Mixture control on C85

[flyguy]

A long time ago I checked the mixture control parts on my 12D and found them to be in excellent condition so I installed a nice vernier control. I haven't been able to prove much of anything up until now except that on the ground at 1800 RPM the control will shut things down to about 1400 RPM with the engine stumbling along but not quiting. Which makes sense considering the way the carburetor works.

I have checked it a few times at altitude with little success, but yesterday I got an inspiration while talking to a fellow pilot about the 75% power, 8,000 ft thing.

So up again today to use a bunch of fuel to climb to 8,500 ft and check my idea.

I went to full throttle cruise at that altitude and tried adjusting the mixture control with the vernier thinking that full throttle is normally a rich mixture condition. It required several tries to be sure as keeping the climb rate to precisely zero was difficult. (so the RPM reading was stable)

I found that I could consistently get an increase in RPM from 2450 to 2500 at a stabilized cruise by tweaking the mixture with the vernier control.

Of course the RPMs would drop off as I screwed the adjuster further out. Fifty RPM. Not much for the effort and money. Interesting though.

Darryl

[Hank Jarrett]

Re: Mixture control on C85

I think what you are seeing is why mixture equipped planes mostly use the mixture control as a panel decoration. I would be really interested in anyone's input who gets in some nice Wave and gets up to 14,000 or 15,000 feet. I have a feeling it will start doing a LOT up there. Don't forget your O2!

Hank

[flyguy]

Re: Mixture control on C85

Thanks for mentioning 15,000. It triggered a train of thought that for sure is new and significant. That is:

I have had this 12D85 to 15,500, but going to 8,500 yesterday the ole' girl seemed to be rather doggy. Dropped to 500 per minute pretty quick and kept getting worse. About 300 ft min at 5-6 thousand. I think it might be the fuel.

I'm running 87 octane car gas WITH ethanol to what ever standard Calif uses. About 7 percent I think; less than 10% anyway. The last (and only) time I have been to 15K plus I was running 100LL. Since the ethanol molecule has a LOT of useless water (already "burned" Hydrogen) the power output is going to be less. It also occurs to me that the effective mixture would be leaner with the ethanol. It is likely not a engine damaging problem as I suspect it has a cooling effect on combustion temperatures. Reference use in high-powered engines in WWII for that very purpose.

As I mentioned before here I have been very pleased with the car fuel as it saved a leaded-up cylinder for me and typically runs excellent for the general flying I do. BUT---now I think I will run a test or two with maybe 50/50 and then 100% LL to see if there really are any performance differences. Zero chance that I will switch back for general flying, but if I should decide to go over the mountains it would be nice to know.

Think I may have to get some oxygen as you say, Chuckle.

Darryl

[Hank Jarrett]

Re: Mixture control on C85

I did some tests with 10% alcohol fuel and straight 87 octane lead free with NO additives. I measured the fuel consumption VERY carefully and did the tests several times to make sure the numbers were correct. What I found was I got 10% better mileage with the straight fuel over the fuel with corn in it. Kind of like the alcohol doesn't carry it's own load, kind of like it might as well be FILLER! There is a bit of a math trick buried in there, but you get the point. It COSTS MORE, does NOTHING for range or economy and now we hear it is actually WORSE for the environment! Add to that we are BURNING FOOD! Who are the idiots that DO this to us? WHY do we put them in office? Early tests SAID this would be the results, but no one would listen to the "planet killers" and we listened to the "environmentalists" with the flowers in their hair and air in their heads.

Hank

Rant over. Going back to work. We are our own worst enemy.

[M Towsley]

Re: Mixture control on C85

The corn growers state it is not food corn, but feed corn. Whatever...

[Hank Jarrett]

Re: Mixture control on C85

Makes good tortillas and chips! STAPLES in my house. ;-) The serious point is farmers are raising hard feed corn when they could be using the same land for our food. The problem with "green fuel" is adding alcohol is a net energy LOOSER. If we didn't use the left over mash as feed we would be better off just doing nothing than growing corn for fuel and in several states the "pure food" Nazis are pushing to make it illegal to use mash as animal feed (Beer mash is also in this class). If that happens we will have to put the left over mash in land fills. The ignorant members of the "save the world" environmentalists have done the exact opposite of what they intended because they wouldn't LISTEN to the scientists who told them this would happen. They claimed we were all in the pockets of the oil industry and being paid off. I wonder where MY checks were for all these years?

If this sounds like I am angry, far from it, especially with Mikes comments. I am just sorry to be found to have been right about a fight I fought decades ago when no one would listen.

Hank

And it AIN'T OVER YET!

[Marv]

Re: Mixture control on C85

Corn does not even make good drinking alcohol. There is several other grains that make better bootleg. The politicians that came up with this either owned farms raising corn or had close relatives in the business.

[flyguy]

Re: Mixture control on C85

We can take blame for that one out here. California was at the forefront of the ethanol in fuel thing. Just as you might suspect, one of our former state politicians owns the biggest ethanol plant in the country. No doubt he was building it as the ethanol law was being voted in (while he was still in office?)

We laugh at the corruption and bribing in third world countries, but we do the same thing here. We just make it legal.

Darryl

[flyguy]

Re: Mixture control on C85

Did something a little different today. I had around 4 gallons of auto fuel left in the tank from yesterdays testing so I put 5 gallons of 100LL in an took it up to 8,500 ft again. Right away I noticed an increase in the rate of climb so when I got to 8,500 I decided to see what effect the mixture had on rate of climb. I did not check that yesterday.

Bottom line is the combination of fuel change and leaning the mixture gave me another 200 foot per minute over the car gas rate when not leaned. I was at almost 9,000 by then and the steady rate was just short of 500 ft/minute.

I think I would have to do some more checks to see which helped the most, the gas type or the leaning. It could come to about 50/50. The lower altitude climb rate also seem considerably improved but it was too bumpy get any numbers.

Cruise at 75% at about 8,800 came to a GPS two-way average of 99 MPH. That is with the mixture leaned to peak.

When I came home the wind was 18kts gusting 22, 20 degrees to the right and on final I had the airspeed jump "instantly" from 60 to 80. (I was trying to hold 70). As you may imagine, I was very busy when I got down near the ground.

Overall a fun and productive morning, Chuckle.

Darryl

[M Towsley]

Re: Mixture control on C85

It is all about the lobbyists putting money into the politicians pocket to push ethanol. The fuel companies also get tax credits for using ethanol. Win-win for everyone but us.