How precise is your fuel mix?

[OM617YOTA]

Question: I've heard that the gasoline in 2mix helps cool the engine by using the heat of the engine to evaporate the fuel. So does reducing the amount of gasoline in 2mix (by increasing the % of oil) cause 2T engines to run hotter? (I guess I'm assuming that the oil in the 2mix is not "evaporated" or "converted into a gas" in the same way as the gasoline is before it gets burned.)

If reducing the % of gasoline in the 2mix does make the engine run hotter, I wonder whether that additional heat is offset at all by reducing the heat of friction by adding oil.

It's kind of an academic discussion, but interesting, at least to me. Testing lab to the courtesy phone!

Don't just dump in a new fuel mix and leave it at that, make sure you tune for your mix. Tuned properly, there's no less fuel going into the engine with a richer fuel : oil ratio, just more oil.

Whatever you run, 16:1 or 100:1, tune for your mix.

 

[HansFranz]

Tuned properly, there's no less fuel going into the engine with a richer fuelil ratio, just more oil.

Oh, OK, I think I follow you. So if you run 16:1 you would richen it up compared to 50:1. Thanks.

 

[OM617YOTA]

Oh, OK, I think I follow you. So if you run 16:1 you would richen it up compared to 50:1. Thanks.

I actually don't subscribe to the more oil means less fuel idea. The oil burns and contributes to the fuel content of the mix. I've run 50:1 in a saw that was tuned for 40:1, and had to richen it up to be in proper tune with 50:1.

Regardless, tune for what you're running. Despite our collective fixation on oil threads, far more saws are destroyed by poor tuning than running 44:1 vs. 50:1.

 

[lloyd786]

When mixing fuel how precise are you?
50:1 uses 2.6 ounces to a gallon. Do you use 2.6 or round off to 3 ounces?
40:1 uses 3.2 ounces. Do you use 3.2 or round up to 3.5 or 4 ounce?
Does using a little extra lessen performance?

I pour 8 oz out of the bottle according to the marks on the bottle and then put 2 gallons of gas in the can (according to the gas pump) shoot roughly for 32-1. I have saws that are used hard almost every day, one is 15 years old and never had engine work.

 

[HansFranz]

Regardless, tune for what you're running. Despite our collective fixation on oil threads, far more saws are destroyed by poor tuning than running 44:1 vs. 50:1.

OK, thanks. One last follow-up question: If you use some off-beat mix like 16:1 (or 10,000-to-1 for the Amsoil folks) can you still generally rely on tuning by ear and listening for the 4-stroke burble or flutter at WOT that cleans up under load -- and be good/safe?

When I started messing with chainsaws, I tried tuning with a tach, but I found that I trusted "tuning by ear" more, and now I never even use the tach. I use 40-to-1 and will continue to tune by ear when using that mix, but if I ever get a saw that needs something different, will tuning by ear still be trustworthy?

 

[OM617YOTA]

OK, thanks. One last follow-up question: If you use some off-beat mix like 16:1 (or 10,000-to-1 for the Amsoil folks) can you still generally rely on tuning by ear and listening for the 4-stroke burble or flutter at WOT that cleans up under load -- and be good/safe?

When I started messing with chainsaws, I tried tuning with a tach, but I found that I trusted "tuning by ear" more, and now I never even use the tach. I use 40-to-1 and will continue to tune by ear when using that mix, but if I ever get a saw that needs something different, will tuning by ear still be trustworthy?

I've run 16:1 a few times (not on purpose), gallons and gallons and gallons of 32:1, gallons of 40:1, and a little 50:1, and tuning to burble out of the cut and clean up in the cut has worked for me. I'd be confident tuning that way for the ratios I've run.

Super lean fuel to oil ratios, I've no clue about tuning for those, as I wouldn't run them. Even 50:1 is leaner than I prefer. Oil is blood for an engine, and I wouldn't run 100:1 in my saw any more than I'd drain 2/3rds of the blood out of my body and then go do physical labor.

 

[Abbeville TSI]

I'm using Red Armor in the 1 gallon mix bottles. I dump the the 2.6 oz +or- into a measured 128 oz (1 gal) container and then fill to the 128 oz line. I dip the little oil bottle in the measured gallon and rinse it. Not into production just a little TSI, retired so never in a hurry!
My saws and other 2 stroke equipment are stock.

 

[KASH]

The old Lawn Boy mowers with with plain bearings called for 16 to 1.
The newer bearing type 32 to1
Kash

 

[echomeister]

not very precise but good enough

 

[Vintage Engine Repairs]

I try to be accurate, but always lean towards a bit too much oil than a bit too little.