engine and drivetrain Pre-Ignition, Can You Hear It?

[glemon]

If your 2002's engine is too far advanced and it detonating early ("pinging" "pinking") can you hear it pretty easily?  I am familiar with the phenomenon and can usually recognize it, but also know that it is easier to hear in some motors than others.  I did a search and got some information on setting timing and detonation, but no reference to how evident the occurrence is when tooling around.

 

Thanks in advance,  Greg

[dbmw2002]

Ive tuned 2s for 20 years and never heard pinging like you do in a V-8, what will be evident if too advanced is a rough idle and a overheating engine, too advanced will def run hotter. Play with your dist by moving it it back and forth at idle, advance it and idle will speed up, then it will get rough, back it off and it will smooth out, the right spot is smooth but just starting to speed up, of course everyone will tell you to get a timing light and do it right but you will learn the sweet spot by playing with it, set correctly with valves perfect, it will be as smooth as a sewing machine.

[glemon]

Thanks very much, that is good to know, and will help me when I get out to fine tune the timing. 

[Mike Self]

Oh an M10 will ping all right...sounds like loose marbles rattling around in a tin can.  If you have too much advance or if you're running too lean (like with a vacuum leak) you'll notice it especially when you're under load and at low rpms.  For example, you're pulling a hill and you're in 4th at maybe 1500-2000 rpm.  Floor it, and if you've too much advance/too lean a mixture, you'll hear the pinging.  

 

A little pinging is OK--too much and you'll burn through your head gasket (ask me how I learned this--a vacuum leak I didn't find until it was too late).

 

cheers

mike

[glemon]

Ive tuned 2s for 20 years and never heard pinging like you do in a V-8, what will be evident if too advanced is a rough idle and a overheating engine, too advanced will def run hotter. Play with your dist by moving it it back and forth at idle, advance it and idle will speed up, then it will get rough, back it off and it will smooth out, the right spot is smooth but just starting to speed up, of course everyone will tell you to get a timing light and do it right but you will learn the sweet spot by playing with it, set correctly with valves perfect, it will be as smooth as a sewing machine.

That is good to know, but I thought all you german car guys only worked with precise scientific instruments, setting cars to factory standards, wearing spotless white lab coats all the while......

Edited December 13, 2013 by glemon

[dbmw2002]

Ya but we haave Autobahn to tist our work, you canos have speed limits and smog schnauzers to deel wit

[TobyB]

The Bosch distributor is by no means a scientific instrument.

 

And yes, you can hear pre- ignition.

 

I don't let mine do it at all, if I can help it.

 

t

[cda951]

FYI, pre-ignition and detonation are two entirely different phenomena, but are sometimes related, as in one can cause the other. They are often confused and mixed up with each other

 

Detonation is spontaneous combustion of any remaining fuel in the combustion chamber AFTER the normal spark-induced ignition event, and can cause a "pinging" noise as discussed. Detonation is caused by the engine running too lean, too hot, timing too far advanced, not enough octane in the fuel, or any combination of the above.

 

Pre-ignition occurs BEFORE the normal ignition event and is caused by a hot spot in the combustion chamber, usually either too "hot" of a spark plug for the application (nose of spark plug protrudes too far into the combustion chamber) or heavy carbon buildup. Preignition is less common but much more insidious as it does not give any prior warning or cause a noise, and it can melt a hole in a piston. Pre-ignition can often lead to detonation and mass destruction.

 

For a far much more comprehensive explanation, read this excellent article by a GM engineer:

 

http://www.944enhancement.com/html/knock_ping.html

Edited December 13, 2013 by cda951

[TobyB]

Ok, that's a dense read!  Thanks!

t

[jimk]

Here is what is coming down the pike on ignition advance control.

http://www.max-boost.co.uk/max-boost/internet_articles/Spark-Advance%20Control%20by%20Ion-Sensing%20and%20Interpretation.htm

[TobyB]

Bowling and Grippo got derailed by that not long after MS1 came out- they were all excited to get a DIY version out.

 

Don't think it ever happened, as far as I could tell...

 

t

[cda951]

Ok, that's a dense read!  Thanks!

t

 

Haha yes it is a dense read, but I have not found a better and more comprehensive explanation of the subject.

 

I work on cars for a living (mostly Porsches) and I have met a number of good mechanics who get detonation and pre-ignition mixed up, and use incorrect terms like "pre-detonation," so you should not feel bad if you didn't know the difference before.

 

My best advice for anyone here is to make sure your ignition timing is spot on and especially make sure that the distributor advance functions properly. A drop of oil in the distributor shaft wick underneath the rotor with each oil change will ensure that the mechanical advance mechanism stays lubed and keeps from seizing up. This is often forgotten even on otherwise well-maintained cars.