Does regular gas burn faster than Supreme

[charismaticmegafauna]

Thanks, certainly part of my answer is here -- C&D: "Relying on these sensors, the engine controller can keep each cylinder's spark timing advanced right to the hairy edge of knock, providing peak efficiency on any fuel and preventing the damage that knock can do to an engine."

They say: "If you're not living on the edge -- you're taking-up too much space."

Sadly , the FJR has no such sensors....

 

[jestal]

There is often controversy over the use of the word "detonation". ... I would say that technically that is a mis-use of the word "detonation" but over the years it has seemed to take on it's own meaning in engine engineering circles. I'm referring to the more perverted use of the word "detonation" to describe pinging or spark knock. Technical handbooks and textbooks on combustion in spark ignited engines refer to "detonation" as spark knock, auto-ignition and.......detonation.......

Thank you for that -- there have been times (in certain circles) when I've been afraid to use the term.

A friend used to have: a Pontiac "Detonator Eight"..... :lol:

To go further with what the English have called "Pinking" or "Tinkling" -- a little bit is okay, correct? At times, if noticed?

Back in the day of the Model A Ford the driver could manually adjust the (static) spark advance with a lever on the steering column (old motorcycles, too). One could readily recognize spark knock and adjust/ride accordingly. But, I've often heard, that being on/at that threshold is a good place. True?

Yes, a tiny bit of pinging is OK and won't hurt a thing. There is a lot of development that takes place in the life of an engine during design to balance compression ratio, spark timing, etc. The ideal is to run the optimum spark advance with the highest compression ratio allowed on the design intent fuel. If the balance is correct the engine will run there and be borderline for detonation. So....working backwards....if you have the engine tuned to borderline detonation (or borderline spark knock or ping) you are probably pretty close to the design limits. This is sort of a rule of thumb and there are plenty of ways to argue against it (weakly) but it is still pretty close at the end of the day.

Calibrators always refer to tuning for maximum fuel economy at part throttle cruising along as "tuning to top dead ping...."

If the engine gets into detonation consistently at full throttle things can get dicey pretty fast. The higher the specific output of the engine the more trouble it can get into fast. Very fast. Production engines are usually protected to 2 degrees of spark advance detonation (2 degrees more advanced than results in trace detonation) at peak power. This is done with spark plug heat range and over-richening the mixture for protection. This is unachievable, however, on some very high output supercharged engines. A 200 HP 5.7 litre, however, can run at full throttle and detonate like crazy with no harm....LOL.

 

[jestal]

Here's a good little article: Car & Driver

Not a bad article. Not much to argue with there as it is pretty much right with the facts.

I would hesitate a little more than they do about drawing conclusions as to whether you need premium or regular based on the very limited sample of cars they tested. Granted, if the engine is designed for regular there is little likelyhood for getting more power on premium but there have been cars in the past that might not follow that logic. Knock systems have changed dramatically over the years. Much advancement in the sophistication of the systems and sensors and control logic from the primative knock control systems of the mid-80's. MANY of those cars would run OK on regular but would noticeably better on premium. So, the conclustions they draw are more for brand new cars rather than the general vehicle fleet.

If the engine has a knock sensor it is pretty safe to run it on most any fuel but if you want the maximum performance under any condition you should put premium in.

Similarily, in an engine like the FJR, regular seems to work fine most all the time but if you are going to be running it hard across the desert in hot weather premium might be recommended just as some insurance against detonation occuring.

One thing not mentioned but that must be considered is that detonation can lead to pre-ignition. Detonation tends to drive a lot of heat into the combustion chamber due to the severe shock wave of the pressure spike upsetting the boundary layer of gas that insulates the chamber surface. Things like valves, coolant and spark plug tips can get very very hot very very quickly when detonation starts at WOT. Get the plug tip hot enough and it will ignite the incoming charge before the spark fires and you have pre-ignition and a hole in your piston. Running premium can help prevent this (by preventing the detonation) but premium typically would not be a consideration for stopping pre-ignition otherwise. This is called detonation induced pre-ignition and is the source of much confusion when examining a failed engine/piston.

 

[vandy]

i wouldnt trust any pinging... a little predetination is ok but by the time you are hearing pinging the severity is bad enough to start causing some damage

 

[fjr]

Whenever I read about ignition spark and advance controlled by ECU and the need for regular

or premium fuel I long for the car I learned to drive on. I could control advance/****** by a

lever mounted on the steering column. I miss the Model A.

 

[Charlie Hoss]

Here in the East, our "regular" gas has a pump octane rating of 87. I was a bit surprised on the ride to WFO that out west the "regular" grade had only an 85 rating. The bike ran fine at 11,000 ft elevation over Bear Tooth Pass and at 149 MPH at Bonneville. I assumed that the higher elevation in general requires less octane.

With the current gas prices, regular is a good thing.

 

[jestal]

i wouldnt trust any pinging... a little predetination is ok but by the time you are hearing pinging the severity is bad enough to start causing some damage

A little trouble in the reading comprehension, eh...?? There is no such thing as pre-detonation. I have a phobia about that word.

 

[Scab]

My wife said I had pre-detonation. But, I went to the "Love Store" and got some cream for it.

 

[sthames]

My wife said I had pre-detonation. But, I went to the "Love Store" and got some cream for it.

Dang Scab,

I thought I was the only one reading these lines with that regard!

Whew :blink: ,

 

[evil_henchman]

My wife said I had pre-detonation. But, I went to the "Love Store" and got some cream for it.

I suffer from premature articulation so I'll keep my mouth shut.

 

[vandy]

ok i dont remember the exact termonoligy but a little detonation is ok but not enough to start hearing it.. thats when the damage actually starts to happen.

now i have had alot of vehicles that i have heard pinging in and never saw the damage it caused..

it just takes time for the damage effects to build up to noticible damage..

and thats the last i will say on that other than ill just keep it in my pants.