Bruceynz
Well-Known Member
Hi Guys,
I have been laying low for a while, I have been thinking and thought would start a debate over RPM range, when you buy an intake it is rated from idle to 5500 eg performer, then the performer rpm 1500 to 6500 and cams are rated something similar.
Lets start with intakes - What's this RPM figure mean, if we look at cams we can say at 50thou its 224 degrees, so now I know that every cam is based to that spec, but how is the RPMs worked out on a manifold, lets use performer, at 5500 does it stop flowing, is this size for a 273, 318, 340, 360 or 408?? Lets move to the performer rpm, it says 1500 to 6500 what happens under 1500rpm (I have an airgap and my car idles fine) if you take a look at a motor trend article they will show on the flow bench the performer rpm has poor flow but then they dive in to telling you that its a very good intake and makes more power than the higher flowing intakes, so that means flow of an intake is not the whole story? Its seems something so trivial but to me seems such unknown. So back to my questions what's it all mean? How does an RPM rating apply, how do you really know the intake you choose is the right one for your setup, bigger always sounds better but is it?
Cams - Same deal, you can look at a cam something like a 274, its operating range is say 1200 - 5700rpm, but in a decent engine it makes max HP at 5200rpm, (look at the comp cams dyno graphs) once again what's it all mean, are those operating ranges like a frequency audio response curve where they measure the 3db points and it gives the operating range of an amplifier, I dunno eh, it seems simple but what manifold you you pair up with a 274, if you go off cam specs the performer rpm, if you go off actual dyno run then a performer would be fine or would it?
Looking forward to your thoughts on this one, its just something I have thought about for many years and never really knew the answer too, sure you can bolt stuff up and it works but what are you leaving on the table. Do those numbers really mean anything?
Thanks
Bruce
I have been laying low for a while, I have been thinking and thought would start a debate over RPM range, when you buy an intake it is rated from idle to 5500 eg performer, then the performer rpm 1500 to 6500 and cams are rated something similar.
Lets start with intakes - What's this RPM figure mean, if we look at cams we can say at 50thou its 224 degrees, so now I know that every cam is based to that spec, but how is the RPMs worked out on a manifold, lets use performer, at 5500 does it stop flowing, is this size for a 273, 318, 340, 360 or 408?? Lets move to the performer rpm, it says 1500 to 6500 what happens under 1500rpm (I have an airgap and my car idles fine) if you take a look at a motor trend article they will show on the flow bench the performer rpm has poor flow but then they dive in to telling you that its a very good intake and makes more power than the higher flowing intakes, so that means flow of an intake is not the whole story? Its seems something so trivial but to me seems such unknown. So back to my questions what's it all mean? How does an RPM rating apply, how do you really know the intake you choose is the right one for your setup, bigger always sounds better but is it?
Cams - Same deal, you can look at a cam something like a 274, its operating range is say 1200 - 5700rpm, but in a decent engine it makes max HP at 5200rpm, (look at the comp cams dyno graphs) once again what's it all mean, are those operating ranges like a frequency audio response curve where they measure the 3db points and it gives the operating range of an amplifier, I dunno eh, it seems simple but what manifold you you pair up with a 274, if you go off cam specs the performer rpm, if you go off actual dyno run then a performer would be fine or would it?
Looking forward to your thoughts on this one, its just something I have thought about for many years and never really knew the answer too, sure you can bolt stuff up and it works but what are you leaving on the table. Do those numbers really mean anything?
Thanks
Bruce