is there anything I can put in the tank to boost the octane from 87 to 91??? I didnt get a manual with the damn thing and I put 87 oct in it.

 

is it pinging, if not don't worry abought it (this Time).

 

i'd go get some octane booster at an autoparts store to be safe and use 93 octane gas from now on (unless your tune is set-up for 91)!!!

 

if it isn't knocking then don't worry about it. The only reason that you want to use higher octane is to avoid pre-detonation. The effect of pre-detonation is that the valves aren't quite closed when the gas goes off, this pust extra stress on the valvetrain, and thus wears it out prematurely. If you're not prematurely detonating then don't worry about the octane. If you're tuned for higher octane then use it, but missing a tank with no predetonation means no problem.

 

Just because you don't hear pinging doesn't mean everything is alright and it is not detonating. If it were me, I would stay out of the throttle until the tank was gone, and I would be extra careful if it was cold outside (lower than 56 deg). Maybe find some 100 octane unleaded race fuel somewhere to even it out.

Octane boost may help, but make sure you follow the instructions on the packaging. Adding too much octane boost will eventually provide no benefit.

 

I drove it easy until I reached 1/4 tank, then filled it with 93 octane, the pinging is gone, what a difference in performance too!

 

FYI - Octane boost in a can works only incrementally.

An advertised "one point" increase in octane means that you go from 89 octane to 89.1 octane.

 

not sure what could get damaged if you're not pinging. I don't mean to call you out or anything, I'm looking to learn here, yysenhimer, what gets damaged if you're not knocking?

 

Just because you can't hear it, doesn't mean it isn't damaging/pre-detonating. Engine and exhaust noise can mask some of this.

 

That's what I meant Amish.

Glad it worked out Leroy

 

ok I gotcha. Thanks for the input.

 

Valves not quite closed......

Please bone up on pre-ignition..

Damage can be anything from holes in pistons to tweaked rods........have never heard or seen any valvetrain damage.

Please understand that to build enough cylinder pressure to ignite fuel without a spark both valves will most certainly be closed up tight.

Also realize if an intake valve was open and ignition occured (by spark) you will get backfires through the intake.


Wifey also did the regular gas thang on the L.........I did run some octane booster and was EXTRA careful to keep from getting on it untill I could get at least a half tank of premium back in.........no harm done.

 

well ok if I'm off then what is the rattle on the top end (pinging) that lets you know it's pre-detonating.

 

Ummmm..........that would be detonation or pre-ignition....not sure what "pre-detonating" is.

The rattle is the mixture lighting off BEFORE the actual spark......basically two ignitions on the compression stroke. (the "real spark" should be around 30-35* BTDC....in other words while the piston is still going up....the compression igniton or detonation I'm "guessing" happens 10-15* BEFORE that)

Again, study up on 4 stroke engine operation............the valves are closed for nearly 1 1/2 full revolutions. As the piston is going up to compress the mixture, valves are closed (how else could compression build?) as the mixture is ignited, the piston is forced down (again the valves must stay closed to create any downward pressure) only on the upward exhaust stroke will the exhaust valve start to open and when the exhaust is forced out at aprox TDC, the intake opens and the piston draws a fresh mixture in.

I realize the Amish aren't supposed to know this stuff........but I won't tell anyone.

 

I have to step in and make some corrections here, some of you are off-base.

Pinging/detonation is when there is more than one ignition within the combustion chamber, and the flames crash into eachother. That forceful crash causes the sound you hear (the rattle). It hammers pistons and will basically destroy them. It has nothing to do with valvetrain and it won't cause valvetrain problems in the rockers or further back, just the valve faces themselves. It happens when the combustion chamber temperature is high enough that it can ignite fuel without a sparkplug fire. It's usually from a sparkplug fire - and another ignition in a different area - that crash.

The different octane ratings have different flashpoints for the fuel.

93 octane requires a little more heat to ignite than 87. If there is no rattle, there is no pinging/detonation and there is no damage. It's either happening or it's not. When you hear it you know it and can identify it. Others brought up pinging/detonation happening when you can't hear it. It can happen on a minor level to where you can't hardly hear it - but that means it's BARELY causing two flames to crash into eachother and therefore is not damaging. This would be as if it were on the verge of full blown pinging/detonation. If you can't hear the rattle then flames arn't really crashing. If you want to get technical, there is some minor pinging/detonation but that is when it's on the verge of actually pinging/detonating. That rattle - is the ping/detonation so if you can't hear it than it's not really pinging/detonating.


It's not the mixture lighting off before the spark. It's not pre-detonating - its called detonation. There is nothing "pre" about it.

Yes, a reason to use higher octane is to avoid detonation. It has nothing to do with the valve position.