Revolver Cam Test! HKS who?
Nov 27, 2005, 06:49 AM
#46
Originally Posted by gofaster87
Where do you get the idea cam duration "kinda of makes power." Try reading up on or taking a course in cam design before you type out misinformation.
The entire evolution board has been consumed with HKS and their line of more and more duration. Im looking foward to the 320's coming out next year
If he took a course in "cam design" he probably wouldn't get too much out of it.
Being that in order to get into any design theory you will have to understand engine theory. Then maybe he can understand how the cam actually controlls the supply of airflow thru the entire intake system. Only then would he/she understand that "duration" ( in relation or comparison to any static increase) is a great thing for a car that is relying on atmospheric pressure to run alone. Forced induction is a completely different animal. So whether or not he came to the conclusion that duration "kinda makes power" from actual theoretical thought or just reading it here, here is still correct.
Nov 27, 2005, 08:09 AM
#47
it's only the vaugeness of his statement that makes him correct however.
cams make power for different reasons, quite obviously two of the reason are lift and duration.
lift increases the head's ve by allowing more air to flow in and out of the cylinder but duration and the overlap associated with it increase volumetric efficiency by allowing air to flow THROUGH the head. very little can actually be accomplished without employing both lift AND duration and it's pretty clear to see that the hks style cams have been maxed out on their duration capacities.
and this is obvious too, you can only do so much with duration just like you can only do so much with lift, however the duration of these avante garde cams was exploited because they don't require anything extra, they make power on the stock valve train.
with this said i think it is important to note that especially in turbocharged engines--where you can get very clean cylinders from the nature of forced induction--that overlap is crucial and is where most of the power comes from, although more lift is a requisite to say the LEAST because in order to take full advatange of the cylinder purging you must first be able to flow the air in and out in the proper amount of time or engine cycle.
all in all it's not fair to say that one is better than the other at making power, you need both, and it's exactly unfair to compare making power between the two methods because how do you objectively compare? is 1mm of lift at some position the equivalent of 3* of duration, duration overlap, duration advanced, duration retarded? how do you compare... the statement is just bunk to begin with.
in this instance you might get away with stating something like this because the "data" presented may back up your claim, but like i said before, the hks style cams already exploited all the duration benefits, any more like precision said is already diminishing in its returns, obviously more lift is in order, hence the obvious increase in power and torque
cams make power for different reasons, quite obviously two of the reason are lift and duration.
lift increases the head's ve by allowing more air to flow in and out of the cylinder but duration and the overlap associated with it increase volumetric efficiency by allowing air to flow THROUGH the head. very little can actually be accomplished without employing both lift AND duration and it's pretty clear to see that the hks style cams have been maxed out on their duration capacities.
and this is obvious too, you can only do so much with duration just like you can only do so much with lift, however the duration of these avante garde cams was exploited because they don't require anything extra, they make power on the stock valve train.
with this said i think it is important to note that especially in turbocharged engines--where you can get very clean cylinders from the nature of forced induction--that overlap is crucial and is where most of the power comes from, although more lift is a requisite to say the LEAST because in order to take full advatange of the cylinder purging you must first be able to flow the air in and out in the proper amount of time or engine cycle.
all in all it's not fair to say that one is better than the other at making power, you need both, and it's exactly unfair to compare making power between the two methods because how do you objectively compare? is 1mm of lift at some position the equivalent of 3* of duration, duration overlap, duration advanced, duration retarded? how do you compare... the statement is just bunk to begin with.
in this instance you might get away with stating something like this because the "data" presented may back up your claim, but like i said before, the hks style cams already exploited all the duration benefits, any more like precision said is already diminishing in its returns, obviously more lift is in order, hence the obvious increase in power and torque
Last edited by trinydex; Nov 27, 2005 at 08:14 AM.
Nov 27, 2005, 10:07 AM
#48
Originally Posted by trinydex
it's only the vaugeness of his statement that makes him correct however.
cams make power for different reasons, quite obviously two of the reason are lift and duration.
lift increases the head's ve by allowing more air to flow in and out of the cylinder but duration and the overlap associated with it increase volumetric efficiency by allowing air to flow THROUGH the head. very little can actually be accomplished without employing both lift AND duration and it's pretty clear to see that the hks style cams have been maxed out on their duration capacities.
and this is obvious too, you can only do so much with duration just like you can only do so much with lift, however the duration of these avante garde cams was exploited because they don't require anything extra, they make power on the stock valve train.
with this said i think it is important to note that especially in turbocharged engines--where you can get very clean cylinders from the nature of forced induction--that overlap is crucial and is where most of the power comes from, although more lift is a requisite to say the LEAST because in order to take full advatange of the cylinder purging you must first be able to flow the air in and out in the proper amount of time or engine cycle.
all in all it's not fair to say that one is better than the other at making power, you need both, and it's exactly unfair to compare making power between the two methods because how do you objectively compare? is 1mm of lift at some position the equivalent of 3* of duration, duration overlap, duration advanced, duration retarded? how do you compare... the statement is just bunk to begin with.
in this instance you might get away with stating something like this because the "data" presented may back up your claim, but like i said before, the hks style cams already exploited all the duration benefits, any more like precision said is already diminishing in its returns, obviously more lift is in order, hence the obvious increase in power and torque
cams make power for different reasons, quite obviously two of the reason are lift and duration.
lift increases the head's ve by allowing more air to flow in and out of the cylinder but duration and the overlap associated with it increase volumetric efficiency by allowing air to flow THROUGH the head. very little can actually be accomplished without employing both lift AND duration and it's pretty clear to see that the hks style cams have been maxed out on their duration capacities.
and this is obvious too, you can only do so much with duration just like you can only do so much with lift, however the duration of these avante garde cams was exploited because they don't require anything extra, they make power on the stock valve train.
with this said i think it is important to note that especially in turbocharged engines--where you can get very clean cylinders from the nature of forced induction--that overlap is crucial and is where most of the power comes from, although more lift is a requisite to say the LEAST because in order to take full advatange of the cylinder purging you must first be able to flow the air in and out in the proper amount of time or engine cycle.
all in all it's not fair to say that one is better than the other at making power, you need both, and it's exactly unfair to compare making power between the two methods because how do you objectively compare? is 1mm of lift at some position the equivalent of 3* of duration, duration overlap, duration advanced, duration retarded? how do you compare... the statement is just bunk to begin with.
in this instance you might get away with stating something like this because the "data" presented may back up your claim, but like i said before, the hks style cams already exploited all the duration benefits, any more like precision said is already diminishing in its returns, obviously more lift is in order, hence the obvious increase in power and torque
With static pressure in the inlet track, stock intake manifold and exhaust manifold cross sectional areas and a 10.5 hotside for our example, Both cam profiles discussed will affect VE in drastic ways thruout the rpm band.
Intake and exhaust ports play the major role in this equation. Usually the stock style port in the EVO will require the increased duration. The overlap associated with degreeing the cam to stock pin points from HKS for example, provide the velocity needed to fill the cylinder, and evacuate the endgas. Lets make something clear here, so everyone understands, that the grind variations HKS and many others produce do a great job. But for the specific application and modifications from the stock VE level or capability if you will.
Now on unmodified ports the increased lift from the revolver cams will aid in low end cylinder filling by utilizing that port velocity to its advantage.
So as you say with an increase in both duration and lift from stock, huge gains can be had.
The issue we face is what is the optimal amount of lift and duration @050"
Do the hks cams provide this or do the revolver with their obviously lower published duration rates.
Keep in mind we need to know about ramp speeds to properly compare the two. We are left with a dyno comparison alone.
Now another thing to mention here, is that Tim has a very highly modified head. As far as the ports are concerned and the 1mm oversized valves. Keep in mind the HKS cams on his particular application with an advertised 272 duration were hampering his flow characteristics. Why? Port velocity was very low. That means that the increased duration actually did not improve cylinder filling as the exhaust side also has very little velocity. NOT that the capacity to higher flow wasn't there. Just that you are working with airflow characteristics that do not want to "run" thru the head as would a stock style more restrictive port would have allowed.
One of the reasons Tim is running into idle problems will be again because of the slower reaction time from the airflow at idle. Basically he is working with a deluted mixture at idle that incorporates a percentage of exhaust endgas that is creating a misfire at idle. Very low VE, Very low heat in the cylinder, and the inability to burn a mixture wich already incorporates burned hydrocarbons.
These cams will be installed in a stock style head this week and we will keep you guys updated in another thread. It should be quite interesting.
Nick
Precision Dyno
Last edited by Precision Dyno; Nov 27, 2005 at 10:16 AM.
Nov 27, 2005, 10:13 AM
#49
that information will in very valuable too, i'm glad you incorperated what you said!
the question next answered is if the revolvers will hamper flow on a stock "high velocity" type porting as opposed to a fully done head with oversized valves and matched ports, or rather if the stock head can take advantage of the revolvers.
the question next answered is if the revolvers will hamper flow on a stock "high velocity" type porting as opposed to a fully done head with oversized valves and matched ports, or rather if the stock head can take advantage of the revolvers.
Last edited by trinydex; Nov 27, 2005 at 10:17 AM.
Nov 27, 2005, 10:21 AM
#50
Originally Posted by trinydex
that information will in very valuable too, i'm glad you incorperated what you said!
the question next answered is if the revolvers will hamper flow on a stock "high velocity" type porting as opposed to a fully done head with oversized valves and matched ports, or rather if the stock head can take advantage of the revolvers.
the question next answered is if the revolvers will hamper flow on a stock "high velocity" type porting as opposed to a fully done head with oversized valves and matched ports, or rather if the stock head can take advantage of the revolvers.
Remember these cams were specifically designed to maximize the stock head, turbo, manifold etc.
Nov 27, 2005, 10:44 AM
#52
All we know at this time is that installed straight up with a ported head, this Revolver set made more power than a HKS 272 set, nothing more. We don't really have enough information to determine exactly why. Without at least detailed cam specs, we can only speculate.
There are too many unknowns:
- Do we know the degree of difference (if any) in flow between the different lifts used by each cam set? I haven't yet seen any good flow data even for a stock head.
- We don't know the effective duration of the Revolver set. It's possible that the effective duration of the Revolver could actually be longer than the HKS 272 set, despite the advertised numbers. This in fact could make the Revolver set actually more comparable to the HKS 280 set for at least that reason.
- We don't know the lobe centerlines of the Revolver set. It's been proven time again that changing the lobe centerlines alone can yield a significant amount of power.
- Since the factory turbo runs out of puff before the engine becomes mechanically inefficient, we can't really know exactly what happens in the upper rpm ranges with a larger, more efficient turbo.
If we had more info, we would be able to determine far more than whose cam set does what. We'd be able to determine, generally speaking, what this application favors with respect to cam design, and where we cross the threshold of diminishing returns.
There are too many unknowns:
- Do we know the degree of difference (if any) in flow between the different lifts used by each cam set? I haven't yet seen any good flow data even for a stock head.
- We don't know the effective duration of the Revolver set. It's possible that the effective duration of the Revolver could actually be longer than the HKS 272 set, despite the advertised numbers. This in fact could make the Revolver set actually more comparable to the HKS 280 set for at least that reason.
- We don't know the lobe centerlines of the Revolver set. It's been proven time again that changing the lobe centerlines alone can yield a significant amount of power.
- Since the factory turbo runs out of puff before the engine becomes mechanically inefficient, we can't really know exactly what happens in the upper rpm ranges with a larger, more efficient turbo.
If we had more info, we would be able to determine far more than whose cam set does what. We'd be able to determine, generally speaking, what this application favors with respect to cam design, and where we cross the threshold of diminishing returns.
Nov 27, 2005, 11:11 AM
#54
This is what we will do. I will have an evo with stock cams come in this week.
Throw a set of HKS 272s on the car. Dyno without a tune. Then with a tune.
Then throw the revolvers in without a tune and get some raw data to see where we are.
The tune and compare results.
I will keep everyone updated this week.
Throw a set of HKS 272s on the car. Dyno without a tune. Then with a tune.
Then throw the revolvers in without a tune and get some raw data to see where we are.
The tune and compare results.
I will keep everyone updated this week.
Nov 27, 2005, 11:19 AM
#56
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this is one of the best discussions i have ever seen on evom, i have been wondering the same about cams for a while, but could not find any definitive information, even after searching for several days total time, it will be interesting to see the results on a stock head...keep us posted precision
Nov 27, 2005, 11:22 AM
#57
Originally Posted by Precision Dyno
This is what we will do. I will have an evo with stock cams come in this week.
Throw a set of HKS 272s on the car. Dyno without a tune. Then with a tune.
Then throw the revolvers in without a tune and get some raw data to see where we are.
The tune and compare results.
I will keep everyone updated this week.
Throw a set of HKS 272s on the car. Dyno without a tune. Then with a tune.
Then throw the revolvers in without a tune and get some raw data to see where we are.
The tune and compare results.
I will keep everyone updated this week.
Nov 27, 2005, 11:45 AM
#60
If we really wanted to make a revealing test that truly exposes the differences between these cams, we'd want to do something like this:
Chuck the Revolver set in the car. Use a degree wheel and dial indicator and record the lift, duration, and lobe centerline specs for both the intake and exhaust cam. Using the duration at 1mm lift specs, select the HKS cam set that most closely matches the Revolver set. As of right now, we don't know which HKS set that is, and we cannot go by advertised duration numbers to make that determination.
Use adjustable cam gears to adjust the Revolver set to match the lobe centerlines of the HKS set as installed straight up. This reduces the effective difference to lift differences, a few degrees of duration (probably not very significant) and ramp design. Tune and dyno. Reset the cam gears to "0" and dyno again.
Next, we install the HKS set straight up, tune, and dyno. Finally, we adjust our cam gears to match the lobe centerlines of the Revolver set as installed straight up, and dyno again.
This tells us quite a lot:
- We now have the specs for the Revolver cams
- We find the HKS set that most closely matches those cams, which gives people a familiar, fair point of reference.
- We know which cam performs better, eliminating lobe centerlines and most of the duration difference as influencing factors.
- We gain some insight as to which lobe centerlines tend to work better for this application.
The testing may seem involved at first, but it really isn't if you have the tools to do it. Changing cam gear settings and making dyno runs back to back is a snap.
Chuck the Revolver set in the car. Use a degree wheel and dial indicator and record the lift, duration, and lobe centerline specs for both the intake and exhaust cam. Using the duration at 1mm lift specs, select the HKS cam set that most closely matches the Revolver set. As of right now, we don't know which HKS set that is, and we cannot go by advertised duration numbers to make that determination.
Use adjustable cam gears to adjust the Revolver set to match the lobe centerlines of the HKS set as installed straight up. This reduces the effective difference to lift differences, a few degrees of duration (probably not very significant) and ramp design. Tune and dyno. Reset the cam gears to "0" and dyno again.
Next, we install the HKS set straight up, tune, and dyno. Finally, we adjust our cam gears to match the lobe centerlines of the Revolver set as installed straight up, and dyno again.
This tells us quite a lot:
- We now have the specs for the Revolver cams
- We find the HKS set that most closely matches those cams, which gives people a familiar, fair point of reference.
- We know which cam performs better, eliminating lobe centerlines and most of the duration difference as influencing factors.
- We gain some insight as to which lobe centerlines tend to work better for this application.
The testing may seem involved at first, but it really isn't if you have the tools to do it. Changing cam gear settings and making dyno runs back to back is a snap.