Spark advance

by **des** » Thu Apr 11, 2013 4:09 pm

If the rotation of the crankshaft the same on any engine at a certain RPM, so the ideal spark advance values can be used in any engine for a particular type of fuel. Is this correct?

by **RPM freak** » Fri Apr 12, 2013 11:04 am

No.

Spark advance is dependent on cylinder volume, cylinder head shape, piston shape, type of fuel(how many octanes it has), engine temperature, air temperature that is entering the engine(supercharged and turbocharged engines have bigger inlet air temp) and few other things.

by **des** » Fri Apr 12, 2013 3:36 pm

Ok.

So since all of these factors, besides air temperature, are constant, which map corrects spark advance, when atmosphere temperature changes, in atmospheric engines?

And another one question:
3000rpm/60sec=50rpsecond
1000millisecond/50rps=1 round per 20 millisecond
(1/8 of 360 degrees is 45 degrees)
20ms\8=2.5 millisecond

crankshaft rotates 45 degrees in 2.5 milliseconds at 3000rpm. Is it right calculations?

by **adriancl** » Fri Apr 12, 2013 3:56 pm

[quote="des"]Ok.

So since all of these factors, besides air temperature, are constant, which map corrects spark advance, when atmosphere temperature changes, in atmospheric engines?

In most sw exist Spark advance correction(air temp, coolant temp,oil temp,and so on)

by **des** » Fri Apr 12, 2013 4:18 pm

adriancl wrote:
In most sw exist Spark advance correction(air temp, coolant temp,oil temp,and so on)

Tnx

by **des** » Sat Apr 13, 2013 7:36 pm

3000rpm/60sec=50rpsecond
1000millisecond/50rps=1 round per 20 millisecond
(1/8 of 360 degrees is 45 degrees)
20ms\8=2.5 millisecond

crankshaft rotates 45 degrees in 2.5 milliseconds at 3000rpm. Is it right calculations? Tell me please!

by **shAGGie** » Tue Apr 16, 2013 2:01 pm

mathmaticly you are right :)
but in reality there are some facts, like piston speed in compression stroke is slower then in ignition stroke and so on

the theory says that the ignition to burning time amounts 2ms
so on 3000 rpm you need less than 45° btdc (before top dead center)

regards

by **des** » Tue Apr 16, 2013 9:37 pm

ty bud

by **des** » Sat Apr 20, 2013 3:36 pm

This is Fiat Albea 1.4(stok) log (File attached but some reason very low quality, here another link http://img14.imageshost.ru/img/2013/04/ ... cac1d3.jpg)

So what range of values is usually using in stok petrol engines? Here it -11.1min to 47.9max on 737rpm to 6300rpm. I guess if engine running on negative spark advance values then spark happens after top dead center. Why? Explain or correct me please.