Advance ignition..

[El Dopa]

So what actually happens when you retard or advance your ignition... I know the spark is triggered sooner on retard and later in the advanced stage.

I think its an emissions thing - a lot of Japanese bikes seem to come like this from the factory to pass the Japanese emissions standards.

A side effect of retarding the ignition is that the engine makes less power than it is actually capable of at certain points in the gearing/rev range. This leads to flat spots.

Advancing the ignition removes the flat spots and allows the engine to make more power.

I think....

[Daffyd]

So what actually happens when you retard or advance your ignition... I know the spark is triggered sooner on retard and later in the advanced stage.

I think you're the wrong way round...sooner on advance and later on retard.
(CMIIW)

[degrom]

I think you're the wrong way round...sooner on advance and later on retard.
(CMIIW)

Okay... That actually makes sense. If the spark is earlier the fuel will have more time to burn before it is pushed out the exhaust. Causing more heat,right?

[DEATH_INC.]

It's all about peak cylinder pressure, you need this to happen at the right time to make max power. The burning gas expands, pushing the piston down, if the rate of this expansion exceeds the piston speed too much (remember the piston is almost stationary at tdc, and moves real fast at the halfway mark of the stroke) the pressure climbs too much and you'll get pinking, so, if you fire the mix too soon it'll overtake the piston at the upper part of the stroke, and if you fire it too late it's chasing it instead of pushing it.You need to exert as much pressure on the piston as possible without going that little bit too far for max power......
Not quite the technically correct way of putting it but the best way to explain it I could come up with.

[riffer]

You also need to remember that in the States they use a lot more crap petrol than we have here.

So RON ratings of 81 are not uncommon, so they need to retard the ignition by 2-3° (like on my RF) to cater for this petrol range.

We have better petrol here so people like me just tweak the pickup plate to cater for it.

Which means that with BP petrol I can run 91, but on Shell I need to run their 95 or else the pinky monkey comes to play (love that phrase - pinky monkey, Stephen)

[roogazza]

I doubt retarding the ign is going to stop people flipping these bikes ? It's more likely to do with the noise and emission police ?

I always disconnect so called wheelie wires but can't say I've noticed any marked difference. A little bit of advance can improve throttle response and smooth things out a bit , but it isn't going to return great amounts of HP if that is what some are thinking ? Gaz.

[imdying]

Degrom, you need to read a bit more on 4 stroke engine principles, it'll take a good book to start to get your head around the concepts. The amount of advance you can at any given point is dictated by huge range of thing; compression, load, fuel quality and type, cam timing, type of metal the cylinder head and piston are made of, shape of the combustion chamber etc etc

What you really need to know is; if you advance it too much, you'll melt a hole in a piston.

[degrom]

Degrom, you need to read a bit more on 4 stroke engine principles, it'll take a good book to start to get your head around the concepts. The amount of advance you can at any given point is dictated by huge range of thing; compression, load, fuel quality and type, cam timing, type of metal the cylinder head and piston are made of, shape of the combustion chamber etc etc

What you really need to know is; if you advance it too much, you'll melt a hole in a piston.

That's the problem with workshop manuals. They show you how to do things with lovely pictures and even number the steps involved to make it easy for you.

What they don't tell you is how things work(The bigger picture)... I will have to take your advice and read a proper book on how things work.

Anyone know of a good book about engine concepts? (How does mechanics learn the stuff?)

[scumdog]

You can run more 'advance' on the timing if you run higher octane fuel.

In my hot rod thingy I can run about 4 or 5 degrees more advance when using avgas than I can using 'pink-special' (so called Super.)

Makes the starter motor grunt a bit more trying to crank the engine over though so you need a good battery.

[imdying]

That's the problem with workshop manuals. They show you how to do things with lovely pictures and even number the steps involved to make it easy for you.

What they don't tell you is how things work(The bigger picture)... I will have to take your advice and read a proper book on how things work.

Anyone know of a good book about engine concepts? (How does mechanics learn the stuff?)

Workshop manuals are aimed at mechanics, who should hopefully know a thing or two..

Have a look on Amazon.com.

[imdying]

How about http://www.amazon.com/Motorcycle-Tec...e=UTF8&s=books

[imdying]

Or Tuning for Speed by the same author http://www.amazon.com/Tuning-Speed-P...e=UTF8&s=books

[Bonez]

http://en.wikipedia.org/wiki/Engine_knocking

[degrom]

http://en.wikipedia.org/wiki/Engine_knocking

Great peace of reading!!!!

Now I understand why my old Mini kept running for a few seconds after the ignition was switched of. The engine was running to hot and started pre-igniting. (Same as a Ignition that is to fast.. Right?)

[riffer]

Now you're getting it Bert.