> From: "Steve Ingels" <[email protected]> > Subject: Re: Why can't I get my timing right? > > Explain this to me. Retarding gives top end and advancing gives torque. Is > that correct?
its not quite that easy. also, you have it backwards. the more advanced your timing, the higher up your power will be. also, note that *advancing* the timing is rotating the distributor CLOCKWISE, or toward the back of the car. all advancing or retarding the timing does is tell the spark when to fire, with respect to the piston. ideally, you want the explosion to occur right when the piston gets to TDC...however, in the real world, the explosion takes time to completely fill the combustion chamber. so if you fire right at tdc, the piston is already travelling down when the gasses fully combust. hence, you want to fire a little bit before tdc, so the explosion occurs right at tdc. thats why our cars are timed to 6 degress advanced--BTDC, or "Before Top Dead Center". now you also have to take into account that the piston is moving way faster at 6000 rpms then at 2000 rpms. if the explosion itself takes pretty much the same time to fully combust regardless of engine speed, you have to change when you first fire the spark, to make sure the explosion occurs right at tdc. if 6 degrees advanced will fully combust right at tdc at 2000 rpms, you might need to advance to 30 degrees BTDC to combust at tdc, if youre at 6000rpms. (i think its somewhere in the 30-40 range at redline, but i'm not sure) unfortunately, with 16v's, you have to settle for one position for timing advance. most 16v guys will go for 12 degrees at idle, cause thats the best all around. you could go more and get a better top end, but you would lose some down low. also, if you are way advanced, your explosion could actually compltely occur BEFORE the piston gets to the top of the cylinder atlower rpms. in that case the explosion is trying to push the piston down, but the engine is still trying to push the piston up. this is a source of pre-detonation, or pinging. its bad. i probably could keep going, but break time is over. ben "blah blah blah" randolph _____________ List Sponsor: http://www.netsville.com To remove yourself from this list, send mail to [email protected] with 'unsubscribe a2_16v' in the body of your message See us on the web at http://www.a2-16v.com Visit the 16V Homepage at http://www.gti16v.org
