Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

Lustle said
Except in this case you overlook a very simple thing. Duration. Duration has a lot to do with operating range. While lower LSA will have a "tighter" operation range - I.E a 106 LSA might have 2200-5800 operating range. While a higher LSA will have a "broader" operation range I.E a 112 LSA might be 2200-6200. Duration will determine when that range starts and ends.

This is shown in your three examples. The MP 484/284 has 241@50 duration on a 108 LSA with a range of 2200-6000 RPM. The MP .474/280 has a 238@50 duration with a 2000-6000 RPM range. This range shows that to you. With that tighter LSA the range is smaller. BUT also lower, it's hard to see but it's there. It's only 200 RPM more than the smaller cam, despite the duration increase. This is further shown with your last example. It has 228/241 @50 duration. And look at how broad the power is, idle - 5800? That's only 200/400 rpm under the other cams. Assuming idle is 850, that's an additional 2000 RPM over the other two cams. That's one broad operating range, thanks at least in part to that wide LSA, the split duration also helps.

It's easy to see a pattern of "wide LSA = rpm operating range goes down" "tight LSA = high rpm range". And overlook the other parts of the cam. A wider LSA on a smaller duration cam makes sense. Helps broaden the power curve. Without a higher LSA the smaller duration cam's would give up before 5000 RPM. While a tighter LSA on high duration cam's makes sense. With a big duration, you are usually missing low end power, which a tighter LSA can fight. Also they generally have more power that comes on harder. The big duration guys are usually racers. So they want the most power they can get and they want it at a certain RPM they run at. They don't need broad, they need power between shift points. Tighter LSA provides that.

I think I mentioned it in this thread (or one of the other six cam threads going on right now), to pick a cam for it's entirety, not just one part. And remember, a good engine is built around all the parts. And how they work together.

very well explained, sir. this single post prompted by the right questions and examples that real general folks see/ and read and draw conclusion explains the LSA. So many questions and arguments on cams lately, but when asked the right questions as how most folks see the cam listings, we get the right explanations easy to understand that hopefully will clarify to many readers the correct explanation of LSA. these couple of post should be a sticky, because it helps.