it tanks full? :wacko2:) from a $7 can.

    Somewhere in here I saw a recommendation that premium gas be used in these tiny engines. Sounds like overkill, but I will get a few gallons next trip into town, and will report on it here when weather permits.

    So far the acetone has not changed the float into glob that looks like half chewed Halloween candy.
    Last edited: Nov 21, 2008
  7. NunyaBidness

    NunyaBidness Member

    I have only seen the opposite, since the HT has a very low compression it is better to use the lower octane.
  8. fastboy9

    fastboy9 Member

    Nice! I have a bottle of it in the garage, but I use mine quite often to clean oil off of things as it breaks it down. Is that not a worry to the lubrication?
  9. DIYMark

    DIYMark Member

    The car Boys are adding 2T oil to their 4T cars to over come the apparent fact that "Acetone reduces lubricity".

    However, I did the calculations and for 1 litre of fuel you need 2ml of 100% Acetone (I managed to find some :pinch: :) ) Thats a dilution of like 0.002% (or 500:1) and that is so small I doubt there would be any negative effects on oil or seals.

    Then again some people think that if it inst enough to effect seals its probably not enough to effect the surface tension of fuel (the sole reason why acetone works).

    Try this - get a bowl of water and sprinkle some ground pepper on it. Now put the tiniest drop of detergent on your finger and touch the center of the bowl.

    See, it took that pathetic amount of detergent to break the surface tension - so me thinks adding acetone is fine. However, I'm not after more economy (would be nice if it in fact does) but I'm after for the extra revs and smoother engine performance.

    Lastly if this tiny amount (500:1) of acetone does infact deteriorate lubricity in the engine - so what. These HT run of 20:1.

    25:1 is the richest Ive ever seen until I got a HT lol. Even then 25:1 is fairly rich ratio. None the less I do run Castrol Power 1 TTS now.

    Later today Ill give the Acetone a whirl at 2ml per 1L and I will use my "old" oil (I got fully synthetic today) so I can compare the bike to how it was before.

    Ill report back with what happens.

    PS - Acetone will also increase the octane rating by a tiny amount. Also the "racing" 2T oils also contain a shot of xylene in them so you get a tad more octane boost (probably explains why the oil I got today claims better acceleration times)!
  10. SirJakesus

    SirJakesus Guest

    I've read good things about xylene. Lots of hypermilers use a couple ounces to 10gal of gas to boost power and decrease fuel consumption. It can be had cheap in most hardware stores too.
  11. DIYMark

    DIYMark Member

    I went for a cruse and my cruzing speed and max speed have been "Shifted" forward by 6Km/h. In addition the engine is smoother but as I predicted Ive lost some bottom end.

    From now on I'll be adding acetone. At 2ml per litre my $10 investment (750mls of 100% Acetone) will last for 187.5 tanks of fuel! Ill be lucky if I have the same engine by then lol!

    Lastly the engine is easier to start - I don't need to use choke any more (only ever used 1/2 choke before otherwise it would die shortly after starting).

    So far the seals are holding up. But in addition Ive redone the carburetor gaskets with High temperature Loctite flange sealant as there was always a slow leak via the gasket.
  12. Flapdoodle

    Flapdoodle Member

    Thanks! Looks like you have verified what I found. The smoother running makes me a believer.

    As for diluting lubrication, I would be more worried that the large amount of gasoline would reduce it rather than acetone. Gasoline is a poor lube.

    A little off topic, but I added a fuel gage. Simply a tee off the main fuel line with clear tubing which is attached to the tank filler with a nylon cable tie. Gives me a little more peace of mind.
  13. fastboy9

    fastboy9 Member

    right! im convinced, in it goes...

  14. BSA

    BSA Guest

    Seems definitely worth a try, STP or Redex her in England seems to work well aswell.

  15. DIYMark

    DIYMark Member


    I'm guessing they are octane boosters. Many people say you only get benefits of them in high compression engines but that's false. Their "surface tension breaking" abilities give similar effects of Acetone.

    Speaking of compression I removed the bottom gasket (between the Crank case and cylinder) and used Loctite high temp flange sealant, in addition I milled my cylinder head by 1.2mm. Sounds like Ive got tons of compression but Ive also "Ported" my engine by filing the skirt near the inlet and at the exhaust and transfers because the exhaust in still not fully opened at TDB (2mm of piton still shows at the exhaust). Same for the transfers. The bottom of the transfer is lined up with the middle of the top piston ring at TDB - talk about a shoddy design lol.

    This then lowered my compression a bit but now its at around 8:1. However, the fuel around here is 91 octane for regular and premium is 98 (I only use 91 though) but adding fully synthetic oil (that contains xylene) and acetone is enough octane boost for me.

    Also the lightened piston happened to balance the engine lol! It revs smoother and higher plus the toque curve has stretched further into the RPM range (I can get a more "fuller" cylinder of fuel/air for longer in the RPM's = more torque).
    Last edited: Nov 25, 2008
  16. Flapdoodle

    Flapdoodle Member

    I looked at a Loctite catalog, and found 7 flange sealers. Some are acrylic, some
    silicone. What was the number of the one you use.

    Mild porting is on my list of to-do.

  17. DIYMark

    DIYMark Member

    I used the 510 sealant - its a pink paste.
  18. DIYMark

    DIYMark Member

    I double checked (I used it today while installing my boost bottle) and its definatley 510.
  19. Flapdoodle

    Flapdoodle Member

    I have about 400 miles now, bought a speedometer. One run without acetone I got it up to 29.7 MPH and could not coax it any higher. Added about 8cc of acetone and got it to 34 MPH. However the wind had come up so this is a bit higher than it should be. The t\return run only got to 25 against the wind. Hit a bump on this lousy back road and went airborne. I am too old to be doing that.
  20. fastboy9

    fastboy9 Member

    wow, acetone seems to be quite a performance enhancer then! in theory it should increase the low end torque because of the better combustion (so I've heard). And if it increases MPG whilst increasing BHP then that sounds like a nice mixture :)