Fuel burn with 0-235

[Dave in Eugene]

I know that Don Denhart has figured out how to get his fuel burn way down to very little for pleasure flying.

I'd like to hear what you guys use for rpm and expected fuel burn.. I have the 0-235 l2c and am especially interested to hear what similar set-ups expect.

Thanks,

Dave

[Waiter]

My setup is a little different (constant speed prop) However, I apply these rules even if I have my old Great American fixed pitch prop installed.

Heres what I do;

I generally cruise at full throttle and 2300 RPM, regardless of altitude.

LEAN LEAN LEAN.  I have 8.5 / 1 pistons, so I generally operate as lean as I can (with the exception of high power modes, like takeoff).

AUTO FUEL. The use of Auto fuel reduces my operating cost by about $1 / gallon. On average, about 75% of the fuel I burn is auto fuel. This percentage is based on auto fuel availability. i.e. when I'm on a trip, I burn 100LL simply because thats whats at the pump. At home, its 100% auto fuel.

TAIL WINDS - Fly as high as tail winds permit, generally, on long distance flights, South-west to North-east, is flown at 17,500 or even FL210 or FL230. This is almost always good for a 50 kt tail wind.

Avoid head winds - find an altitude to provide best ground speed.

If time or speed isn't a factor, reduce throttle setting AND/OR lower rpm to 2100 or even 1900. (constant speed prop)

Regardless of throttle setting, lower RPMs produce lower HP, equates to lower fuel burn.

Although the O-320 power/RPM curve isn't linear, At sea level with full throttle, I figure approximately 10hp per 100 rpm when operating between 2100 rpm and 2900 rpm (2700 rpm will produce rated 160 hp).

This is one of the Apples/ Oranges comparisons I see when someone compares a constant speed prop to a fixed prop. A fixed prop turning at 2900 rpm is producing about 180hp. A constant speed prop at 2300 rpm is only producing about 120 hp.

Hope this helps a little.

Waiter

[Dave in Eugene]

"AUTO FUEL. The use of Auto fuel reduces my operating cost by about $1 / gallon. On average, about 75% of the fuel I burn is auto fuel. This percentage is based on auto fuel availability. i.e. when I'm on a trip, I burn 100LL simply because thats whats at the pump. At home, its 100% auto fuel. "

 I have read that auto fuel and our glass birds are a bad combination...something about certain additives reacting with the composite... I''ve wondered if this is bull as I met Fergus Fay in Roseburg who built and still fly's one of he 1st Vari-Ez's and always run auto gas....

The 0-320 / 160 hp is not certified for auto fuel if my memory is right...the 150 hp is right...

Thoughts?


"LEAN LEAN LEAN. I have 8.5 / 1 pistons, so I generally operate as lean as I can (with the exception of high power modes, like takeoff). "

Can you help my understand how compression relates to Leaning...thx

Dave

[Drew]

With high compression pistons, you just have to be a little more careful with leaning.  The higher force with the higher compression-----mixed with lots of heat from aggressive leaning (leaning towards peak temps)----and mixed with being at 75% or greater----can be a bad combination.

Under normal conditions, don't aggressively lean until below 75%.  With high compressions pistons----be a little more careful.  Don't know that I can tell you what a little more careful is.  If there is a rule of thumb, I'd like to know too.

[Waiter]

As for auto fuel, I've always burned it. Before my EZ, I had an O-320 160hp Cherokee. I had the EAA STC for it.

Additives like MTBE and Alcohol that are (were) used in auto fuel can degrade epoxy, Fortunately, MTBE is no longer used (Not only is it bad for epoxy, it also causes cancer). However, Alcohol is becoming a popular additive. Fortunately, its easy to test for, it absorbs water.

I stick to popular name brand fuels, and I always top off the cars tank at the same time I fill the airplane containers.

As for leaning;

If you run higher compression pistons (greater than 8.5 /1) you can start having pre-ignition problems with the lower octane fuel. A hot spot in the cylinder will ignite the mixture before the ignition system. This causes two problems, Its like whacking the piston with a BIG hammer (the "pinging sound" and it further heats the hot spot. Pinging is aggravated by a combination of these; lower octane fuel, very lean mixture, high compression pistons, hot cylinders.

One of the big problems with Aviation "pinging", you won't hear it, like you do in a car, so you don't know its happening.

Remember , I said a rich mixture "cools", without the cooling the "hot spots" are heated up faster.

The best way to avoid "pinging" is to don't get aggressive with the leaning until the power output is less than 75% of the engine rating as determined by altitude, throttle setting, manifold pressure. I lean a little but I usually don't try for 25 deg below peak until I'm below the 75% power factor.

Waiter
 

Waiter

[Joe Dubner]

I'd like to hear what you guys use for rpm and expected fuel burn.. I have the 0-235 l2c and am especially interested to hear what similar set-ups expect.Dave

Dave,

My Long-EZ has an O235-L2C turning a Hertlzer prop.  On any kind of XC (75 NM or more) I generally cruise above 10,000 MSL (higher when possible) and lean to LOP as best one can with a  carburetored engine (WOT).  RPM is generally above 2500 and TAS about 145K.  I flight plan at 5 GPH and always achieve that or slightly better.

BTW, this is on 91 octane mogas (always tested for absence of alcohol) except for TO, initial climbout, and landing.

For low altitude hair-on-fire flying such as a R.A.C.E., everything is different of course.  100 LL only, leaning for max power (or acceptable CHT/oil temperature), and fuel burn around 8 GPH.  Oh yeah, and better than 170 KTAS  :-)

--
Joe

[Dave in Eugene]

How do you test for Alchohol? ...thanks for the info... I need to set up for o2...any advice on this one?

Dave

[Joe Dubner]

How do you test for Alchohol?

I use a small glass bottle about the size and shape of an AA battery.  I placed a mark at about 10% of its volume and fill to exactly that level with water (just a few drops).  Then I add fuel enough to almost fill the bottle.  Shake for a few seconds and the water is combined with the fuel.  Allow it to settle for a few minutes and look at the level of the water in the bottom of the bottle.  If it's right on the mark the fuel is pure petrol; if alcohol is present the water level is _above_ the original mark.

It's my understanding the EAA sells a test kit but I have no firsthand knowledge of it.

I need to set up for o2...any advice on this one?

I use a medical oxygen cylinder and individual flowmeters (p/n 13-00131) and cannulas (p/n 13-00140) from Aircraft Spruce for each cockpit.  The advantage of medical oxygen over aviation is in the cost of getting it refilled when XC.  (Keep a copy of your prescription in your aircraft).  Originally I used a D-size cylinder but have traded it for a "Super-D" since my girlfriend decided she wanted to breathe at altitude too :-)   E-size would be better (more O2) if you have room.

Makes all the difference in the world with respect to feeling good after a long day flying even when not required by FARs.  And having O2 gives options (like popping up to 15,500 MSL) to get above the clouds, rough air, not to mention the terrain.

--
Joe

[Dave in Eugene]

thank you Joe,

I will look for some kind of container to use your alcohol test.  Sounds fascinating.  What brands of fuel have you found in the past that to use alcohol?  What brands have you found to be reliable in not using alcohol?

Mounting an oxygen bottle will be a good test for me.  I'd like to see a few other people's setups to see how you done it.

Thank you for the information.

Dave

[Drew]

Here is a cool installation...

http://www.berkut13.com/berkut52.htm

[Joe Dubner]

What brands of fuel have you found in the past that to use alcohol?  What brands have you found to be reliable in not using alcohol?

It's not a question of brands -- it's a matter of location.  Oxygenated gas is government-mandated in many localities especially in the winter.  Here in the Lewiston, ID/Clarkston, WA area it is not but it's a different story in Phoenix, for instance.

BTW, I never got around to mounting my oxygen cylinder; it rests in my right strake.  This is not a bad solution as I'm able to access the regulator and turn it on in flight if I so decide.

--
Joe