SLORYDER Posted June 3, 2009 Report Share Posted June 3, 2009 I was curious as to how degrees of transfer / exhaust port timing related to mm of material removed from the port roof.. I was told to take about 1.5 mm of material off the roof of my exhaust to add some top end; and I wanted to know if anyone knew about what that would put my timing at with a stock crank. Also how much more agressive could I go for a non drag port and how much can I go before I need to move the transfers. Thanks, Marcus Quote Link to comment Share on other sites More sharing options...
278 Posted June 3, 2009 Report Share Posted June 3, 2009 Im pretty sure its kind of like the degrees of duration of a cam in a four stroke. THe more material you take out of the top the more degrees of duration you have which is a way to measure how long the exhaust port is open. Quote Link to comment Share on other sites More sharing options...
odaen Posted June 3, 2009 Report Share Posted June 3, 2009 I was curious as to how degrees of transfer / exhaust port timing related to mm of material removed from the port roof.. I was told to take about 1.5 mm of material off the roof of my exhaust to add some top end; and I wanted to know if anyone knew about what that would put my timing at with a stock crank. Also how much more agressive could I go for a non drag port and how much can I go before I need to move the transfers. Thanks, Marcus I don't remember the stock port timing or distance from the deck that the ports open, so I can't help ya. If you knew the distance from the deck to where you want the roof of the port to be, I could tell you the duration. Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 4, 2009 Author Report Share Posted June 4, 2009 I don't remember the stock port timing or distance from the deck that the ports open, so I can't help ya. If you knew the distance from the deck to where you want the roof of the port to be, I could tell you the duration. I'll have to check on that and get back with you Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted June 4, 2009 Report Share Posted June 4, 2009 (edited) i have a program at home on my computer. when i get home from work, i can tell you. stock i if remember, is right around 180*-183*. raising 1.5mm should put you around 186* duration, if i recall. what brand of base gaskets are you using.....OEM, Moose, Wiseco, Cometic? Edited June 4, 2009 by mopar1rules Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 4, 2009 Author Report Share Posted June 4, 2009 (edited) i have a program at home on my computer. when i get home from work, i can tell you. stock i if remember, is right around 180*-183*. raising 1.5mm should put you around 186* duration, if i recall. what brand of base gaskets are you using.....OEM, Moose, Wiseco, Cometic? OEM base gaskets... I just had a thought. If 180 deg. = 54mm, then 90=27, 45=13.5, 22.5=6.75,11.25=3.3725, 5.625=1.6375 So....raising 1.5mm should be roughly 5.5 degrees..? I may be totally wrong tho. I'm sure at the top and bottom of the stroke there may be less lateral movement as compared to rotation, but does that mean in the middle of the stroke there is more... Can I go any higher w/o totally screwing up my powerband? Edited June 4, 2009 by SLORYDER Quote Link to comment Share on other sites More sharing options...
278 Posted June 4, 2009 Report Share Posted June 4, 2009 I could be wrong, but I dont think stock is 183, because I have an agressive trail port with exhaust raised 1mm. and its at like 183.somoething now, 1.5mm. would give you a little better top, but I think a little more would give you more top end. But you have to take into account your transfers too. Quote Link to comment Share on other sites More sharing options...
blowit Posted June 4, 2009 Report Share Posted June 4, 2009 I could be wrong, but I dont think stock is 183, because I have an agressive trail port with exhaust raised 1mm. and its at like 183.somoething now, 1.5mm. would give you a little better top, but I think a little more would give you more top end. But you have to take into account your transfers too. Stock is 176-178* open on exhaust. Brandon Quote Link to comment Share on other sites More sharing options...
odaen Posted June 5, 2009 Report Share Posted June 5, 2009 OEM base gaskets... I just had a thought. If 180 deg. = 54mm, then 90=27, 45=13.5, 22.5=6.75,11.25=3.3725, 5.625=1.6375 So....raising 1.5mm should be roughly 5.5 degrees..? I may be totally wrong tho. I'm sure at the top and bottom of the stroke there may be less lateral movement as compared to rotation, but does that mean in the middle of the stroke there is more... Can I go any higher w/o totally screwing up my powerband? It's not nearly that simple, I can assure you. Here's a program I wrote that can calculate durations given all of the needed parameters, and a whole bunch of other stuff. As a footnote, I refer to negative deck height as pistons rising above the top of the deck. First you have to download and install this: ftp://ftp.ni.com/support/labview/windows/...VRunTimeEng.exe Then download this, unzip it, and copy the contents anywhere on your pc. http://www.redline-racing.net/PortMapper/PortMapper.zip Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted June 5, 2009 Report Share Posted June 5, 2009 It's not a linear equation because crank dwell has a major effect on the relationship of port timing to a linear measurement. This is because as the piston approaches BDC or TDC the pistons speed decreases even though the crankshafts speed stays the same. That being said the more you raise the exhaust port roof towards top dead center you will gain more port open time per amount of linear material removed. Also, connecting rod length affects crank angle and therefore will affect your port open time. Base gasket thickness, decking the bottom of the cylinders and piston selection will also have an effect on port timing. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted June 5, 2009 Report Share Posted June 5, 2009 It's not nearly that simple, I can assure you. Here's a program I wrote that can calculate durations given all of the needed parameters, and a whole bunch of other stuff. As a footnote, I refer to negative deck height as pistons rising above the top of the deck. First you have to download and install this: ftp://ftp.ni.com/support/labview/windows/...VRunTimeEng.exe Then download this, unzip it, and copy the contents anywhere on your pc. http://www.redline-racing.net/PortMapper/PortMapper.zip having troubles with the link Quote Link to comment Share on other sites More sharing options...
odaen Posted June 5, 2009 Report Share Posted June 5, 2009 having troubles with the link I installed it last night from home from the links.... which link is giving you problems? Quote Link to comment Share on other sites More sharing options...
dajogejr Posted June 5, 2009 Report Share Posted June 5, 2009 It's not nearly that simple, I can assure you. Here's a program I wrote that can calculate durations given all of the needed parameters, and a whole bunch of other stuff. As a footnote, I refer to negative deck height as pistons rising above the top of the deck. First you have to download and install this: ftp://ftp.ni.com/support/labview/windows/...VRunTimeEng.exe Then download this, unzip it, and copy the contents anywhere on your pc. http://www.redline-racing.net/PortMapper/PortMapper.zip HOLY SHIT you're still alive... Quote Link to comment Share on other sites More sharing options...
AKheathen Posted June 5, 2009 Report Share Posted June 5, 2009 the first one, but i'm checking to see if it's my comp. Quote Link to comment Share on other sites More sharing options...
odaen Posted June 5, 2009 Report Share Posted June 5, 2009 HOLY SHIT you're still alive... Yeah, just got another 4mm motor done, and it re-invigorated my love for banshees. :beer: Quote Link to comment Share on other sites More sharing options...
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