Detonation vs. Pre-Ignition

[Gamerse]

Makes me feel a bit smarter, I remember reading this verry article in highschool. Yes I'm a youngN... Excelent post +1
To add some some good basic info, I offer a general snipet from Gary Donavan. This guy has made a turbo plymouth reliant run 9s, so he knows his stuff.


The best pistons to buy for a very high output engine are forged pistons from J&E or Arias. If you plan on buying it's a good idea to purchase J&E's from Forward Motion, they sell singles in case you have an "accident." J&E nor Arias will sell singles, just complete sets.

Not even the best forged pistons will survive if you ignore your EGT gauge.
A popular question I'm often asked is how much boost/hp can I safely run with factory cast or Mahle cast pistons? Quite frankly it's not how much boost is the determining factor but how much detonation! I have made well over 300 hp with cast pistons with boost pressures over 30 psi... If you run into even minor detonation at those power levels however.. you are the proud owner of a set of ashtrays.


(Joe O'Connor had a little detonation in cylinder #1)
Don't be lulled into a false sense of security because you have had experience with detonation at stock or near stock horsepower- most motors will come through with no damage at those power levels. At 300+ hp it's a hammer blow that will instantly destroy piston ring lands before you are even aware of the "death rattle". Go slow and watch your plugs for signs of damage. Forged pistons are a good investment and will tolerate occasional detonation at high horsepower levels but will break if constantly abused as well.
Be warned, the clips from floating pin pistons have been known to come out and score the cylinder wall. LRE has steel spring retainers that are safer. The is no horsepower to be found from floating pins- Sources inside Chrysler say that the floating pins were done for marketing reasons!
Here is a good warning! If you're getting your engine bored out, make sure the machine shop has the pistons on hand so the final bore and hone match the pistons. A GOOD machine shop will even number the pistons and hone each bore to the individual pistons measurements.
Stock rings work great as do Sealed Power replacements - Gapless rings have been tried on our cars with generally less then stellar results.
Piston Coatings-


(Dave St. Louis's Turbo III pistons)

There are a variety of skirt and top coatings for pistons- The Teflon coatings on the skirts reduce wall friction, coatings on the underside help shed oil and ceramic coatings on the top help reflect heat back into the combustion chamber and help protect the piston in case of excessive EGT temperatures.

Note: A noted engine builder has warned me that coatings on the top of the piston may protect the piston but will reflect more heat back into the engine making it more prone to detonation.

[klamathpro]

Ouch. Even the best forged pistons have a breaking point. I always ran a little rich with my DR-500's to help prevent that, though other factors need to be considered..