Engine gurus... Detonation

[76Broncofromhell]

X3 or 4 for tuning it. Throwing parts at it will never get it to run as well as proper tuning.

 

[WheelHorse]

If you are running hyperT pistons, need to make sure your max all in timing is under 35. If forged disregard.

With your setup, I highly recommend a trip to the tuner and let them tweek it into specs. Best $500 you'll ever spend. I'm using a carb and still letting the tuner message mine when rolling.

What? And forgo all this wonderful speculation?

Who in their right mind doesn't want to chase a simple tune for months when it could be had in just a few hours?

 

[WheelHorse]

KB? Keith Black? Is he using Keith Black or are you assuming so? I'll go from my hundreds of engines I've built experience, enlighten me smart guy.

My guess is, he read it here:

While the piston photo is of a cast, the Westlotorn guy goes into great detail about the KB issues and hyper (cast) vs forged. Forged bends, cast breaks.

http://forums.corvetteforum.com/c1-and-c2-corvettes/2929086-piston-failure.html

You could also see where he got his two degrees less timing from, supposedly due to hyper's higher silicone reflecting more heat instead of transferring it the way a forged would.

Then you could also get into this as well.



"Hypereutectic" means over eutectic. The word eutectic refers to a condition in chemistry when two elements can be alloyed together on a molecular level, but only up to a specific percentage, at which point any additional secondary element will retain a distinct separate form.

Although internal combustion engine pistons commonly contain trace amounts (less than 2% each) of copper, manganese, and nickel, the major element in automotive pistons is aluminum due to its light weight, low cost, and acceptable strength. The alloying element of concern in automotive pistons is silicon.

Silicon in this context can be thought of as "powdered sand". Any silicon that is added to aluminum above a 12% content will retain a distinct granular form instead of melting. At a blend of 25% silicon there is a significant reduction of strength in the piston alloy so stock hypereutectic pistons commonly use a level of silicon between 16% and 19%. Special molds, casting, and cooling techniques are required to obtain uniformly dispersed silicon particles throughout the piston material.

The biggest drawback of adding silicon to pistons is that the piston becomes more brittle as the ratio of silicon is added. This makes the piston more susceptible to cracking if the engine experiences pre-ignition or detonation as well as when power adders are installed. Performance replacement alloys.

When auto enthusiasts want to increase the power of the engine they may add some type of forced induction. By compressing more air and fuel into each intake cycle, the power of the engine can be dramatically increased. This also increases the heat and pressure in the cylinder.

The 4032 performance piston alloy has a silicon content of approximately 11%. This means that it expands less than a piston with no silicon, but since the silicon is fully alloyed on a molecular level (eutectic), the alloy is less brittle and more flexible than a stock hypereutectic "smog" piston. These pistons can survive mild detonation with less damage than stock pistons.

Aftermarket performance pistons are most commonly made from 4032 and 2618 alloys and are typically forged. The 2618 performance piston alloy has less than 2% silicon. This alloy is capable of experiencing the most detonation and abuse while suffering the least amount of damage.

Taken from:http://www.probeindustries.com/Articles.asp?ID=144


Hypers are a good choice for a street engine, I'll agree, but they are less forgiving of detonation/preign. Goes back to the granular structure leaving electron microscopic weak links.

'73 was just getting at the point that not everyone knows that hypers are less detonation resistant than a true forged 2618 style piston and to seek dyno help before he damages a piston.

 

[Ourobos]

Good info.. I've sprayed a 150 shot on a hyper piston with no issues.. It is all in avoiding detonation for sure.

 

[baddad457]

You're likely just noticing the detonation now with the warmer weather, that's pretty common. Back off the timing a tad and see if it goes away before doing anything else.