Camshaft profiling..
Camshaft profiling..
I'm trying to decide upon another camset as my hks280's got ruined in the drastic accident
I've been looking and searching for an ideal set.
I've looked at Tomei and Jun among others.
I'm curious as to what makes what.
Lift vs duration what makes power and what makes torque/spool? I'm going to start doing some road racing and running a 50 trim...and I'd like to retain and keep as much midrange as possible.
I'm just really curious as to whether more duration or more lift is better for more torque and spool and whatnot.....
I've been looking and searching for an ideal set.
I've looked at Tomei and Jun among others.
I'm curious as to what makes what.
Lift vs duration what makes power and what makes torque/spool? I'm going to start doing some road racing and running a 50 trim...and I'd like to retain and keep as much midrange as possible.
I'm just really curious as to whether more duration or more lift is better for more torque and spool and whatnot.....
In a nutshell, and in very basic terms . . .
- Effective duration directly influences the usable rpm range. The longer duration, the more mechanically efficient the engine can be at higher rpm. Of course, this depends upon the ability of turbo, manifolds, head flow, and various other parts to support it. If the cam duration is too short, the power will drop off quickly at high rpm. If it is too long, the engine will be very soggy at low rpm. Ideally, the cams should be matched to the turbo and realistic anticipated usage. Just remember that to get something, one almost always gives up something else.
- Lift is how far the valves are opened, and there is a point whereby opening the valves further will not measurably improve airflow. A stock EVO head doesn't respond on the flowbench to anything above ~10.2mm or so of lift. Some ported heads can make use of upward of 11.5mm or so, but there is a lot of variation in various vendors' ported heads. More lift than the head can realistically use just makes it harder on the valvetrain.
- Increasing lift and/or duration increases overlap, and we haven't even talked about lobe centerlines and lobe separation angle, all of which affect the operational characteristics of the engine, and all of which can be adjusted using cam gears.
- We haven't mentioned ramp rates either.
As for your question, if torque, spool, and midrange punch are your first priorities, you want a cam set that has enough lift to maximize airflow through the ports (not a common issue with EVOs), fairly aggressive ramp rates, and moderate effective duration. You want slightly advanced LCs, and a relatively tight LSA. With careful consideration and adjustment, you can get what you want, and not significantly impact high rpm potential of that turbo.
- Effective duration directly influences the usable rpm range. The longer duration, the more mechanically efficient the engine can be at higher rpm. Of course, this depends upon the ability of turbo, manifolds, head flow, and various other parts to support it. If the cam duration is too short, the power will drop off quickly at high rpm. If it is too long, the engine will be very soggy at low rpm. Ideally, the cams should be matched to the turbo and realistic anticipated usage. Just remember that to get something, one almost always gives up something else.
- Lift is how far the valves are opened, and there is a point whereby opening the valves further will not measurably improve airflow. A stock EVO head doesn't respond on the flowbench to anything above ~10.2mm or so of lift. Some ported heads can make use of upward of 11.5mm or so, but there is a lot of variation in various vendors' ported heads. More lift than the head can realistically use just makes it harder on the valvetrain.
- Increasing lift and/or duration increases overlap, and we haven't even talked about lobe centerlines and lobe separation angle, all of which affect the operational characteristics of the engine, and all of which can be adjusted using cam gears.
- We haven't mentioned ramp rates either.
As for your question, if torque, spool, and midrange punch are your first priorities, you want a cam set that has enough lift to maximize airflow through the ports (not a common issue with EVOs), fairly aggressive ramp rates, and moderate effective duration. You want slightly advanced LCs, and a relatively tight LSA. With careful consideration and adjustment, you can get what you want, and not significantly impact high rpm potential of that turbo.