Camshaft Discussion part II
10-09-2003, 04:34 PM
#61
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Re: Camshaft Discussion part II From what I understand of 93Pony's methods (he can answer for himself, for sure). He like the cam and the lobes to be right, and not use advance ground into the cam as a crutch. So, hence his recommendation. If it is 114 he'd like a 114ICL instead of a 110ICL from getting 4 degrees advance.
Same with a 111LSA, 111ICL. From my understanding of his methodology (what little I understand) that advance on the cams blows his VE's out of the water. The LSA, etc, might not be ideal but with the advance its way worse.
Just my assumptions based upon what I have gathered.
Same with a 111LSA, 111ICL. From my understanding of his methodology (what little I understand) that advance on the cams blows his VE's out of the water. The LSA, etc, might not be ideal but with the advance its way worse.
Just my assumptions based upon what I have gathered.
10-09-2003, 06:36 PM
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Re: Camshaft Discussion part II He like the cam and the lobes to be right, and not use advance ground into the cam as a crutch.
I would disagree with the notion that grinding advance/retard into a camshaft is a "crutch" though. You may not want a larger/smaller lobe due to other constraints, (change lobe "size"), or you may not want to change your overlap - but you need to alter your valve timing.
I don't think there is any airflow based mechanics that would dictate that intake center line and lsa should be the same.
10-09-2003, 07:59 PM
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Re: Camshaft Discussion part II BIGELLER...where did you get your cam? I'm in the DFW area, and just curious. The only shop I know that is pushing the 228/.588 cam is 21MC, in Carrollton. Did you get it there?
I also have a Vig 3200, and 3:73's, and I think it would be a good comparison also.
BTW, I currently dyno at 385 rwtq, through the Vig converter and the gears. Left that out earlier.
NIGHTMARE
I also have a Vig 3200, and 3:73's, and I think it would be a good comparison also.
BTW, I currently dyno at 385 rwtq, through the Vig converter and the gears. Left that out earlier.
NIGHTMARE
10-09-2003, 09:01 PM
#64
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Re: Camshaft Discussion part II Her is a quote from up above. I think his view on advance cut into the cam was outlined earlier.
Not saying these are my theories just trying to clarify what I understand is 93Pony's perspective.
As for myself, I am simply trying to share information...
I tend to approch things a little differently with these EFI intake restricted motors. Due to runner length & the current lack of cost effective shorter runner intakes, the LS1 is limited to a 4800rpm torque peak....& thus 6200-6400rpm HP peak (due to the wave of the incoming intake aircharge as it bonces between the closed intake valve & open air plenum). When I do a cam for a setup like this, I go for max cylinder pressure under 6200rpm.
The area most cam companies error on is the exhaust. This causes problems with these limited intake designs. The exhaust VE's are the most important on these setups.
Simply put, on an N/A motor the intake aircharge is not assisted. (leaving wave dynamics of the aircharge out for a moment).
After the combustion stroke there is tremendous pressure in the cylinder. As soon as the exhaust valve cracks open it flows a LOT of air. It's basically boosted out of the cylinder if you want to look at it like this. Having the exhaust valve open too early not only costs heat (power) & velocity through the exhaust runners, it also empties the cylinder before the intake valve is open enough to take advantage of the pressure differential. (in a limited overlap/smogable camshaft this is especially true) This causes exhaust reversion & is one of the key factors in surging problems. By the airflow reversing course it is loosing a lot of it's inertia. Typically this is overcome before peak torque however. So only low-speed issues are present. At the track these motors are always above 4500rpm so this does not affect track times too much. Stilll....there is significant power lost by allowing reversion. So it makes sense to open the exhaust valve a little later & increase the overlap a bit. By adding advance into the camshaft this makes the problem even worse as now you're opening the exhaust a few more degrees earlier.....& shortening the effectiveness of the intake unless you have significant overlap flow to over come this.
Simply put, advancing a cam makes it more exhaust bias relative to TDC. Retarding a cam makes it more intake bias relative to TDC.
The area most cam companies error on is the exhaust. This causes problems with these limited intake designs. The exhaust VE's are the most important on these setups.
Simply put, on an N/A motor the intake aircharge is not assisted. (leaving wave dynamics of the aircharge out for a moment).
After the combustion stroke there is tremendous pressure in the cylinder. As soon as the exhaust valve cracks open it flows a LOT of air. It's basically boosted out of the cylinder if you want to look at it like this. Having the exhaust valve open too early not only costs heat (power) & velocity through the exhaust runners, it also empties the cylinder before the intake valve is open enough to take advantage of the pressure differential. (in a limited overlap/smogable camshaft this is especially true) This causes exhaust reversion & is one of the key factors in surging problems. By the airflow reversing course it is loosing a lot of it's inertia. Typically this is overcome before peak torque however. So only low-speed issues are present. At the track these motors are always above 4500rpm so this does not affect track times too much. Stilll....there is significant power lost by allowing reversion. So it makes sense to open the exhaust valve a little later & increase the overlap a bit. By adding advance into the camshaft this makes the problem even worse as now you're opening the exhaust a few more degrees earlier.....& shortening the effectiveness of the intake unless you have significant overlap flow to over come this.
Simply put, advancing a cam makes it more exhaust bias relative to TDC. Retarding a cam makes it more intake bias relative to TDC.
Not saying these are my theories just trying to clarify what I understand is 93Pony's perspective.
As for myself, I am simply trying to share information...
10-09-2003, 10:04 PM
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Re: Camshaft Discussion part II Enjoyed you guys cam discussion, JROD, however little of it I am able to assimilate! 
I've read several of your posts on corvetteforum.com.
I've read several of your posts on corvetteforum.com.
10-09-2003, 11:31 PM
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Re: Camshaft Discussion part II J-rod - no problem, I was just responding in general to the idea!
I don't necceceraly disagree with what he said, I am just trying to get more. All that is great, but it still boils down to application - taking that and turning it into a number. One can say "take xxx and yyy into acount", but how are you actually doing that when you pick a cam.
A specific question - why only 4 degrees retarding, why not 6 degrees, or 8 degrees? I am definitely NOT saying it is happening here, but there is a tendency to "take stuff into account" by throwing "a few degrees" here or there. Nitrous? Add 10 degrees to exhaust. Emissions? Add 2 degrees to the lsa. Want more rpm - retard 4 degrees, etc.
Problem is those are all way to arbitrary - if you are really taking all the stuff mentioned above into account you need wayy more information (what the heads flow, cross sectional area (average), etc.
What am trying to figure out is how you take what you know (runner length, head flow characteristics, etc.) and turn that into a number.
I don't necceceraly disagree with what he said, I am just trying to get more. All that is great, but it still boils down to application - taking that and turning it into a number. One can say "take xxx and yyy into acount", but how are you actually doing that when you pick a cam.
A specific question - why only 4 degrees retarding, why not 6 degrees, or 8 degrees? I am definitely NOT saying it is happening here, but there is a tendency to "take stuff into account" by throwing "a few degrees" here or there. Nitrous? Add 10 degrees to exhaust. Emissions? Add 2 degrees to the lsa. Want more rpm - retard 4 degrees, etc.
Problem is those are all way to arbitrary - if you are really taking all the stuff mentioned above into account you need wayy more information (what the heads flow, cross sectional area (average), etc.
What am trying to figure out is how you take what you know (runner length, head flow characteristics, etc.) and turn that into a number.
10-10-2003, 08:11 AM
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Re: Camshaft Discussion part II What am trying to figure out is how you take what you know (runner length, head flow characteristics, etc.) and turn that into a number.
10-10-2003, 08:45 AM
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Re: Camshaft Discussion part II Agreed Chris. That has been my point in all this. To have an understanding of why 93Pony feels like his VE's are more optimal than many of the other cams out there, and to come up with some basic models that could be applied to camshaft selection. One of the things I have noticed about his two most important VE's is that they are close to one another. Let me show an example:
93Pony's VE's
IVC EVO
45 44
47 43
49 48
50 49
Competitors Cams
IVC EVO
39 47
41 52
44 56
See how if his IVC is 45 ABDC his EVO is 44 BBDC. Versus many of the other cams which the intake valve closes earlier, and the Exhaust valve opens earlier. But, those events seem to correlate in degrees very closely with the IVC leading the EVO by about 1 degree... I know there is more to it than that, but since those are the two most important valve evetns (according to him) I have been trying to understand that relationship, and work from there.
As an example, here is a BIG cam using his VE's 236/234 XE-R lobes 108 LSA 108 ICL
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 283 234 155 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 108 108 108
Intake Valve opens - IVO 34.5 10 -29.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 70.5 46 6.5 ABDC
Exhaust Valve Opens - EVO 69.5 45 5.5 BBDC
Exhaust Valve Closes - EVC 33.5 9 -30.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 108 108 108
Overlap 68 19 -60 degrees
IVC and EVO using the preferrred VE's. Now, go up to a 111LSA 111ICL
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 283 234 155 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 111 111 111
Intake Centerline - ICL 111 111 111
Intake Valve opens - IVO 31.5 7 -32.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 73.5 49 9.5 ABDC
Exhaust Valve Opens - EVO 72.5 48 8.5 BBDC
Exhaust Valve Closes - EVC 30.5 6 -33.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 111 111 111
Overlap 62 13 -66 degrees
Less overlap, and the same 1 degree spread from IVC to EVO. But, that doesn't get back to the why. This is more of a monkey-see monkey-do exercise. I can get the VE's but I'd prefer to know why he prefers them to check them against some other things.
93Pony's VE's
IVC EVO
45 44
47 43
49 48
50 49
Competitors Cams
IVC EVO
39 47
41 52
44 56
See how if his IVC is 45 ABDC his EVO is 44 BBDC. Versus many of the other cams which the intake valve closes earlier, and the Exhaust valve opens earlier. But, those events seem to correlate in degrees very closely with the IVC leading the EVO by about 1 degree... I know there is more to it than that, but since those are the two most important valve evetns (according to him) I have been trying to understand that relationship, and work from there.
As an example, here is a BIG cam using his VE's 236/234 XE-R lobes 108 LSA 108 ICL
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 283 234 155 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 108 108 108
Intake Valve opens - IVO 34.5 10 -29.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 70.5 46 6.5 ABDC
Exhaust Valve Opens - EVO 69.5 45 5.5 BBDC
Exhaust Valve Closes - EVC 33.5 9 -30.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 108 108 108
Overlap 68 19 -60 degrees
IVC and EVO using the preferrred VE's. Now, go up to a 111LSA 111ICL
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 283 234 155 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 111 111 111
Intake Centerline - ICL 111 111 111
Intake Valve opens - IVO 31.5 7 -32.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 73.5 49 9.5 ABDC
Exhaust Valve Opens - EVO 72.5 48 8.5 BBDC
Exhaust Valve Closes - EVC 30.5 6 -33.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 111 111 111
Overlap 62 13 -66 degrees
Less overlap, and the same 1 degree spread from IVC to EVO. But, that doesn't get back to the why. This is more of a monkey-see monkey-do exercise. I can get the VE's but I'd prefer to know why he prefers them to check them against some other things.
10-10-2003, 08:48 AM
#69
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Re: Camshaft Discussion part II Oh, one other thing. I believe the 4 degrees was based on the fact that most cams are ground 4 degrees advanced, so 4 degrees retarded get you to the some LSA/ICL in the case of most cams.
10-10-2003, 10:25 AM
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Re: Camshaft Discussion part II Good observation, but if that is infact the reasoning behind the change I can't see any theory that would back that up?
One could argue for a fixed amount of overlap for a given RPM HP peak goal, but then if you change from say manifolds to kooks 2" longtube headers the effect of that overlap will be very different, so you would want to change the overlap. Yet with a given set of lobes the formula would give you the same icl/lsa/ecl for either setup, when it's pretty obvious they should be different.
One could argue for a fixed amount of overlap for a given RPM HP peak goal, but then if you change from say manifolds to kooks 2" longtube headers the effect of that overlap will be very different, so you would want to change the overlap. Yet with a given set of lobes the formula would give you the same icl/lsa/ecl for either setup, when it's pretty obvious they should be different.
10-10-2003, 03:23 PM
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Re: Camshaft Discussion part II What do you cam gurus think about this cam for my setup? An XE-R 3725 intake lobe and a 3723 exhaust lobe on a 110 to 112 LSA? It would be 230/226 .592/.585... Headers are goin on pretty soon, ill be running stock heads for awhile, proabably til about next summer when i get heads. Just wantin some opinions from the pros. 
10-10-2003, 03:46 PM
#72
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Re: Camshaft Discussion part II I'm by no means an expert. Here they are with the VE's similar to the one mentioned, which required a bigger exhaust lobe. Not saying this is the bestt cam of all time, simply using the data already posted. This may be a total pig of a cam...
110
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 279 230 151 3725
Exhaust Duration - ED 277 228 149 3724
Lobe Center Angle - LCA (also known as LSA) 110 110 110
Intake Centerline - ICL 110 110 110
Intake Valve opens - IVO 29.5 5 -34.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 69.5 45 5.5 ABDC
Exhaust Valve Opens - EVO 68.5 44 4.5 BBDC
Exhaust Valve Closes - EVC 28.5 4 -35.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 110 110 110
Overlap 58 9 -70 degrees
112
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 279 230 151 3725
Exhaust Duration - ED 277 228 149 3724
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 112 112 112
Intake Valve opens - IVO 27.5 3 -36.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 71.5 47 7.5 ABDC
Exhaust Valve Opens - EVO 70.5 46 6.5 BBDC
Exhaust Valve Closes - EVC 26.5 2 -37.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 112 112 112
Overlap 54 5 -74 degrees
110
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 279 230 151 3725
Exhaust Duration - ED 277 228 149 3724
Lobe Center Angle - LCA (also known as LSA) 110 110 110
Intake Centerline - ICL 110 110 110
Intake Valve opens - IVO 29.5 5 -34.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 69.5 45 5.5 ABDC
Exhaust Valve Opens - EVO 68.5 44 4.5 BBDC
Exhaust Valve Closes - EVC 28.5 4 -35.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 110 110 110
Overlap 58 9 -70 degrees
112
Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 279 230 151 3725
Exhaust Duration - ED 277 228 149 3724
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 112 112 112
Intake Valve opens - IVO 27.5 3 -36.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 71.5 47 7.5 ABDC
Exhaust Valve Opens - EVO 70.5 46 6.5 BBDC
Exhaust Valve Closes - EVC 26.5 2 -37.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 112 112 112
Overlap 54 5 -74 degrees
10-10-2003, 04:01 PM
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Re: Camshaft Discussion part II J-Rod,
You have a firm grasp on how I do things. The 'why' is the key I will not post....can't give away all my secrets you know. Thanks for helping to explain. You've done it quite well.
The theories behind the VE's I choose are based on the restrictions of the EFI manifold. I'm sorry you guys are having a hard time grasping this...but the keys to the VE's I choose are all in this thread....somewhere. LOL
There are no 'set' VE's I use. It's all very application specific. Depends on the combo & the goals of the owner. I've not yet made 2 cams the exact same.
SSEUL8R,
Given stock heads I'd use a little more intake bias. Perhaps using a slighlty larger XE-high lift lobe on the exhaust. Given ported heads....well, it really depends on which heads you choose.
You have a firm grasp on how I do things. The 'why' is the key I will not post....can't give away all my secrets you know. Thanks for helping to explain. You've done it quite well.
The theories behind the VE's I choose are based on the restrictions of the EFI manifold. I'm sorry you guys are having a hard time grasping this...but the keys to the VE's I choose are all in this thread....somewhere. LOL
There are no 'set' VE's I use. It's all very application specific. Depends on the combo & the goals of the owner. I've not yet made 2 cams the exact same.
SSEUL8R,
Given stock heads I'd use a little more intake bias. Perhaps using a slighlty larger XE-high lift lobe on the exhaust. Given ported heads....well, it really depends on which heads you choose.
10-10-2003, 07:38 PM
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Re: Camshaft Discussion part II He didn't even tell me what would happen, if I retarded my cam the suggested 4 degrees??? 
I even promised him my question wouldn't give him a headache...and that didn't work???
I even promised him my question wouldn't give him a headache...and that didn't work???
10-10-2003, 08:56 PM
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Re: Camshaft Discussion part II 93Pony - I still don't see anything that answers this question:
That I posted earlier?
Also if you are saying J-rod is correct in his theory that you are trying to make the ICL and LSA the same numerically could you please explain this - as I have never seen any evidence to support this, as well as it just doesn't make sense.
Explaining that won't give away any of your "trade secrets" - since people can duplicate the results easily if they so choose, as J-rod illustrated. Posting a why in the case would help explain what you are doing (as well as give some validity to it?)
Thanks,
93Pony - what exactly are you looking at to determine that the camshafts in question should be retarded?
Assuming the lobes are the same one is a 111lsa while the other is a 114lsa - so if you retard them both 4 degrees as you suggest they are going to have different valve events (they will of course no matter what unless the cam is reground - I am just curious as to the reasoning behind retarding them both 4 degrees since they are different?)
Assuming the lobes are the same one is a 111lsa while the other is a 114lsa - so if you retard them both 4 degrees as you suggest they are going to have different valve events (they will of course no matter what unless the cam is reground - I am just curious as to the reasoning behind retarding them both 4 degrees since they are different?)
Also if you are saying J-rod is correct in his theory that you are trying to make the ICL and LSA the same numerically could you please explain this - as I have never seen any evidence to support this, as well as it just doesn't make sense.
Explaining that won't give away any of your "trade secrets" - since people can duplicate the results easily if they so choose, as J-rod illustrated. Posting a why in the case would help explain what you are doing (as well as give some validity to it?)
The theories behind the VE's I choose are based on the restrictions of the EFI manifold. I'm sorry you guys are having a hard time grasping this...but the keys to the VE's I choose are all in this thread....somewhere.
Thanks,
10-11-2003, 03:21 AM
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Re: Camshaft Discussion part II Nightmare,
You'd have better idle quality & power accross the board would increase. I've seen gains of 2mph in the 1/4 from moving a cam 6 degrees.
It's all about getting the correct valve events. Plain & simple, LSA & ICL are just #'s that tell you where the valves will open and close given the lobes.
Chris,
Plug the 2 ICL's for the given cams into that VE caculator & re-read why I choose the VE's that I do. The answers to the questions you've asked have been covered in previous posts. You just have to put the info together.
You'd have better idle quality & power accross the board would increase. I've seen gains of 2mph in the 1/4 from moving a cam 6 degrees.
It's all about getting the correct valve events. Plain & simple, LSA & ICL are just #'s that tell you where the valves will open and close given the lobes.
Chris,
Plug the 2 ICL's for the given cams into that VE caculator & re-read why I choose the VE's that I do. The answers to the questions you've asked have been covered in previous posts. You just have to put the info together.
10-11-2003, 09:58 AM
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Re: Camshaft Discussion part II It has been stated how you arrive at the numbers - at least with regards to the mechanical computation.
I do not believe it has been stated why you want to hit those values. I have seen some of the "theories" you posted, and I do agree with most of them, but there is no "translation" step between the theories and numbers. You mention taking into account intake, exhaust, etc. Yet when it comes down to giving out recommendations it is just a generic "retard 4 degrees" without knowing really what is on the car. I just can't reconcile the two?
For instance headflow is *not* just a "flow" value. With the same runner length 320cfm through a 200CC head will work with a different camshaft than 320cfm through a 240cfm head.
I do not believe it has been stated why you want to hit those values. I have seen some of the "theories" you posted, and I do agree with most of them, but there is no "translation" step between the theories and numbers. You mention taking into account intake, exhaust, etc. Yet when it comes down to giving out recommendations it is just a generic "retard 4 degrees" without knowing really what is on the car. I just can't reconcile the two?
For instance headflow is *not* just a "flow" value. With the same runner length 320cfm through a 200CC head will work with a different camshaft than 320cfm through a 240cfm head.
10-11-2003, 01:25 PM
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Re: Camshaft Discussion part II Chris,
Why use an exhaust bias cam on an intake restricted motor? ICL also plays a large role in intake/exhaust bias....relative to TDC. It's all about getting some good VE's. Not only do the lobes determine if the cam is intake or exhaust bias, the VE's also play a large role in this.
Yes, flow #'s are only part of the equation, cross-section also plays a BIG role...but so does intake to exhaust ratio. Have you ever run accross an LS1 head that flows less then 75% intake to exhaust ratio with intake & stub pipe???
I have my reasons & take things into account when I give advise on cams. I'm sorry you don't understand my ways. J-Rod seems to have no problems picking up on 'generally' what I do. & that's as much info as I'll post. You're not going to get specific VE's....or 'rules of thumb' with requards to certain modifications... I do not limit myself to these types of rules.... Every application is different & is approached in generally the same way, but as of yet, I have not made 2 identical camshafts. Ford or Chevy.
Why use an exhaust bias cam on an intake restricted motor? ICL also plays a large role in intake/exhaust bias....relative to TDC. It's all about getting some good VE's. Not only do the lobes determine if the cam is intake or exhaust bias, the VE's also play a large role in this.
Yes, flow #'s are only part of the equation, cross-section also plays a BIG role...but so does intake to exhaust ratio. Have you ever run accross an LS1 head that flows less then 75% intake to exhaust ratio with intake & stub pipe???
I have my reasons & take things into account when I give advise on cams. I'm sorry you don't understand my ways. J-Rod seems to have no problems picking up on 'generally' what I do. & that's as much info as I'll post. You're not going to get specific VE's....or 'rules of thumb' with requards to certain modifications... I do not limit myself to these types of rules.... Every application is different & is approached in generally the same way, but as of yet, I have not made 2 identical camshafts. Ford or Chevy.