Lobe Seperation Angle
Lobe Seperation Angle Ok, I realize the general idea of lsa, and what results it gives such as a choppy idle...but when you change your lsa, what are you actually changing? What benefits and disadvantages does it actually have and is it good to have a higher or lower lsa???
take 2 cams with identical duration and lift but 2 different lsa. just for an example, lets compare a 224/224 .563/.563 112 lsa and 224/224 .563/.563 114 lsa. the tighter the lsa, the more valve overlap(the time measured in degrees that both the intake and exhaust valve are open at the same time) you produce. this gives you that choppy idle. of course a wider lsa will produce a smoother idle, though it will suffer in the low rpm range where good torque for the street is desired. correct me if im wrong Predator or Patrick, but i believe a tighter lsa will bring on power a little sooner, but the wider lsa will give you a nice flatter/broader curve...and might hold power a little longer at the end of each gear.
Last edited by Raise; Jul 25, 2007 at 01:01 AM.
Originally Posted by N4cer
Here's a basic idea of how I've seen it play out in the cars in my area. This is just a general idea I drew really quickly, but you can get the point:
Good graphic!
i thought basically the lower lsa would just shift the power curve to a higher rpm, much like the diff between the v.2 and the v.3 torquer from tsp, the v.2 even with a longer intake duration has its power starting 600 rpm less then the v.3, mainly because the v.3's standard lsa is 111 and the v.2's is 114.... also,the v.3's intake lobe is higher, but that should have no effect on peak hp (in rpm band, not the actuall hp value)and rpm range.
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You thought wrong. And how do you know where the power starts with every setup anyway? Those ranges are just examples. They're not accurate. That's why you can't compare those numbers between two companies.
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Originally Posted by N4cer
Here's a basic idea of how I've seen it play out in the cars in my area. This is just a general idea I drew really quickly, but you can get the point:
yhea but you can compare within the same company.... look at tsp, compare the V.2 and the v.3 and there power curves, the v.2's specs are 232/234 .595/.598 114 Standard LSA and the power band from TSP is 1800 - 6400 rpm. The v.3 is 231/234 .643/.598 111 Standard LSA, and the power band fron TSP, the same company that rates both, is 2300-6700. and the PEAK is 6400. To me, it seems like the peak hp in the v.3 is right on top of the RPM power band range for the v.2 Even with its bigger duration its power band is lower, that to me, seems like it has to do with the LSA being 3 bigger then the v.3
thanks for sharing those! 
LSA alone is meaningless sort of. Lobe seperation combined with duration is where you get most of your valve events from and is what determines your overlap period, which really will determine how much your motor chops. For a given duration on a cam if you make the LSA numerically higher the overlap period decreases.
The more overlap you have the choppier the car will idle and run at low RPM because more overlap causes there to be less vacuum in the engine, but at high rpm it aids in forcing a fast rush of air through the engine. Its like the rush of exhaust gas out sucks along fresh air in during overlap, and this rushing is great at high rpm. Thats why big cam cars breathe so well up top.
The more overlap you have the choppier the car will idle and run at low RPM because more overlap causes there to be less vacuum in the engine, but at high rpm it aids in forcing a fast rush of air through the engine. Its like the rush of exhaust gas out sucks along fresh air in during overlap, and this rushing is great at high rpm. Thats why big cam cars breathe so well up top.
