cam lsa question
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From: Richmond, VA Where fast cars, well......are hard to come by.
cam lsa question From what I've gathered, lowering the lsa will make the power peak come in sooner, but will also make it more 'peaky'. I noticed that one of the 'reverse split' cams posted about recently had a 111 lsa to it. I'm planning on getting the tr224 112 cam, but has anybody tried a 111 or 110 lsa on a cam of similar duration/lift/ramp rates <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> ? I'm just interested in trying to keep the shifts lower to be less taxing on the engine.
Re: cam lsa question Tightening up the LSA results in more overlap (for the same duration numbers/ramp rates), which usually means a lopier idle and power that comes on a little bit earlier.
As for a 110 LSA, that's what the GM ASA cam is... a cam that's meant to run between @3500-@6500 all the time. Frankly, it would idle like poo, so most folks stick with something with a little more lobe sep in the name of having something that is livable with an idle under 1200.
I'm not saying that it can't be done (a LOT of traditional hydraulic flat tappet cams are ground on a 110), but for a daily driver I think it would be a major PITA. Just my $.02...
As for a 110 LSA, that's what the GM ASA cam is... a cam that's meant to run between @3500-@6500 all the time. Frankly, it would idle like poo, so most folks stick with something with a little more lobe sep in the name of having something that is livable with an idle under 1200.
I'm not saying that it can't be done (a LOT of traditional hydraulic flat tappet cams are ground on a 110), but for a daily driver I think it would be a major PITA. Just my $.02...
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Joined: Jan 2002
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From: Carrollton, TX
Re: cam lsa question 110lsa's don't idle like poo. Perhaps in EFI cars they do, nothing that can't be cured with correct computer tuning.
Generally:
tighter LSA will have more overlap, which means
at lower speeds you have slightly less cyllinder pressure, but higher speeds you have more cyllinder pressure than a wider LSA cam.
tight LSA tend to make high peak TQ numbers. Curves are not necessary peaky, simply more pronounced over desired RPM range.
tighter LSA's use the exhaust system more to fill the cyllinder. This is why the air must get moving first, once it gets moving, with a properly designed exhaust system you will be packing those cyllinders tight.
tigher LSA's are usually run at a earlier intake centerline. Means that intake valve is more open during strongest portion of induction cycle. Also means its open more when piston moving up - so you better have proper valve clearance.
tighter LSA will cause "blow down" to occur later, making a bit more power, exhaust valve will also close later.
"blow down" actually occurs while piston is still moving downward.
tighter LSA mean intake valve closes earlier, which means you trap more cyllinder pressure - as piston chases closing intake valve for a very short moment during compression. Hopefully intake tract is tuned to continue to pack cyllinder during this period.
Once you look at what the valves and pistons are doing it helps duration, overlap, lsa to be easier to understand.
Generally:
tighter LSA will have more overlap, which means
at lower speeds you have slightly less cyllinder pressure, but higher speeds you have more cyllinder pressure than a wider LSA cam.
tight LSA tend to make high peak TQ numbers. Curves are not necessary peaky, simply more pronounced over desired RPM range.
tighter LSA's use the exhaust system more to fill the cyllinder. This is why the air must get moving first, once it gets moving, with a properly designed exhaust system you will be packing those cyllinders tight.
tigher LSA's are usually run at a earlier intake centerline. Means that intake valve is more open during strongest portion of induction cycle. Also means its open more when piston moving up - so you better have proper valve clearance.
tighter LSA will cause "blow down" to occur later, making a bit more power, exhaust valve will also close later.
"blow down" actually occurs while piston is still moving downward.
tighter LSA mean intake valve closes earlier, which means you trap more cyllinder pressure - as piston chases closing intake valve for a very short moment during compression. Hopefully intake tract is tuned to continue to pack cyllinder during this period.
Once you look at what the valves and pistons are doing it helps duration, overlap, lsa to be easier to understand.
