BLB350
01-16-2007, 10:00 PM
Mike, you just helped me out with some cyl honing questions ? thx.
I went to your web site last week (saw it in some magazine ad or article?) and immediately noticed all of the posted dyno charts. I have had a decade fascination with exhaust flow (bordering on obsession) and have often thought about approaching local shops to ask for data to model what?s happening in the exhaust pipe on HD?s. Your numerous posted charts have piqued my interest. I want to ask you a question about your listings if that would be OK. If not, that?s cool too!
In your file names for the individual charts, have you always listed the cam in the bike (e.g. ?2005 FXDWG, PROSTRT, 251, HICK? refers to SE251) if it?s not stock? To use the torque curves in my modeling I need to know when the exhaust valve opens.
What I would like to do is to make use of the dip in the torque curves on some of the runs to calculate what conditions would be necessary (i.e. pressure amplitude wave speed) to have the first reflection at the end of the open pipe appear back at the exhaust valve at TDC overlap at that RPM. By making the math fit the actual data in these curves, it may be possible to predict what combinations of pipe length (and cross over tubes) should, or should not be used with a given cam timing. As I?m guessing you probably already know, there are two things going on in the exhaust pipe when the exhaust valve opens. There is the mass flow out of the cylinder, and there is a ?sound? wave generated (pressure amplitude wave) much like the sound we make when speaking (although much greater in amplitude). It is these pressure waves that reverberate back and forth at junctions, and at open/closed ends. When a positive pressure wave arrives at combustion chamber on overlap, it interferes (and mixes) with the intake charge, greatly lowering the efficiency. I used to watch this wave reflection from the end of my exhaust pipe coming out of the carburetor (the wrong way!) on my shovelhead with large overlap and long timing.
What I am working on is very simplistic in comparison to what the industry can do. I do not have the financial resources to be able to model this using the current industry software, such as what Buell uses (Ricardo Industries). Wadda? think?
:)
I went to your web site last week (saw it in some magazine ad or article?) and immediately noticed all of the posted dyno charts. I have had a decade fascination with exhaust flow (bordering on obsession) and have often thought about approaching local shops to ask for data to model what?s happening in the exhaust pipe on HD?s. Your numerous posted charts have piqued my interest. I want to ask you a question about your listings if that would be OK. If not, that?s cool too!
In your file names for the individual charts, have you always listed the cam in the bike (e.g. ?2005 FXDWG, PROSTRT, 251, HICK? refers to SE251) if it?s not stock? To use the torque curves in my modeling I need to know when the exhaust valve opens.
What I would like to do is to make use of the dip in the torque curves on some of the runs to calculate what conditions would be necessary (i.e. pressure amplitude wave speed) to have the first reflection at the end of the open pipe appear back at the exhaust valve at TDC overlap at that RPM. By making the math fit the actual data in these curves, it may be possible to predict what combinations of pipe length (and cross over tubes) should, or should not be used with a given cam timing. As I?m guessing you probably already know, there are two things going on in the exhaust pipe when the exhaust valve opens. There is the mass flow out of the cylinder, and there is a ?sound? wave generated (pressure amplitude wave) much like the sound we make when speaking (although much greater in amplitude). It is these pressure waves that reverberate back and forth at junctions, and at open/closed ends. When a positive pressure wave arrives at combustion chamber on overlap, it interferes (and mixes) with the intake charge, greatly lowering the efficiency. I used to watch this wave reflection from the end of my exhaust pipe coming out of the carburetor (the wrong way!) on my shovelhead with large overlap and long timing.
What I am working on is very simplistic in comparison to what the industry can do. I do not have the financial resources to be able to model this using the current industry software, such as what Buell uses (Ricardo Industries). Wadda? think?
:)