Ok, look i can't find this answer and the aacure dealership was dumbfounded, but here goes, Why can't you run a high lobe cam, like say a june 3 cam with a turbo application? and if you can, can someone give me information on where I can read about it? This is for a H22 vtec motor. thanks for the help. I'm not saying that it can't be done, but i've never heard about it, I just know that there is turbo cams for turbo applications, hopefully someone can answer this for me. thanks. Bill

 

it has to do with the amount of time the valeves stay open

 

You don't want to increase overlap much (the time both the intake and exhaust valves are open at the same time) because with a forced induction engine you may blow a portion of the fresh fuel/air mixture right out the exhaust valves. Obviously, any fuel that goes out the exhaust isn't going to be turned into power. There are a lot of factors involved but you usually can make good power with a stock cam with forced induction. There are some things you can do to get even more power with the cam to suit it to the turbo like opening the exhaust valve a little bit earlier to help bleed down some of the pressure in the cylinder. This will reduce the 'pumping losses' encountered when the piston begins travelling upward and has to push the burned gases out the exhaust valves. You can gain some power by opening the valve a little further, so if that is what you meant by 'high lobe' then what you heard is wrong. In a naturally aspirated engine you can only open the valve so far until you reach a point where no more air will flow through the valve, no matter how far you open it. With a forced induction engine, however, because the intake charge is under pressure, opening the valve a little further will flow more.

Unfortunately, most people on this forum and all the others I visit are drawn in by the marketing of camshafts rather than the actual technical specifications. This is not because they are not interested, it's because a lot of the cam companies don't supply sufficient information, the marketing people are the ones who write the information a lot of the time, and the camshaft is the most complicated and least understood mechanical part of the engine. Terms like 'Stage 2' or 'Turbo-Cam' or 'High Lift' don't have any meaning unless backed up by technical specs. A camshaft is all about comprimises. For any given RPM, there is one correct amount of lift and duration - but engines don't run at only one RPM so you have to choose a cam aimed at the powerband you are interested in. It always pays to listen to the cam grinder if they offer you specific information and a recommendation because there are so many variable that go into choosing the right cam. A cam company that copies other peoples designs (which is very easy to do, it's not like you can put copy-protection on them) will most likely not know how camshafts work - otherwise they wouldn't need to copy other peoples designs. I've also seen a lot of quality issues from second rate cam grinders because they don't think about what they are making. They think if they have a CNC grinder that their cams will be more accurate than others. This is extremely false, it only means they can make more per hour. A good camshaft grinding machine operator can hold tolerances extremely close and more importantly - know when something is going wrong.

Rather than spend hundreds of dollars on cams for your turbo engine you would be better off spending the money on detonation control or a larger intercooler. They would give you more bang for the buck. If you are building an all out 800 HP turbo engine then you probably should be having a custom cam ground anyway.