vanquish

That could be it If it was properly tuned for 93 octane and you not running 93 octane. The noise you're describing could be pre-detonation.

hpwrestler220

doesn't detonation only occur upon full throttle?

I would think that maybe it is a slight valve tick. Maybe some thicker oil would help? Change the oil and put some heavier oil in no? Someone back me up

cliffyk

Detonation can happen at any throttle position, however high load and WOT combined are the hardcore detonation inducing circumstances. It's also important to distinguish plain ol' pre-ignition and detonation, and pre-ignition caused by detonation.

Pre-ignition (aka "knock") is a situation in which something--a hot spot in the combustion chamber, too hot a plug, etc.--initiates the fuel burn (NOT detonation, but an even burn) before the plug fires. If this happens too soon before TDC then the combustion pressure can try to force the engine to rotate backwards, this is the audible knock.

Detonation ("pinging" or "pinking" as the Brits say) occurs when the fuel charge is ignited by the spark, however for a variety of reasons the fuel does not burn evenly but instead "explodes"--I.e. detonates. Lighting it up too early in the compression stroke is the most common reason for detonation--the partially compressed fuel charge can be an explosive mixture.

The shock wave from the blast can severely damage pistons, and again if it happens too soon before TDC it will try to turn the engine backwards.

Pre-ignition caused by detonation ("ka-boom") is all of this coming together. High temperatures and charge pressures in the combustion chamber cause the fuel to detonate before the plug fires and it all hits the fan--the ultrasonic shock waves and elevated pressures slam valves shut, and take out pistons, rods, and anything else that can't take the load.

dmaizer

im tryn to get all the 86 octane fuel out the tank, so i can add the 93 octane, and ill be changing the oil on it too. which oil is recommended to use????