Compare/Contrast these two Cams....
04-08-2006, 08:51 AM
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Compare/Contrast these two Cams.... How will these two cams behave differently from each-other, assuming a completely stock intake and exhaust system (incl stock heads and manifolds), AND stock Convertor (A4)?
A) 204/211 .525" 116 (Stock LS2 camshaft)
B) 212/218 .565" 116 +4 (assume Comp XE lobes)
Overlap on Cam (A): -24.5 at .050".
Overlap on Cam (B): -17.0 at .050".
Idle quality between the two, at 700rpm? Will Cam (B) be almost indistinguishable from Cam (A) with the stock exhaust in place?
Where is peak-torque and peak-HP for Cam (B)? Would it run to 6400rpm, or beyond?
How would the low-end torque (below 2500rpm/3000rpm) compare?
Would Cam (B) suffer in low-end performance with a stock stall (2100 rpm)?
Sensitivity to exhaust backpressue? Cam (A) obviously runs well on a stock setup, would Cam (B) also be just as effective on a stock system?
IVCs for Cam (A) versus Cam (B)?
Max Tq & HP differences between the two cams?
I am trying to get a better understanding of cam basics after reading all of the Cam FAQs, 'searches', etc. etc. I have an idea as to how the two would compare, but I am looking for unbiased comments to confirm my growing understanding. Thought these two cams would be good to use as an example for a comparison...
TIA!!!
A) 204/211 .525" 116 (Stock LS2 camshaft)
B) 212/218 .565" 116 +4 (assume Comp XE lobes)
Overlap on Cam (A): -24.5 at .050".
Overlap on Cam (B): -17.0 at .050".
Idle quality between the two, at 700rpm? Will Cam (B) be almost indistinguishable from Cam (A) with the stock exhaust in place?
Where is peak-torque and peak-HP for Cam (B)? Would it run to 6400rpm, or beyond?
How would the low-end torque (below 2500rpm/3000rpm) compare?
Would Cam (B) suffer in low-end performance with a stock stall (2100 rpm)?
Sensitivity to exhaust backpressue? Cam (A) obviously runs well on a stock setup, would Cam (B) also be just as effective on a stock system?
IVCs for Cam (A) versus Cam (B)?
Max Tq & HP differences between the two cams?
I am trying to get a better understanding of cam basics after reading all of the Cam FAQs, 'searches', etc. etc. I have an idea as to how the two would compare, but I am looking for unbiased comments to confirm my growing understanding. Thought these two cams would be good to use as an example for a comparison...
TIA!!!
Last edited by 02RedHawk; 04-18-2006 at 06:36 PM.
04-08-2006, 09:44 AM
#2
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Originally Posted by JakeFusion
Okay--I may confuse you, but the two biggest factors of determing how a cam will perform is the Dynamic Compression Ratio (DCR) and Intake Centerline (ICL).
Basically, though, a 224/224 cam is not going to make the same peak power as a 234/234 cam, because the duration is measured at .050" lift and tells us how long the valve is held open. The longer it is held open, the more air that can enter the engine. A wider LSA (numerically higher number) will peak later, offer a better idle, and provide a wider powerband. Lower LSAs do the opposite, producing narrower and more peaky powerbands that usually produce more torque. The LSA tells us how the valve events (VE) will take place. This is where the ICL can affect performance. Still with me?
For example, a 224/224 114 LSA installed at 114 ICL will peak higher in the RPM range than a 224/224 112 LSA installed on a 112 ICL. That usually is good for a small percentage of extra ponies, because the powerband is shifted slightly up and broadened slightly. The difference is the midrange is softer on the 114. That's because a tighter ICL is crucial to upping the DCR (which itself is a derivative of the static compression, or the number you see like 10.1:1 for the LS1). More DCR means more torque, because DCR is basically cylinder pressure for this discussion.
Now, you can have a 224/224 114 LSA cam installed on a 112 ICL, which is usually shown as 114+2 LSA on a website or cam card. This is known as advance. This does the same thing, but gives you slightly different VEs from a 224/224 112+0 (112 ICL and no advance). Advance will widen the exhaust VEs and cause even more cylinder pressure to build.
Now, a 234/234 cam will have a much lower DCR for a given static compression (like 10.1 of the LS1) if the LSA and ICL are the same as the 224/224. That's because a larger cam will "bleed" compression and reduce vacuum due to it having more overlap. Overlap means high RPM power, but more overlap reduces overall drivability (however, a good tune can reduce most of these affects within reason).
If you combine these two we have the following: A 224/224 114+2 cam will peak lower and provide more torque than a 234/234 114+2 cam. The 234/234 will make a lot more peak horsepower and will feel "peaky." But, a 234/234 110+2 cam will provide similar torque (due to similar DCR), and will peak about the same place. But it will make more midrange and topend power of the smaller 224/224 cam, because more air is getting into the engine. But it will make a lower absolute topend number than the same 234/234 on a 114+2. The 114+2 would be a dyno queen and the 110+2 would win the race due to more power in usable RPM range. The 110+2 will also idle a lot rougher and may not clear some aftermarket cylinder heads.
So, if you want just a nice cam for the street, you might look into a 224/228 split with an aggressive lobe like the Comp Cams XE-R or LSK (harder on springs, but provides better fuel economy, drivability, and low end torque) with a 112+2 LSA or 112+4 LSA.
Basically, though, a 224/224 cam is not going to make the same peak power as a 234/234 cam, because the duration is measured at .050" lift and tells us how long the valve is held open. The longer it is held open, the more air that can enter the engine. A wider LSA (numerically higher number) will peak later, offer a better idle, and provide a wider powerband. Lower LSAs do the opposite, producing narrower and more peaky powerbands that usually produce more torque. The LSA tells us how the valve events (VE) will take place. This is where the ICL can affect performance. Still with me?
For example, a 224/224 114 LSA installed at 114 ICL will peak higher in the RPM range than a 224/224 112 LSA installed on a 112 ICL. That usually is good for a small percentage of extra ponies, because the powerband is shifted slightly up and broadened slightly. The difference is the midrange is softer on the 114. That's because a tighter ICL is crucial to upping the DCR (which itself is a derivative of the static compression, or the number you see like 10.1:1 for the LS1). More DCR means more torque, because DCR is basically cylinder pressure for this discussion.
Now, you can have a 224/224 114 LSA cam installed on a 112 ICL, which is usually shown as 114+2 LSA on a website or cam card. This is known as advance. This does the same thing, but gives you slightly different VEs from a 224/224 112+0 (112 ICL and no advance). Advance will widen the exhaust VEs and cause even more cylinder pressure to build.
Now, a 234/234 cam will have a much lower DCR for a given static compression (like 10.1 of the LS1) if the LSA and ICL are the same as the 224/224. That's because a larger cam will "bleed" compression and reduce vacuum due to it having more overlap. Overlap means high RPM power, but more overlap reduces overall drivability (however, a good tune can reduce most of these affects within reason).
If you combine these two we have the following: A 224/224 114+2 cam will peak lower and provide more torque than a 234/234 114+2 cam. The 234/234 will make a lot more peak horsepower and will feel "peaky." But, a 234/234 110+2 cam will provide similar torque (due to similar DCR), and will peak about the same place. But it will make more midrange and topend power of the smaller 224/224 cam, because more air is getting into the engine. But it will make a lower absolute topend number than the same 234/234 on a 114+2. The 114+2 would be a dyno queen and the 110+2 would win the race due to more power in usable RPM range. The 110+2 will also idle a lot rougher and may not clear some aftermarket cylinder heads.
So, if you want just a nice cam for the street, you might look into a 224/228 split with an aggressive lobe like the Comp Cams XE-R or LSK (harder on springs, but provides better fuel economy, drivability, and low end torque) with a 112+2 LSA or 112+4 LSA.
04-08-2006, 11:16 AM
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Indeed, a very good description.
But I'm looking for more specifics pertaining to the two cams. Having the LS2-Cam (Cam "A") being a known comparitor (ie, known HP & tq curves, peak rpms, driveability, etc...), I think more specific numerical comparisons of Cam B can be made to it....not just generalizations. (ie, how much the rpms will shift for HP/Tq, etc...the questions I listed in my first posting)
But I'm looking for more specifics pertaining to the two cams. Having the LS2-Cam (Cam "A") being a known comparitor (ie, known HP & tq curves, peak rpms, driveability, etc...), I think more specific numerical comparisons of Cam B can be made to it....not just generalizations. (ie, how much the rpms will shift for HP/Tq, etc...the questions I listed in my first posting)
04-08-2006, 10:23 PM
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Well, let's see if I can answer my own questions, based upon my "knowledge". I was hoping to have some responses before posting this, soas to get more of an unbiased response versus just confirming my (mis)information. Ah well.
Anyways, here I go. I would greatly appreciate some feedback on whether I'm accurate or not.
The stock LS2 motor with Cam (A) installed has a 400hp peak at 6000rpm, and a 400 ft-lb peak at 4400rpm. I'll use this as basis for my "comparison".
I believe the overlap on Cam (B) will still provide a very "smooth" idle with the stock exhaust manifolds+catback, comparable to Cam (A) and barely noticable as being different, if at all.
Hmm.... The stock cam peaks at 6k, and really starts to drop off after 6500rpm. The higher duration & overlap of Cam (B) will shift the power-band up approx 400rpm. However, the 4-degrees advance of Cam (B) will shift the power-band DOWN approx 200rpm. Thus, the net "change" in power-band between Cam (A) and (B) is a peak-shift of approx +200rpm, or at 6200rpm.
The higher lift of Cam (B) should produce more torque, and the minimal power-curve shift of only 200rpm should not reduce/change the low-end performance significantly. As a guess, I'd say a reduction of ~5-10 ft-lbs below 2500rpm with Cam (B), versus Cam (A).
Cam (B)'s low-end torque could be improved by changing the LSA to 115 or 114, at the expense of decreasing the idle stability. (115LSA = -15.0 overlap, 114LSA = -13.0 overlap) Would this change really be noticable at idle? In addition, the cam may/will become more sensitive to exhaust backpressure, meaning the stock manifolds/cats may not allow the cam to work as effectively. Can anyone quantify this?
Low-end Tq could also be increased by decreasing the duration, I realize.
Probably not enough to notice in a daily-driver situation. The benefits of Cam (B) at the track would be enhanced with the usage of a ~2600-2800rpm stall.
I would think with the 116 LSA and the -17.0 overlap that Cam (B) should be very similar in its (in)sensitivity to using stock manifolds/cats/exhaust. Similar to TR's CheaTR cam or the Old-Man cam.
I have no idea. Still researching.... I have "heard" that to shoot for a 6000rpm peak, the IVC needs to be around 40-degrees. Li'l help, anyone?
Again, I have no idea. As a guess, I would say 15-20rwhp, peak.
Hopefully this will help generate some discussion...? How much RPM would the Cam's power-range be reduced if the intake duration was changed to 210?
Anyways, here I go. I would greatly appreciate some feedback on whether I'm accurate or not.
A) 204/211 .525" 116 (Stock LS2 camshaft)
B) 212/218 .565" 116 +4 (assume Comp XE lobes)
Overlap on Cam (A): -24.5 at .050".
Overlap on Cam (B): -17.0 at .050".
B) 212/218 .565" 116 +4 (assume Comp XE lobes)
Overlap on Cam (A): -24.5 at .050".
Overlap on Cam (B): -17.0 at .050".
Idle quality between the two, at 700rpm? Will Cam (B) be almost indistinguishable from Cam (A) with the stock exhaust in place?
Where is peak-torque and peak-HP for Cam (B)? Would it run to 6400rpm, or beyond?
How would the low-end torque (below 2500rpm/3000rpm) compare?
Cam (B)'s low-end torque could be improved by changing the LSA to 115 or 114, at the expense of decreasing the idle stability. (115LSA = -15.0 overlap, 114LSA = -13.0 overlap) Would this change really be noticable at idle? In addition, the cam may/will become more sensitive to exhaust backpressure, meaning the stock manifolds/cats may not allow the cam to work as effectively. Can anyone quantify this?
Low-end Tq could also be increased by decreasing the duration, I realize.
Would Cam (B) suffer in low-end performance with a stock stall (2100 rpm)?
Sensitivity to exhaust backpressue? Cam (A) obviously runs well on a stock setup, would Cam (B) also be just as effective on a stock system?
IVCs for Cam (A) versus Cam (B)?
Max Tq & HP differences between the two cams?
Hopefully this will help generate some discussion...? How much RPM would the Cam's power-range be reduced if the intake duration was changed to 210?
Last edited by 02RedHawk; 04-10-2006 at 08:39 PM.
04-10-2006, 08:56 PM
#7
Both cams are very similar, but as I have stated before, an identical IVC is only part of figuring how a cam will work.
The larger cam, due to more duration, will produce more power everywhere and carry it beyond peak better. With the advance, instead of carrying the power way up like an exponential graph building on itself, it will be like a straw being pushed at both ends, contracting the ends closer together and pushing the middle of the straw up. That's about like how a bigger cam with similar valve events reacts. Usually it's skewed more toward the upper rpm range, but the point is it will make more "violent" power in the midrange. However, both are so small that all of your concerns can be eliminated with a good tune.
The larger cam, due to more duration, will produce more power everywhere and carry it beyond peak better. With the advance, instead of carrying the power way up like an exponential graph building on itself, it will be like a straw being pushed at both ends, contracting the ends closer together and pushing the middle of the straw up. That's about like how a bigger cam with similar valve events reacts. Usually it's skewed more toward the upper rpm range, but the point is it will make more "violent" power in the midrange. However, both are so small that all of your concerns can be eliminated with a good tune.
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04-18-2006, 05:37 PM
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Originally Posted by JakeFusion
Both cams are very similar, but as I have stated before, an identical IVC is only part of figuring how a cam will work.
With the advance, instead of carrying the power way up like an exponential graph building on itself, it will be like a straw being pushed at both ends, contracting the ends closer together and pushing the middle of the straw up. That's about like how a bigger cam with similar valve events reacts. Usually it's skewed more toward the upper rpm range, but the point is it will make more "violent" power in the midrange. However, both are so small that all of your concerns can be eliminated with a good tune.
With the advance, instead of carrying the power way up like an exponential graph building on itself, it will be like a straw being pushed at both ends, contracting the ends closer together and pushing the middle of the straw up. That's about like how a bigger cam with similar valve events reacts. Usually it's skewed more toward the upper rpm range, but the point is it will make more "violent" power in the midrange. However, both are so small that all of your concerns can be eliminated with a good tune.
04-19-2006, 08:20 PM
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How much is considered a "lot" of advance? Shift points would be ~6500rpm for 1-2, and 6400rpm for 2-3 / 3-4.
Others' thoughts on comparing the cams, and the questions in post #1?
Others' thoughts on comparing the cams, and the questions in post #1?
04-19-2006, 08:51 PM
#11
Its common to see 4* advance, but 4* frequently makes a cam pretty exhaust biased.
I'm not wild about either cam, but I'm not certain of your goals. Where do you want your power? I guess with 6500 shift point you want the power up top. I'd think about 212/218 114 114 or 212/222 115 115. For power up top, both cams have no advance. -13 overlap can be made to idle at 700 rpm with carefull tuning; maybe you'll need 725 rpm. Use fast ramps and tuning will be easier.
I'm not wild about either cam, but I'm not certain of your goals. Where do you want your power? I guess with 6500 shift point you want the power up top. I'd think about 212/218 114 114 or 212/222 115 115. For power up top, both cams have no advance. -13 overlap can be made to idle at 700 rpm with carefull tuning; maybe you'll need 725 rpm. Use fast ramps and tuning will be easier.
04-20-2006, 05:38 AM
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Originally Posted by Ragtop 99
Its common to see 4* advance, but 4* frequently makes a cam pretty exhaust biased.
I'm not wild about either cam, but I'm not certain of your goals. Where do you want your power? I guess with 6500 shift point you want the power up top. I'd think about 212/218 114 114 or 212/222 115 115. For power up top, both cams have no advance. -13 overlap can be made to idle at 700 rpm with carefull tuning; maybe you'll need 725 rpm. Use fast ramps and tuning will be easier.
I'm not wild about either cam, but I'm not certain of your goals. Where do you want your power? I guess with 6500 shift point you want the power up top. I'd think about 212/218 114 114 or 212/222 115 115. For power up top, both cams have no advance. -13 overlap can be made to idle at 700 rpm with carefull tuning; maybe you'll need 725 rpm. Use fast ramps and tuning will be easier.
Actually just the opposite - I want the power down low, as its going on a 4600# SUV (stock LS2 motor, already with cam "A"), but it needs to still idle as stock as absolutely possible and not run out of steam at 6000rpm (with still 500rpm to go before it shifts). Stock stall (2100 rpm), stock exhaust. Hence, the 116LSA for a -17.0 overlap & good idle and the +4 to pull the power-band back down in the rpm range. Comp XE lobes.
Anything bigger than a ~212/218 and I'll be getting into requiring a higher stall, which isn't an option for the truck right now.
04-20-2006, 08:31 AM
#13
I don't think you can accomplish your goals. Realisticaly, cams do not make big power over a 4000 rpm range. You might get a small pick up accross the wide range by staying with a high LSA cam, but the gains will be small in all areas.
If I had a 4600 pound truck with a stock stall, I wouldn't be worrying about shifting at 6500. I'd put the torque down lower. With an LS2, you can go -15 overlap or -13 and still idle decently at a low rpm. Use faster ramps and control your overlap at .006.
Something like a 206/216 113 with no advance will get the job done better.
If I had a 4600 pound truck with a stock stall, I wouldn't be worrying about shifting at 6500. I'd put the torque down lower. With an LS2, you can go -15 overlap or -13 and still idle decently at a low rpm. Use faster ramps and control your overlap at .006.
Something like a 206/216 113 with no advance will get the job done better.
04-20-2006, 12:01 PM
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Originally Posted by Ragtop 99
I don't think you can accomplish your goals. Realisticaly, cams do not make big power over a 4000 rpm range. You might get a small pick up accross the wide range by staying with a high LSA cam, but the gains will be small in all areas.
If I had a 4600 pound truck with a stock stall, I wouldn't be worrying about shifting at 6500. I'd put the torque down lower. With an LS2, you can go -15 overlap or -13 and still idle decently at a low rpm. Use faster ramps and control your overlap at .006.
Something like a 206/216 113 with no advance will get the job done better.
If I had a 4600 pound truck with a stock stall, I wouldn't be worrying about shifting at 6500. I'd put the torque down lower. With an LS2, you can go -15 overlap or -13 and still idle decently at a low rpm. Use faster ramps and control your overlap at .006.
Something like a 206/216 113 with no advance will get the job done better.
The issue with throwing in a cam with gobs of low-end torque is that it'd not be utilized once you're past the initial 2100 rpm launch. The truck shifts @ 6500 whether I like it or not (6400rpm 2-3, 3-4), and doesn't drop the RPMs enough to utilize say, a 1500-5000rpm stump-puller cam before it'd be out of the cam's "sweet spot" and back into a 1000+rpm weak top-end. Hence, I think finding something that gives a more broad power-range ought to be better all-around, even if it only gives minimal low-end improvement. Make sense? Or am I all wet?
04-20-2006, 01:03 PM
#15
Unless you're not tuning, the truck will shift where you tell it to. 
As to what works best for you, that's really a function of how plan to drive it. If most of your need is power from a roll, then you are correct to focus on 4000 - 6500 power. If you are starting from a dead stop, 60' needs to be the focus and a good 60' comes from torque and traction.
As to what works best for you, that's really a function of how plan to drive it. If most of your need is power from a roll, then you are correct to focus on 4000 - 6500 power. If you are starting from a dead stop, 60' needs to be the focus and a good 60' comes from torque and traction.