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Old 02-04-2013, 12:12 PM   #1
Joey GT-R
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Understanding Camshaft Specifications

Quote:
Originally Posted by Lunati Cams
LIFT

Lift refers to maximum valve lift. This is how much the valve is "lifted" off its seat at the cam lobe’s highest point.

How is it measured?

Valve Lift is the amount (usually in inches) that the valve is lifted off of its seat. It is usually measured with a dial indicator at the tip of the valve. Lobe Lift is the amount (usually in inches) that the cam lobe increases in radius above the cam base circle.

Tip: To quickly find maximum lobe lift, measure the base circle of the cam and subtract it from the thickness across the cam lobe’s highest point (see the diagram below).

Tip: Maximum valve lift can be calculated by multiplying the maximum lobe lift times the rocker ratio. For example, a 0.310" lobe lift cam yields 0.496" of valve lift when using a 1.6 ratio rocker arm.

Formula: valve lift = lobe lift x rocker ratio

What does it do?

The intake and exhaust valves need to open to let air/fuel in and exhaust out of the cylinders. Generally, opening the valves quicker and further will increase engine output. Increasing valve lift, without increasing duration, can yield more power without much change to the nature of the power curve. However, an increase in valve lift almost always is accompanied by an increase in duration. This is because ramps are limited in their shape which is directly related to the type of lifters being used, such as flat or roller.



DURATION

Duration is the angle in crankshaft degrees that the valve stays off its seat during the lifting cycle of the cam lobe.

How is it measured?

"Advertised duration" is the angle in crankshaft degrees that the cam follower is lifted more than a predetermined amount (the SAE standard is 0.006") off of its seat. "Duration @.050" is a measurement of the movement the cam follower, in crankshaft degrees, from the point where it’s first lifted .050" off the base circle on the opening ramp side of the camshaft lobe, to the point where it ends up being .050" from the base circle on the closing ramp side of the camshaft lobe. This is the industry standard, and is a good value to use to compare cams from different manufacturers. Both are usually measured with a dial indicator and a degree wheel.

What does it do?

Increasing duration keeps the valve open longer, and can increase high-rpm power. Doing so increases the RPM range that the engine produces power. Increasing duration without a change in lobe separation angle will result in increased valve overlap.



LOBE SEPARATION

Lobe separation is the angle in camshaft degrees between the maximum lift points of the intake and exhaust valves. It is the result of the placement of the intake and exhaust lobes on the camshaft.

How is it measured?

Lobe separation can be measured using a dial indicator and a degree wheel, but is usually calculated by dividing the sum of the intake centerline and the exhaust centerline by two.

What does it do?

Lobe separation affects valve overlap, which affects the nature of the power curve, idle quality, idle vacuum, etc.



OVERLAP

Overlap is the angle in crankshaft degrees that both the intake and exhaust valves are open. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Increasing lift duration and/or decreasing lobe separation increases overlap.

How is it measured?

Overlap can be calculated by adding the exhaust closing and the intake opening points. For example, a cam with an exhaust closing at 4 degrees ATDC and an intake opening of 8 degrees BTDC has 12 degrees of overlap.
But keep in mind that since these timing figures are at 0.050" of valve lift, this therefore is overlap at 0.050". A better way to think about overlap is the area that both lift curves overlap, rather than just the crankshaft angle that both valves are open. Therefore, one can see that decreasing the lobe separation only a few degrees can have a huge effect on overlap area.

What does it do?

At high engine speeds, overlap allows the rush of exhaust gasses out the exhaust valve to help pull the fresh air/fuel mixture into the cylinder through the intake valve. Increased engine speed enhances the effect. Increasing overlap increases top-end power and reduces low-speed power and idle quality.



CENTERLINES

The intake centerline is the point of highest lift on the intake lobe. It is expressed in crankshaft degrees after top dead center (ATDC). Likewise the exhaust centerline is the point of highest lift on the exhaust lobe. It is expressed in crankshaft degrees before top dead center (BTDC). The cam centerline is the point halfway between the intake and exhaust centerlines.



ADVANCE/RETARD

Advancing or retarding the camshaft moves the engine’s torque band around the RPM scale by moving the valve events further ahead or behind the movement of the piston. Typically, a racer will experiment with advancing or retarding a cam from "straight up" and see what works best for their application.

How is it measured?

A cam with a 107 degrees intake lobe centerline will actually be centered at 103 degrees ATDC when installed 4 degrees advanced.

Some camshafts have a certain amount of advance ground in. "Ground-in advance" can also be found by subtracting the intake lobe centerline from the lobe separation.

What does it do?

Advance improves low-end power and response. For a general summary of the affects of camshaft timing, refer to the following tables:


Advance
begins intake event sooner
opens intake valve sooner
builds more low-end torque
decreases piston-to-intake-valve clearance
increases piston-to-exhaust-valve clearance


Retard
delays intake event
opens intake valve later
builds more high-end power
increases piston-to-intake-valve clearance
decreases piston-to-exhaust-valve clearance


As an example I would like to post a couple of profiles for educational references, as well as my own purposes as well. For those that do answer I will probably re-edit your answers so that this can remain a sticky. But I do ask that you guys who do respond leave most of the subjective jargon out.


For the profiles that I will list later, if you know who they are don't point it out, I don't want to publicly endorse anyone. The smart ones will figure it out eventually, or they won't. But they will at least know what to look for.
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Quote:
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Old 03-05-2014, 12:33 AM   #2
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H22 Cam Specs

Stock Camshaft Specs

USDM H22A1 (94-96) Stock 288/308 231/234 .448"/.415" 11.38/10.54

JDM H22A (92-96) Stock 296/300 232/228 .456"/.420" 11.58/10.67

JDM H22A (Type S) Stock 306/310 230/230 .469"/.438" 11.91/11.12




Skunk2 Pro Series H-series Camshaft Specs

H-series Pro 1 - IN. 264* / 12.6 ; EX. 264* / 11.9

H-series Pro 2 - IN. 270* / 12.8 ; EX. 276* / 12.0

H-series Pro 3 - IN. 277* / 13.0 ; EX. 284* / 12.4




Skunk2 Tuner Series H-Series Camshaft Specs

Stage 1: IN - 0.473,254; EX - 0.437,258

Stage 2: IN - 0.473,254; EX - 0.437,258




Brian Crower Camshaft Specs

Turbo Stage 2

304/306
214/216
210/216 233/235
184/192
176/184 .464"/.448"
.324"/.312"
.262"/.247" 11.78/11.38
8.23/7.92
6.65/6.27


Normally Aspirated Stage 2


312/310
220/220
216/218 255/248
200/198
198/196 .470"/.469"
.325"/.308"
.280"/.264" 11.94/11.91
8.25/7.82
7.11/6.70


Normally Aspirated Specification Stage 3


318/316
228/226
224/224 263/255
216/212
198/194 .470"/.470"
.360"/.354"
.268"/.256" 11.94/11.94
9.14/8.99
6.80/6.50





Blox Tuner Series Type-B VTEC Camshaft Specs

12.8mm / 272, 11.9mm / 280




Jun H22 Camshaft Specs

#1 (Pri) #2 (Mid) #3 (2nd)
Duration Lift Duration Lift Duration Lift VC
INT 62 (248) 9.2 74 (296) 12.2 60 (240) 7.7 0.17
EXH 61 (244) 7.7 74 (296) 11.9 63 (252) 9.0 0.19
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Quote:
Originally Posted by deevergote
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Old 03-05-2014, 09:27 AM   #3
toycar
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I think you should have some elaborate post(s) explaining some of this stuff so that normal people wanting to learn, actually can.



For example, the post says increasing valve overlap will affect lower rpm performance and idle quality.


Well, explain why. You know, its impossible for the engine to make pressure in the port with that configured valve timing but it will rev to 10k because blah blah blah.





Or, how adjusting valve timing will adjust the powerband. So users can better understand what they need to get what they really want.

Maybe there should be a section on vtec, and why it actually makes sense. Even in sohc engines. Its all about pressure in the port, the choke point of that pressure and managing it across the rpm range you plan on running the engine through.


With the valves wide open the ports flow 100% to their potential right? But the engine couldn't make compression happen with valves open 100% of the time. So, degreeing a cam, TDC and BDC should all have their subsections of this post so that people can better understand their relationship. I mean, how often are people swapping heads with different stroke original motors and running stock cams?


Just saying, this post has the potential to be great for the community but it needs to be heavily expanded on if you want it to be right. I've mentioned a few things but there are probably 15-20 in depth parts that really need to be covered for this to be what you want it to be.




-CFM. Why? Well, you need to know how much air you are compressing to know how long the valve needs to be open to actually let all the gasses out. You already know the diameter of the valve, so figuring out the rest is just a simple math lesson.

-Valve duration to stroke length. Why does that matter? Well, this crowd is always coming up with new head/crank combos, and nobody really understands that the valve timing is configured to run on the length of stroke the original motor had. This matters when trying to accomplish max cylinder pressure. Custom cam is a must.

-Piston to valve clearance. What is it, how is it measured and why does it matter?

-Fuel atomization and how changing the lift will affect this.

-Scavenging. Yup. Cam profile will affect scavenging. Why? Is that good? Bad?

-Springs and when do you know you've reached their limit.

-Why you would need better springs/retainers.

-Floating a valve; how does it happen and how to avoid it.

-Determine safe piston speed? Why does that matter? Well, what engine speed do you plan to run your motor to? Because, that will affect your cam profile. You desired engine speed, well, you should keep piston speed in mind when determining that.

-Temps. How do temps affect flow. Why?

-How do cam profiles affect temps?

-Spacers? What are those? When would you need them?



Just a few things that come to mind. If you want to delete my post and use it for reference, thats coolio with me. Just wanted to offer my .02 to making this worth keeping at the top of the page. I'm sure others will have things to bring up just like this, and if everything gets put together, you're going to have yourself one handy guide to understand cam(s) and valve trains.
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im a douchebag to people and i don't even own a lambo. whats your point? we, douchbags, come in all sorts of shapes and colours.
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Old 03-05-2014, 09:52 AM   #4
sonikaccord
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I know this is in the NA section, but could we add a thread in FI and how cams affect that application as well?
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Old 03-05-2014, 10:32 AM   #5
toycar
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Quote:
Originally Posted by sonikaccord View Post
I know this is in the NA section, but could we add a thread in FI and how cams affect that application as well?
Whole different ballgame with FI.


With a turbocharged engine, you want the turbo to dictate airflow so the ideal cam profile(s) are drastically different.
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Quote:
Originally Posted by wed3k View Post
im a douchebag to people and i don't even own a lambo. whats your point? we, douchbags, come in all sorts of shapes and colours.
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Old 03-05-2014, 05:35 PM   #6
Joey GT-R
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Quote:
Originally Posted by toycar View Post
I think you should have some elaborate post(s) explaining some of this stuff so that normal people wanting to learn, actually can.



For example, the post says increasing valve overlap will affect lower rpm performance and idle quality.


Well, explain why. You know, its impossible for the engine to make pressure in the port with that configured valve timing but it will rev to 10k because blah blah blah.





Or, how adjusting valve timing will adjust the powerband. So users can better understand what they need to get what they really want.

Maybe there should be a section on vtec, and why it actually makes sense. Even in sohc engines. Its all about pressure in the port, the choke point of that pressure and managing it across the rpm range you plan on running the engine through.


With the valves wide open the ports flow 100% to their potential right? But the engine couldn't make compression happen with valves open 100% of the time. So, degreeing a cam, TDC and BDC should all have their subsections of this post so that people can better understand their relationship. I mean, how often are people swapping heads with different stroke original motors and running stock cams?


Just saying, this post has the potential to be great for the community but it needs to be heavily expanded on if you want it to be right. I've mentioned a few things but there are probably 15-20 in depth parts that really need to be covered for this to be what you want it to be.




-CFM. Why? Well, you need to know how much air you are compressing to know how long the valve needs to be open to actually let all the gasses out. You already know the diameter of the valve, so figuring out the rest is just a simple math lesson.

-Valve duration to stroke length. Why does that matter? Well, this crowd is always coming up with new head/crank combos, and nobody really understands that the valve timing is configured to run on the length of stroke the original motor had. This matters when trying to accomplish max cylinder pressure. Custom cam is a must.

-Piston to valve clearance. What is it, how is it measured and why does it matter?

-Fuel atomization and how changing the lift will affect this.

-Scavenging. Yup. Cam profile will affect scavenging. Why? Is that good? Bad?

-Springs and when do you know you've reached their limit.

-Why you would need better springs/retainers.

-Floating a valve; how does it happen and how to avoid it.

-Determine safe piston speed? Why does that matter? Well, what engine speed do you plan to run your motor to? Because, that will affect your cam profile. You desired engine speed, well, you should keep piston speed in mind when determining that.

-Temps. How do temps affect flow. Why?

-How do cam profiles affect temps?

-Spacers? What are those? When would you need them?



Just a few things that come to mind. If you want to delete my post and use it for reference, thats coolio with me. Just wanted to offer my .02 to making this worth keeping at the top of the page. I'm sure others will have things to bring up just like this, and if everything gets put together, you're going to have yourself one handy guide to understand cam(s) and valve trains.


I actually lack that knowledge personally. If you may not have noticed, I made this post a year ago, and another member happened to post this elsewhere off the forum. I asked him to finish his contribution, but he declined. I was hoping more knowledgeable members might chime in.

You more than likely have the insight, but I'm not going to attempt to make you divulge all of that, but the opportunity is there; for you and others to do so.




Quote:
Originally Posted by sonikaccord View Post
I know this is in the NA section, but could we add a thread in FI and how cams affect that application as well?
I have a couple turbo cams in that posting, so I may move this to the general section as a sticky for future reference.
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