Dyno2000 Cam Trade
03-21-2002, 01:03 AM
#1
Racer
Thread Starter
Dyno2000 Cam Trade
Quickie summary; for a powerful street cam:
-Closing the intake valve late is more important than large intake durations.
-Large valve overlap is not needed.
-Big exhaust durations extend the power band.
-Chevy does all of the above.
-Why don’t the aftermarket cam manufactures?
Cam Trade Goals
The purpose of this cam trade was:
1.Learn something about cams and how they work
2.Try to understand Chevy’s stock cam design choices
3.Look for a higher performance cam for my Vette
Choosing a performance cam for your Vette is a frustrating experience that leads you to “go with the experts” or risk an expensive development on your own. Simply collecting info on the Net can lead to conflicting expert opinion. After reading the simplified descriptions in the Hot Rod type magazines and also several cam catalogs, I decided to expand the available data base by doing a large computer based engine simulation trade. This data base would allow me to plot cam geometries vs. predicted performance. Also, the variations due to the geometries would give some insight as to the important variables. This is an age old engineering practice in simulation that looks more for the trends than the absolutes.
Chevy’s LS6 cams are commonly described as “too mild” to be considered as performance cams. The short intake duration is usually given as sufficient proof that these are weaklings. The fact remains that the LS6 is a very strong performer and that it does respond to modifications. I wanted to know why these cams worked and what the limitations were. I will give The General credit for knowing what makes power and try to understand the compromises that are made to make a warranted, emissions legal street car.
I own a 2002 M6 Coupe which I bought to do some hot rodding. Part of this hobby is modifying the engine for more power. The ’02 Z06 sets the bar pretty high so I “need” more power than a plain-old, store-bought car. About 450 at the clutch ought to do it.
Dyno2000 Engine Simulation Program
http://www.motionsoftware.com/
I used Motion Software’s Dyno2000 engine simulation program. Any program needs to be correlated with a truth model before it is used for effect. To us engine types that can only mean comparing to dyno data. I used two engines to correlate Dyno2000. The low power engine was the ’02 LS6 straight from Chevy. The high power engine was a typical “take no prisoners” Camaro setup that is from the LS1 web sites. This is a ~500FWHP modified LS1 using the C1 MTI Hammer cam. The results of this correlation work are a set of equivalent cam definitions that translated Dyno2000 cam-speak into common cam catalog duration @ 0.050” nomenclature. The translation matrix I used is:
206 @ 50 equals 267 Dyno2000 seat to seat
222 @ 50 equals 278 Dyno2000 seat to seat
Think of this as a universal translator or my Rosetta Stone of Dyno2000 cam-speak.
Dyno2000 is menu driven for some of the engine descriptions like the type of intake. This is helpful and quick for general work but limiting when you are chasing a specific engine geometry. Some if the inputs can be specific like cam timing events. I traded the available parameters to get a best match to the power curves for the two reference cams. This led to some choices that seemed wrong at first look. The most obvious is the type of cam. Only the solid-flat tappet cam model produced a good power match even though I was correlating against roller cams. The roller cam model in Dyno2000 was over predicting power for the same lift and duration indicating that the “area-under-the-curve” with this program option was too high. Varying the intake and exhaust durations to get a best-match to the dyno data resulted in the duration-translation mentioned above.
Engine modeling is a relatively new science/art and I am thrilled to have a program like Dyno 2000 for only 40 bucks. I recommend it as great way to waste countless hours proving that your car “could be” faster than Little “E’s”.
LS6 Cam Correlation in Dyno2000
http://www.idavette.net/hib/02ls6/index.htm
The LS6 cam is interesting in that it makes a lot of power with very little intake duration. The lift of 0.550” is very aggressive for 206 @ 50 indicating an aggressive cam profile. In fact, even the most aggressive Comp Cams profile has 0.561 lift @ 206. The 117.5 LCA is huge for a performance cam, but it works! The question is: “Why?” The thing that pops-out when you look at the cam opening and closing events is the every late intake closing. This was the “small” cam that I used for correlation.
The Dyno2000 inputs I used to match the published ’02 LS6 power curve are:
-Bore 3.9; stroke 3.62. Stock.
-Heads: wedge/fully ported, large valves; intake:2.02; exhaust:1.6. This gave an OK match with the flow data I have seen for stock LS6 heads.
-Compression ratio: 10.5. Stock, I did not trade this parameter.
-Induction flow: 660 cfm. This number was chosen because it caused some restriction which allowed me to model a better intake system later on by going to 800 cfm.
-Manifold type: single-plane manifold. This is the only chose that gave a power shape match.
-Exhaust system: H.P. manifolds and mufflers. Stock and the increments to headers seemed about right.
-Camshaft lifters: solid. The roller lifter model over predicted power throughout the whole range.
-Cam specs: seat-to-seat; intake lift: 0.550; exhaust lift: 0.550; lobe center: 117.5; ICA: 120. All stock numbers.
The cam events with these inputs are:
IVO (BTDC): 13.5; IVC (ATDC): 73.5; ICA: 120.0
EVC (ATDC): 22.5; EVO (BBDC): 72.5; ECA: 115.0
These inputs produced this result compared to Chevy’s data:
C1 MTI “Hammer” Cam Correlation in Dyno2000
http://xs-fx.com/raughammer/ The C1 Hammer cam seems to be some sort of milestone in LS cam-ology. It’s proven power and equal intake and exhaust duration fuels the endless discussions about Chevy’s use of dual-pattern cams where the exhaust duration is longer than the intake. The story goes: The old, obsolete small block had a poor exhaust flow in comparison to intake flow. This forced the now retired Chevy Engineers of Old to use excessive amounts of exhaust duration to make up for this liability. The new-improved LS series of Super Engines doesn’t have this design flaw and equal intake and exhaust durations give a higher power potential for the same overlap.
The Dyno2000 inputs I used to match several M6 Camaros with C1 Hammer cams are:
-Bore 3.9; stroke 3.62. Stock.
-Heads: wedge/fully ported, large valves; intake: 1.94; exhaust:1.6. I lowered the intake flow for LS1 heads compared to LS6.
-Compression ratio: 11.0. I raised this ½ point assuming the heads were milled.
-Induction flow: 700 cfm. This number is better then a stock Vette but not as good as a bolt-ons + LS6 intake. I used 800 cfm for the bolt-ons + LS6 intake.
-Manifold type: single-plane manifold. This is the only chose that gave a power shape match.
-Exhaust system: Small-tube headers and open exhaust. These cars ran headers with cut-outs.
-Camshaft lifters: solid. The roller lifter model over predicted power throughout the whole range.
-Cam specs: seat-to-seat; 278/278; intake lift: 0.566; exhaust lift: 0.566; lobe center: 112; ICA: 108. These cams were advanced 4 degrees. (The “real” cam duration as listed in the MTI catalog is: 222/222 @ 50.)
The cam events with these inputs are:
IVO (BTDC): 31.0; IVC (ATDC): 67.0; ICA: 108.0
EVC (ATDC): 23.0; EVO (BBDC): 75.0; ECA: 116.0
The inputs above produced this comparison to RoughHammer’s data:
Cam Trade Results
I ran about 350 cases in Dyno2000. About 185 or so were of interest after the first sorting. This through out really poor power curves. I covered the design space from the Chevy LS6 cam (405 HP @ 6500) to a common performance cam that is used by Camaro drag racers (~500 HP @ 6200).
All of these simulations were run with my best estimates of ported LS6 heads, headers with mufflers and a low restriction air inlet. I kept the lift at 0.550 for all the runs as more is always better and even low duration cams are now available with this much lift.
The figure of merits I used for power was the average power from 4500-to-6500 and the average from 5000-to-7000. These numbers where chosen based on expected shift points. After running many car acceleration computer runs it was a predictable result that the engine with the highest average was always the winner. This allowed me to ignore the shape of the power curves and just plot the averages. Any strange looking power curve also had a low average, so it worked out OK.
Intake Valve Closing
The most interesting result is that the intake closing point is the most important variable, much more so than the duration or overlap. This is something I saw in the Chevy cams. The late closing makes them look bigger without adding a lot of overlap. I tied compression ratio to intake closing to hold the dynamic compression ratio constant. I used the Chevy motors dynamic compression as a guide. The general conclusion is that you must know your intake closing point even more so that intake duration.
Valve Overlap
I set a maximum limit to the valve overlap based on desired idle quality, emissions and to limit changes the computer. The power peaked somewhere in the 50 to 55 degree overlap range which is where the C1 cam is at 54. The LS6 engine has 36. Cams in the low 40’s worked out real good for average power. A low overlap means that the computer should be happy with the mod and that it will be hard to tell there is a cam in the car. (Well, you may not want that!) My general conclusion on overlap is that you have got to have some, but it sure looks like you don’t need a lot, and if you add too much you could lose a lot of power.
Intake Duration
Average power was not as strong a function of duration as it is intake duration. In general, bigger is better but it is a weak function in this trade space. Please keep the trade goals in mind. I was not looking for a drag racer.
Exhaust Duration
Exhaust duration is a controversial subject in that some people claim that programs like Dyno2000 over predict the need for exhaust and you will be mislead. Well, sure enough, this trade shows that the exhaust duration is a little stronger function than intake duration in that you must have a bigger exhaust duration but a short intake duration is OK with a late intake closing. Chevy likes bigger exhaust too. During the computer runs, you could see how a longer exhaust would extend the power curve at high rpms.
Lobe Center Angle
It seems that the conventional wisdom on LCA is right on in that values of 112 to 114 show the best power potential. It also looks like you can really screw up by going too far in either direction. This is really good news because many cam cores are built in this range and if you needed a cam ground at 120 LCA, you maybe out of luck.
Intake Valve Opening
It sure looks like early intake valve opening is a bad thing. That’s to the right on the chart because it’s BTDC. This means that a short intake duration with a late timing to keep the valve open longer has a good power potential. Hey! That’s what Chevy’s doing! How’d they know that without my help? I want royalties!
Exhaust Valve Closing
Moderate exhaust valve closing is a good thing. Both of the correlation cams look like they close the exhaust valve too soon for best power. This is a trade with overlap.
Exhaust Valve Opening
Exhaust valve opening is sometimes called “blow down” because the cylinder pressures are real high due to combustion during this event. This chart says that it’s possible to have too little or too much but there is a broad acceptable region.
Selected Cam
My goal for this trade was ~450FWHP with near stock dynamic compression, small headers with mufflers and ported LS6 heads. Using an overlap constraint of less than 50 degrees, I selected this cam:
206/218 114/120 0.560/0.560 with 10.5 CR
The cam events for the Dyno2000 run are:
IVO (BTDC): 13.5; IVC (ATDC): 73.5; ICA: 120.0
EVC (ATDC): 29.5; EVO (BBDC): 65.5; ECA: 108.0
A cam similar to this is available from Comp Cams at a 110 intake centerline which is 4 degrees advanced. An adjustable timing chain would allow a 120 intake centerline which is 6 degrees retarded. As you retard the cam, the exhaust valve clearance decreases. The predicted power curve compared to both an LS1 and LS6 is:
This cam isn’t far from the ’02 LS6 cam. It really only has a tighter lobe center (114 vs. 117.5). So what’s up? Well, when I started looking into it I found that I had never seen a heavily modified motor with “only” an LS6 cam! It seems that everybody just goes ahead and throws a cam in it at the same time. This cam does have an increased overlap and a little more lift and the magic 112/114 LCA and a late intake closing. So, maybe this trade is telling us something?
I hope you enjoyed this work, I’ll be interested in your thoughts and experiences.
Bye for now,
Steve
:seeya
Intro To Cam Jargon
If you are a new-be to cam jargon, please read this:
Duration is the length that the cam holds the valve open. There are different standards used to define “open”. The common ones are duration at 0.050” valve lift and duration at 0.0006”. These are commonly called “duration @ 50” and “seat-to-seat duration. Duration @ 50 is always a smaller number than seat-to-seat duration.
Lift is how high the valve comes off the seat. Sometimes you will see “lobe lift” which is how much the lifter will move. The valve lift equals the lobe lift times the rocker ratio.
Range: 0.475/0.650”
Lobe Center Line is the position of the intake lobe relative to the crankshaft. The intake is commonly used as the reference but you may also hear “exhaust lobe centerline”. We normally assume that the lobes are symmetric so that the centerline is halfway the opening and closing points of each lobe. Not all lobes are symmetric.
Range: 108/120
Lobe Center Angle is the distance between the intake and exhaust lobe centerlines. Bigger numbers with the same intake & exhaust duration means a lower overlap.
Range: 104/116
Advance or Retard is the term used to describe whether the cam lobes are symmetric in respect to TDC. A cam with no advance or retard has the centerline of the exhaust lobe an equal distance from TDC as the intake lobe. You can calculate the advance/retard by subtracting the intake centerline from the LCA. A/R = LCA – CL. Most factory Chevy cams for the old small blocks were ground with 4 degrees of advance. Many people think that all cams should be ground at +4 degrees. When you move the cam relative to the crank by using an adjustable timing chain, you are advancing or retarding the cam.
I name cams using this convention:
Intake dur./exhaust dur. In. lift/ex. lift Lobe center angle/Intake centerline
Examples of Cams
206/218 .550/.550 117.5/120
This is the ’02 LS6 cam. The intake duration is low and the exhaust duration is moderate. The 117.5 LCA is very large which indicates that Chevy was interested in keeping the valve overlap low. The 120 intake centerline is a very late timing which keeps the valves open longer than the duration number alone would indicate. The high centerline angle also means that this cam is retarded 2.5 degrees (117.5 -120 = -2.5)
220/220 .565/.565 112/108
This is the C1 or “Hammer” cam by MTI. The intake duration is big for a street car but moderate for a racer. The 112 LCA is the lower end of common street cams which will have a moderate amount of valve overlap. The centerline at 108 is common for this duration cam. The fact that the LCA is bigger than the centerline means that the cam is advanced 4 degrees (112 -108 = +4).
[Modified by SNW Vette, 1:06 PM 3/22/2002]
-Closing the intake valve late is more important than large intake durations.
-Large valve overlap is not needed.
-Big exhaust durations extend the power band.
-Chevy does all of the above.
-Why don’t the aftermarket cam manufactures?
Cam Trade Goals
The purpose of this cam trade was:
1.Learn something about cams and how they work
2.Try to understand Chevy’s stock cam design choices
3.Look for a higher performance cam for my Vette
Choosing a performance cam for your Vette is a frustrating experience that leads you to “go with the experts” or risk an expensive development on your own. Simply collecting info on the Net can lead to conflicting expert opinion. After reading the simplified descriptions in the Hot Rod type magazines and also several cam catalogs, I decided to expand the available data base by doing a large computer based engine simulation trade. This data base would allow me to plot cam geometries vs. predicted performance. Also, the variations due to the geometries would give some insight as to the important variables. This is an age old engineering practice in simulation that looks more for the trends than the absolutes.
Chevy’s LS6 cams are commonly described as “too mild” to be considered as performance cams. The short intake duration is usually given as sufficient proof that these are weaklings. The fact remains that the LS6 is a very strong performer and that it does respond to modifications. I wanted to know why these cams worked and what the limitations were. I will give The General credit for knowing what makes power and try to understand the compromises that are made to make a warranted, emissions legal street car.
I own a 2002 M6 Coupe which I bought to do some hot rodding. Part of this hobby is modifying the engine for more power. The ’02 Z06 sets the bar pretty high so I “need” more power than a plain-old, store-bought car. About 450 at the clutch ought to do it.
Dyno2000 Engine Simulation Program
http://www.motionsoftware.com/
I used Motion Software’s Dyno2000 engine simulation program. Any program needs to be correlated with a truth model before it is used for effect. To us engine types that can only mean comparing to dyno data. I used two engines to correlate Dyno2000. The low power engine was the ’02 LS6 straight from Chevy. The high power engine was a typical “take no prisoners” Camaro setup that is from the LS1 web sites. This is a ~500FWHP modified LS1 using the C1 MTI Hammer cam. The results of this correlation work are a set of equivalent cam definitions that translated Dyno2000 cam-speak into common cam catalog duration @ 0.050” nomenclature. The translation matrix I used is:
206 @ 50 equals 267 Dyno2000 seat to seat
222 @ 50 equals 278 Dyno2000 seat to seat
Think of this as a universal translator or my Rosetta Stone of Dyno2000 cam-speak.
Dyno2000 is menu driven for some of the engine descriptions like the type of intake. This is helpful and quick for general work but limiting when you are chasing a specific engine geometry. Some if the inputs can be specific like cam timing events. I traded the available parameters to get a best match to the power curves for the two reference cams. This led to some choices that seemed wrong at first look. The most obvious is the type of cam. Only the solid-flat tappet cam model produced a good power match even though I was correlating against roller cams. The roller cam model in Dyno2000 was over predicting power for the same lift and duration indicating that the “area-under-the-curve” with this program option was too high. Varying the intake and exhaust durations to get a best-match to the dyno data resulted in the duration-translation mentioned above.
Engine modeling is a relatively new science/art and I am thrilled to have a program like Dyno 2000 for only 40 bucks. I recommend it as great way to waste countless hours proving that your car “could be” faster than Little “E’s”.
LS6 Cam Correlation in Dyno2000
http://www.idavette.net/hib/02ls6/index.htm
The LS6 cam is interesting in that it makes a lot of power with very little intake duration. The lift of 0.550” is very aggressive for 206 @ 50 indicating an aggressive cam profile. In fact, even the most aggressive Comp Cams profile has 0.561 lift @ 206. The 117.5 LCA is huge for a performance cam, but it works! The question is: “Why?” The thing that pops-out when you look at the cam opening and closing events is the every late intake closing. This was the “small” cam that I used for correlation.
The Dyno2000 inputs I used to match the published ’02 LS6 power curve are:
-Bore 3.9; stroke 3.62. Stock.
-Heads: wedge/fully ported, large valves; intake:2.02; exhaust:1.6. This gave an OK match with the flow data I have seen for stock LS6 heads.
-Compression ratio: 10.5. Stock, I did not trade this parameter.
-Induction flow: 660 cfm. This number was chosen because it caused some restriction which allowed me to model a better intake system later on by going to 800 cfm.
-Manifold type: single-plane manifold. This is the only chose that gave a power shape match.
-Exhaust system: H.P. manifolds and mufflers. Stock and the increments to headers seemed about right.
-Camshaft lifters: solid. The roller lifter model over predicted power throughout the whole range.
-Cam specs: seat-to-seat; intake lift: 0.550; exhaust lift: 0.550; lobe center: 117.5; ICA: 120. All stock numbers.
The cam events with these inputs are:
IVO (BTDC): 13.5; IVC (ATDC): 73.5; ICA: 120.0
EVC (ATDC): 22.5; EVO (BBDC): 72.5; ECA: 115.0
These inputs produced this result compared to Chevy’s data:
C1 MTI “Hammer” Cam Correlation in Dyno2000
http://xs-fx.com/raughammer/ The C1 Hammer cam seems to be some sort of milestone in LS cam-ology. It’s proven power and equal intake and exhaust duration fuels the endless discussions about Chevy’s use of dual-pattern cams where the exhaust duration is longer than the intake. The story goes: The old, obsolete small block had a poor exhaust flow in comparison to intake flow. This forced the now retired Chevy Engineers of Old to use excessive amounts of exhaust duration to make up for this liability. The new-improved LS series of Super Engines doesn’t have this design flaw and equal intake and exhaust durations give a higher power potential for the same overlap.
The Dyno2000 inputs I used to match several M6 Camaros with C1 Hammer cams are:
-Bore 3.9; stroke 3.62. Stock.
-Heads: wedge/fully ported, large valves; intake: 1.94; exhaust:1.6. I lowered the intake flow for LS1 heads compared to LS6.
-Compression ratio: 11.0. I raised this ½ point assuming the heads were milled.
-Induction flow: 700 cfm. This number is better then a stock Vette but not as good as a bolt-ons + LS6 intake. I used 800 cfm for the bolt-ons + LS6 intake.
-Manifold type: single-plane manifold. This is the only chose that gave a power shape match.
-Exhaust system: Small-tube headers and open exhaust. These cars ran headers with cut-outs.
-Camshaft lifters: solid. The roller lifter model over predicted power throughout the whole range.
-Cam specs: seat-to-seat; 278/278; intake lift: 0.566; exhaust lift: 0.566; lobe center: 112; ICA: 108. These cams were advanced 4 degrees. (The “real” cam duration as listed in the MTI catalog is: 222/222 @ 50.)
The cam events with these inputs are:
IVO (BTDC): 31.0; IVC (ATDC): 67.0; ICA: 108.0
EVC (ATDC): 23.0; EVO (BBDC): 75.0; ECA: 116.0
The inputs above produced this comparison to RoughHammer’s data:
Cam Trade ResultsI ran about 350 cases in Dyno2000. About 185 or so were of interest after the first sorting. This through out really poor power curves. I covered the design space from the Chevy LS6 cam (405 HP @ 6500) to a common performance cam that is used by Camaro drag racers (~500 HP @ 6200).
All of these simulations were run with my best estimates of ported LS6 heads, headers with mufflers and a low restriction air inlet. I kept the lift at 0.550 for all the runs as more is always better and even low duration cams are now available with this much lift.
The figure of merits I used for power was the average power from 4500-to-6500 and the average from 5000-to-7000. These numbers where chosen based on expected shift points. After running many car acceleration computer runs it was a predictable result that the engine with the highest average was always the winner. This allowed me to ignore the shape of the power curves and just plot the averages. Any strange looking power curve also had a low average, so it worked out OK.
Intake Valve Closing
The most interesting result is that the intake closing point is the most important variable, much more so than the duration or overlap. This is something I saw in the Chevy cams. The late closing makes them look bigger without adding a lot of overlap. I tied compression ratio to intake closing to hold the dynamic compression ratio constant. I used the Chevy motors dynamic compression as a guide. The general conclusion is that you must know your intake closing point even more so that intake duration.
Valve OverlapI set a maximum limit to the valve overlap based on desired idle quality, emissions and to limit changes the computer. The power peaked somewhere in the 50 to 55 degree overlap range which is where the C1 cam is at 54. The LS6 engine has 36. Cams in the low 40’s worked out real good for average power. A low overlap means that the computer should be happy with the mod and that it will be hard to tell there is a cam in the car. (Well, you may not want that!) My general conclusion on overlap is that you have got to have some, but it sure looks like you don’t need a lot, and if you add too much you could lose a lot of power.
Intake Duration
Average power was not as strong a function of duration as it is intake duration. In general, bigger is better but it is a weak function in this trade space. Please keep the trade goals in mind. I was not looking for a drag racer.
Exhaust Duration
Exhaust duration is a controversial subject in that some people claim that programs like Dyno2000 over predict the need for exhaust and you will be mislead. Well, sure enough, this trade shows that the exhaust duration is a little stronger function than intake duration in that you must have a bigger exhaust duration but a short intake duration is OK with a late intake closing. Chevy likes bigger exhaust too. During the computer runs, you could see how a longer exhaust would extend the power curve at high rpms.
Lobe Center Angle
It seems that the conventional wisdom on LCA is right on in that values of 112 to 114 show the best power potential. It also looks like you can really screw up by going too far in either direction. This is really good news because many cam cores are built in this range and if you needed a cam ground at 120 LCA, you maybe out of luck.
Intake Valve Opening
It sure looks like early intake valve opening is a bad thing. That’s to the right on the chart because it’s BTDC. This means that a short intake duration with a late timing to keep the valve open longer has a good power potential. Hey! That’s what Chevy’s doing! How’d they know that without my help? I want royalties!
Exhaust Valve Closing
Moderate exhaust valve closing is a good thing. Both of the correlation cams look like they close the exhaust valve too soon for best power. This is a trade with overlap.
Exhaust Valve Opening
Exhaust valve opening is sometimes called “blow down” because the cylinder pressures are real high due to combustion during this event. This chart says that it’s possible to have too little or too much but there is a broad acceptable region.
Selected Cam
My goal for this trade was ~450FWHP with near stock dynamic compression, small headers with mufflers and ported LS6 heads. Using an overlap constraint of less than 50 degrees, I selected this cam:
206/218 114/120 0.560/0.560 with 10.5 CR
The cam events for the Dyno2000 run are:
IVO (BTDC): 13.5; IVC (ATDC): 73.5; ICA: 120.0
EVC (ATDC): 29.5; EVO (BBDC): 65.5; ECA: 108.0
A cam similar to this is available from Comp Cams at a 110 intake centerline which is 4 degrees advanced. An adjustable timing chain would allow a 120 intake centerline which is 6 degrees retarded. As you retard the cam, the exhaust valve clearance decreases. The predicted power curve compared to both an LS1 and LS6 is:
This cam isn’t far from the ’02 LS6 cam. It really only has a tighter lobe center (114 vs. 117.5). So what’s up? Well, when I started looking into it I found that I had never seen a heavily modified motor with “only” an LS6 cam! It seems that everybody just goes ahead and throws a cam in it at the same time. This cam does have an increased overlap and a little more lift and the magic 112/114 LCA and a late intake closing. So, maybe this trade is telling us something?
I hope you enjoyed this work, I’ll be interested in your thoughts and experiences.
Bye for now,
Steve
:seeya
Intro To Cam Jargon
If you are a new-be to cam jargon, please read this:
Duration is the length that the cam holds the valve open. There are different standards used to define “open”. The common ones are duration at 0.050” valve lift and duration at 0.0006”. These are commonly called “duration @ 50” and “seat-to-seat duration. Duration @ 50 is always a smaller number than seat-to-seat duration.
Lift is how high the valve comes off the seat. Sometimes you will see “lobe lift” which is how much the lifter will move. The valve lift equals the lobe lift times the rocker ratio.
Range: 0.475/0.650”
Lobe Center Line is the position of the intake lobe relative to the crankshaft. The intake is commonly used as the reference but you may also hear “exhaust lobe centerline”. We normally assume that the lobes are symmetric so that the centerline is halfway the opening and closing points of each lobe. Not all lobes are symmetric.
Range: 108/120
Lobe Center Angle is the distance between the intake and exhaust lobe centerlines. Bigger numbers with the same intake & exhaust duration means a lower overlap.
Range: 104/116
Advance or Retard is the term used to describe whether the cam lobes are symmetric in respect to TDC. A cam with no advance or retard has the centerline of the exhaust lobe an equal distance from TDC as the intake lobe. You can calculate the advance/retard by subtracting the intake centerline from the LCA. A/R = LCA – CL. Most factory Chevy cams for the old small blocks were ground with 4 degrees of advance. Many people think that all cams should be ground at +4 degrees. When you move the cam relative to the crank by using an adjustable timing chain, you are advancing or retarding the cam.
I name cams using this convention:
Intake dur./exhaust dur. In. lift/ex. lift Lobe center angle/Intake centerline
Examples of Cams
206/218 .550/.550 117.5/120
This is the ’02 LS6 cam. The intake duration is low and the exhaust duration is moderate. The 117.5 LCA is very large which indicates that Chevy was interested in keeping the valve overlap low. The 120 intake centerline is a very late timing which keeps the valves open longer than the duration number alone would indicate. The high centerline angle also means that this cam is retarded 2.5 degrees (117.5 -120 = -2.5)
220/220 .565/.565 112/108
This is the C1 or “Hammer” cam by MTI. The intake duration is big for a street car but moderate for a racer. The 112 LCA is the lower end of common street cams which will have a moderate amount of valve overlap. The centerline at 108 is common for this duration cam. The fact that the LCA is bigger than the centerline means that the cam is advanced 4 degrees (112 -108 = +4).
[Modified by SNW Vette, 1:06 PM 3/22/2002]
03-21-2002, 03:52 AM
#3
Race Director
Member Since: Aug 1999
Location: GARDENA Ca, State Of Konfusion
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St. Jude Donor '05
Re: Dyno2000 Cam Trade (Viprklr)
Wow, that was interesting, I just had an advanced lesson in Cam 101. It will take a while to digest all this info. A lot of us want to stay emission legal, thats why I didn't go to aggressive, but satisfied with the results!
03-21-2002, 01:26 PM
#6
Safety Car
Re: Dyno2000 Cam Trade (SNW Vette)
GREAT POST GUY!! I am interested in seeing some of the tuners chime in here, maybe they can shed some light on whyk the program seems to match better with flat tappet lifters. Is it because the program uses solids for rollers Vs. hydraulic? :smash: :chevy
03-21-2002, 11:55 PM
#7
Melting Slicks
Member Since: Sep 1999
Location: Houston, TX
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Re: Dyno2000 Cam Trade (6Speeder)
Thanks for sharing your data. I've only scratched the surface of the Dyno2000 software...it will be helpful to have something to compare with.
Are you planning on swaping your cam out anytime soon as to see a real world result?
Thanks again! :cheers:
Are you planning on swaping your cam out anytime soon as to see a real world result?
Thanks again! :cheers:
03-22-2002, 01:58 PM
#8
Racer
Thread Starter
Re: Dyno2000 Cam Trade (C5Cemo)
Hi,
Thanks for your comments.
I was planning on trying an LS6 cam in my LS1 car first but I am having trouble getting one from Chevy that is not rusted or ground off-centerline. This experience is what motivated me to do a cam trade. Right now, I am thinking of getting a Comp Cams with a 114 LCA and experimenting with a couple of different intake centerlines. I already have a Comp adjustable timing chain, which allows just about any centerline adjustment. A two-piece front cover would really help a trade like this but I haven't seen anything available except for small or big blocks.
As the retarded cams could use a higher CR than the advanced positions, you need to carefully choose a baseline CR. At the moment I am thinking of using the standard LS6 CR of 10.5, which I will get when I change to the LS6 heads I am readying at this time. This CR is used with both the ’01 & ’02 LS6 engine with an intake closing as late as 73.5 ABDC. Then, I would both advance and retard the cam, getting dyno data at each point. My experience with similar trades using small blocks and some foreign cars is that you would need at least 2 degrees in either direction to feel a change.
I'll certainly post results when I get them.
Bye for now,
Steve
Thanks for your comments.
I was planning on trying an LS6 cam in my LS1 car first but I am having trouble getting one from Chevy that is not rusted or ground off-centerline. This experience is what motivated me to do a cam trade. Right now, I am thinking of getting a Comp Cams with a 114 LCA and experimenting with a couple of different intake centerlines. I already have a Comp adjustable timing chain, which allows just about any centerline adjustment. A two-piece front cover would really help a trade like this but I haven't seen anything available except for small or big blocks.
As the retarded cams could use a higher CR than the advanced positions, you need to carefully choose a baseline CR. At the moment I am thinking of using the standard LS6 CR of 10.5, which I will get when I change to the LS6 heads I am readying at this time. This CR is used with both the ’01 & ’02 LS6 engine with an intake closing as late as 73.5 ABDC. Then, I would both advance and retard the cam, getting dyno data at each point. My experience with similar trades using small blocks and some foreign cars is that you would need at least 2 degrees in either direction to feel a change.
I'll certainly post results when I get them.
Bye for now,
Steve
03-25-2002, 03:18 PM
#9
Racer
Re: Dyno2000 Cam Trade (SNW Vette)
Steve,
As usual, I'm impressed with your research. Now I know what you do all day at work!
I've been thinking of installing an ATI Procharger kit rather than do cam/heads. This way, I don't have to go into the engine at all. One of the guys put his dyno numbers for the supercharge in the following thread. I put his numbers into Excel, then put his HP/torque chart on the wall next to yours. The supercharger route yields very impressive numbers. For $6500 for the supercharger, how does this compare in cost to what you'll spend for heads/cam?
http://forums.corvetteforum.com/zerothread?id=256730
-Jim
BTW, did you ever install the 3.90 rear end?
As usual, I'm impressed with your research. Now I know what you do all day at work!
I've been thinking of installing an ATI Procharger kit rather than do cam/heads. This way, I don't have to go into the engine at all. One of the guys put his dyno numbers for the supercharge in the following thread. I put his numbers into Excel, then put his HP/torque chart on the wall next to yours. The supercharger route yields very impressive numbers. For $6500 for the supercharger, how does this compare in cost to what you'll spend for heads/cam?
http://forums.corvetteforum.com/zerothread?id=256730
-Jim
BTW, did you ever install the 3.90 rear end?
