With all of the questions lately about detonation, and after personally breaking two piston ring lands, I was very curious as to why this phemomenon happes, as i am the type of person that has to know why things do what they do I will discuss what I have learned recently, from many web sites, and people I have talked to. Most of this is fact, although some may have their own opionions, which is excellent for discussion. Lets make this an informative post, and lets all learn what we can do to prevent detonation. I'll start off by a technical definiton of detonation.

Detonation is basically an uncontrolled, uneven burn of the air/fuel mixture. Ideally, the mixture, will be ignited by the spark plug, at the top of the mixture. It will then ignite, and burn outward in an even, controlled manner, to the end of the mixture, closest to the piston, also called the "end gas". Detonation is when the top of the mixture ignites, and then the middle or the end gas ignites suddenly. The two flame fronts collide, and cause an EXTRMELY high cylinder pressure, which makes the cyliner walls and other components go into oscillation, causeing the "knock" or "ping". Factors that can promote detonation:
Increased cylinder pressure( ie. more boost pressure)
Lean air/fuel ratios
Increased intake air temps ( reason why an IC is so important)
Advanced igniton timing
Over heating of the cooling system (insufficient cooling, esp the radiator)
Low octane fuel

-Increased cylinder pressure: This happens when we run more boost.
The more boost we run, the greater the chance for detonation to
occur. Higher compression engines will have a much greater chance
for detonation, because there greater cylinder pressure (pretty
much why most will advise going low compression and turbo)

-Lean Air/fuel ratios: One of the greastes causes of detonation. Lean
A/F caused a very rapid heating of the cylinder and cylinder
pressure, causing detonation.

-Increased intake air temps: Again, this raises the temp of the air
charge, makeing detonation more likely. Thats why an IC is so
important to use no matter what boost you run. The cooler the intak
air is, the less likely detonation is to occur

-Advanced igniton timing: This again causes very hot air temps in the
cylinder, which caused the end gas of the mixture to ignite, that
= detonation

-overheating of the cooling system: Our cooling system IMO, cannot
sufficiently handle 15+ psi of boost effectivly. The more boost you
run, the more heat generated. And the more heat, the greater the
chance of detonation. A fluidyne or better cooling radiator is a
def good choice. When the coolant is too hot, it keeps the
cylinder walls too hot, thus making a greater chance for detonation

-low octane fuel: Dont run it. When i detonated, i was running 93
octane. My A/F was a consistant .93-.94 at WOT. The higher the
octane, the slower it will burn, which is perfect to help deter
detonation. Even with 93, i detonated because of too much timing
advance.

So what can us turbo and N2o guys do to get rid of this engine killer?

From my own personall experience, any boost pressure over 8 psi, you will need to retard igniton timing. How much, well, that is still up in the air. Dyno tuning will be the best if not the only way to dial ignition retard in. Timing retard is THE best step to take, and an imperative step to take when turboed. This is esp true for stock internal turboed people, as stock cast pistons will easily crack ring lands off of them with just enough detonation. Lower the compression ratio of the engine. I have gathered that 8.5:1 is a general rule of thumb, some may digress. A higher compression engine will need more ign retard to prevent detonation. More retard= less power. Upgrade your cooling system. Get a fluidyne or similar radiator to help coolant cooling. Be sure your fans are working properly. Get a 160 degree thermostat, this will help lower the engine temps slightly. Get the drift so far? Lower intake air temps, retard timing, keep the engine from getting to hot, and run the highest octane fuel you can.

Igntion timing: When I get my engine built, this will be the MOST tuned part of the engine. How much retard, and when to dial it in, is THE key factor to getting no detonation, regardless of how much psi of boost, and how much retard with each pound of boost. Many use the Crane unit, and it works, but is limited to 15 psi. To run more boost than that, you will have to pull out too much timing at 15 psi, to run lets say 20 psi. I, as others, have brought up the product J&S safeguard. Technically, this will work wonders for our cars, but could be rather "touchy". It uses an aftermarket knock sensor to detect detonation, and will retard timing on an individual cylinder basis, becuase it will know exactly when and which cylinder just detonated. The J&S will keep ignition timing to the "right before detonation" point in time in the fuel burn, and this has been proven to be the point in which max HP is made, Right before detonation happens. Hopefully now we can discuss detonation and igniton timing in more detail, from those who are boosting using igniton retard units, and what they are doing, how much power they are making, ect.. Hopefully we can all ask questions, and try and learn from eachother here, as no one wants to blow an engine any more than the other guy. The key for all of us should be to retard the timing just enough to not get any detonation. This is where max HP is made. And another side note, detonation does not occur in every cylinder. All the factors listed above can be slightly different, which is why all-cylinder retard can hurt power. Unfortunately, my ignorance on this topic broke my piston Knowledge is power !

13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)
My webpage: http://eclipsed4evr.home.comcast.net
-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)