What is more important in a cam? Lift vs. Duration
07-03-2007, 02:13 AM
#1
What is more important in a cam? Lift vs. Duration Lift vs Duration?
It seems as though there are overlaps in performance. Like when I see someone with a smaller cam (220) put down more power and have a better torque curve than someone with a larger cam (~230) as things.
But then someone with a mid 230s cam will put down like 20 more rwhp than someone with a similar cam and only a little less duration (like low 230s).
What is the give an take? I know a lot can be done with tuning and such it plays a big role but what is the equilibrium with the lift vs duration?
So would a 228/228 .580/.580 be better than a 232/232 .560/.560?
It seems as though there are overlaps in performance. Like when I see someone with a smaller cam (220) put down more power and have a better torque curve than someone with a larger cam (~230) as things.
But then someone with a mid 230s cam will put down like 20 more rwhp than someone with a similar cam and only a little less duration (like low 230s).
What is the give an take? I know a lot can be done with tuning and such it plays a big role but what is the equilibrium with the lift vs duration?
So would a 228/228 .580/.580 be better than a 232/232 .560/.560?
07-03-2007, 04:22 AM
#4
TECH Senior Member
Originally Posted by Justin00SS
Lift vs Duration?
It seems as though there are overlaps in performance. Like when I see someone with a smaller cam (220) put down more power and have a better torque curve than someone with a larger cam (~230) as things.
But then someone with a mid 230s cam will put down like 20 more rwhp than someone with a similar cam and only a little less duration (like low 230s).
What is the give an take? I know a lot can be done with tuning and such it plays a big role but what is the equilibrium with the lift vs duration?
So would a 228/228 .580/.580 be better than a 232/232 .560/.560?
It seems as though there are overlaps in performance. Like when I see someone with a smaller cam (220) put down more power and have a better torque curve than someone with a larger cam (~230) as things.
But then someone with a mid 230s cam will put down like 20 more rwhp than someone with a similar cam and only a little less duration (like low 230s).
What is the give an take? I know a lot can be done with tuning and such it plays a big role but what is the equilibrium with the lift vs duration?
So would a 228/228 .580/.580 be better than a 232/232 .560/.560?
Dyno numbers are just that, numbers. Track performance is what tells the story.
07-03-2007, 04:55 AM
#5
Blah blah blah. I know that dyno numbers are just that.
But you can't argue with torque curves and the times people are running.
How about this. Why is it that I'm seeing where people with cam and bolt-ons 224 cams are running the same times as people with 230+ cams. Which is the high 11s area.
But you can't argue with torque curves and the times people are running.
How about this. Why is it that I'm seeing where people with cam and bolt-ons 224 cams are running the same times as people with 230+ cams. Which is the high 11s area.
07-03-2007, 05:20 AM
#6
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Originally Posted by Justin00SS
How about this. Why is it that I'm seeing where people with cam and bolt-ons 224 cams are running the same times as people with 230+ cams. Which is the high 11s area.
Most the people who buy the big cams are idiots and get the big cams for all the wrong reasons and their "total package" isnt optimized. Their running cams in the upper 230's with 3.42's, a half assed tune, mostlikley a stock pulley, and have paceshitter headers and y-pipe.
With the smaller cams, they make more power where you need it so you can keep the 3.42's, they're easier to tune and get it right the first time around, instead of the needed dual spings they had money to go towards an aftermarket pulley, they're not as sensitive to exhaust flow (low overlap) so you dont have to have the most free flow exhaust (also more money towards a pulley).
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07-03-2007, 08:34 AM
#9
both are matters you cant judge wich one is matters or we will end up lookin for lift intake only for cam swap or duration.
lookin at these numbers for a cam choise it is just like lookin for what best for your car mods.
let say you are runin cam only and headers so choosing a big cam like 232-240 600-600 110lsa will be useless.
because that cam needs a bigger intake and exhauste valve(alot of air) and more DCR and alot of over lap and needs a good rear end like 4.10 because the power range of that cam ,
its in the mid to high and you will got your peak at the end of the rpms like 7000
so that big cam was a bad choise for your mods now what is better for a car runin
cam only and headers
smaller intakes and valve lift and tight duration will give you more throttle response
and quick low end lift ,plus a good power all over the rpm .
on the street low end and mid to high is what matters because you gonna use that
area alot like most of the racing start from idle to 6500 and dont forget shifting gears
will bring you back to the mid of rpm area so you need your car strong on that area
you need a quick lift to lift the rpms so you can pass your opponent
however lookin at a cam like 224-224 563-563 114 or 112lsa or even
216-220 525-535 114lsa will be reasonable for a car with cam only
all these numbers make one figure POWER CURVE AND PEAK NUMBER
so you can choose where you wanna put your power range where and how much.
At the end you cant just pick one thing and leave the rest you will end up wasting time and effort.
i hope this will help a little GOOD LUCK.
lookin at these numbers for a cam choise it is just like lookin for what best for your car mods.
let say you are runin cam only and headers so choosing a big cam like 232-240 600-600 110lsa will be useless.
because that cam needs a bigger intake and exhauste valve(alot of air) and more DCR and alot of over lap and needs a good rear end like 4.10 because the power range of that cam ,
its in the mid to high and you will got your peak at the end of the rpms like 7000
so that big cam was a bad choise for your mods now what is better for a car runin
cam only and headers
smaller intakes and valve lift and tight duration will give you more throttle response
and quick low end lift ,plus a good power all over the rpm .
on the street low end and mid to high is what matters because you gonna use that
area alot like most of the racing start from idle to 6500 and dont forget shifting gears
will bring you back to the mid of rpm area so you need your car strong on that area
you need a quick lift to lift the rpms so you can pass your opponent
however lookin at a cam like 224-224 563-563 114 or 112lsa or even
216-220 525-535 114lsa will be reasonable for a car with cam only
all these numbers make one figure POWER CURVE AND PEAK NUMBER
so you can choose where you wanna put your power range where and how much.
At the end you cant just pick one thing and leave the rest you will end up wasting time and effort.
i hope this will help a little GOOD LUCK.
Last edited by gts500; 07-03-2007 at 08:41 AM.
07-03-2007, 10:07 AM
#11
TECH Senior Member
Originally Posted by Justin00SS
Blah blah blah. I know that dyno numbers are just that.
But you can't argue with torque curves and the times people are running.
How about this. Why is it that I'm seeing where people with cam and bolt-ons 224 cams are running the same times as people with 230+ cams. Which is the high 11s area.
But you can't argue with torque curves and the times people are running.
How about this. Why is it that I'm seeing where people with cam and bolt-ons 224 cams are running the same times as people with 230+ cams. Which is the high 11s area.
I said valve events (IVO/IVC-EVO/EVC) that is what gives the edge on smaller cams VS bigger ones in a stock cube stock compression combo. That is where COMBO comes in effect.
As mentionned, if you have a 224/224 112+4 VS a 230/230 110+4 the 230 cam will walk all over the 224
Why? Let's look at the VEs:
224 cam
IVO>4
IVC>40
EVO>48
EVC>-4
0* Overlap
230 cam
IVO>9
IVC>41
EVO>49
EVC>1
10* Overlap
As you can see the IVC/EVO are very close with 1* difference on the bigger cam, the bigger difference is the Intake valve on the 230 is opening 8* sooner (bigger charge in= more power) also the overlap, opening the exhaust valve while the intake valve is opened to allow air in, will create a sucking effect and increase the air charge density allowed in. This is true to a certain degree, too much overlap and then the intake charge starts to exit through the exhaust before being burned and you are then bleeding and loosing power.
EVO is where to look at. the cam with the lower EVO will produce trq earlier in the band and make you accelerate faster. If the 230 cam above was with a much later EVO, it would be more sluggish (poeple compensate with gears)
This one will produce more trw than the 224 and walk all over it.
So in theory the bigger cam will make more power. Now why if we stick it in a 346 with stock 10:1 SCR (static compression) we see the 224 putting out more trq earlier in the power band?
Well because the DCR (Dynamic compression) is lower on the 230 due to the duration value at .006 lift. So how do we cure that?
We mill the heads or reduce gasket thickness to increase SCR and DCR.
That is a matching combo.
Now the 230 cam is optimized to achieve its powerband potential and kick some 224 ***.
Now on the lift part: Lift is how far your valves open at a certain duration. To understand pick 2 equal duration cams but different lifts.
Cam A opens the valve for a period X time and a distance Y (certain lift)
Cam B opens the valve for a period X time and a distance Y+Z (higher lift)
so mathematicaly speaking, cam B will make more power because more air was allowed in, therefore you could add more fuel and make more power.
This is relative to the flow capability of the head. There is where you match the cam to the heads.
I hope you understand, I tried to make it Lehman and simple.
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Torqueonboost (03-23-2022)
07-03-2007, 11:19 AM
#12
http://www.compcams.com/Community/Ar...ID=-2026144213
Read VERY CAREFULLY.
Vizard is one of the TRUE camshaft gurus.
And his take on it is LIFT is more important to overall power than DURATION.
Its also miscalculations in duration that throw off the valve events that are so important to making power.
Its critical that the intake valve events arent at the wrong time, because as stated in that article, once thats screwed you cant make up for it in the rest of the cycle.
Again, this is why some make more power with less, and some can never get some cams to work right. Too much is not always a good thing.
Rule of thumb; run as much lift as possible within the means of the rest of the setup, and then tailor the duration and LSA to come up with the desired overlap.
Read VERY CAREFULLY.
Vizard is one of the TRUE camshaft gurus.
And his take on it is LIFT is more important to overall power than DURATION.
Its also miscalculations in duration that throw off the valve events that are so important to making power.
Its critical that the intake valve events arent at the wrong time, because as stated in that article, once thats screwed you cant make up for it in the rest of the cycle.
Again, this is why some make more power with less, and some can never get some cams to work right. Too much is not always a good thing.
Rule of thumb; run as much lift as possible within the means of the rest of the setup, and then tailor the duration and LSA to come up with the desired overlap.
07-03-2007, 11:33 AM
#13
TECH Senior Member
Originally Posted by edcmat-l1
http://www.compcams.com/Community/Ar...ID=-2026144213
Read VERY CAREFULLY.
Vizard is one of the TRUE camshaft gurus.
And his take on it is LIFT is more important to overall power than DURATION.
Its also miscalculations in duration that throw off the valve events that are so important to making power.
Its critical that the intake valve events arent at the wrong time, because as stated in that article, once thats screwed you cant make up for it in the rest of the cycle.
Again, this is why some make more power with less, and some can never get some cams to work right. Too much is not always a good thing.
Rule of thumb; run as much lift as possible within the means of the rest of the setup, and then tailor the duration and LSA to come up with the desired overlap.
Read VERY CAREFULLY.
Vizard is one of the TRUE camshaft gurus.
And his take on it is LIFT is more important to overall power than DURATION.
Its also miscalculations in duration that throw off the valve events that are so important to making power.
Its critical that the intake valve events arent at the wrong time, because as stated in that article, once thats screwed you cant make up for it in the rest of the cycle.
Again, this is why some make more power with less, and some can never get some cams to work right. Too much is not always a good thing.
Rule of thumb; run as much lift as possible within the means of the rest of the setup, and then tailor the duration and LSA to come up with the desired overlap.
When designing a cam for max effort (within the rest of combo parameters), 1st choose your desired IVC, then your EVO (to decide where in the band you want that trq) and then LSA/ICL (to decide where and how far do you want that powerband at).
Lift is relative to the intake/head capability of flow at various lifts.
See, in LSx applications, the best intake so far on the market (non sheetmetal) is the FAST. It can only move 280cfm max. There is your crutch and what you should base your cam design seriously on. Ported maybe 300cfm if done right.
Going beyond that parameter is pointless.
So creating a combo with a cam and/or heads that will suck more than 300 cubig feet/ minute of air is not gonna make any more power once that ceiling is reached.
Further than that requires custom intake.
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Torqueonboost (03-23-2022)
07-03-2007, 12:19 PM
#14
Originally Posted by PREDATOR-Z
I dissagree with that theory in LSx application.
When designing a cam for max effort (within the rest of combo parameters), 1st choose your desired IVC, then your EVO (to decide where in the band you want that trq) and then LSA/ICL (to decide where and how far do you want that powerband at).
Lift is relative to the intake/head capability of flow at various lifts.
See, in LSx applications, the best intake so far on the market (non sheetmetal) is the FAST. It can only move 280cfm max. There is your crutch and what you should base your cam design seriously on. Ported maybe 300cfm if done right.
Going beyond that parameter is pointless.
So creating a combo with a cam and/or heads that will suck more than 300 cubig feet/ minute of air is not gonna make any more power once that ceiling is reached.
Further than that requires custom intake.
When designing a cam for max effort (within the rest of combo parameters), 1st choose your desired IVC, then your EVO (to decide where in the band you want that trq) and then LSA/ICL (to decide where and how far do you want that powerband at).
Lift is relative to the intake/head capability of flow at various lifts.
See, in LSx applications, the best intake so far on the market (non sheetmetal) is the FAST. It can only move 280cfm max. There is your crutch and what you should base your cam design seriously on. Ported maybe 300cfm if done right.
Going beyond that parameter is pointless.
So creating a combo with a cam and/or heads that will suck more than 300 cubig feet/ minute of air is not gonna make any more power once that ceiling is reached.
Further than that requires custom intake.
While I agree that some of the article doesnt exactly pertain to LSx motors, the basis for most of the theory is still supported in the LS motors.
think about it. These engines run lift numbers right around what is stated by Vizard. .600 lift seems to be the norm. And that right where he states it should be, for the intake valve size.
That being said, both IVC and EVO are CRITICAL to making power, no doubt.
But, the one spec that seems to have the biggest affect/effect, whichever, is lift.
Also, the intake events can only be manipulated so much. In these engine in particular, only a few degrees,without having an adverse affect on either low speed power, or overall power.
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Torqueonboost (03-23-2022)
07-03-2007, 01:14 PM
#16
TECH Senior Member
Originally Posted by edcmat-l1
If you read the article, one of the key points is the lift in relation to valve diameter.
While I agree that some of the article doesnt exactly pertain to LSx motors, the basis for most of the theory is still supported in the LS motors.
think about it. These engines run lift numbers right around what is stated by Vizard. .600 lift seems to be the norm. And that right where he states it should be, for the intake valve size.
That being said, both IVC and EVO are CRITICAL to making power, no doubt.
But, the one spec that seems to have the biggest affect/effect, whichever, is lift.
Also, the intake events can only be manipulated so much. In these engine in particular, only a few degrees,without having an adverse affect on either low speed power, or overall power.
While I agree that some of the article doesnt exactly pertain to LSx motors, the basis for most of the theory is still supported in the LS motors.
think about it. These engines run lift numbers right around what is stated by Vizard. .600 lift seems to be the norm. And that right where he states it should be, for the intake valve size.
That being said, both IVC and EVO are CRITICAL to making power, no doubt.
But, the one spec that seems to have the biggest affect/effect, whichever, is lift.
Also, the intake events can only be manipulated so much. In these engine in particular, only a few degrees,without having an adverse affect on either low speed power, or overall power.
Well, it is known for awhile now that there is no such thing as the "mother of all cams".
There always has to be a compromise. One can't just have it all.
believe me when I say that bigger is not always better. Matching parts for the job at hand is where it is at. Every combo is different, that is why I'm no longer a fan of off the shelf cams. Even those can be tweaked and make more power, but there is still a compromise.
My advice in choosing a cam is to be realistic with yourself as to what are the goals of your application. Whatever it is, there is a price to pay.
07-03-2007, 01:23 PM
#17
Originally Posted by PREDATOR-Z
Well, it is known for awhile now that there is no such thing as the "mother of all cams".
There always has to be a compromise. One can't just have it all.
believe me when I say that bigger is not always better. Matching parts for the job at hand is where it is at. Every combo is different, that is why I'm no longer a fan of off the shelf cams. Even those can be tweaked and make more power, but there is still a compromise.
My advice in choosing a cam is to be realistic with yourself as to what are the goals of your application. Whatever it is, there is a price to pay.
There always has to be a compromise. One can't just have it all.
believe me when I say that bigger is not always better. Matching parts for the job at hand is where it is at. Every combo is different, that is why I'm no longer a fan of off the shelf cams. Even those can be tweaked and make more power, but there is still a compromise.
My advice in choosing a cam is to be realistic with yourself as to what are the goals of your application. Whatever it is, there is a price to pay.
And for compromise, I choose hi lift, shorter duration cams, with wider LSA. Usually in the 112 range.
Been buildin motors for 20 years, and been spec-ing cams like that, high lift, shorter duration, long before I ever read that article.
As for bigger is not always better, I am a firm believer in that philosophy. And it directly pertains to duration and overlap.
07-03-2007, 01:45 PM
#18
TECH Fanatic
Originally Posted by edcmat-l1
If you read the article, one of the key points is the lift in relation to valve diameter.
While I agree that some of the article doesnt exactly pertain to LSx motors, the basis for most of the theory is still supported in the LS motors.
think about it. These engines run lift numbers right around what is stated by Vizard. .600 lift seems to be the norm. And that right where he states it should be, for the intake valve size.
That being said, both IVC and EVO are CRITICAL to making power, no doubt.
But, the one spec that seems to have the biggest affect/effect, whichever, is lift.
Also, the intake events can only be manipulated so much. In these engine in particular, only a few degrees,without having an adverse affect on either low speed power, or overall power.
AND:
Oh yeah. I agree completely. We do not use off the shelf cams, ever.
And for compromise, I choose hi lift, shorter duration cams, with wider LSA. Usually in the 112 range.
Been buildin motors for 20 years, and been spec-ing cams like that, high lift, shorter duration, long before I ever read that article.
As for bigger is not always better, I am a firm believer in that philosophy. And it directly pertains to duration and overlap.
Listen to the man. ^^^
Also one should consider that it is differential pressure that moves air. Every engine combination is different and asks for it's own particular valve events and lift curves.
07-03-2007, 01:51 PM
#19
Originally Posted by Old SStroker
Listen to the man. ^^^
Also one should consider that it is differential pressure that moves air. Every engine combination is different and asks for it's own particular valve events and lift curves.
Also one should consider that it is differential pressure that moves air. Every engine combination is different and asks for it's own particular valve events and lift curves.
07-03-2007, 02:20 PM
#20
Wow. Awsome tech. To add to the discussion, how does positive manifold pressure effect these calculations? It would seem that all of the aforementioned science pertains to motors that have to suck in their own intake charge, what about FI?
This is especially critical in my application, I am running a turbocharged engine, but am limited to .550 lift. How should I manipulate the valve events to "work around" lift limitations?
My thinking is to engineer the motor to make the best peak power within the constraints of the rules, and then tune the chassis around the "less than streetable" torque curves. Furthermore, with a turbo and a properly set up converter, I believe I will have more torque than is hook-able anyway. Does this seem reasonable?
This is especially critical in my application, I am running a turbocharged engine, but am limited to .550 lift. How should I manipulate the valve events to "work around" lift limitations?
My thinking is to engineer the motor to make the best peak power within the constraints of the rules, and then tune the chassis around the "less than streetable" torque curves. Furthermore, with a turbo and a properly set up converter, I believe I will have more torque than is hook-able anyway. Does this seem reasonable?