Question on Cams
07-03-2002 | 02:40 PM
#1
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Question on Cams
Im looking to buy some cams...now ive done some searchin and i need to ask a few questions.. it sounds like a good buy is the 1.8 GT cam, but i hear talks of cams wtih variable degrees ie 240-255, etc... now what would be the best cam to get?
im looking for good power without a huge lag on straight line acceleration (what degree and lift should i get?)
also what would replacing the springs do?
im looking for good power without a huge lag on straight line acceleration (what degree and lift should i get?)
also what would replacing the springs do?
07-03-2002 | 07:33 PM
#3
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From: Rancho Palos Verdes, CA
Vehicle: 2008 Toyota Prius 2006 Suzuki SV650S
Replacing the springs only becomes necessary when the cam duration and/or lift stresses the stock springs. For example, RPW does not reccomend replacing the valve springs on the 220 degree intake cam, however, they do reccomend it on the cams that are over 222 degree.
Make sure that when you compare cams, you make sure they are using the same measurement system. Hyundai stock cam figures are 0 to 0. meaning that they measure from 100% closed back to 100% closed. HVE and RPW use 0.050 to 0.050. That means they don't measure the duration of the cam untill the valve has lifted 0.050" off the valve seat, and they consider it closed when the valve returns to 0.050" to the valve seat.
The stock figures that RPW claims (using the 0.050 to 0.050 method).
Beta I 200 degrees
Beta II 199 degrees
Hyundai's figures for the cams using 0 to 0 are
Beta I 228 Degrees
Beta II 231 Degrees
Apparently the HLA equipped BetaI cam opens faster, or closes slower than the Beta II. That is why there is a difference in the measurements from RPW's method vs Hyundai's method. This makes sense as the HLA drivetrain has more inherent "slop" due to the HLA filled/pushing out oil.
Anyway...enough rambling. Back to your question
The BetaII intake cam would be a good choice for top end power, without loosing low end torque. Ditto for the RPW Stage I cam. The RPW Stage 2 or 3 cam will affect idle, and also may loose some low end power (under 3000 rpm). For the price difference, I would go with the BetaII intake cam unless you want to go Gonzo with your N/A mods.
Make sure that when you compare cams, you make sure they are using the same measurement system. Hyundai stock cam figures are 0 to 0. meaning that they measure from 100% closed back to 100% closed. HVE and RPW use 0.050 to 0.050. That means they don't measure the duration of the cam untill the valve has lifted 0.050" off the valve seat, and they consider it closed when the valve returns to 0.050" to the valve seat.
The stock figures that RPW claims (using the 0.050 to 0.050 method).
Beta I 200 degrees
Beta II 199 degrees
Hyundai's figures for the cams using 0 to 0 are
Beta I 228 Degrees
Beta II 231 Degrees
Apparently the HLA equipped BetaI cam opens faster, or closes slower than the Beta II. That is why there is a difference in the measurements from RPW's method vs Hyundai's method. This makes sense as the HLA drivetrain has more inherent "slop" due to the HLA filled/pushing out oil.
Anyway...enough rambling. Back to your question
The BetaII intake cam would be a good choice for top end power, without loosing low end torque. Ditto for the RPW Stage I cam. The RPW Stage 2 or 3 cam will affect idle, and also may loose some low end power (under 3000 rpm). For the price difference, I would go with the BetaII intake cam unless you want to go Gonzo with your N/A mods.
07-04-2002 | 02:20 AM
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Just my two cents BUT
IF your are Going FI then I would go with stage 2 or 3 From RPW.. My reason to go that route is you already have lag. You car is now setup to almost dog off the line (NA cars will take you in launch) but you shinning moment is in the upper rpm range (after you are fully spooled) So thats where you want your power..
IF you are shifting into gear under 3500 to 4000 rpms on a turbo during a drag then you are not doing something right.
(but Im not saying you do..)
Other things to rember is this a daily low boost setup or are you going HOG WILD AS SEEN ON TV WITH CARZY COLLEGE CO-ED'S..
If this is daily and you don't like a lumpy idle go stage one or the GT cam.
But hey what do I know Im random's bitch when it comes to this and Just about everybody owns me LOL.
IF your are Going FI then I would go with stage 2 or 3 From RPW.. My reason to go that route is you already have lag. You car is now setup to almost dog off the line (NA cars will take you in launch) but you shinning moment is in the upper rpm range (after you are fully spooled) So thats where you want your power..
IF you are shifting into gear under 3500 to 4000 rpms on a turbo during a drag then you are not doing something right.
(but Im not saying you do..)Other things to rember is this a daily low boost setup or are you going HOG WILD AS SEEN ON TV WITH CARZY COLLEGE CO-ED'S..
If this is daily and you don't like a lumpy idle go stage one or the GT cam.
But hey what do I know Im random's bitch when it comes to this and Just about everybody owns me LOL.
07-04-2002 | 03:17 AM
#6
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From: Rancho Palos Verdes, CA
Vehicle: 2008 Toyota Prius 2006 Suzuki SV650S
Actually the RPW stage 2 or 3 would be a BAD idea for a turbo cam.
Forced Induction cams(using both) need to have very little overlap. The RPW Stage2 and Stage3 cams both increase in duration a great deal. This would cause both intake and exhaust to be open at the same time. Right now the Exhaust valve closes 10 Degrees after Top Dead Center, and the intake valve opens 8 Degrees BEFORE top Dead Center. This gives you 18 degrees of valve overlap, where both valves are open. In a N/A Motor, using 0.050 to 0.050 cam timing, you can have those values overlap, as very little gas/air flow happens at under 0.050 of lift at atsomphereic pressure. However, with a turbo or supercharger, when you are dealing with 10 to 15 pounds of boost (or more), you would get some fairly significant gas flow at 0.050 of valve lift. You can litterally have fresh intake air/fuel mixture blow into the combustion chamber, and right out your still open exhaust ports.
I can't compare the RPW cams to the stock cams as RPW did not provide valve open/close degree timing for their intake cam, but, since they are adding duration they must be adding at least SOME of it to opening Intake valve earlier. On a Forced induction motor, this would be a bad thing.
Usually, Forced induction cams have very little valve overlap, but are quick opening, and stay open longer on the intake side, and quick opening, with higher lift, on the exhaust side.
I know there are some companies in Korea that make specific cams for Turbo setups, but at $1500 a pop, I'm not sure who would want to test them.
Forced Induction cams(using both) need to have very little overlap. The RPW Stage2 and Stage3 cams both increase in duration a great deal. This would cause both intake and exhaust to be open at the same time. Right now the Exhaust valve closes 10 Degrees after Top Dead Center, and the intake valve opens 8 Degrees BEFORE top Dead Center. This gives you 18 degrees of valve overlap, where both valves are open. In a N/A Motor, using 0.050 to 0.050 cam timing, you can have those values overlap, as very little gas/air flow happens at under 0.050 of lift at atsomphereic pressure. However, with a turbo or supercharger, when you are dealing with 10 to 15 pounds of boost (or more), you would get some fairly significant gas flow at 0.050 of valve lift. You can litterally have fresh intake air/fuel mixture blow into the combustion chamber, and right out your still open exhaust ports.
I can't compare the RPW cams to the stock cams as RPW did not provide valve open/close degree timing for their intake cam, but, since they are adding duration they must be adding at least SOME of it to opening Intake valve earlier. On a Forced induction motor, this would be a bad thing.
Usually, Forced induction cams have very little valve overlap, but are quick opening, and stay open longer on the intake side, and quick opening, with higher lift, on the exhaust side.
I know there are some companies in Korea that make specific cams for Turbo setups, but at $1500 a pop, I'm not sure who would want to test them.
07-04-2002 | 06:13 AM
#8
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I found that the Shark racing 2.0L cam gave the idle a slight lope, espically with the A/C/ Also the lobes on the cam are narrow then the stock ones. On the dyno, with all my mods, its dynoed a 6.9 WHP gain, at 6342 RPM.
-Steve
-Steve
07-04-2002 | 07:55 AM
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Best in terms of power? Very aggressive cams, high lift/duration, with a fair bit of overlap.
As you get more aggressive though, you get a rough idle, and lose some drivability for daily use. You will also tend to lose fuel efficiency quite quickly after a point.
Forced induction is putting pressure on your intake side. If you have a lot of overlap, when both the inlet & exhaust valves are open, you are going to be taking this nicely pressurized air and spewing it straight out the exhaust valve along with the fuel you squirted into it. The pressure in the cylinder will not build up as high, less fuel & air = less power. Forced induction works better with much lower overlap--so you really can't tune for both.
If you want optimal NA cams you will have to replace them if & when you go with a turbo. So 'best' is completely up to you wink
As you get more aggressive though, you get a rough idle, and lose some drivability for daily use. You will also tend to lose fuel efficiency quite quickly after a point.
Forced induction is putting pressure on your intake side. If you have a lot of overlap, when both the inlet & exhaust valves are open, you are going to be taking this nicely pressurized air and spewing it straight out the exhaust valve along with the fuel you squirted into it. The pressure in the cylinder will not build up as high, less fuel & air = less power. Forced induction works better with much lower overlap--so you really can't tune for both.
If you want optimal NA cams you will have to replace them if & when you go with a turbo. So 'best' is completely up to you wink
07-05-2002 | 02:20 AM
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Actually, that is a common misconception. Pressurized air from the intake on a turbocharger rarely gets spewed out the exhaust.
The problem on a turbocharged car is that the EXHAUST is highly pressurized between the cylinder head and the turbo... In some cases, this pressure can hit as high as 3 bar (44psi). On wide overlap, what happens is the EXHAUST flows backwards into the cylinder because of all the pressure -- thus you get a lot less "intake".
Since exhaust is all kinds of hot and is basically now non-flammable, you get less power.
This is why wild N/A cams work well with superchargers. That exhaust pressure is non-existant, and the cam overlap combined with the pressurized intake actually helps evacuate all the exhaust out of the cylinder.
The problem on a turbocharged car is that the EXHAUST is highly pressurized between the cylinder head and the turbo... In some cases, this pressure can hit as high as 3 bar (44psi). On wide overlap, what happens is the EXHAUST flows backwards into the cylinder because of all the pressure -- thus you get a lot less "intake".
Since exhaust is all kinds of hot and is basically now non-flammable, you get less power.
This is why wild N/A cams work well with superchargers. That exhaust pressure is non-existant, and the cam overlap combined with the pressurized intake actually helps evacuate all the exhaust out of the cylinder.