Camshaft discussion: CFM requirements by RPM.
06-09-2004, 04:55 PM
#381
FormerVendor
Originally Posted by Cstraub
Carl,
If you are after every bit of power, it is my opinion you should flow the induction system you are using and the exhaust manifold that will be on the car. Now to take it a step further, optimum intake lengths can be calculated and exhaust primary lengths can be calculated for air pulse tuning. . .this further increases the "potential power". For this I need port lengths.
Food for thought Carl, with an exhaust port flowing 90% of what the intake side is, does it make sense to think an efficent engine needs camshaft duration and lift on the exhaust that exceeds the intake?
Chris
PS. Anyone read the rule changes in NHRA Pro Stock. . .no more light ceramic composite rods. . .wonder why?
If you are after every bit of power, it is my opinion you should flow the induction system you are using and the exhaust manifold that will be on the car. Now to take it a step further, optimum intake lengths can be calculated and exhaust primary lengths can be calculated for air pulse tuning. . .this further increases the "potential power". For this I need port lengths.
Food for thought Carl, with an exhaust port flowing 90% of what the intake side is, does it make sense to think an efficent engine needs camshaft duration and lift on the exhaust that exceeds the intake?
Chris
PS. Anyone read the rule changes in NHRA Pro Stock. . .no more light ceramic composite rods. . .wonder why?
They're trying to slow Greg Anderson down, that's all. Plus keep costs down for everyone. Mainly though they're trying to slpw Greg down just like the NMRA is doing with the Booze's big dump truck engine!
06-09-2004, 05:48 PM
#382
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Originally Posted by Cstraub
PS. Anyone read the rule changes in NHRA Pro Stock. . .no more light ceramic composite rods. . .wonder why?
Gee and I thought I was the only one that paid attention to that!!!
Ronnie spoke to Gordie Riveira and he was ready to get some Jager rods after finding out who ran them.
Guess it's all moot now...
So are the ceramic valves and wrist pins and...
I thought this was heads up racing???
Originally Posted by racer7088
I still haven't even seen these new AFR heads and we have ten sets on order or something. Maybe Chuck cancelled on them but I've been up to my eyeballs in race engines and this week will go back to regular stuff. I'd love to see one of the new AFR deals for real. We have all their other heads.
<back to our regularly scheduled cam discussion>
Ed
06-10-2004, 09:32 AM
#383
6600 rpm clutch dump of death Administrator
Guess that means the Jaegers work, and a lot of NHRA contingency sponsors stood to loose some money...
Now, since we are back on the cam talk lets talk Chris' comment a bit further. I think you are spot on. Also with the uber gigantic cams out there, you end up hitting the engines "sweet" spot at part lift even if the valve events are wrong. So, you end up with some of the surging and idling issues, but you still make good power. The big thing is making more power, with less cam, and not having some of the drivability issues that some of the cams out there have without having to resort to a big cam with an 115-117LSA to smooth out the idle.
Now, one of the subjects that has come up before, which I think is going to be key with the new AFR heads coming out is port velocity.
One of the things that was discussed was selection of rocker arms, and selection of ramp speeds (how fast you open the valve). Now, how about a discussion on big fat lazy ports vs small efficient ports. Most notably what you would want to look for in selecting a cam for that port.
Lets say a GMPP CNC head with a 250CC intake runner which flows about what a AFR 205 flows. Short duration lobe with a fast ramp vs a slower opening lobe with more duration. And now the big question why do you select a lobe. What is the criteria for selecting a lobe like that. Logic would seem to dictate that on an inefficent port that you would open the port up and leave it open as long as you could to get air moving, and on a efficent port that you would take advantage of that ports inherent velocity advantage, and use a smaller cam as you can pack the air in there in less time. But, in talk with folks, they have actually recommended the opposite.
Now, since we are back on the cam talk lets talk Chris' comment a bit further. I think you are spot on. Also with the uber gigantic cams out there, you end up hitting the engines "sweet" spot at part lift even if the valve events are wrong. So, you end up with some of the surging and idling issues, but you still make good power. The big thing is making more power, with less cam, and not having some of the drivability issues that some of the cams out there have without having to resort to a big cam with an 115-117LSA to smooth out the idle.
Now, one of the subjects that has come up before, which I think is going to be key with the new AFR heads coming out is port velocity.
One of the things that was discussed was selection of rocker arms, and selection of ramp speeds (how fast you open the valve). Now, how about a discussion on big fat lazy ports vs small efficient ports. Most notably what you would want to look for in selecting a cam for that port.
Lets say a GMPP CNC head with a 250CC intake runner which flows about what a AFR 205 flows. Short duration lobe with a fast ramp vs a slower opening lobe with more duration. And now the big question why do you select a lobe. What is the criteria for selecting a lobe like that. Logic would seem to dictate that on an inefficent port that you would open the port up and leave it open as long as you could to get air moving, and on a efficent port that you would take advantage of that ports inherent velocity advantage, and use a smaller cam as you can pack the air in there in less time. But, in talk with folks, they have actually recommended the opposite.
06-10-2004, 10:43 AM
#384
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Originally Posted by J-Rod
how about a discussion on big fat lazy ports vs small efficient ports. Most notably what you would want to look for in selecting a cam for that port.
Looking at the XER 224 lobe, its rated at 273 degrees and has 145 degrees at .200 lift. That puts 128 total degrees in the .200 and under lift range. How much of the actual air fuel mix is filled by the low lift durations?
06-10-2004, 01:55 PM
#385
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(346/2*6400)/1728 = 640.74
640.74/8 = 80.09
assume 235 thur stock LS1 heads and intake
80.09/x = 235
x = .3408
640.748*.3408 = 218.36
? does this mean on a stock LS1 the TR224 is even to big
640.74/8 = 80.09
assume 235 thur stock LS1 heads and intake
80.09/x = 235
x = .3408
640.748*.3408 = 218.36
? does this mean on a stock LS1 the TR224 is even to big
06-10-2004, 04:42 PM
#386
Velocity. . .key point of any cylinder head. Runner volume needs to be matched to CID's operating range. . .I repeat. . . matched to the CID's operating range. A 346 CID running 6500 rpm max and a 421 CID running 6500 do not use the same heads. For example the last Super Late model I cammed was 421CID and had 265cc heads on it and turned 8000 rpm.
My only comment about big heads vs "matched" heads and what cam is needed is. . .well it is kinda like index racing. ..if you are slower. . . you need a head start. . .if you are faster. . .you leave later.
Now as for me, I am at my info limit. I think their is a good base of info to help all of you make a good camshaft selection. Previous camshaft threads by J-rod I found informative. As a board for a whole, their is very good tech on this one. We are now getting into areas that. ..for me are what give my customers an edge. . .just last night I had a customer set 2 track records in circle track in Canada with my sticks. He now has a competitive edge.. . he didn't before. He paid for that edge. He didn't even question what I would do next for him with a dirt late model. . .just do it and bill me. The trust has now been earned. This is my satisfaction. . but it also allows me to buy my toys with the money that is earned. Plus money over the last 10 years has paid for the $20K in software design charges I have had to pay out to put paper calulations into a program.
I don't mind to answer questions, as those of you that have e-mailed or called know, I'll spend as much time helping as I can, but I have a mortgage to pay. I hope you understand where I am coming from. I would not expect anyone to tell me how. . .I expect learn it with trial and error.
Chris Straub
Stef's Performance
My only comment about big heads vs "matched" heads and what cam is needed is. . .well it is kinda like index racing. ..if you are slower. . . you need a head start. . .if you are faster. . .you leave later.
Now as for me, I am at my info limit. I think their is a good base of info to help all of you make a good camshaft selection. Previous camshaft threads by J-rod I found informative. As a board for a whole, their is very good tech on this one. We are now getting into areas that. ..for me are what give my customers an edge. . .just last night I had a customer set 2 track records in circle track in Canada with my sticks. He now has a competitive edge.. . he didn't before. He paid for that edge. He didn't even question what I would do next for him with a dirt late model. . .just do it and bill me. The trust has now been earned. This is my satisfaction. . but it also allows me to buy my toys with the money that is earned. Plus money over the last 10 years has paid for the $20K in software design charges I have had to pay out to put paper calulations into a program.
I don't mind to answer questions, as those of you that have e-mailed or called know, I'll spend as much time helping as I can, but I have a mortgage to pay. I hope you understand where I am coming from. I would not expect anyone to tell me how. . .I expect learn it with trial and error.
Chris Straub
Stef's Performance
06-11-2004, 12:13 AM
#388
Originally Posted by J-Rod
Logic would seem to dictate that on an inefficent port that you would open the port up and leave it open as long as you could to get air moving, and on a efficent port that you would take advantage of that ports inherent velocity advantage, and use a smaller cam as you can pack the air in there in less time. But, in talk with folks, they have actually recommended the opposite.
06-11-2004, 06:56 AM
#389
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Wow! This is the best thread ever! I just read it (up to now) in one sitting and the level of professionalism without juvenile flames is absolutely a joy to behold. I've been "hotrodding" for 40+ years (enthusiast, not a builder) and thought I knew some things. Thanks to you all for the additional insight and knowledge. Although I've read a lot by David Vizard and others, finding such a great assortment of knowledge is indeed heartening. Thank you, gentlemen. 
06-11-2004, 09:11 AM
#390
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Originally Posted by Cstraub
Now as for me, I am at my info limit. I think their is a good base of info to help all of you make a good camshaft selection.
I would like to say thanks for all the info and direction, and I understand. I have learned much here and been forced to rethink my assumptions.
06-11-2004, 12:45 PM
#391
6600 rpm clutch dump of death Administrator
Originally Posted by critter
Chris,
I would like to say thanks for all the info and direction, and I understand. I have learned much here and been forced to rethink my assumptions.
I would like to say thanks for all the info and direction, and I understand. I have learned much here and been forced to rethink my assumptions.
I do appreciate all the of the comments from the folks out there who do have the know how and expertise to help educate the "great unwashed masses" out here.
Anyhow, if there are topics around what we have discussed that can help educate folks without compromising the hard work of the folks out there who have spent their time and money in real R&D I'd like to keep the technical discussions going. So, if there are some points we can discuss, I say lets do so...
06-21-2004, 06:33 PM
#393
Originally Posted by critter
Chris,
I would like to say thanks for all the info and direction, and I understand. I have learned much here and been forced to rethink my assumptions.
I would like to say thanks for all the info and direction, and I understand. I have learned much here and been forced to rethink my assumptions.
Thanks for the Thread J-Rod. 
joel
06-28-2004, 09:10 PM
#394
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Originally Posted by DenzSS
This will get you the velocity and acceleration curves, the cfm is fairly easy after that.
You can see how it is much easier to do in an application...
You can see how it is much easier to do in an application...
08-26-2004, 08:26 AM
#398
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Originally Posted by J-Rod
Ok, let review... Bigger isn't always better...
Crap... All that money in ***** enlargement pills was for nothing???
BTW...
Just had some "in between" lobes developed...
Not as severe as the XER but a tad bit quicker than the Extreme...
Perfect for the AFR head's flow characteristics...
Jarrod: Thought we were doing "something" for your project????
Ed
08-26-2004, 09:47 AM
#399
6600 rpm clutch dump of death Administrator
Originally Posted by EDC
Crap... All that money in ***** enlargement pills was for nothing???
TMI baby TMI...
BTW...
Just had some "in between" lobes developed...
Not as severe as the XER but a tad bit quicker than the Extreme...
Perfect for the AFR head's flow characteristics...
Just had some "in between" lobes developed...
Not as severe as the XER but a tad bit quicker than the Extreme...
Perfect for the AFR head's flow characteristics...
Jarrod: Thought we were doing "something" for your project????
Ed
Ed
