what is actually happening when people say there is detonation? i know it's a bad thing, but what is actually happening? this could be a newbie question...but i would like it answered...thanks.

 

when i get to about the 3k rpm range, i start to hear a ping...i checked the plugs and they're all brown...there is a loss in power also...i know i need to get it tuned, but just wondering if it's detonation even though the plugs are brown and not white...thanks in advance.

 

What you are experiencing is pre-ignition. You are firing the mixture when the piston is still on it's way up. The reult is your motor wants to start the power stroke when it still hasn't finished it's compression stroke- That motion repeated over and over can put a beating on a piston.

 

i'm running about 12:1 compression on 92 octane(i used a can of octane booster, just to see if it'll help)...i retard the timing a little, so it's around 13-14 degrees now...so the pinging starts at around 3k for about 100-200 rpms only, and then it goes away...i know it's not safe to be driving the car like this...but it's my only car, and plus i dont smash on it or anything, just drive it to work(about 10 miles) and back home...that's it.

 

not running enough octane for that kind of compression. you can always go about lowering your compression a little with a thicker headgasket or some pistons with a little less compression, what pistons are you using ctr? or an aftermarket piston?

 

Instead of octane booster spend $10 on two gallons of Xylene and your octane will be close to 98 if you blend it with 8 gallons of gas

 

add a little of fuel in that area to see if it helps. back off timing as your last resort.
I see that there is a misunderstanding about pre-ignition and detonation.

https://honda-tech.com/zerothread?id=1180205

 

PREIGNTION (PING)
-A/F mixture ignited before spark
-caused by hot spots (carbon particles, plug electrode, sharp edge, running lean, too hot plug range)

DETONATION (KNOCK)
-A/F ignited after spark due to heat and pressure
-burns about 6x faster when this happens
-caused by too much spark advance, too low octane
-occurs under low load/low RPM

 

I am confused by your explanation.

You said detonation: air fuel ratio burned after spark.....

What would be there to burn after the mixture has seen a spark?

Pre-Ignition is ussually a result of too high of compression and not enough octane.

Low octane fuel burns easier and high compresion alone can cause pre-ignition. Sort of like a diesel car that ignites fuel off of like 18:1 compression ratios and no spark plug.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by asubennett &raquo;</TD></TR><TR><TD CLASS="quote">I am confused by your explanation.

You said detonation: air fuel ratio burned after spark.....

What would be there to burn after the mixture has seen a spark?

Pre-Ignition is ussually a result of too high of compression and not enough octane.

Low octane fuel burns easier and high compresion alone can cause pre-ignition. Sort of like a diesel car that ignites fuel off of like 18:1 compression ratios and no spark plug.</TD></TR></TABLE>

i think he meant something like, there's left over spark or something in the chamber, that'll spark it self...something like that...i read it somewhere, unless i'm just talking out of my ***...hahahaha.

 

detonation is end gasses in the chamber self combusting( because of octane, pressure, with the help of a hot spot..whatever)
This happens AFTER the spark plug has ignited the mixture. The ping that you hear are the pressure waves of the multiple flame fronts colliding with each, chamber, piston, etc.
they resonate and create vibration. Kinda like hitting the pistons with a hammer.
Detonation usually breaks things because of the shock.

pre-ignition happens BEFORE the spark plug ignites the mixture, it usually happens close to bottom dead center.
Its created by a hot spot acting like a glow plug. pre- ignition usually melts because of the extreme heat.
An engine Will be lucky enough to see pre-ignition once or twice in its life. You can NOT be pre-igniting all the time..
Pre- ignition gives NO warning.
read the link that i posted above, it has some pretty good info

edit: spelling owns me..


Modified by mmuller at 3:49 PM 3/24/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">detonation is end gasses in the chamber self combusting( because of octane, pressure, with the help of a hot spot..whatever)
This happens AFTER the spark plug has ignited the mixture. The ping that you hear are the pressure waves of the multiple flame fronts colliding with each, chamber, piston, etc.
they resonate and create vibration. Kinda like hitting the pistons with a hammer.
Detonatuion usually breaks things because of the shock.

pre-ignition happens BEFORE the spark plug igntes the mixture, it usually happens close to bottom dead center.
Its created by a hot spot acting like a glow plug. pre- ignition usually melts because of the extreme heat.
An engine wil be lucky enough to see pre-ignition once or twice in its life. You can NOT be pre-igniting all the time..
Pre- ignition gives NO warning.
</TD></TR></TABLE>
good explanation

 

Agreed, Thanks mmuller

 

Yes, detonation happens after spark. The ping is caused by sharp (very fast) explosion of gasses which cause the engine block to resonate at ~6600Hz. This is a frequency that a knock sesnor would monitor btw. The damage seen in vehicles the experience detonation is due to breakdown of the boundary layer of air that protects piston and clyinder wall against heat. Non-engineers - Look up what a boundary layer is if you want. During normal combustion the boundary layer is not affected because combustion is burn NOT explosion.

Also, because Hp/Cu-in in a Honda is high &gt;1.5 typically, detonation has higher potenial to cause engine damage.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SlothSi &raquo;</TD></TR><TR><TD CLASS="quote">Yes, detonation happens after spark. The ping is caused by sharp (very fast) explosion of gasses which cause the engine block to resonate at ~6600Hz. This is a frequency that a knock sesnor would monitor btw. The damage seen in vehicles the experience detonation is due to breakdown of the boundary layer of air that protects piston and clyinder wall against heat. Non-engineers - Look up what a boundary layer is if you want. During normal combustion the boundary layer is not affected because combustion is burn NOT explosion.

Also, because Hp/Cu-in in a Honda is high &gt;1.5 typically, detonation has higher potenial to cause engine damage.

</TD></TR></TABLE>

One of the best 1st posts i've ever had the pleasure of reading

 

You need to have your ECU modified to pull pat throttle/ low RPM advance in the area you are getting detonation. Hi vacume low RPM may have over 40 degrees advance, get a chipped/ custom ECU.

 

Learned somthing new today on h-t!

 

what happens is the fuel is burned before the sparkplug fires, and before the piston moves up. thats when you hear a clapping/or pinging sound. This is bad. Check your ignition timing use higher octane fuel.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by asefi944 &raquo;</TD></TR><TR><TD CLASS="quote">what happens is the fuel is burned before the sparkplug fires, and before the piston moves up. thats when you hear a clapping/or pinging sound. This is bad. Check your ignition timing use higher octane fuel. </TD></TR></TABLE>

The question has been answered.....correctly. Read the thread.