low lift headflow figures and how they relate to streetable performance
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Grand HDF Member
Joined: May 2014
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From: florida
low lift headflow figures and how they relate to streetable performance
hey folks,
Most of the time that i see here, when people are talking about heads and cams, they are talking about peak hp and tq numbers. i was hoping to get some more info on how to interpret how the lower than max lift flow numbers from a head can be used to A) help to choose a cam B) how to choose a cam for a particular riding style(bike type too) and hopefully to use the info to help predict how a particular build will ride once put together and tuned properly.
It is a given that the proper tune, a quality exhaust system and the proper peripheral parts and techniques are in place and use. Most of the dyno runs that are graphed are 100% roll on runs, and while the info is useful, it is still only part of the picture of how a bike rides. I'm kinda hoping that some more info/explanation of the low lift flow numbers might help shed some light on how the bike will run everywhere else, besides 100% throttle. Driveability and general fun, spirited riding, but not all out, all the time.
My bagger is pretty good, but i'd like to make it the best that i can afford, but i'm not racing it, i don't have an unlimited budget to work with, and it still has to maintain a certain level of reliability and I would like to use the info to help my customers also when we are trying to make decisions on what they would like to get when upgrading their bike.
Any info and discussion, please!
m
Most of the time that i see here, when people are talking about heads and cams, they are talking about peak hp and tq numbers. i was hoping to get some more info on how to interpret how the lower than max lift flow numbers from a head can be used to A) help to choose a cam B) how to choose a cam for a particular riding style(bike type too) and hopefully to use the info to help predict how a particular build will ride once put together and tuned properly.
It is a given that the proper tune, a quality exhaust system and the proper peripheral parts and techniques are in place and use. Most of the dyno runs that are graphed are 100% roll on runs, and while the info is useful, it is still only part of the picture of how a bike rides. I'm kinda hoping that some more info/explanation of the low lift flow numbers might help shed some light on how the bike will run everywhere else, besides 100% throttle. Driveability and general fun, spirited riding, but not all out, all the time.
My bagger is pretty good, but i'd like to make it the best that i can afford, but i'm not racing it, i don't have an unlimited budget to work with, and it still has to maintain a certain level of reliability and I would like to use the info to help my customers also when we are trying to make decisions on what they would like to get when upgrading their bike.
Any info and discussion, please!
m
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Joined: Dec 2007
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Peak flow numbers are important, and are mid-lift numbers, as the valve is in that area twice, on each opening/closing event.
We look at the mid-lift average, (.200', .300", .400") among many other things.
We also look/can look at the port using Bettes probes/flags.
We have 2 flow benches here.
Scott
We look at the mid-lift average, (.200', .300", .400") among many other things.
We also look/can look at the port using Bettes probes/flags.
We have 2 flow benches here.
Scott
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Grand HDF Member
Joined: May 2014
Posts: 3,822
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From: florida
Thanks Scott, I was truly hoping that YOU were one of the folks to chime in here. I think that i might have miss-stated what i was thinking, but you got to it sort of, the MID lift averages is a good way to say it i think.
If i was to be looking at flow sheets on 2 different sets of heads, what would I want to be looking for? Is it still just as basic as the the head with the larger numbers in those areas is going to run/feel better on the road? I understand that the engine will go through its cycle, but throttle position and load will affect flow. If you don't open the the throttle all the way, max flow is not achieved. Am I over thinking it?
m
If i was to be looking at flow sheets on 2 different sets of heads, what would I want to be looking for? Is it still just as basic as the the head with the larger numbers in those areas is going to run/feel better on the road? I understand that the engine will go through its cycle, but throttle position and load will affect flow. If you don't open the the throttle all the way, max flow is not achieved. Am I over thinking it?
m
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Joined: Sep 2009
Posts: 3,569
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From: deland,florida
low lift #`s wont give more power at low RPM`s like most think,but it will give more power thu out the whole RPM range as the charge gets moving quicker.we always look for good flow #`s from right off the seats to max lift on our street heads,low lift #`s in very high RPM or racing engines are not so important
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Joined: Dec 2007
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We like to see the head continue to pull past the cams peak lift, and also look to establish a dedicated 75-80% ratio from the exhaust side.
On another message board, there was an individual that displayed evidence of not taking his medication for several days, and that had utterly rediculous claims that an exhaust was running more than the intake......entertaining....lol!
Scott
On another message board, there was an individual that displayed evidence of not taking his medication for several days, and that had utterly rediculous claims that an exhaust was running more than the intake......entertaining....lol!
Scott
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