Blower cams
#12
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Maybe the Crane 651 is also doing those specs for heat management ?
#13
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In regards to splits I did look up lunatis and did notice their blower cams do have less split than others. 4+- on blower cams and 8+- for non blower cams. Just a quick search I didn't go through all of them but..
#14
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With a hydraulic lifter, the exhaust opening can be fairly critical in a boosted application. In theory, and as seen in software modeling, opening the exhausts sooner to initiate blowdown pays off in hp. What I've seen in the real world is, opening too early against all that cylinder pressure can cause the lifter to bleed down, or beat your valve train up if you've got really stout lifters. Sometimes a slightly later exhaust opening will actually make more power due to better valvetrain control. It can also be boost dependent. A cam with an early exhaust opening might work great with 6 or 7 lbs boost, but start to have issues at 10-12.
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And to clarify. That's not a knock against simulation software, which is an incredibly valuable tool. But some one who has never built a supercharged marine engine before could sell a hobbyist cams designed by that software and run in to trouble. Just because it says you make more power with a bunch of lift and an early exhaust opening doesn't mean it will live in the real world.. But I digress.. Does the 651 cam have a boost psi recommendation?
#16
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With a hydraulic lifter, the exhaust opening can be fairly critical in a boosted application. In theory, and as seen in software modeling, opening the exhausts sooner to initiate blowdown pays off in hp. What I've seen in the real world is, opening too early against all that cylinder pressure can cause the lifter to bleed down, or beat your valve train up if you've got really stout lifters. Sometimes a slightly later exhaust opening will actually make more power due to better valvetrain control. It can also be boost dependent. A cam with an early exhaust opening might work great with 6 or 7 lbs boost, but start to have issues at 10-12.
#17
And to clarify. That's not a knock against simulation software, which is an incredibly valuable tool. But some one who has never built a supercharged marine engine before could sell a hobbyist cams designed by that software and run in to trouble. Just because it says you make more power with a bunch of lift and an early exhaust opening doesn't mean it will live in the real world.. But I digress.. Does the 651 cam have a boost psi recommendation?
#18
I think Haxby nailed a topic, mentioning opening the exhaust valve too soon, can be hard on parts. The cylinder pressure can be very high at exhaust valve opening.
Performance wise, I am guessing , that opening the valve earlier, with a poor flowing exhaust port, might get the cylinder evacuated better, but with a good flowing port, might be a waste? I don't really know. Or, maybe its relative to the level of boost..
Maybe I'll have to run 2 dyno sims, one with stock GM heads, and one with a dart or afr head, using both cam designs, and see what happens.
Good stuff.
#19
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That part I get. My question was more or less related to actual valve timing events. People tend to get so wrapped up in LSA's, ICL's, .050 numbers, and rarely look at what the valves are doing relative to all that, and that imo, is what matters. The engine doesnt know or see, LSA's, ICL's, etc. It just sees what the valves are doing.
I think Haxby nailed a topic, mentioning opening the exhaust valve too soon, can be hard on parts. The cylinder pressure can be very high at exhaust valve opening.
Performance wise, I am guessing , that opening the valve earlier, with a poor flowing exhaust port, might get the cylinder evacuated better, but with a good flowing port, might be a waste? I don't really know. Or, maybe its relative to the level of boost..
Maybe I'll have to run 2 dyno sims, one with stock GM heads, and one with a dart or afr head, using both cam designs, and see what happens.
Good stuff.
I think Haxby nailed a topic, mentioning opening the exhaust valve too soon, can be hard on parts. The cylinder pressure can be very high at exhaust valve opening.
Performance wise, I am guessing , that opening the valve earlier, with a poor flowing exhaust port, might get the cylinder evacuated better, but with a good flowing port, might be a waste? I don't really know. Or, maybe its relative to the level of boost..
Maybe I'll have to run 2 dyno sims, one with stock GM heads, and one with a dart or afr head, using both cam designs, and see what happens.
Good stuff.
#20
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isn't it just easier to google a supercharger build to fit your needs and copy it.will save you a trash barrel full of cams that were suppose to work on paper and in an computer syms.