Spark knock /detonation, same thing?

[zach1900]

I live near a fairly busy intersection , and have noticed what seems to be a lot of newer model V6 Honda and Acuras (Odyssey, Pilot mainly) with spark knock from a dead stop, I don't know if I am describing it correctly as "spark knock" and if that's even a negative occurence, is it that these engines are tuned so efficiently that sligt knock under load is okay? I hear this sometimes in my Camry from a dead stop if I really step on it, if the radio is off, fan off and windows up, it's never triggered a check engine light and still runs perfectly , sorry I am not well versed in spark timing.

 

[4wheeldog]

Detonation is a related, but entirely different animal. Preignition/spark knock is when the mixture burns a bit too quickly, so it rattles the inside of the cylinder. Almost all cars now have knock sensors to minimize this, by retarding the timing. Use of low octane/poor quality fuel can cause this.

Detonation is when mixture spontaneously combusts (Actually, explodes, rather than burns in a controlled fashion), from heat and pressure, in an area of the cylinder trapped away from the normal ignition point. It is almost immediately destructive, putting holes in pistons, destroying spark plugs, and even breaking cylinder walls. There are a number of possible causes, but in the end, heat and pressure overcome the normal process of combustion.

 

[wirelessF]

It's usually injectors or the VVT valvetrain. On my toyota truck the injectors are noticeably loud which makes it sound like a small diesel.

 

[Quest]

if it's DI engine, most likely the typical DI injector noise.

if it's non DI gasoline type (ported fuel injection), then it maybe something else.

Q

 

[Astro14]

Originally Posted By: 4wheeldog
Detonation is a related, but entirely different animal. Preignition/spark knock is when the mixture burns a bit too quickly, so it rattles the inside of the cylinder. Almost all cars now have knock sensors to minimize this, by retarding the timing. Use of low octane/poor quality fuel can cause this.

Detonation is when mixture spontaneously combusts (Actually, explodes, rather than burns in a controlled fashion), from heat and pressure, in an area of the cylinder trapped away from the normal ignition point. It is almost immediately destructive, putting holes in pistons, destroying spark plugs, and even breaking cylinder walls. There are a number of possible causes, but in the end, heat and pressure overcome the normal process of combustion.


This makes little sense.

You're saying that the flame front travels faster in some cases? How would that happen exactly?

You describe two circumstances and ascribe them to differing flame speeds.

When they only differ by timing.

 

[JimPghPA]

It could be that some gas stations are still selling winter gasoline. Winter gasoline will vaporize too fast in hot weather.

 

[y_p_w]

Originally Posted By: 4wheeldog
Detonation is a related, but entirely different animal. Preignition/spark knock is when the mixture burns a bit too quickly, so it rattles the inside of the cylinder. Almost all cars now have knock sensors to minimize this, by retarding the timing. Use of low octane/poor quality fuel can cause this.

Not quite. Preignition is a result of a heat source (other than the spark) igniting part of the mixture.

 

[BearZDefect]

I have also heard modern v6 engines make that knocking sound briefly at launch in warm weather. I assume it is spark knock due to using regular unleaded when the engine is optimized for premium, although my assumption makes more sense to me for a Toyota 2GR than a Honda J35 since Honda has never recommended premium while Toyota does concede better performance on premium.

In warm weather my 1997 i30 (the old VQ30DE with no VVT, no DI, no electronic throttle) will also do this briefly on a sudden quick launch from standstill if I don't use premium. So I only use regular unleaded in this car in the winter.