teach me about turbo cams
09-26-2011, 09:47 PM
#1
teach me about turbo cams
say someone had had a forged 5.3 with nicely worked 243s and a 76mm front mount with some N2O, what would be a good cam? i have seen 212/212 on a 112 and 218/218 on a 112 but no split durations or split lifts and nothing over 218 duration, say the same person already had a 224/224 on a 110 with .563" lift, would that be an alright cam to use? just looking for some knowledge, thanks.
09-26-2011, 10:39 PM
#2
My opinion...lift becomes less important, LSA becomes more important, and duration stays about the same.
Flow numbers at given lift ratings are at 28" of water, but that changes entirely when you pressurize the other side of the valve. You can get away with low lift with a turbo because the flow rating on your heads shoots up when you add boost. Thats why plenty of people make good power by just slapping a turbo on a totally stock engine.
As for LSA, you have to match it with exhaust housing size. Tighter the lobe separation, the bigger exhaust side you need. Flow reversion is a big issue in boosted applications because of the pressure imbalance between the intake and the exhaust. Too much exhaust backpressure will keep too much exhaust in the cylinder and you lose power. Slap on a giant T6 if you want a cam with some overlap to pull harder up top, and it'll feel pretty healthy. If you go to the track and check out the real fast turbo cars, they've often got pretty gnarly cams, and the turbo is massive. Helps to keep that exhaust moving. Another example is Joey's (chevyboy.520) new setup. I had been curious to see how his truck reacts to a turbo being built for NA. He's running a T6 exhaust housing and a cam with 111LSA. At only 5psi it keeps up with a mid-12 second camaro. He was running high 13s with a better intake when he was NA, so over a second improvement is pretty sweet for only a few pounds of boost.
Duration plays along with LSA in determining your powerband, so thats still a player. The characteristics of the exhaust, intake ports, type of cam lobe are all important in deciding how much duration the cam should have.
Again, thats all my opinion so you won't find it in a book (yet)
Just from my experience and what I have seen in real world application.
Flow numbers at given lift ratings are at 28" of water, but that changes entirely when you pressurize the other side of the valve. You can get away with low lift with a turbo because the flow rating on your heads shoots up when you add boost. Thats why plenty of people make good power by just slapping a turbo on a totally stock engine.
As for LSA, you have to match it with exhaust housing size. Tighter the lobe separation, the bigger exhaust side you need. Flow reversion is a big issue in boosted applications because of the pressure imbalance between the intake and the exhaust. Too much exhaust backpressure will keep too much exhaust in the cylinder and you lose power. Slap on a giant T6 if you want a cam with some overlap to pull harder up top, and it'll feel pretty healthy. If you go to the track and check out the real fast turbo cars, they've often got pretty gnarly cams, and the turbo is massive. Helps to keep that exhaust moving. Another example is Joey's (chevyboy.520) new setup. I had been curious to see how his truck reacts to a turbo being built for NA. He's running a T6 exhaust housing and a cam with 111LSA. At only 5psi it keeps up with a mid-12 second camaro. He was running high 13s with a better intake when he was NA, so over a second improvement is pretty sweet for only a few pounds of boost.
Duration plays along with LSA in determining your powerband, so thats still a player. The characteristics of the exhaust, intake ports, type of cam lobe are all important in deciding how much duration the cam should have.
Again, thats all my opinion so you won't find it in a book (yet)
Just from my experience and what I have seen in real world application.
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09-27-2011, 01:18 PM
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I'm in for more info to. From what ive seen turbo cams are pretty boring same duration same lift and a high lsa. I've had pat g spec me one and it was a smaller version of what I already had.
