Advanced Engineering Tech - camming for high altittude
09-26-2011, 07:19 PM
I live in Guadalajara,Mexico the city is at 5200 feet , scanners read 83kpa of pressure on cars. people here says that cams with tight lsa doesnt work around here.
They use 114 lsa cams , and most of them are below 226 degrees at .050. Are their setups wrong? or they learned the bad way what works around here?
Thanks for your help
10-10-2011, 07:09 PM
I live at about 4500 ft and I have noticed that a slightly wider lobe separation seems to work a little better but as for the duration, you can still run a lot more than that broom stick handle if you want to make some bigger hp. The tuning is a lot more tricky with the low air pressure and you could probably run a few degrees less exhaust duration. You wont have near as much cylinder pressure as you would at low elevation so more compression really helps a lot. Guys running a cam that small are probably just trying to make up for not having enough compression to start with. Just for an example (not the best one) my yamaha banshee has 170psi cranking pressure at 2000 feet and only 135psi at 4500 feet.
10-10-2011, 09:10 PM
I have heard tales about people runnign as high as 12 static CR wirh the big cams on 91 octane... I should work with high static CR and tell the cam designer were the car will be raced
10-11-2011, 05:56 PM
At that elevation you could get away with 12:1 scr pretty easy with a moderate cam, but there are a lot of variables. Im running a 25x /25x cam on a 112 cl with a 11.65:1 scr at 4500 feet and it still runs fine on pump at low elevation as well. Using TR7 plugs. Make sure you knock of all the sharp edges on your piston tops and cumbustion chamber and get the quench set at .040. You might talk to some of the fast colorado guys and see whats working for them being a mile high. FI is the best way to go for high elevation if you have the $. Some diesel manufacturers refer to a turbo as an alltitude compensator lol.
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