Announcements

Over the last couple years the priorities in my life have changed. Had Matrix Garage grown big enough to hire enough employees and leave them to running it while I pursued other things I would have happily taken that route but it has generally stayed just big enough to keep me working overtime. 
I have decided to start focusing my carreer and passions elsewhere and that means that supporting the AW, AE, 4A and related communities has had to be moved much lower on the priority list. I have decided to keep the store up to provide parts that only we offer, or other things that are hard to come by elsewhere. You will notice many big name, readily available products have been taken down and we will continue to do so. It's just not worth our time trying to compete with the big corporations selling at cutthroat prices and it just takes up more of my time. 
I will try to keep providing those parts that we make or that we have developed and sell as a service to the community but understand that now this is something I do in my spare time because I don't want to leave people hanging. 
I try to make shipments and process orders at least twice a week. If you want Amazon next day shipping buy from Amazon. I will do my best to keep order time and customer service at a reasonable level but have some understanding. I am not making money on this and it takes away from my other work and other issues that are very important to me right now. 
I have always wanted to make our designs and other information open source and available to the community but to do so properly would take a lot of time making sure that models and drawings were complete, accurate, or properly described. To go through everything and make sure it was something that I felt comfortable releasing to the community. I would love to find someone who was willing to help me do this. Someone in engineering school or passionate about this to help go through 3D scans, CAD designs, and information to prepare it. If you are interested feel free to email me. 


 

 


 

Understanding basic principles of cam timing.

Someone  posted on one of the facebook groups asking why cams needed to close so far after bottom dead center.
This was a bit of typing so I had to post it here too. Like all my quickly blurted out articles I need to try to improve on it and edit it when I have time.
This article also closely ties into my article on why DCR is such a load of BS.

If one thinks in static terms you would assume that the cam should close at BDC as that is where the cylinder would be most full of air.
You have to remember that at 6k RPM the motor is spinning 100 times a second. That's hard to fathom.
The compression stroke is happening 50 times a second.
At 12k RPM on a Formula Atlantic or sport bike engine it's happening twice as fast.

You have to try to imagine things taking place hundreds of times a second. Then you have to remember that even air has mass and takes time to change direction.
At close to 0 RPM you are right, the piston will travel down and at BDC the cylinder will get as full as it's going to get.
As RPM increases it takes longer in relation of crank timing for everything to happen.
The intake valve opens while the piston is still traveling upwards so the overlap and exhaust momentum can help start pulling the fresh air in. After TDC the exhaust cam closes and the piston travels downwards. The air can't accelerate as fast as the piston so the piston creates a low pressure zone as it acceleraes downward at a mind boggling rate. The air starts to rush into the intake valve as it tries to fill that low pressure zone. When the piston hits BDC the pressure in the cylinder is still below the pressure in the port so that air is still rushing in through the valve.
The piston starts accelerating upward at a mind boggling rate but that air will take time to change direction. The piston will hit the air at the bottom of the cylinder and create a high pressure zone but there is still lower pressure at the top of the cylinder so air is still rushing in.
Perfect valve timing is closing the valve right as that pressure wave traveling upward hits the valve and pressure equalizes on each side of the valve. If the valve closes right then the cylinder will have as much air in it as it can get and the most power potential it will have.
The faster the motor spins the more duration you need for this to happen so a static cam can only hit that perfect point at one RPM. The rest of the time it will be a little off. If the valve closes too early it will stop air still flowing in. If it closes a little too late it will allow a little air to be pushed back out.

 

courtesy of webmatter.de