Overlap and Valve Events Editorial - Page 3 - LS1TECH - Camaro and Firebird Forum Discussion

Notices
Generation III Internal Engine 1997-2006 LS1 | LS6
Sponsored by:
Sponsored by:

Overlap and Valve Events Editorial

 
Old 04-08-2017, 01:48 AM
  #41  
TECH Junkie
 
Tuskyz28's Avatar
 
Join Date: Sep 2014
Posts: 3,277
Default

🤔very interesting on how two motors are the same cubic inch basically but have two different configurations and the valve events to be different from one another.
Tuskyz28 is offline  
Old 04-09-2017, 05:44 AM
  #42  
Staging Lane
 
Join Date: Jan 2017
Location: Sydney, Australia
Posts: 95
Default

Originally Posted by JakeFusion View Post
The Lingenfelter cams use some brutal lobes... LSK. They make insane power. But you have to build the rest of the valvetrain to support it. Lingenfelter sells Ferrea valve springs to support the LSK with the LS7 1.8 rockers.

But the Thunder Racing cam was designed for use with stock manifolds. So you had nothing helping the engine breathe on that side.


I didn't know that about this cam, thanks for the info. I had considered it since its actually available off the shelf down here but with those lobes it won't work for me. Tick Performance used to make a cam close to the 218/230 .612"/.595" 115+4 you recommend. It was a 218/230 .595"/.609" 117+2 but no longer appears on their website.

Past that my options would be:

EPS:

214/232 .605"/.598" 117 (-11 overlap)

CamMotion:

218/226 .595"/.587" 116 (-10 overlap)

CamTech:

216/226 .600"/.598" 115+4 (-9 overlap)

VCM:

216/228 .600"/.600" 115 (-8 overlap)


All except the last two are more difficult to get and more expensive to buy and have tuned down here so if that's the path I take I want it to be right (I have priced up the CamMotion but didn't pull the trigger).

Anyway, im probably taking this excellent thread off track. Thanks for the advice you have provided.
Pulse Red is offline  
Old 04-09-2017, 10:58 AM
  #43  
TECH Senior Member
 
Join Date: Jun 2016
Location: Central Cal.
Posts: 8,993
Default

No worries Pulse Red! More good info is always welcome!
G Atsma is offline  
Old 04-10-2017, 02:13 AM
  #44  
Staging Lane
 
Join Date: Jan 2017
Location: Sydney, Australia
Posts: 95
Default

Originally Posted by G Atsma View Post
No worries Pulse Red! More good info is always welcome!
Thank you sir, just making sure I'm not disrupting good high level technical discussion
Pulse Red is offline  
Old 04-10-2017, 10:56 AM
  #45  
TECH Senior Member
 
Join Date: Jun 2016
Location: Central Cal.
Posts: 8,993
Default

Originally Posted by Pulse Red View Post
Thank you sir, just making sure I'm not disrupting good high level technical discussion
It is THAT!
G Atsma is offline  
Old 09-28-2017, 10:45 PM
  #46  
Teching In
 
Join Date: Sep 2017
Posts: 5
Default

I think I'm a bit confused. I think I understand the concept of overlap. a positive overlap allows for high end power, Low or negative overlap enhances power in the low RPM range, adds low RPM torque but limits top end.
A popular Speed Shop with their own branded Cams advertise a 224/224 600/.600 available in a 114 and 112 LSA. They add comment " The 112 LSA helps to bring the camshafts power band lower in the rpm band. The lower LSA also creates a slightly rougher idle".
The 114 would yield an overlap of -4, the 112 an overlap of 0
Wouldn't the -4 (114 LSA) result in more low end performance than an overlap of 0?
What am I missing?

Last edited by Bossdog1; 09-28-2017 at 11:22 PM.
Bossdog1 is offline  
Old 09-28-2017, 11:28 PM
  #47  
TECH Senior Member
 
Join Date: Jun 2016
Location: Central Cal.
Posts: 8,993
Default

That would be correct. By lower in the RPM band I think he meant lower in the mid range band. As far as off-idle, the 114 LSA would be more responsive than the 112 LSA.
G Atsma is offline  
Old 09-28-2017, 11:29 PM
  #48  
TECH Senior Member
 
Join Date: Jun 2016
Location: Central Cal.
Posts: 8,993
Default

Mods- This thread STILL should be a sticky....
G Atsma is offline  
Old 09-29-2017, 10:16 AM
  #49  
Old School Heavy
iTrader: (16)
 
speedtigger's Avatar
 
Join Date: May 2010
Location: Florida
Posts: 8,794
Default

Originally Posted by Bossdog1 View Post
I think I'm a bit confused. I think I understand the concept of overlap. a positive overlap allows for high end power, Low or negative overlap enhances power in the low RPM range, adds low RPM torque but limits top end.
A popular Speed Shop with their own branded Cams advertise a 224/224 600/.600 available in a 114 and 112 LSA. They add comment " The 112 LSA helps to bring the camshafts power band lower in the rpm band. The lower LSA also creates a slightly rougher idle".
The 114 would yield an overlap of -4, the 112 an overlap of 0
Wouldn't the -4 (114 LSA) result in more low end performance than an overlap of 0?
What am I missing?
Unfortunately, none of this is correct. For starters, the LSA does not determine how early the powerband comes in or how high it carries. LSA itself does not mean anything. This is a myth that will not die.

But, there is a reason that LSA gets confused in this way. Here is the reason: both the intake lobe and the exhaust lobe have a centerline. A typical example of this is a camshaft ground on a 112 degree LSA. On an LS engine, this camshaft will also typically have about 2 degrees of advance ground in. This means that this camshaft will have an intake centerline of 110 and an exhaust centerline of 114. This is where LSA comes from. You add those two numbers together and divide by two. That is literally all that LSA represents.

Here is where the confusion comes in. The number one determining factor on the engines power curve on a given duration camshaft is the INTAKE CENTERLINE. The more advanced the camshaft intake centerline (and the lower the ICL value) the earlier the power will come in. And, the later the ICL (larger the ICL number) the later the powerband will come in. Again, it is the ICL not the LSA. With that said, the intake centerline or ICL is one of the two numbers and comprise the lobe center angle or LSA. So, a lower ICL will affect the LSA number. But, because the LSA is comprised of two numbers, you cannot count on the LSA alone.

Take two camshafts with the same duration but different lobe centers:



In this example, you have two camshafts with identical intake and exhaust durations. However, one has a 110 degree LSA and the other a 112 degree LSA. The LSA's are circled in orange. Of these two camshafts, the 112 LSA camshaft will have the have more peak torque and have an earlier (lower RPM) horsepower peak than the camshaft with the 110 LSA. This is exactly the opposite of the LSA myth. Why? It is the intake centerline. Notice the numbers circled in green. Even though the one camshaft has a 110 degree LSA, it also has a 110 degree ICL. However the wider LSA camshaft on 112 has an ICL of 108 degrees. That is because the 112 degree camshaft has more "advance" ground in. This is the perfect illustration why LSA is not a good indicator of powerband. LSA does not take "advance" into consideration. LSA does not communicate lobe centers at all. It merely communicates the two lobe centers relationship to one another, not where the lobe are centered. And, where lobes are centered is what determines valve events and thus powerband.

If you really want to understand what is going on, download this calculator and start experimenting with the numbers. You will learn quickly that the LSA alone means nothing.

http://www.cammotion.com/cam-timer
speedtigger is offline  
Old 09-29-2017, 10:23 AM
  #50  
Teching In
 
Join Date: Sep 2017
Posts: 5
Default

Originally Posted by G Atsma View Post
That would be correct. By lower in the RPM band I think he meant lower in the mid range band. As far as off-idle, the 114 LSA would be more responsive than the 112 LSA.
I am looking for a cam for my C5 Z06, well suited for HPDE road course activity. Would you expect a noticeable difference between the 112 and 114 coming out of a slow corner with said cam ( 224/224 600/600) mods are LS 2 TB/ fast 92 intake, Livernois stage 2 ported heads and AR headers
Bossdog1 is offline  
Old 09-29-2017, 01:34 PM
  #51  
11 Second Club
iTrader: (2)
 
A.R. Shale Targa's Avatar
 
Join Date: Feb 2011
Location: Fredonia,WI
Posts: 3,723
Default

We also tend to talk about overlap with an @.050" number when advertised duration and flank speed can manipulate the hell outta the overlap scavenging effect.
Even my old EPS 117 LS(-12 deg @.050 OL) cam changed idle sound when I went from shorty headers and four cats to long tubes and big 3" cats......indicating that a generally regarded wide lobe separation does still have overlap. The old Geoff Skinner lobes were 49 degree intensity and I have no idea if they were asymmetrical or not in shape.
A.R. Shale Targa is offline  
Old 09-29-2017, 02:36 PM
  #52  
Teching In
 
Join Date: Sep 2017
Posts: 5
Default

Originally Posted by speedtigger View Post
Unfortunately, none of this is correct. For starters, the LSA does not determine how early the powerband comes in or how high it carries. LSA itself does not mean anything. This is a myth that will not die.

But, there is a reason that LSA gets confused in this way. Here is the reason: both the intake lobe and the exhaust lobe have a centerline. A typical example of this is a camshaft ground on a 112 degree LSA. On an LS engine, this camshaft will also typically have about 2 degrees of advance ground in. This means that this camshaft will have an intake centerline of 110 and an exhaust centerline of 114. This is where LSA comes from. You add those two numbers together and divide by two. That is literally all that LSA represents.

Here is where the confusion comes in. The number one determining factor on the engines power curve on a given duration camshaft is the INTAKE CENTERLINE. The more advanced the camshaft intake centerline (and the lower the ICL value) the earlier the power will come in. And, the later the ICL (larger the ICL number) the later the powerband will come in. Again, it is the ICL not the LSA. With that said, the intake centerline or ICL is one of the two numbers and comprise the lobe center angle or LSA. So, a lower ICL will affect the LSA number. But, because the LSA is comprised of two numbers, you cannot count on the LSA alone.

Take two camshafts with the same duration but different lobe centers:



In this example, you have two camshafts with identical intake and exhaust durations. However, one has a 110 degree LSA and the other a 112 degree LSA. The LSA's are circled in orange. Of these two camshafts, the 112 LSA camshaft will have the have more peak torque and have an earlier (lower RPM) horsepower peak than the camshaft with the 110 LSA. This is exactly the opposite of the LSA myth. Why? It is the intake centerline. Notice the numbers circled in green. Even though the one camshaft has a 110 degree LSA, it also has a 110 degree ICL. However the wider LSA camshaft on 112 has an ICL of 108 degrees. That is because the 112 degree camshaft has more "advance" ground in. This is the perfect illustration why LSA is not a good indicator of powerband. LSA does not take "advance" into consideration. LSA does not communicate lobe centers at all. It merely communicates the two lobe centers relationship to one another, not where the lobe are centered. And, where lobes are centered is what determines valve events and thus powerband.

If you really want to understand what is going on, download this calculator and start experimenting with the numbers. You will learn quickly that the LSA alone means nothing.

http://www.cammotion.com/cam-timer
Thank you for the excellent summary of the info from the beginning of this thread.
So if i understand, the lower the ICL, the sooner the power increases in the RPM range.
The example on the #1 post uses the example of the following cam, describing it as a "top end screamer"
234/242 111 +3 advance. In this case the ICL is 108, with an overlap of +16, and is described as a "high end screamer". The large duration numbers and large overlap would indicate a "high end screamer", to me. the 108 ICL would indicate the opposite???
In the initial post he indicates a large overlap # pushed the power higher into the power band and a low or negative overlap number is low end torque.

I am looking for a cam with as much power in the low end the the power bans a possible, I rarely exceed 6000 - 6200 rpm.
Am I looking for a cam with negative overlap? Low ICL? Both? or do I need to add additional considerations to these when selecting a Cam for road racing application
Bossdog1 is offline  
Old 09-30-2017, 04:06 PM
  #53  
Super Hulk Smash
Thread Starter
iTrader: (7)
 
JakeFusion's Avatar
 
Join Date: Aug 2004
Location: Pace, FL
Posts: 10,722
Default

Originally Posted by A.R. Shale Targa View Post
We also tend to talk about overlap with an @.050" number when advertised duration and flank speed can manipulate the hell outta the overlap scavenging effect.
Even my old EPS 117 LS(-12 deg @.050 OL) cam changed idle sound when I went from shorty headers and four cats to long tubes and big 3" cats......indicating that a generally regarded wide lobe separation does still have overlap. The old Geoff Skinner lobes were 49 degree intensity and I have no idea if they were asymmetrical or not in shape.
They are still available from Comp as LSG lobes.. 49 degree intensity. But they were based on the LSL lobe. So very similar... but more aggressive off the seat with a tad less curtain area with a little less lift. So, in essence, a more stable, XE-R asymmetrical lobe.

I'm running LSL now and it's a very good lobe. I would almost recommend the LSG over it, though. LSG/XE or LSG/LXL would be a very good combination from Comp.
JakeFusion is offline  
Old 10-02-2017, 09:58 AM
  #54  
Old School Heavy
iTrader: (16)
 
speedtigger's Avatar
 
Join Date: May 2010
Location: Florida
Posts: 8,794
Default

Originally Posted by Bossdog1 View Post
Thank you for the excellent summary of the info from the beginning of this thread.
So if i understand, the lower the ICL, the sooner the power increases in the RPM range.
The example on the #1 post uses the example of the following cam, describing it as a "top end screamer"
234/242 111 +3 advance. In this case the ICL is 108, with an overlap of +16, and is described as a "high end screamer". The large duration numbers and large overlap would indicate a "high end screamer", to me. the 108 ICL would indicate the opposite???
In the initial post he indicates a large overlap # pushed the power higher into the power band and a low or negative overlap number is low end torque.
That is correct thinking. As the durations get higher, this will move the RPM range higher. However, more advance, or a lower ICL tends to move the RPM range lower. It is not uncommon to see a larger duration camshaft that is very advanced and is a narrow lobe separation angle. These type camshafts tend to have a lot of overlap and are typically naturally aspirated racing camshafts where no concession are made for drivability or low RPM operation.

Originally Posted by Bossdog1 View Post
I am looking for a cam with as much power in the low end the the power bans a possible, I rarely exceed 6000 - 6200 rpm.
Am I looking for a cam with negative overlap? Low ICL? Both? or do I need to add additional considerations to these when selecting a Cam for road racing application
If you notice in the example I gave above, The Cam Motion Cam Timer displays the 4 valve events. I tend to look at the 4 valve events more than anything. So my criteria is more like IVO (intake valve open), IVC(intake valve close), EVO(exhaust valve open), EVC(exhaust valve close), Overlap and lift.

For your desired RPM range, I like these events @ .050" lifter lift:
IVO: 4
IVC: 40
EVO: 50
EVC: 0
4 degrees of overlap
.621 intake lift and .603 exhaust lift

These equate to these specs:
224/230 duration on a 111.5 degree lobe separation with 3.5 degrees if advance and .621"/.604" lift.
This camshaft would have a mild lope and idle and excellent torque and acceleration to 6200 RPM. It will also have a very tractable power band that will be strong and predictable.

This is a custom camshaft. I work at Cam Motion and we make a custom camshaft like this at no extra charge. So, you can get exactly what you need.
speedtigger is offline  
Old 10-04-2017, 07:12 PM
  #55  
TECH Senior Member
 
joecar's Avatar
 
Join Date: Apr 2002
Location: So.Cal.
Posts: 6,067
Default

+1 excellent thread


can someone please post a link to Martin's thread (I am having trouble searching, it never completes).

edit: my apologies, I just saw that thread is a sticky (some days I'm just not firing on all neurons)

Last edited by joecar; 10-05-2017 at 12:50 PM.
joecar is offline  
Old 10-04-2017, 08:41 PM
  #56  
10 Second Club
iTrader: (4)
 
Darth_V8r's Avatar
 
Join Date: Jul 2014
Location: My own internal universe
Posts: 6,597
Default

https://ls1tech.com/forums/showthrea...1738022&page=1

Most posts say Matt at Tick because Matt took over martins user name
Darth_V8r is offline  
Old 10-04-2017, 08:44 PM
  #57  
TECH Senior Member
 
joecar's Avatar
 
Join Date: Apr 2002
Location: So.Cal.
Posts: 6,067
Default

Thanks, appreciated.
joecar is offline  
Old 10-04-2017, 08:53 PM
  #58  
10 Second Club
iTrader: (4)
 
Darth_V8r's Avatar
 
Join Date: Jul 2014
Location: My own internal universe
Posts: 6,597
Default

That thread should be required reading
Darth_V8r is offline  
Old 10-04-2017, 10:31 PM
  #59  
TECH Senior Member
 
joecar's Avatar
 
Join Date: Apr 2002
Location: So.Cal.
Posts: 6,067
Default

I now remember reading it back then, it's very educational and thorough.
joecar is offline  
Old 10-05-2017, 03:54 AM
  #60  
Staging Lane
 
Join Date: Jan 2017
Location: Sydney, Australia
Posts: 95
Default

So I have very recently had installed a Cam Motion 218/226 .595"/.587" 116 +3 (-10 overlap) mentioned in my post above in my 5.7 LS1 that I imported to my country from the USA along with PAC 1218 valve springs. It achieved what I wanted by delivering completely stock like manors with only a bit of lope plus a more quiet valvetrain. Good stuff!

However, compared to the Comp cam it replaced (216/220 .600"/.600" 112 -6.0 overlap) this cam dropped a pretty decent chunk of power, although that wasn't unexpected despite it being larger. Where I was caught out is that this cam feels quite lazy and the change created a hole at lower rpm which is important in a heavy car like mine. Most would say that's due to going from 112 to 116 lsa but as this thread shows that's not right. Its the ICL and advance that matters.

If I were prepared to drop another $4,000 to chase the lost performance and replace this new cam while still retaining its excellent manors, I think I would go back to a 216/220 but have it ground on 114 lsa. So 216/220 .6xx"/.6xx" 114 +4 (-10 overlap). This would have to be a custom cam of course, probably a Comp like the previous cam as they seem to have something very similar already.
Pulse Red is offline  

Thread Tools
Search this Thread
Quick Reply: Overlap and Valve Events Editorial


About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: