Fuel Octane/Grade and cleaning effects

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Folks -

Hypothetical situation:

A bit older beater, been cleaned up real nice, crankcase real clean, no oil comsumption, engine in perfect tune, good compression numbers, ALL new hoses, rubber, belts, bushings, etc. Car generally nice, in an old perfect fit shoe, kinda ugly skin way.....got the picture in your mind?

One problem: Car still has combustion chamber (cc) deposits. The car pings like a marble factory on regular 87 (R-MON), medium ping on midrgrade, and generally OK on 92+. New car did not ping of regular and deposits observed with bore scope. Some liquid in the gas tank cleaners will tried before more radical approaches are attempted. The products are selected.

OK - Does (in general) the grade of fuel used with the in tank products make a difference?

Please resist the urge to push your favorite product (ok to mention how one or the other products works with this or that grade of fuel).

My null hypothesis: Regular fuel (ping and all) has a better cleaning effect when combined with in-tank cleaners. No science to back my claim - just crap flying out of the exhaust pipe.

[ February 26, 2003, 10:28 AM: Message edited by: Pablo ]
 
Hey fellow brickster. It’s been my observation that I an engine does not require high-octane fuel, it will run cleaner on the fuel it was designed for. For example, and this is only antidotal, when I run high octane fuel in my low compression Jeep 4.0, I get a lot of soot/carbon around and in the exhaust pipe. Standard 87 octane does not do this. My theory is that the slower burning high-octane fuel doesn’t fully combust, leaving behind lots of deposits. This, however, shouldn’t affect the intake valves.

Why not just run a slug of BG44K through it and be over with it?
 
I've read many good reports on the bg44k, no experience with it myself. Is there a spray can version? If so, it may be what Chrysler sells as their spray can combustion cleaner. If not, a can of the Chrysler spray cleaner, followed by an immediate oil & filter change, might just do the trick. Does bg44k have any octane-boosting effect? If it has a *Lot* of octane boost to it, might try using it in a tank of 87, but it would be safest to use a tank of Super Unl while cleaning, when you're sure chambers are clean, then go back to Reg 87. One (more)tank of super won't increase your deposits any, especially when running a good cleaner in that tank.
 
Pablo,

My guess is that it depends on your application. BG44K is a strong polyether amine (esentially pure "Techron"). In the past BG used to supply Chevron with the polyether amine for their use in fuels and additives. Don't know if this is still true. If it were me, I'd use it in regular unleaded.
 
Pardon my ignorance but what is BG44K? Maybe it's because I live in Canada and have an excuse to not know, if it's not sold here. I also have no idea what a brickster is but that's
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BG44K is a very agressive FI and CC cleaner. I have seen it work miracles on Volvos.

Now to the meat of the thing:

No one really touched on it - I think when an engine goes into ping mode in the presence of a good cleaner it sorta helps the cleaning effects. No?
dunno.gif
 
Regular octane (maybe mid-grade if your ping is bad) may be a good choice because you can hear the ping at the beginning of treatment and should notice a decrease as it gets cleaned out.

High octane may be at a disadvantage during clean up in that it may not burn as completely as lower octane. I tend to look at octane in the same way as ignition advance vs retard and fuel lean vs rich. So the low octane would give a more complete burn during clean up along with possibly higher combustion chamber temps.
 
If the owner keeps the car - new or old - accurately tuned to factory specs using factory tune up parts there is no "combustion chamber desposit" problem that the owner is ever faced with.

However, as the major oil company websites (like Chevron) explain, the octane requirements of ANY gas engine will increase after the first 10,000 miles which may require the use of mid-grade octane gas to keep ping under control.

Car makers always say "use 87 octane OR HIGHER." So they really have no objection to owners running high octane gas. Since I like to be able to drive a car for hundreds of thousands of miles without any fuel system problems at all I simply run high octane in all my cars. Then I never have to be concerned about "combustion chamber deposites" or rebuilding injectors or overhauling carburetors since high octane gas eliminates any tendency to ping and the high detergency of high octane keeps fuel injectors and carburetors clean for decades.
 
Malibu: Gotta disagree with your last statement there, "high detergency of high octane keeps fuel injectors and carburetors clean for decades."

High octane gas has no more additives or cleaners than lower octane gas. Octane rating is a measure of the fuel's resistance to pre-ignition ie. it tends to burn slower than lower octane gas. High octane is specified by manufacturers when the engine requires it. High compression, high temps, or turbo engines will do better with high octane due to its slower burn rate. Put the high octane in an engine designed for 87 and you have incomplete combustion and a waste of 20 cents per gallon.

My '85 240 at 239,000mi runs very nice on 87 octane. 92 octane shows no improvement in performance only a loss of about 2mpg. My '02 S40 gets better mileage on 92 than on 87 because it is designed for it.

[ February 27, 2003, 12:11 AM: Message edited by: mormit ]
 
I disagree with the argument that higher octane fuels lead to less complete combustion.

They are simply more resistant to self ignition, and the ridiculous pressure spikes that come with them. Once combustion starts, then it continues to the best abilities of the engine and combustion chamber design regardless.

More octane than the engine needs is a waste of money and resources, but won't wreck your engine or increase carbon deposits (unless detonation is removing deposits as they form on the lower octane stuff).

Down here, the highest octane fuels are also high density, low aromatic, high detergent fuels.
 
quote:

Originally posted by Pablo:


No one really touched on it - I think when an engine goes into ping mode in the presence of a good cleaner it sorta helps the cleaning effects. No?
dunno.gif


Nope, don't work that way
 
quote:

Originally posted by Malibu:
If the owner keeps the car - new or old - accurately tuned to factory specs using factory tune up parts there is no "combustion chamber desposit" problem that the owner is ever faced with.
Since I like to be able to drive a car for hundreds of thousands of miles without any fuel system problems at all I simply run high octane in all my cars. Then I never have to be concerned about "combustion chamber deposites" or rebuilding injectors or overhauling carburetors since high octane gas eliminates any tendency to ping and the high detergency of high octane keeps fuel injectors and carburetors clean for decades.


It does not work that way either,,you guys are blanketing combustion chamber design,efficiency and total quench area as if all are the same,,they are not equal :)Neither are the timing events of the cams and smog equipment.

[ February 27, 2003, 05:44 AM: Message edited by: dragboat ]
 
Dragboat - I understand. But here is what I observed when I have been resusitating old carboned up beaters -In a very condensed nutshell:

When I put in hi octane and good cleaner and floor in not much sh#t out tail pipe and slow cleaning effect.

When I put in el cheaporama gasoline and same good cleaner in - TONS of brownish crap comes smoking and blowing out the back when car starts pinging and walla combustion chambers ARE cleaner. Plus car doesn't ping quite as easily any more. I think more crap blown out...

What gives? Please explain your answer.
 
Briefly cause theres alot to it the motors exhaust cam events are taken into consideration of the heads intake to exhaust flow ratio and some scavenging effect is gained when a well put together combination is used" the exhaust can actually help pull in the intake charge as well". This detonation causes a huge amount of combustion chamber pressure and interferes with the exhaust extraction,,the brown I beleive is the rust from the muffler and other surfaces of the tail pipe internaly, from the explosions occuring. Grey is usually carbon. I'm not there to see, small,here and drink beer in green bottles
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I think a motor will run cleaner,longer on 87 octane if designed for it,,I have never seen evidence that a higher octane fuel helps keep a chamber clean and with a aluminum head it could actually in theory create more deposits,an aluminum head needs more heat to be efficient but that alone does not cover all bases here because of newer and higher compression motors out now and a whole lot more,,,

I think your motor is lean,,easy to check though.

[ February 27, 2003, 07:48 AM: Message edited by: dragboat ]
 
My 302 V8 used to ping on 87.

I used Techron to clean it out, then backed down the timing a bit, and installed a 160F t-stat (carbureted). no more pinging on 87!
 
Octane rating is an indicator as to how resistant any given fuel is to spontaneous ignition under heat and pressure.

Looking at the octane thing logically, every car needs an infinitely variable octane fuel.

Idling, no load, and high vacuum gives low chamber temperatures and pressures. Octane requirements for this mode of operation would be lucky to be in the 70s.

Cruising at freeway speeds needs a higher octane fuel, while roll on to full throttle needs an even higher octane.

Towing up a hill needs a higher octane still.

Taken to it's extreme, you need a different octane across the chamber. At ignition, the temperature and pressure are relatively low. As the burn progresses, the pressure and temperature increase, giving you a theoretical need of more octane at the last bit of combustion than the start.

You do need this, end gas autoignition is the knock that you hear on acceleration.

However, we can only buy a tank full of x octane fuel, so we buy the fuel that best suits our needs and driving style (and engine add-ons, knock sensors etc).

If too much octane was a cause of unburned fuel, then having 20 or so too many octane points at idle (like we all have) would make it impossible to pass an emissions test.
 
you want to know how to really clean out a combustion chamber and valves?

very slowly pour a quart of water down the intake while the engine is good and hot. it shocks the crap out of there.

it also quiets the lifters by letting the valve seal better because of the missing carbon. you do that and pull the head, itll look nice and clean enough to eat off. i know it sounds crazy but iv done it on 6 cars so far and havent had any problems. probably someone will flame me for this, but hey it works what can i say.
 
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