- Feb 5, 2009
- 3,183
- 63
I see that we have a lot folks here with some great question's .
So I have decided that it would be of great benefit to all here if I were to post up a weekly segment on some performace upgrades as well as infomation what certain terms mean, and what certain parts do for performance. To start off the first segment, I thought I would do a cam explaination as many are now looking at that performance mod.
Camshaft:
Duration (2xx/2xx) means how long the valves are open with each rev of the camshaft. Longer valve opening time usually means more power to a certain extent but you can go overboard. Duration also will increase emissions. There are split cams where the second number (exhaust valve duration) is bigger, this is usually for super/turbo/nitrous, since your intake is now more efficient than your exhaust, so it keeps the exhaust valve open longer. Reverse split is becoming popular for naturally aspirated, since our cars typically have very good flowing exhausts and the intake needs some extra help to keep up. The first number (intake) is larger on this type. Duration seems to affect the width of the powerband. Duration is a measure of degrees but I can't figure out exactly how it is measured. But one way to look at it is the width of the lobe.
Lift (.5xx/.5xx or .6xx/.6xx if you're nuts) seems to be the point where the most power is available. Doesn't seem to affect emissions much but allows more air to go in and out in the same period of time. Higher lift necessitates better springs, since they are moving a lot more in the same amount of time and compressing a lot more. Broken springs can ruin your engine, so duals are a very safe bet. Lift seems to push the middle 80% of your HP/torque curve upwards. Lift is measured in inches, the height from the core of the cam to the top of the lobe.
LSA is the angle between the intake and exhaust lobes. This determines the time between when the intake valve closes and the exhaust opens. Too small and you get overlap, where they are both open at the same time and you can get fresh air and exhaust mixing (that's bad). Duration and LSA coupled together cause this. Lower LSA typically moves your power down a tad in the RPM range, higher moves it up.
ID is timing ground into the cam. Personally I'd rather let my adjustable timing chain do this job, but many order theirs with -2 or -4 timing, if you don't have an adjustable timing chain this can gain you some extra power, and -2 and -4 don't seem to cause any problems with the car that I've read about, in fact -2 seems to be what a lot of people order by default. Like I said, the adjustable chain makes it a lot more flexible and less permanent.
LSA and Lift affect the "sound" and idle quality of the car. 112 LSA even with a moderate lift can cause stalling or sputtering, especially on an A4 car.
Camshaft Basics:
-Lobes are the bumps on the cam that indirectly push the valves open
-Duration (2xx/2xx) is the width of the lobe and determines how long the valve stays open, and correlates somewhat to the height and width of your powerband.
-Lift (.5xx/.5xx) is the height of the lobe and determines how far/high the valves open, and correlates somewhat to the height of your powerband, also contributes to the sound and idle quality.
-LSA is the time between when the intake valve opens/closes and the exhaust valve opens/closes, or really any combination of those two depending on where you are in the cycle, and correlates to the position of your powerband on the RPM scale (lower LSA = lower on the scale and higher = higher), also contributes to sound and idle quality.
Ok so there it is the first segment .
Just ask away and we will try to best answer your questions.
Next segment will be on heads
Thx
[email protected]
So I have decided that it would be of great benefit to all here if I were to post up a weekly segment on some performace upgrades as well as infomation what certain terms mean, and what certain parts do for performance. To start off the first segment, I thought I would do a cam explaination as many are now looking at that performance mod.
Camshaft:
Duration (2xx/2xx) means how long the valves are open with each rev of the camshaft. Longer valve opening time usually means more power to a certain extent but you can go overboard. Duration also will increase emissions. There are split cams where the second number (exhaust valve duration) is bigger, this is usually for super/turbo/nitrous, since your intake is now more efficient than your exhaust, so it keeps the exhaust valve open longer. Reverse split is becoming popular for naturally aspirated, since our cars typically have very good flowing exhausts and the intake needs some extra help to keep up. The first number (intake) is larger on this type. Duration seems to affect the width of the powerband. Duration is a measure of degrees but I can't figure out exactly how it is measured. But one way to look at it is the width of the lobe.
Lift (.5xx/.5xx or .6xx/.6xx if you're nuts) seems to be the point where the most power is available. Doesn't seem to affect emissions much but allows more air to go in and out in the same period of time. Higher lift necessitates better springs, since they are moving a lot more in the same amount of time and compressing a lot more. Broken springs can ruin your engine, so duals are a very safe bet. Lift seems to push the middle 80% of your HP/torque curve upwards. Lift is measured in inches, the height from the core of the cam to the top of the lobe.
LSA is the angle between the intake and exhaust lobes. This determines the time between when the intake valve closes and the exhaust opens. Too small and you get overlap, where they are both open at the same time and you can get fresh air and exhaust mixing (that's bad). Duration and LSA coupled together cause this. Lower LSA typically moves your power down a tad in the RPM range, higher moves it up.
ID is timing ground into the cam. Personally I'd rather let my adjustable timing chain do this job, but many order theirs with -2 or -4 timing, if you don't have an adjustable timing chain this can gain you some extra power, and -2 and -4 don't seem to cause any problems with the car that I've read about, in fact -2 seems to be what a lot of people order by default. Like I said, the adjustable chain makes it a lot more flexible and less permanent.
LSA and Lift affect the "sound" and idle quality of the car. 112 LSA even with a moderate lift can cause stalling or sputtering, especially on an A4 car.
Camshaft Basics:
-Lobes are the bumps on the cam that indirectly push the valves open
-Duration (2xx/2xx) is the width of the lobe and determines how long the valve stays open, and correlates somewhat to the height and width of your powerband.
-Lift (.5xx/.5xx) is the height of the lobe and determines how far/high the valves open, and correlates somewhat to the height of your powerband, also contributes to the sound and idle quality.
-LSA is the time between when the intake valve opens/closes and the exhaust valve opens/closes, or really any combination of those two depending on where you are in the cycle, and correlates to the position of your powerband on the RPM scale (lower LSA = lower on the scale and higher = higher), also contributes to sound and idle quality.
Ok so there it is the first segment .
Just ask away and we will try to best answer your questions.Next segment will be on heads
Thx
[email protected]
Last edited:
