New Street Porting Work
03-02-2005, 01:56 AM
#11
Senior Member
Join Date: Jun 2004
Location: Oregon
Posts: 131
Originally Posted by BDC' date='Mar 1 2005, 11:22 PM
Hi Greg, thanks for the comments. I've thought off and on about making a radius on the closing edge of the side ports, but the reason why I haven't is because I'm not sure if it will make a substantial difference or not. You're right on the 90-degree part; that's why I focus so much effort on the short radius of the port outlet, plus the port tunnel where it transitions into the port outlet. I spent alot of time trying to keep the charge up to speed, avoiding the hard edges the stock casting offers.
What were you recommending again on the exhaust port? I wasn't sure exactly what you meant.
B
What were you recommending again on the exhaust port? I wasn't sure exactly what you meant.
B
03-02-2005, 02:00 AM
#12
Member
Join Date: Aug 2004
Location: Houston
Posts: 76
Originally Posted by GMON' date='Mar 2 2005, 01:41 AM
B- 
, No round edge on the closing edge of side ports or arround the ex-ports.
Air flows arround a radius better than it does a 90 deg angle.
Looks great otherwise.
My 2 cents.
GregW
Air flows arround a radius better than it does a 90 deg angle.
Looks great otherwise.
My 2 cents.
GregW
"3. Cutting a large radius on the roof of an exhaust port. (12A, or 13B) A generous radius is helpful if the exhaust port is close to stock size, but if it has been widened considerably, a large radius will absolutely kill the flow. This is one of the most sensitive areas of any of the ports in a rotary engine, and you can lose 10% to 15% flow in a hurry. The difference between a .050" radius, and a .070" radius can easily cost you 25 cfm."
http://www.yawpower.com/Flow%20Testing.html
03-02-2005, 02:03 AM
#13
Senior Member
Thread Starter
Join Date: Jun 2003
Location: Grand Prairie, TX
Posts: 917
Originally Posted by rotarygod' date='Mar 2 2005, 12:00 AM
Check out this article on airflow from Paul Yaw. You may have already seen it. I'll copy and paste one particular sentence though.
"3. Cutting a large radius on the roof of an exhaust port. (12A, or 13B) A generous radius is helpful if the exhaust port is close to stock size, but if it has been widened considerably, a large radius will absolutely kill the flow. This is one of the most sensitive areas of any of the ports in a rotary engine, and you can lose 10% to 15% flow in a hurry. The difference between a .050" radius, and a .070" radius can easily cost you 25 cfm."
http://www.yawpower.com/Flow%20Testing.html
"3. Cutting a large radius on the roof of an exhaust port. (12A, or 13B) A generous radius is helpful if the exhaust port is close to stock size, but if it has been widened considerably, a large radius will absolutely kill the flow. This is one of the most sensitive areas of any of the ports in a rotary engine, and you can lose 10% to 15% flow in a hurry. The difference between a .050" radius, and a .070" radius can easily cost you 25 cfm."
http://www.yawpower.com/Flow%20Testing.html
Hi Fred, long time no talk buddy
B
03-02-2005, 03:25 AM
#14
Junior Member
Join Date: Oct 2004
Posts: 12
B.D.C, great port work looks stunning, but have two questions? Why did you not carry the 2mm radius around the exhaust ports and also how come you have not rounded the closing line on the inlet ports as per Itos comments and Lynes comments! it is great to have this site as it is far more informative than any site here in australia they are to secretive here! keep up the great work and information sharing!
03-02-2005, 12:50 PM
#17
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Thread Starter
Join Date: Jun 2003
Location: Grand Prairie, TX
Posts: 917
Originally Posted by DAT.rota' date='Mar 2 2005, 01:24 AM
B.D.C, great port work looks stunning, but have two questions? Why did you not carry the 2mm radius around the exhaust ports and also how come you have not rounded the closing line on the inlet ports as per Itos comments and Lynes comments! it is great to have this site as it is far more informative than any site here in australia they are to secretive here! keep up the great work and information sharing!
Hey DAT, I didn't round the closing edge of the intake port because I didn't extend the width of the port outlet any. These secondary intake ports were left skinnier on purpose; they have future use as bridgeports. I didn't take any of the iron out towards the inner o-ring land for the purpose of having a thicker bridge for a bridgeport later. Hence, I found no need to round out the closing edge if the side seal is not exposed to the open hole of the port outlet.
B
03-02-2005, 01:45 PM
#19
Senior Member
Join Date: Dec 2003
Location: Minneapolis,MN
Posts: 500
Originally Posted by BDC' date='Mar 2 2005, 10:50 AM
Hey DAT, I didn't round the closing edge of the intake port because I didn't extend the width of the port outlet any. These secondary intake ports were left skinnier on purpose; they have future use as bridgeports. I didn't take any of the iron out towards the inner o-ring land for the purpose of having a thicker bridge for a bridgeport later. Hence, I found no need to round out the closing edge if the side seal is not exposed to the open hole of the port outlet.
B
B
I still "think" every port flows better with a sligt curv on the exit. The air along the port wall is laminar(wants to stay connected to the wall) a slight curv helps it spread out into the chamber better and sling shots the air above it better than a 90 deg turn that just creates vortecies arround its perimiter.
Velocity stacks use the same principal.
Thats what me and DAT are getting at. With or without a BP, with or witout comprimising the side seal, its an added edge over those who dont do it.
You can screw this up though as paul yaw wrote about. Think of the inside air (not the laminar air) like tubing behind a boat. When you make a quick(radius) yet not abrupt(90) turn the tube is going much faster than the boat. If you make a 90 degree turn the boat nearly stops and the tube does the same shortly after. The oppisite happens with a large radius. Not engough sling shot and the air moves slower.
The radus essentailly supercharges the air and it can keep doing so becuse the laminar air has enough velocity becuse of the radius to get out of the way and keep pulling in more air and accelertating it.
Thats how it was explained to me by a guy in Southern MN that has engines he built running in NASCAR.
Like I said though, great work!
03-02-2005, 01:48 PM
#20
Senior Member
Join Date: Dec 2003
Location: Minneapolis,MN
Posts: 500
B, could you please post a pic or a link of the abrasives your using to get that finish consistantly through the port.
I know you posted it onece before but I lost all my links and cant find **** anymore.
Thanks
GregW
I know you posted it onece before but I lost all my links and cant find **** anymore.
Thanks
GregW