Dumb A$$ Questions (detonation, Car battery)

[Mr GT 02]

Hi,

People say they are having "detonation" problems. WHat does that mean? And ..how do you determine if you are having "detonation" problem?
And....WHat causes "detonation" ...and.....how bad is that for the car?


OH and another question? When DISCONNECTING the car battery, so that the computer resets......what wire do you disconnect first? Positive..or..negative? Or does it even matter what which line you disconnect?

Please excuse my LIMITED MECHANICAL knowledge....

 

[xseler8]

The owners manual will explain the battery sequence. Also,it explains what to do after reconnecting.

 

[Mr GT 02]

The owners manual will explain the battery sequence. Also,it explains what to do after reconnecting.

\

Riiiiight......

I dont have the manuel. I lost it.
So...can anyone answer my questions?

 

[twogts4us]

Disconnect the negative first and reconnect it first. You have to leave it off for some period of time though...the least time I have done it was 30 min, while I was doing whatever I had to do. Actual necessary time is likely less. Your gauges will peg when you turn the key on afterward, then fall back to zero - this will tell you that the conputer has been reset.
Detonation, or pre-ignition, is when the air/fuel mixture is ignited so much before TDC that it rattles the cylinder and the piston in the cylinder (as it is still moving up!) with a sonic wave that creates the sound you hear - kinda scary, huh? The are many causes for this - too much compression, too much timing, carbon build-up, poor gas quality...just to name a few common ones.

 

[Go HoTO!]

Sure! Here is the deal and a little lesson on fuel and spark.

As a piston moves upwards, the fuel and air mixture gets compressed. Pressure increases as it moves to TDC (Top Dead Center). Before this ocurrs, the spark ignites the mixture and BAM, you get force. Make sense so far?

The spark is generally said to be advanced because it happens before TDC. On a stock Mustang the advance is generally 10 degrees before TDC. You want the spark on the upward motion as this generates the most power.

If the fuel/air ignites before the spark, this is called ignition or actually "pre-ignition." This condition is also called "knock" or "ping". It can be extremely bad for the motor, or just a minor problem depending on how much and how long it has taken place.

This condition can happen for three of the following most common reasons:

1 - The amount of spark advance is not enough. If the advance gets turned back incorrectly, then pre-ignition will occur.

2 - If too low of octane fuel is used, you will get pre-ignition. Lower octane fuel will ignite without spark at lower temp and pressure than higher octane fuel. This is why diesel engines do not need spark plugs as the fuel will ignite easily by itself.

3 - Dirty cyclinder heads. If the compression chambers build up with carbon, then pressure will build prematurely thus resulting in fuel to ignite without a spark.

Regarding the battery question: Allways remove the negative or black terminal. You only need to remove this wire.

 

[twogts4us]

How you know you are detonating is the tell-tale pinging sound, especially present when the engine is under load - when you're gettin' on it.
Hey, and don't call 'em dumb a$$ questions! It's the dumba$$ who guesses or never disconnects their battery 'cause "It won't happen to me".

 

[Go HoTO!]

twogt is CORRECT! Factors like engine load and high ambient temperatures can also increase the tendency for pinging. When I am towing with my Suburban on a hot day up a big hill, I will sometimes get this.

Some cars (Mustangs do) are equipped with knock sensors. They act to change the timing when they sence that pinging is taking place, but they can only help to a point.

 

[JohnyD05]

disconnect the battery

when you disconnect the batter you don't have to wait long if u turn on your dome light or, headlights. it kills and residual power that is leftover and it can be done in less than a minute, you probably won't even see your headlights come on but believe it works for me.
-john

 

[Mr GT 02]

Thanks for all the feedback..
..I dont think I have experienced detonation, because i dont really hear anything out of the ordinary when STEPPING on it.