Some clearifcation need on advance under load/vacuum
Posted: Mon Jan 25, 2010 1:40 pm
I'm a little confused as I've read it many different ways and I don't have a solid understanding of this yet, so I'll explain my situation as it stands and hopefully someone can clear this up for me.
I have an old VW air cooled engine, running MAP to the mjlj. At idle my vacuum reading is 97 kpa, acceleration increases vacuum, therefore the number drops. Not sure if this is backwards from other motors, but it seems to be. I have the vacuum line connected to the vacuum advance on the carb where the old dizzy was connected to. It started out confusing as at idle/no load the MJLJ mapping starts out in the bottom left of the program, instead of top left. Under acceleration the vacuum drops to around 85 kpa.
Now I've seen people say it both ways and I'm a bit confused. Under load do I want to advance the ignition or retard it? At around 1500 RPM no load I'm running at 15 deg, do I want to increase or decrease the advance, people have said pinging will occur under load so that makes believe it needs to be retarded, but with more full mixture it needs longer to burn, so it needs to be advanced right? Right now I'm retarding it, and under load at low RPM i have no power, which makes me think it's burning after TDC thus = no power.
I have an old VW air cooled engine, running MAP to the mjlj. At idle my vacuum reading is 97 kpa, acceleration increases vacuum, therefore the number drops. Not sure if this is backwards from other motors, but it seems to be. I have the vacuum line connected to the vacuum advance on the carb where the old dizzy was connected to. It started out confusing as at idle/no load the MJLJ mapping starts out in the bottom left of the program, instead of top left. Under acceleration the vacuum drops to around 85 kpa.
Now I've seen people say it both ways and I'm a bit confused. Under load do I want to advance the ignition or retard it? At around 1500 RPM no load I'm running at 15 deg, do I want to increase or decrease the advance, people have said pinging will occur under load so that makes believe it needs to be retarded, but with more full mixture it needs longer to burn, so it needs to be advanced right? Right now I'm retarding it, and under load at low RPM i have no power, which makes me think it's burning after TDC thus = no power.