How do uprated cams work?

1. Byard Regular Poster Joined: Jan 2009 Chesterfield Posts: 263 BMW 330d, Arctic Steel Silver TU5JP4, 1.8 Focus

   #1 18th May 2010, 10:47

   Do they just open the valves more than normal and therfore let more air and fuel in and let gasses escape quicker?
2. Colin Saxperience Forum Bum Joined: Jan 2006 Banbury Posts: 4623 Saxo Rally Car Evo 6

   #2 18th May 2010, 10:53

   They hold the valves open for longer and further, so more air/fuel is drawn in. Tuning the valve "overlap" is key to good running too. In a nutshell....
3. Sparco_Tom Saxperience Addict Joined: Jan 2007 Aylesbury, Bucks Posts: 12836 Yeaaahh Fiesta

   #3 18th May 2010, 11:01

   nail on the head ^
4. Byard Regular Poster Joined: Jan 2009 Chesterfield Posts: 263 BMW 330d, Arctic Steel Silver TU5JP4, 1.8 Focus

   #4 18th May 2010, 14:07

   Thought so, thanks Colin
5. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #5 18th May 2010, 14:52

   If you look into it a little deeper, it's quite interesting how performance camshafts work. They change the valve opening and closing times in such a way, that they help keep a constant acceleration of the air / fuel mixture into the cylinders.
   
   When the piston moves upwards on the exhaust cycle, the inlet valve opens a little early, allowing the flow of fuel / air to maintain momentum. The exhaust valve will be open at this time too, so there'll be some waste, and also a rough idle. "overlap" is actually really difficult to describe IMO.
   
   Take a look here, this web site is excellent: http://auto.howstuffworks.com/camshaft.htm

   1 user thanked this post: user_16990
6. user_39613 Established Member Joined: Dec 2009 Essex Posts: 1006

   #6 18th May 2010, 17:10

   http://www.motorsport-developments.c...AF245_tech.pdf