LSA and LCA ??

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steve cowan
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Re: LSA and LCA ??

Post by steve cowan »

cjperformance wrote: Thu Jul 12, 2018 9:53 am hi guys,
i am more than happy to be corrected but OP is talking about DV and his rule of thumb deal,
i just re-read how to build horsepower pages 103-107 and DV talks of LCA lobe centreline angle and no mention of LSA thats why i mentioned it as i did in my earlier post, i understand what Walter and Craig are saying but i interpreted as per DV as the OP was talking about,if i am incorrect that is fine as i may of been a bit confused myself
I dont have that book Steve, in what context is LCA used?
[/quote]

hi Craig,
DV uses LCA in his book as an example
106 LCA rough idle,low manifold vacuum etc
114 LCA smooth idle,high manifold vacuum etc
you and I call it LSA lobe seperation angle
i only remembered it from reading it in his books hence my they are the same reply but after Walter and yourself pointed out in your posts i can see where the terminology is mixed
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Re: LSA and LCA ??

Post by cjperformance »

steve cowan wrote: Thu Jul 12, 2018 4:52 pm
cjperformance wrote: Thu Jul 12, 2018 9:53 am hi guys,
i am more than happy to be corrected but OP is talking about DV and his rule of thumb deal,
i just re-read how to build horsepower pages 103-107 and DV talks of LCA lobe centreline angle and no mention of LSA thats why i mentioned it as i did in my earlier post, i understand what Walter and Craig are saying but i interpreted as per DV as the OP was talking about,if i am incorrect that is fine as i may of been a bit confused myself
I dont have that book Steve, in what context is LCA used?
hi Craig,
DV uses LCA in his book as an example
106 LCA rough idle,low manifold vacuum etc
114 LCA smooth idle,high manifold vacuum etc
you and I call it LSA lobe seperation angle
i only remembered it from reading it in his books hence my they are the same reply but after Walter and yourself pointed out in your posts i can see where the terminology is mixed
[/quote]

Ah i see, yes as you say definitely referring to LSA.
This is why i say to double check ANY terminology with the person/company so you get it right. The ammount of times I call a cam or any parts company and ask stuff about terminology is rediculous, they probably see mu number come up and think "ffs not this clown again" ! :lol: but it certainly helps clear up some othewise possibly problems.

Madbill - yes Elderbrock - how annoying ! Just as bad as a Weland intake manifold ! #-o
Craig.
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Re: LSA and LCA ??

Post by BigBro74 »

exhaustgases wrote: Thu Jul 12, 2018 3:30 pm
BigBro74 wrote: Thu Jul 12, 2018 1:54 pm
MadBill wrote: Thu Jul 12, 2018 1:37 pm I've been guilty most of my life of using the LCA term by preference, but interchangeably with LSA, to indicate the angle in cam degrees between lobe centerlines, but as per this thread only the latter is correct. However the terms remain interchangeable in popular use to such an extent that no one should assume a difference.
It's like torque measurement: the correct unit is pound-foot, but more often than not foot/pound is incorrectly used.
(and then of course there's "El-de-brock", but let's not go there...) :)
I am in the same boat here Bill, and at many sources may be somewhat ambiguous.

From Isky glossary of terms (they stayed out of it lol)

"LOBE CENTERS: The distance measured in degrees between the center line of the intake lobe and the center line of the exhaust lobe of the same cylinder."

http://www.iskycams.com/glossary.html

Jason
Deleted . No time to finish it.
? :?:
Intake centerline (ICL)= Crank degrees (centered between open close events)
Exhaust centerline (ECL)= Crank Degrees (center of open/close also)
Lobe center angle (LCA)= Camshaft degrees (the angle in degrees between ICL and ECL)
Lobe separation angle (LSA)= (from CC catalog) "The number of degrees separating the PEAK LIFT POINT of the intake and exhaust lobes"- and interestingly comps graph is as such (shows peak LIFT points, in Camshaft degrees), while the other diagrams I have seen draw a line through the whole center of the lobe.
I also think that maybe these terms could be more/less descriptive as the lobe becomes less symmetrical (which I know is often)
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Re: LSA and LCA ??

Post by David Redszus »

Lobe center angle (LCA)= Camshaft degrees (the angle in degrees between ICL and ECL)

Lobe separation angle (LSA)= (from CC catalog) "The number of degrees separating the
PEAK LIFT POINT of the intake and exhaust lobes"-


I think both definitions have merit and should be universally adopted nomenclature.

However, I fail to see much value in either number, unless the valve event degrees are
included, and NOT at 0.050". They can be used to indicate camshaft indexing which is another matter.

My preference for camshaft description, would be:
IVO ICL IVC lift for each lobe.

As an example: 18 - 108 - 66 - .375 would provide a great deal more
information than is commonly available. And the numbers can be used to determine duration,
overlap, blowdown, and input for time/area analysis.
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Re: LSA and LCA ??

Post by Turbo231 »

[

My preference for camshaft description, would be:
IVO ICL IVC lift for each lobe.

As an example: 18 - 108 - 66 - .375 would provide a great deal more
information than is commonly available. And the numbers can be used to determine duration,
overlap, blowdown, and input for time/area analysis.
[/quote]

These definitely are the most important and ultimately encompass everything else.
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Re: LSA and LCA ??

Post by gmrocket »

Walter R. Malik wrote: Wed Jul 11, 2018 7:08 pm
Turbo231 wrote: Wed Jul 11, 2018 4:45 pm Just got through the post started by David Vizard on Rule of Thumb. All I can say as a newbie is, you guys can be pretty passionate about your opinions. Of course as a newbie, there is no way in heck I am getting into one of these discussions. At least for now :) .

I do have a question though: I saw LSA and LCA and they seemed to be used interchangeably. From my understanding, LSA is "lobe separation angle" and is actual cam degrees (not crankshaft) between intake and exhaust lobes. I have not seen LCA which looks to be "lobe center angle". Are these the same or not? If they are same, what does majority on this site use? Thanks.
Sometimes those terms are incorrectly interchanged:
Lobe Separation Angle is indeed the number of cam degrees between the intake and exhaust lobes.
Lobe Center Angle is the angle in crankshaft degrees of THAT particular lobe in relation to top dead center of the engine for that cylinder being measured.

They are usually NOT the same number but, sometimes are.
Yup...and if someone is mixed up on it, they don't understand.

When it's used in a sentence, that's where it makes sense to those who understand. You automatically know which variation is being referred too.
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Re: LSA and LCA ??

Post by John Wallace »

As an example: 18 - 108 - 66 - .375 would provide a great deal more
information than is commonly available.
Wouldn't you need to know at what lift measurement the open/close was used?
(like .004"/.006" or .050" or whatever)

The 108 is redundant unless it means LSA, which could be used to find the exhaust numbers with just those 4 data points.

:?:
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Re: LSA and LCA ??

Post by DrillDawg »

In the old days, lol, they installed the cams by checking the opening and closing numbers, but someone along the way wanted a faster (maybe easier) way to do the checking and started using the intake centerline method. Then everyone forgot about the opening and closing numbers or never knew about them in the first place.
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Re: LSA and LCA ??

Post by user-23911 »

Well that was a long discussion.

A bit like a half race.....lol....... (wade 260) cam at 20, 60, 60 , 20 and a 3/4 race (wade 280) cam at 30, 70, 70 , 30.
Both have common LCA. LSA, ICL and ECL of 110.
One has a 40 deg overlap, the other a 60 deg overlap.
Have different idle characteristics and different power band.
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Re: LSA and LCA ??

Post by gmrocket »

BigBro74 wrote: Thu Jul 12, 2018 1:54 pm
MadBill wrote: Thu Jul 12, 2018 1:37 pm I've been guilty most of my life of using the LCA term by preference, but interchangeably with LSA, to indicate the angle in cam degrees between lobe centerlines, but as per this thread only the latter is correct. However the terms remain interchangeable in popular use to such an extent that no one should assume a difference.
It's like torque measurement: the correct unit is pound-foot, but more often than not foot/pound is incorrectly used.
(and then of course there's "El-de-brock", but let's not go there...) :)
I am in the same boat here Bill, and at many sources may be somewhat ambiguous.

From Isky glossary of terms (they stayed out of it lol)

"LOBE CENTERS: The distance measured in degrees between the center line of the intake lobe and the center line of the exhaust lobe of the same cylinder."

http://www.iskycams.com/glossary.html

Jason
I take iskys "lobe centers" to mean in relationship to each other, not where it's installed at. I think that's why it's plural.
So the way that is written, to me means the same as LSA... no confusion

If it said "lobe centerline" that would mean singular, as in one lobe in relation to the point at which the mid point of the lobe is installed at.

The confusion comes from both being shortened to LC and then adding the A.... notice isky does not add "angle" after lobe centers

When someone uses the term LCA, they have to be specific or use it in context .. not just blurt out LCA
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Re: LSA and LCA ??

Post by BigBro74 »

I know that this is all semantics and that we understand what is going on - like long thread for not much........so sorry... I will quit after this

GMR- I agree with you on most of this completely, the exception is that I feel that when we say “lobe center angle” (which I do most😐time) that we are discussing the included angle (happens to be camshaft degrees) that falls between the intake and exhaust lobe center lines. Those lobe centerlines are described or located by a crank angle, and can change by cam phasing (advance/ret.) to be whatever we want within reason, but the LCA (and LSA) on two valve pushrod V8 engines will be the same angle and still in cam degrees (unless dual cams!, and then only if we just change one) . I never do any work on dual cam engines though so not really m deal there, but could be really important to their timing as well to know I guess.....
Sorry long post- just thinking out loud here- Jason
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Re: LSA and LCA ??

Post by gmrocket »

BigBro74 wrote: Sun Jul 15, 2018 1:05 pm I know that this is all semantics and that we understand what is going on - like long thread for not much........so sorry... I will quit after this

GMR- I agree with you on most of this completely, the exception is that I feel that when we say “lobe center angle” (which I do most😐time) that we are discussing the included angle (happens to be camshaft degrees) that falls between the intake and exhaust lobe center lines. Those lobe centerlines are described or located by a crank angle, and can change by cam phasing (advance/ret.) to be whatever we want within reason, but the LCA (and LSA) on two valve pushrod V8 engines will be the same angle and still in cam degrees (unless dual cams!, and then only if we just change one) . I never do any work on dual cam engines though so not really m deal there, but could be really important to their timing as well to know I guess.....
Sorry long post- just thinking out loud here- Jason
Gotcha..I understand it either way.
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