thoughts on the tr230/224 cam
02-14-2010, 02:51 PM
#12
02-16-2010, 11:45 AM
#13
On The Tree
what transmission are u getting? I have the level 2 I think. Whichever one says it'll hold 700 hp and I've had nothin but problems with it. This weekend I lost all gears except 1st and 2nd. Neutral is my new first gear and 2nd works in D,3,2,1. It's f*#^€d...oh and I have a tr220 cam and a procharger pushin 10psi. Love the cam tho.
02-16-2010, 09:49 PM
#15
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i always liked MTI's 230/227 reverse split cam....
http://www.youtube.com/watch?v=C_hyn...eature=related
http://www.youtube.com/watch?v=C_hyn...eature=related
02-17-2010, 12:31 AM
#16
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This is a sticky on HardcoreLS1.com:
Preface.... The Reverse Split Ideology:
The whole "theory" on why LS engines need a reverse split, that being a cam with more intake duration than exhaust duration is as follows from what I take:
1. My Version: Since a LS motor for example has a 80% E/I ratio in bare form and then when a intake manifold is installed it increases that ratio even more so the exhaust is much more than 75% of the intake, we need to match the to camshaft that flow imbalance hence changing the duration to this configuration.
2. LS1Toke: A reverse split cam is best for someone who has limited mods on the intake side and good mods(such as LT, ORY, and cat-back) on the exhaust side.
3. LS1Toke: A reverse split cam is better for your current application if you don't have the best intake flow and if you have full exhaust. What it does is allow more air into the cylinders. So since you have a LS1 intake you would benefit from it because the flow isnt as good as LS6.
And the real kicker a "Advanced Tech" thread on the matter...
https://ls1tech.com/forums/showthread.php?t=925980
Ok so now I guess we have down that with a good exhaust system like a standard bolt on car has, you now have LOTS of exhaust flow after the head so it's not a restriction to the exhaust flow, but with the intake manifold design of the LS motor you have a choked off intake port since the manifold can't FLOW as much as the cylinder head. Therefore this makes the intake to exhaust ratio flow around something stupid like 90%.
Now on to why this is all horse hockey. (bonus points for who can tell me where I get that from)
Just the FACTS mam:
The people who stumble on this "theory" are comparing data from static flow testing only and basing their choices for a camshaft on things that don't really happen in the working motor.
The first rule here that this is a BS idea is the straight fact that the LS motor makes 100% VE or greater very easily. Engine dyno tests show that a stock LS6 motor for example will make 430HP in stock trim without the accessories on it. That's right at or above 100% VE. Now consider that if the LS6 cam is retarded 2° which is normal, the IVC is around 68° ABDC. So there is only 112° of time when the air/fuel is "trapped" in the cylinder, or 62% of 180°.
So how can a head that can flows 250+ cfm in stock form that is being choked off by a intake manifold make 100%+ VE on top of 346 cubes?
How does it do it in stock form, especially with all the stock cams being "traditional" split cams? 196/202, 201/210, 204/218, 204/211 etc....
The real problem here is that these guys are looking at FLOW, and not the depression or delta P, that is causing that flow in the first place. That leads to looking at the intake manifold, the same flow robbing bandit turns out to be the positive pressure producing part of the motor that is causing 100% VE in stock form! Yep our old buddy pressure wave tuning is rearing his ugly head to make this concept of flow irrelevant to the average Joe's easy thinking.
Pressure Wave Tuning the basic and expanded explaination:
Pressure waves are produced from a Helmholtz resonance, which has best been described as air acting like mass on a spring in the intake port from valve to plenum.
A excerpt from Wikipedia that is good on this...
"Qualitative explanation
When air is forced into a cavity, the pressure inside increases. Once the external force that forces the air into the cavity disappears, the higher-pressure air inside will flow out. However, this surge of air flowing out will tend to over-compensate, due to the inertia of the air in the neck, and the cavity will be left at a pressure slightly lower than the outside, causing air to be drawn back in. This process repeats with the magnitude of the pressure changes decreasing each time.
This effect is akin to that of a bungee-jumper bouncing on the end of a bungee rope, or a mass attached to a spring. Air trapped in the chamber acts as a spring. Changes in the dimensions of the chamber adjust the properties of the spring: a larger chamber would make for a weaker spring, and vice-versa.
The air in the port (the neck of the chamber) is the mass. Since it is in motion, it possesses some momentum. A longer port would make for a larger mass, and vice-versa. The diameter of the port is related to the mass of air and the volume of the chamber. A port that is too small in area for the chamber volume will "choke" the flow while one that is too large in area for the chamber volume tends to reduce the momentum of the air in the port."
Here is a easy to read article that relates this phenomenon closer to internal combustion engines... http://www.dinamoto.it/DINAMOTO/on-l...suonatore.html
Or if you feel like you want to a more direct explaination of all of this it can be found in a paper here titled: The Acoustics of Racing Engine Intake Systems
Very cool paper if you are into super geeky engine stuff!
How all of this works to make HP:
So now that we have the idea that pressure waves going back and fourth between the plenum and valve cause a building and dropping of pressure in the intake port. The tuning of this wave is relative to the length of the tract from plenum to valve and is either very good at certain RPM or very bad and also has a order as to how many times it cycles per engine revolution at that RPM. These are called harmonics....
Harmonics are the key to the strength of the pulse, by reading the excerpt above on Helmholtz resonance you can see that the pressure pulse is stronger the longer the runner. Now each RPM has a length associated with each harmonic. The harmonics going from one to six get weaker with every additional harmonic, the first being the strongest and longest, but you have to calculate the appropriate length relative to RPM and cylinder displacement.
A LS motor works on the 2nd Harmonic so it is a very strong, thus producing high pressure in the intake port. High pressure above a low cylinder pressure creates a large depression.... a lot like a flow bench makes. Now with that idea we can relate this to how the average Joe looks at head data.
This large difference or large depression causes the head to act like it is being flowed on a flow bench at a higher depression than the standard 28" of flow. It can be over 100" of depression on a stock LS6 at HP peak. So now the flow of the intake port in this dynamic environment is much more than the 250cfm or so that the flow bench tell us. Actually around .500" lift where the head statically flows 250cfm @ 28" on a flow bench it actually moves about 320cfm on the running motor.
The only issue with using these numbers is that from IVO to IVC the depression between the head port and cylinder changes and it does so at every RPM as well. Either way this points out that with the 2nd order harmonic that the LS motor works on we fill the cylinder much more than the flow bench data says we can. That's why we can fill the cylinder at or more than 100% VE on a stock motor hence how this all makes HP!
So how does this relate to the "split" of the cam?:
What you put into a motor you have to get out... now since time in camshaft terms is relative to duration we have to get out what we get in. Since there are no restrictions in the system to filling the cylinder and as we have seen the motor does so better than we can imagine due to resonance tuning.
The only issue with the resonance tuning is that it's highly sensitive to the intake valve timing and if we leave the valve open too long the motor will lose what it put into the cylinder (late IVC) or not create enough of a pressure build up to start filling the cylinder well at IVO, so that means we have a set intake duration range that is relative to our working RPM range we can use.... (hence why big cams are wrong for street cars!)
So now since we have a limit on the intake side of the cam since it's a compromise between optimal valve events for a range of RPM, we have to figure out what it takes to get out what the motor put in.
The exhaust side of the motor is much, much harder to guess at. The pressures are very high when the exhaust valve is cracked @ EVO and decays from there until EVC. The flow happening here makes very little sense if any at all to even the best in the industry and flow numbers of a static flow bench tell us little to if anything about what is going on.
Conclusion:
What we do know is that with the added depression that the intake port sees due to the 2nd harmonic pressure pulse we put more in the cylinder during the time the intake valve was open than what the cylinder head statically flows.... so we have to get all of that out, and get it out through a smaller hole!
This simple fact is why you need more duration on the exhaust than on the intake in a LS motor.
Preface.... The Reverse Split Ideology:
The whole "theory" on why LS engines need a reverse split, that being a cam with more intake duration than exhaust duration is as follows from what I take:
1. My Version: Since a LS motor for example has a 80% E/I ratio in bare form and then when a intake manifold is installed it increases that ratio even more so the exhaust is much more than 75% of the intake, we need to match the to camshaft that flow imbalance hence changing the duration to this configuration.
2. LS1Toke: A reverse split cam is best for someone who has limited mods on the intake side and good mods(such as LT, ORY, and cat-back) on the exhaust side.
3. LS1Toke: A reverse split cam is better for your current application if you don't have the best intake flow and if you have full exhaust. What it does is allow more air into the cylinders. So since you have a LS1 intake you would benefit from it because the flow isnt as good as LS6.
And the real kicker a "Advanced Tech" thread on the matter...
https://ls1tech.com/forums/showthread.php?t=925980
Ok so now I guess we have down that with a good exhaust system like a standard bolt on car has, you now have LOTS of exhaust flow after the head so it's not a restriction to the exhaust flow, but with the intake manifold design of the LS motor you have a choked off intake port since the manifold can't FLOW as much as the cylinder head. Therefore this makes the intake to exhaust ratio flow around something stupid like 90%.
Now on to why this is all horse hockey. (bonus points for who can tell me where I get that from)
Just the FACTS mam:
The people who stumble on this "theory" are comparing data from static flow testing only and basing their choices for a camshaft on things that don't really happen in the working motor.
The first rule here that this is a BS idea is the straight fact that the LS motor makes 100% VE or greater very easily. Engine dyno tests show that a stock LS6 motor for example will make 430HP in stock trim without the accessories on it. That's right at or above 100% VE. Now consider that if the LS6 cam is retarded 2° which is normal, the IVC is around 68° ABDC. So there is only 112° of time when the air/fuel is "trapped" in the cylinder, or 62% of 180°.
So how can a head that can flows 250+ cfm in stock form that is being choked off by a intake manifold make 100%+ VE on top of 346 cubes?
How does it do it in stock form, especially with all the stock cams being "traditional" split cams? 196/202, 201/210, 204/218, 204/211 etc....
The real problem here is that these guys are looking at FLOW, and not the depression or delta P, that is causing that flow in the first place. That leads to looking at the intake manifold, the same flow robbing bandit turns out to be the positive pressure producing part of the motor that is causing 100% VE in stock form! Yep our old buddy pressure wave tuning is rearing his ugly head to make this concept of flow irrelevant to the average Joe's easy thinking.
Pressure Wave Tuning the basic and expanded explaination:
Pressure waves are produced from a Helmholtz resonance, which has best been described as air acting like mass on a spring in the intake port from valve to plenum.
A excerpt from Wikipedia that is good on this...
"Qualitative explanation
When air is forced into a cavity, the pressure inside increases. Once the external force that forces the air into the cavity disappears, the higher-pressure air inside will flow out. However, this surge of air flowing out will tend to over-compensate, due to the inertia of the air in the neck, and the cavity will be left at a pressure slightly lower than the outside, causing air to be drawn back in. This process repeats with the magnitude of the pressure changes decreasing each time.
This effect is akin to that of a bungee-jumper bouncing on the end of a bungee rope, or a mass attached to a spring. Air trapped in the chamber acts as a spring. Changes in the dimensions of the chamber adjust the properties of the spring: a larger chamber would make for a weaker spring, and vice-versa.
The air in the port (the neck of the chamber) is the mass. Since it is in motion, it possesses some momentum. A longer port would make for a larger mass, and vice-versa. The diameter of the port is related to the mass of air and the volume of the chamber. A port that is too small in area for the chamber volume will "choke" the flow while one that is too large in area for the chamber volume tends to reduce the momentum of the air in the port."
Here is a easy to read article that relates this phenomenon closer to internal combustion engines... http://www.dinamoto.it/DINAMOTO/on-l...suonatore.html
Or if you feel like you want to a more direct explaination of all of this it can be found in a paper here titled: The Acoustics of Racing Engine Intake Systems
Very cool paper if you are into super geeky engine stuff!
How all of this works to make HP:
So now that we have the idea that pressure waves going back and fourth between the plenum and valve cause a building and dropping of pressure in the intake port. The tuning of this wave is relative to the length of the tract from plenum to valve and is either very good at certain RPM or very bad and also has a order as to how many times it cycles per engine revolution at that RPM. These are called harmonics....
Harmonics are the key to the strength of the pulse, by reading the excerpt above on Helmholtz resonance you can see that the pressure pulse is stronger the longer the runner. Now each RPM has a length associated with each harmonic. The harmonics going from one to six get weaker with every additional harmonic, the first being the strongest and longest, but you have to calculate the appropriate length relative to RPM and cylinder displacement.
A LS motor works on the 2nd Harmonic so it is a very strong, thus producing high pressure in the intake port. High pressure above a low cylinder pressure creates a large depression.... a lot like a flow bench makes. Now with that idea we can relate this to how the average Joe looks at head data.
This large difference or large depression causes the head to act like it is being flowed on a flow bench at a higher depression than the standard 28" of flow. It can be over 100" of depression on a stock LS6 at HP peak. So now the flow of the intake port in this dynamic environment is much more than the 250cfm or so that the flow bench tell us. Actually around .500" lift where the head statically flows 250cfm @ 28" on a flow bench it actually moves about 320cfm on the running motor.
The only issue with using these numbers is that from IVO to IVC the depression between the head port and cylinder changes and it does so at every RPM as well. Either way this points out that with the 2nd order harmonic that the LS motor works on we fill the cylinder much more than the flow bench data says we can. That's why we can fill the cylinder at or more than 100% VE on a stock motor hence how this all makes HP!
So how does this relate to the "split" of the cam?:
What you put into a motor you have to get out... now since time in camshaft terms is relative to duration we have to get out what we get in. Since there are no restrictions in the system to filling the cylinder and as we have seen the motor does so better than we can imagine due to resonance tuning.
The only issue with the resonance tuning is that it's highly sensitive to the intake valve timing and if we leave the valve open too long the motor will lose what it put into the cylinder (late IVC) or not create enough of a pressure build up to start filling the cylinder well at IVO, so that means we have a set intake duration range that is relative to our working RPM range we can use.... (hence why big cams are wrong for street cars!)
So now since we have a limit on the intake side of the cam since it's a compromise between optimal valve events for a range of RPM, we have to figure out what it takes to get out what the motor put in.
The exhaust side of the motor is much, much harder to guess at. The pressures are very high when the exhaust valve is cracked @ EVO and decays from there until EVC. The flow happening here makes very little sense if any at all to even the best in the industry and flow numbers of a static flow bench tell us little to if anything about what is going on.
Conclusion:
What we do know is that with the added depression that the intake port sees due to the 2nd harmonic pressure pulse we put more in the cylinder during the time the intake valve was open than what the cylinder head statically flows.... so we have to get all of that out, and get it out through a smaller hole!
This simple fact is why you need more duration on the exhaust than on the intake in a LS motor.
02-17-2010, 09:23 AM
#17
Figure out what your budget/timeframe is and we can help you. That cam with a 2800 stall in your heavy truck is not going to get the job done though.
02-17-2010, 05:55 PM
#18
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Last edited by MPFD; 02-17-2010 at 07:02 PM.
02-17-2010, 06:59 PM
#19
My post count or me being a mod has nothing to do with how I percieve myself or any way correlate to my knowledge of these engines so you can shut that wagon train down right there. Im not going to go back and forth with you like I have in the past, simple fact of the matter is MANY people have had great results with reverse split cams regardless of what all the links you post say. There is a difference between real world results and what someone says on the internet.
Say what you will about this site and tech but for some reason you keep coming back. If you dont like what there is to offer here then you have teh option to no longer visit. Obviously you are mistaken about people who dont know anything about racing, us truck guys are the craziest of the bunch and in case you havent noticed theres quite a few fast *** trucks on this site so there again Id have to say youre wrong
Say what you will about this site and tech but for some reason you keep coming back. If you dont like what there is to offer here then you have teh option to no longer visit. Obviously you are mistaken about people who dont know anything about racing, us truck guys are the craziest of the bunch and in case you havent noticed theres quite a few fast *** trucks on this site so there again Id have to say youre wrong
02-17-2010, 07:06 PM
#20
Apparently the fourth time editing your post is the charm huh?
Its obvious the OP has no idea what he wants to do. He didnt mentioning ANYTHING about FI until after you posted that book so the comment on boost and a reverse split is totally irrelevant. Besides the fact that reverse splits have worked well in turbo apps, may not be optimal but they still work regardless of the fact that if/when he changes setups hes talking a whole new motor and at that time a new cam would be a good idea anyway to optimize what he is wanting to do.
Its obvious the OP has no idea what he wants to do. He didnt mentioning ANYTHING about FI until after you posted that book so the comment on boost and a reverse split is totally irrelevant. Besides the fact that reverse splits have worked well in turbo apps, may not be optimal but they still work regardless of the fact that if/when he changes setups hes talking a whole new motor and at that time a new cam would be a good idea anyway to optimize what he is wanting to do.