Turbo cam difference discussion
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TECH Junkie
Joined: Dec 2012
Posts: 3,605
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From: Iowa
Turbo cam difference discussion So I'm trying to pick the brains of all the cam gurus on the tech today. I'm discussing cams with a buddy of mine that races subarus and we are comparing some of the most popular options for high hp (800+) subarus with similarly high hp LS engines.
From what I have found, most of the large subie cams are 282 intake/278-282 exhaust at .006. 240 intake/236-240 exhaust at .050.
Most LS cams range in similar duration for the "large" turbo cams (thinking the ljms stage 3 or 4)
The duration differences I can attribute to how the cylinder heads flow, but what really throws me for a loop is the ICL and LSA
Most LS turbo stuff seems to hang out in the 108-112 ICL and 115 ish LSA
But Subaru stuff is WAY different. 130 ICL and 122 LSA seems to be about the norm
What would be the cause/effect of bleeding off that much cylinder pressure by closing the intake valve so late. Also. There seems to be little to no overlap compared to v8 stuff. I'm trying to simplify the valve events to a cylinder vs cylinder matchup and can't see why they would be so drastically different.
Could someone chime in on how these differences would affect the engines behavior. The power curve. What would happen if the cam specs were swapped between the engines? I'm just genuinely trying to understand things a little better today.
From what I have found, most of the large subie cams are 282 intake/278-282 exhaust at .006. 240 intake/236-240 exhaust at .050.
Most LS cams range in similar duration for the "large" turbo cams (thinking the ljms stage 3 or 4)
The duration differences I can attribute to how the cylinder heads flow, but what really throws me for a loop is the ICL and LSA
Most LS turbo stuff seems to hang out in the 108-112 ICL and 115 ish LSA
But Subaru stuff is WAY different. 130 ICL and 122 LSA seems to be about the norm
What would be the cause/effect of bleeding off that much cylinder pressure by closing the intake valve so late. Also. There seems to be little to no overlap compared to v8 stuff. I'm trying to simplify the valve events to a cylinder vs cylinder matchup and can't see why they would be so drastically different.
Could someone chime in on how these differences would affect the engines behavior. The power curve. What would happen if the cam specs were swapped between the engines? I'm just genuinely trying to understand things a little better today.
