I run 100LL in my Cessna, all it does is foul the plugs every couple thousand hours. The lead content is so low, and is only there to cool the engine.

 

Pretty much the truth. While greater efficiency is obtained out of more advanced timing and higher compression, and higher octane allows for both, the energy and cost factor of refining such fuels outweighs the cost/efficiency benefit in the engine. Since most manufacturers design their engines around 87, 87 is the way to go with out either mechanical or computer modifications. In fact, some non scientific trials with cars that say they require 89 or 93 show that many dont actually need it.

So keep the 93 for your stallion and the 87 for your mule.

 

advancing timing is moving the timing BEFORE TDC. If you move the timing close to TCD it would be 0 degrees of timing. if timing is 10 degrees advanced it is 10 degrees BTDC (Before TDC)

Knocking also can happen from the timing being too far advanced, knocking is not the proper word, it is Pre-Ignition or Detonation.

 

If you retard the timing you are firing before knocking happens.

I see that my terminology was wrong. Still, my point stands. :)

 

if you retard timing, you are firing after the piston reaches TDC, this isnt where the timing is supposed to be
try retarding your timing and keep it running right and not overheat, let us know how that works out lol

 

I believe the lead content is for both anti-knock and lubrication. I don't think it is for cooling however without it, it would most likely overheat and eventually fail due to the detonation and excessive wear. A few thousand hours on plugs before they foul? Are you sure you don't mean a few hundred hours? Or if its a flight school where students are afraid to lean the mixture, a few hours.

Of course like anything else in aviation, it will probably break anyway and you'll still have to pay out the *** to have it fixed. Just when you think it cost a lot to learn how to fly, you then realize how much it costs to keep flying once you know how!

What kind of Cessna do you have?

 

A 172 M, The float edition. But I have it on wheels. with a 160 lycoming piped.

 

When I had my Cadillac Catera which was to be run on premium (91 octane), when gas prices started hitting well over $1/L, I started putting 87 in it with no ill effects. The owners manual said I could run 87 in it, but could cause decreased performance or pinging. I never had any ill effects until my timing belt decided to grenade the motor....and that was just because it was a 3.0 GM engine that was prone to doing so.

 

Sweeeeeet. There a guy out here who has a grand caravan on floats. The thing is a MONSTER jacked up on those floats. He used to come into N04 before it closed. All 1800ft by about 20ft wide. I'd swear he'd have it the reverse range before he hit the ground.

 

Oh yeah, Prob Air breaks with vaiable pitch, the prop just turns around on most

 

Yea on those when you pull the throttle into the reverse range, it reverses the pitch of the blades. Its a pain in the *** landing a warrior or 172 on that runway. And this guy comes in with that beast.

 

CBFranger, one thing going for you is confidence but that does not make you right no matter how much you think you are.

Where in auto-mechanics 101 does it state that "advancing the timing is moving it closer towards TDC"? You should ask for your money back, they didn't teach you very well. Typically full advance on an engine is around 32 degrees Before TDC. If you advance the timing it will be a number greater than 32 degrees Before TDC (like 34 degrees BTDC). That makes it farther away from TDC. Retarding the timing moves the timing closer to TDC until you go After TDC. If you are stupid enough to time an engine After TDC, I will not waste my time on this discussion anymore.

Knocking happens because of more than two reasons but I don't want write a book here trying to explain it. Gasoline is made up of mostly hydrocarbon molecules not carbon chains. I am not going to discuss the rest of your attempt at chemistry because you obviously do not know what you are taking about. Here is something for you to consider. Toluene, it is used to boost octane and is very good at it. It is a cyclic aromatic hydrocarbon and is not a chain.

I quote you "higher octane can advance the timing". I only read what is written. Maybe a writing communication class is in order for you. I really don't need to benefit my life. I am very comfortable with my career as a successful Chemist in the Aerospace industry for more than 30 years.

 

OWNED!!!

 

All of the above, plus few people buy it, so think of how long it's been sitting in storage...probably more water in it then anything. Causes major problems with guys that have high compression snowmobiles and need premium. All they do is clean ice out of their carb bowls.

 

More dis-information from a supposed expert.



There are two issues.
1) Energy in the fuel
2) Octane

Energy in the fuel is something thats not known about much. And so you internet arm chair quarterbacks just don't have a clue.
Here is a start

Octane is nothing more than the fuels ability to *not* detonate. The popular perception is that the higher the octane the slower it burns. Not true.

Our stock tune runs in the 28deg area for hwy speeds / throttle position. And the knock sensor has about 5-7 degrees it can advance timing.
Get your self a high quality 87 octane and you'll go further per gallon. Get yourself a low quality 93 octane and you'll go shorter per gallon.

The secret is to run a high quality 93 octane and increase the timing.
This is what I've done and it works.

If I was stuck with a stock tune.. I'd run shell 87 and call it good.

Rich

 

Excuse me? What exactly did I say that was wrong? Nothing you quoted from me had anything to do with what you wrote. If I'm wrong, then you are you claiming that running 93 in an engine tuned and designed for 87 does not degrade performance or cause the other issues I stated? Yea ok. I agree with everything you said. What the hell are you talking about?

Either you quoted the wrong person, you read it completely wrong (which is hard since it is in plain english), or you are smoking something.

 

My '00 4.0 4X2 does exactly the same
Avg. is 17-18 on 87, 14-15 on 93

 

I'm still waiting for an answer on how I'm wrong. I can only assume by him no longer posting in this thread that he knows he's mistaken and doesn't want to admit it?

 

I've not been on the net much in the last two weeks. Let alone paying attention to threads where guys play armchair expert.

It's not degrading "performance". By performance I take it you mean power. Octane has nothing to do with the energy in the fuel.

MPG reduction? No it's not. MPG is directly a function of load. Load goes up and more fuel is added. Load goes down and fuel is taken away. The more energy in the fuel.. the less that will be used because of "load".

Matt, you clearly don't understand what your MBT table is, what it means in your tune, and what your KS is doing. If you did you'd not make such bold and arrogant statements.
As a point of reference.. I've been working on MPG gains with differing octanes and tuning my fuel - timing (SCT PRP). MPG gains between 87 octane and 93 octane with the timing adjusted for each, really is not much different. The B-I-G gains come from using a quality fuel. I've found that shell 93 V-power and adjusting my timing to the same thresholds as the stock 87 tune, has resulted in the best gains. I step back to a off name fuel and my KS readings are the same. But the loads go up and so does the fuel consumption.

I'm tellin ya.. it's not octane. It the energy in the fuel!


Long term carbon build up because of excess octane? Wrong again. Actually you'll have less carbon build.. but not because of the octane. More than likely the more expensive fuel will have better cleaners in it. That is subject to the brand though. There is only one company that I know of (who's not a top tier supplier) that has more additives in their high octane. And that's marathon. I only know that because I so happen to know an executive in the company who told me they only add it to the 92-93 octanes.


Rich

 

Sorry Rich, but here is another example of you being DEAD WRONG!!! Matt is correct, running high octane gasoline in an engine designed for 87 octane WILL carbon up!! Ford even came out with a TSB about this:






Many people believe that “premium” gas is the best gas. Not true. Premium simply means “premium price” for higher octane. Octane is a simple measurement for a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders.

Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump. The misnomer about octane is that the higher the rating, the better or more smoothly your car will run. In fact, premium gas can be bad for your engine if it was not designed to run at a high-octane level.

Although it may seem that the term “premium” or “high octane” implies that more energy is available, premium gas does not produce more energy than regular or mid-grade fuel. The octane grades are designed to accommodate engines with different compression ratios. High compression engines, found in most performance cars, require a fuel that burns efficiently at a higher temperature. That’s what premium fuel does, it burns hot under high compression. In a normal engine, premium fuel does not burn completely, resulting in excess carbon build-up and carbon fouling of the spark plugs. The end result is a less efficient engine that requires tune-ups more frequently. Oh, yeah, did I mention it also wastes money?
The only time you might need to switch to a higher octane fuel is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars. Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.




Ford TSB:

Article No:
01-19-7

10/01/01

^ ENGINE - 4.0L OHV - CARBON KNOCK ON ACCELERATION

^ NOISE - CARBON KNOCK ON ACCELERATION - VEHICLES EQUIPPED WITH 4.0L OHV ENGINE ONLY

FORD:
1990-1997 AEROSTAR
1990-2000 EXPLORER, RANGER

ISSUE
Some vehicles equipped with the 4.0L OHV engine may exhibit an engine noise which may be perceived by the customer as a piston/connecting rod bearing knock. This carbon knock is heard only under load during the drive cycle. Carbon knock is a customer drive duty-cycle phenomenon that cannot be repaired with an engine exchange. This may be caused by carbon build-up within the combustion chamber.

ACTION
Verify condition. If normal diagnostics fail to correct the condition, de-carbon the combustion chamber to help quiet the carbon knock noise. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

1. Use Motorcraft Carburetor Tune-up Cleaner PM-3.

2. Carbon removal:
a. Disconnect canister purge line from throttle body.
b. Attach a vacuum line to the canister purge port.
c. At hot engine idle, allow the engine to ingest 1/2 to 2/3 of a can of Motorcraft Carburetor Tune-up Cleaner. Use caution not to ingest too quickly due to potential hydro-lock issues.
d Shut engine off and allow it to soak for one hour.
e. Start engine, allow engine to ingest the remainder of the Motorcraft Carburetor Tune-up Gleaner.
f. Remove vacuum line and re-install canister purge line.
g. Road test vehicle at 3500 RPM for 2-3 miles.
h. Repeat above procedure two times for a total of three times.
i. Change oil and filter.


3. Review the customers' driving habits. The recommended drive cycle should include daily periods of engine operation above 3,000 RPM, such as a brisk acceleration from a stop position. This will break/burn the carbon off the piston head.

4. Use regular unleaded fuel, 87 Octane. Mid-grade and Premium fuels may increase the probability of carbon buildup, leading to a knock noise.


And on a Ducati motorcycle:

So for my 6000 mile service (actually had about 7100 miles) the valve guides, and exhaust valves had to be replaced. This is a potential problem with all of the 1000ds motors and something people should be aware of. Bad valve guides may also contribute to the surging/poor running of the bike and compound the problems may of us have had at low rp, and have ascribed to O2 sensor/closed loop running problems. Anyhow, be aware...

Another thing; there was a huge amount of carbon build up on the intake valves and inside the cyclinder head. Now, I have been reading the octane threads, and have run 93 r+m/2 in the bike. I was advised that this may be responsible, at least in part, for the huge carbon build up on my intake valves according to the Ducati techs that did my service (BCM). They said I should run 87 in the bike because there is no need for 93 as the efficiency of combustion in the 1000ds is high and the compression ratio is relatively low. Another factor that may have contributed to carbon build up is running the bike at constant rpm and that I should rev it hard (not abuse but rev it hard). They also recomend running 12 oz of Techron (Chevron) thought the bike every 3000 miles.

 

???

 

Seriously. What are you smoking.

I don't care what freakin' section of the periodic table of the elements is causing it. It doesn't matter what MBT timing blah blah whatever I allegedly don't understand. Let me try to restate this so you can understand what I've said several times.


IF YOU PUT A FUEL IN YOUR TRUCK THAT IT IS NOT TUNED TO MAKE PROPER USE OF, YOUR PERFORMANCE AND MPG WILL GO DOWN.

Period. End of story.

So to recap. You deny that putting 93 in a truck tuned for 87 will hinder performance and mpg? Because thats all I've been saying and you keep saying I'm wrong. I suppose the sky is purple too, then?

 

It's not just tuning Matt, the biggest factor that determines octane requirements is compression ratio......

And I absolutely hate it when people post WRONG INFORMATION on R-F!!! I see a pattern.......people hear technical "buzz words", don't have a clue what they mean,
and try to use them!!!!

 

You guys are a lost cause. Bob generalizes everything down to what "ford says". Then calls me a liar because he can't understand something that's not published by Ford. And you Matt. You just flat out ignore science because it doesn't fit your paradigm. And you ask what I'm smoking?

ok guys.. you win.


Goodby and peace. And for the rest interested in this subject. Here is another lie based on science.

Rich

 

Rich, just as in the past, I've shown references to high octane fuel causing carbon build up (other than Ford) in engines not designed to run high octane.
How about you showing something that says it doesn't??????

This falls in the same category as thermostats, MAF sensors, K&N intakes and filters, motor oil, etc..........