Valve timing
Sun, 21/02/2010 - 21:28
Can the characteristics of an engine be significantly altered by somebody who knows what they're doing with a dial gauge and protractor without the risk of Mr Piston and Mrs Valve (and her sisters, oo-er) having an unexpected snog?
Mon, 22/02/2010 - 23:30
#2
Thanks Kev, I was actually wondering whether
Thanks Kev, I was actually wondering whether the midrange could be improved at the expense of some top end, and guess from what you've said that that would involve retarding the inlet cam for less overlap. Will pop in to Smiths again and read your full explanation!
Cheers
You want to mess with this?
http://www.youtube.com/watch?v=VSDa-EUT3ZE
Because you can't alter the valve duration or lift that way you can't make a big change to the character of an engine. But some production engines have had their top end power increased a bit by having the inlet cams advanced by 10 degrees or so, with no other changes. This increases valve overlap which suits high power better (that's MCN for you next week Wobbly... not one of yours this time though!) and the ignition timing will have to be adjusted to suit. But that sort of thing is about as far as you can go, and even then it'd be worth checking valve and piston are still keeping a respectful distance from each other.
To really affect the character you'd need to change lift and duration, and with those done you'd need to alter compression ratio, then the exhaust and inlet dimensions, and the valve sizes too.... the whole thing cascades through the motor and into the transmission, there's no single thing you can do to make a big difference.