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Porting question


WNARACE

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I have a set of jugs which have the stage 3 prologic race porting done on them. My question is what effects does raising the transfer ports do to the overall power band? Will it bring in the power band lower, higher, or does it just widen the overall rpm range? The transfer windows have not been touched as of this time, and racelogic recommends raising them 1mm.

 

Thanks for you help in advance.

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If you want midrange power, you should't raise the transfers. Maybe widen them a little bit (barely any), and make sure the bottom of the port window lines up with the top of the piston at bdc.

 

The more you raise them, the more it orientates the exhaust pulse wave for scavenging at higher rpm. However, this is based on what your exhaust duration is setup at. What do you do with this bike, and what pipes are on it?

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I typically trail ride, along with some recreational drag. The bike currently has a milled stock head, t-5 pipes, v-3 reeds, 28pwks, and this so called stage three racelogic port job. I know that there has been no work done to the transfers. I spoke to the guys at Racelogic, and all they said to do was to raise the transfer windows 1mm. The bike is due for an overbore, and I am seriously considering sending the jugs off to have the portwork redone, attempting to optimize my setup at this time. I am open to suggestions as to who to send them to, my fear is that whoever did the porting may have messed it up some how.

 

Thanks for any and all your advise

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I typically trail ride, along with some recreational drag. The bike currently has a milled stock head, t-5 pipes, v-3 reeds, 28pwks, and this so called stage three racelogic port job. I know that there has been no work done to the transfers. I spoke to the guys at Racelogic, and all they said to do was to raise the transfer windows 1mm. The bike is due for an overbore, and I am seriously considering sending the jugs off to have the portwork redone, attempting to optimize my setup at this time. I am open to suggestions as to who to send them to, my fear is that whoever did the porting may have messed it up some how.

 

Thanks for any and all your advise

 

Increase transfer ports for more bottom end and smoother , broader bottom end power delivery(note: the higher the transfer ports in respect to a given ex port height, the less explosive upper mid-top end power you will receive... 1

do not make them any wider in the cylinder, it will slow down the entering speed of gases into the cylinder, you can open it up at the base of the cylinder...

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Increase transfer ports for more bottom end and smoother , broader bottom end power delivery(note: the higher the transfer ports in respect to a given ex port height, the less explosive upper mid-top end power you will receive... 1

do not make them any wider in the cylinder, it will slow down the entering speed of gases into the cylinder, you can open it up at the base of the cylinder...

 

 

So if im understanding you correctly, if I have the transfer windows raised, it will smooth out the power delivery, and decrease the higher rpm hit? Thus, making the bike more trial friendly, and less likely to be so dogish in the lower rpm range.

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So if im understanding you correctly, if I have the transfer windows raised, it will smooth out the power delivery, and decrease the higher rpm hit? Thus, making the bike more trial friendly, and less likely to be so dogish in the lower rpm range.

 

 

Yes.. but it all depends how high your exhaust port is..

Edited by 2strokespirit
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Raising transfer port height will make the power band stronger across the entire rpm range, but its based upon exhaust duration as to how well it works. Thats why I say increase transfer window area a scoche on the corners (square up the port) and widen the transfer port windows in the sleeve a little bit to match the aluminum casting of the cylinder. Leave the bump in the auxillary transfer port radius just behind the opening. Thats what directs the auxillary transfer flow. The open time of the exhaust (duration) relies on wether the exhaust scavenges the transfers, otherwise you have to rely on transfer case pressure to push the charge out into the cylinder.

 

We can make a better recommendation if you measure your exhaust port height relative to the deck on the top of the cylinder.

Edited by Snopczynski
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All I can say is if you are not watching your port-time area or degrees of open duration, you are shooting blanks. Measurements do not mean much if you do not calculate that into open degrees. That is where you will understand what the motor will and won't do for you.

 

 

Achieving better bottom end performance is obtainable but requires someone that knows porting and not a winner on the guessing network channel. The things that will determine good bottom end are comp ratio, squish angle and clearance, port timing, port velocity, carb size, pipe selection, reed selection, and ignition advance. If you want all bottom end, there will be a compromise so you will have to set goals. You will want FMF fatties, PT mids, or a two into one pipe for good grunt.

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its true yo u will make better torque and a wider powerband by manipulating the transfers but it iwll involve more than simply raising them and it must be in relationship to the exhaust duration this is done for optimum blowdown,pitching.aiming the angles and sizes of the ports also can make a dramatic difference for the given range ,takes some know how and years of experimnetation this is the difference between a somewhat quick motor and a screaming fast motor. my 2 pennies

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