Polishing intake runners - Page 2

***TitaniumTT*** · 11-14-2010, 03:39 PM

Here's how I do it.

Lets say you're matching the UIM to the LIM.

There are a few studs on the LIM so place the gasket over them. There should be little wiggle room but there will be some. If there is enough such that the gasket is interfering with the ports, you need to tape that gasket in place. But do this before you put a few bolts through the upper intake manifold and make sure the same thing doesn't occur.

Once you're satisfied that the gasket is in the right position and tapped off such that it won't move, assembly the sandwich. Take a small 3/32 or 1/16" drill bit and drill through the Upper intake mani, the gasket and into the LIM.

Remove upper intake.

Place drill bit through hole in gasket and into hole in LIM. Mark with whatever what needs to be ported.

Port

Place drill bits through UIM and gasket and mark with whatever what needs to be ported

Port

Clean throughoughly

Place drill bit through UIM, place gasket over drill bits, place gasket, UIM, and bits over LIM until bits fall into previously made holes on LIM.

Bolt UIM to LIM.

Remove drill bits.

PayPal me some form of compensation and go touch yourself repeatedly infront of the mirror while your neighbor watchs.

NoDOHC · 11-14-2010, 06:52 PM

I think you understand this issue better than most already.

The purpose of port matching is to avoid any steps in the intake runners (where the ports do not match) which impede flow.

There are various factors that can impede flow, one of which is a step in the pipe.

Bad flow results in a loss of power (pressure drop in the intake runners will reduce the pressure in the chamber when the intake port closes, thus decreasing the volumetric efficiency of the engine)

The air must flow at a certain velocity in the pipe in order to acheive a certain flow rate. Losses are related to velocity (slightly greater than the 2nd power). Larger diameter pipe will result in a lower velocity (fewer losses).

The effective diameter is what I call the center portion of the intake runner that is able to carry air (not effected by the boundary layer). The boundary area is determined by surface roughness of the material. Polishing the runners will decrease the boundary layer, increasing the effective diameter of the runner. Bear in mind that increasing the size of the runner has it's own implications.

Larger runners will help high end and hurt low end (due to fuel mixing problems and lack of energy for inertial or resonance tuning).

Please remember that with any intake-injected engine, it is not all about air flow, but fuel mixing and mixture distribution are equally important. On a DI engine, it is only air, so make it flow as well as you can.

On no account should the intake port be larger in cross-sectional area than the runner (unless this is a track-only engine). This will result in a poor low end performance and excessive fuel consumption as some of the fuel will fall out of suspension in the runner as it expands.

If a runner diameter can't be maintained constant, it should decrease area as it goes toward the engine as this will keep the fuel in suspension.

I wish I could explain this simply, maybe Vex can help me out:

Any step in the wall of the pipe disturbs the flow of the air, so does any change in cross-sectional area (as it requires a change in the velocity of the gas). Turns also create losses.

Basically, any time the air changes velocity (magnitude or direction) it requires energy to do so. This energy is absorbed from the incoming air as a pressure drop in the intake runner.

To make a long story short, what you say is true. If you gasket-match the intake manifold to the block without addressing the cross sectional ares of the intake runners or the block, it would probably have been better to have left it alone. If you gasket-match the intake and then make sure that the runners also match the cross-sectional ares of the intake manifold gaskets, you should have a very good flowing engine.

It is completely acceptable to polish the exhaust ports to a mirror-like finish. This will do no harm to the engine. It will have two effects:

Nominally better heat reflection (less exhaust heat absorbed by the inserts).
Slightly louder exhaust note (less sound energy absorbes by the exhaust ports).

Exhaust ports should increase in size as they leave the engine. sharp steps are a no-no, but the gas is expanding and cooling, so it will need more cross-sectional area as it moves away from the port.

My friend who taught me to port always said "If you think bigger is better, leave the exhaust port alone."

I hope this helps. It helped me when it was explained to me.

JustJeff · 11-14-2010, 07:20 PM

^NoDOHC

Makes perfect sense to me and helps solidfy what seemed logical in concept. Explaining it in terms of energy spent follows right along with what I was thinking.

My thoughts were that if you suddenly give pressurized air MORE space it's going to create "turbulance" as it expands. Then when the chamber/runner constricts back down it requires more energy to press the air back into the smaller area. You're pressing the air against an angled surface and the suspended fuel is going to hit the side and come out of suspension.

That scenario seems equally damaging to the process as having a lip exposed.

NoDOHC · 11-14-2010, 07:32 PM

The issue that we have with your runners is that we have to worry about both fuel suspension and air flow. The good news is that changes in area and steps will both hurt both.

I wish that I had dyno'ed my engine before the intake maifold modification, but I am reasonably sure that it helped.

***TitaniumTT*** · 11-15-2010, 07:21 AM

Agreed..... to a certain extent...
Smooth transitions are key. I had to open up the RE mani's to the point where I had to cut the gasket. To make sure they were always the same, I built a template out of some 1/4" AL so that I can quickly and accurately trim the gaskets. I then smoothed the runners and tapered them as much as possible. This was on the UIM to LIM. The LIM to the block was closer, but still a little off.

t_g_farrell · 11-15-2010, 12:18 PM

Just poking my nose in here for a second but what about reversion? Isn't that
supposed to be preserved when porting the intakes on a rotary?

***TitaniumTT*** · 11-15-2010, 01:14 PM

That's port timing, not port matching

***TitaniumTT*** · 11-15-2010, 01:22 PM

It's definately a good discussion to have but it's a whole different can of worms that's been opened a few times before. However, you're right, and it should be preserved. It's one of the reasons I believe that when it comes to port timing, less is more when porting. For example, I never touch the closing of the exhaust or the opening of the intake......

***TitaniumTT*** · 11-15-2010, 10:08 PM

It's the little details that make an entire package perform at it's peak.

Take mine for example

And FWIW, I'm an OCD perfectionist as well.

scotty305 · 11-16-2010, 12:04 AM

Cool thread. I have occasional access to a flow bench if people are interested in before/after testing or comparisons. There are some rough assumptions that must be made: mainly that the engine doesn't suck a smooth steady stream of air like the pump in the flowbench, there are quick pressure (vacuum) fluctuations as the engine 'gulps' air in while the intake ports are open. It will probably be a while before I get around to testing intake manifold porting or modifications on my car, but if anyone local wants to stop by and measure their setup(s) feel free to send a PM.

11-14-2010, 03:39 PM	#1
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	Here's how I do it. Lets say you're matching the UIM to the LIM. There are a few studs on the LIM so place the gasket over them. There should be little wiggle room but there will be some. If there is enough such that the gasket is interfering with the ports, you need to tape that gasket in place. But do this before you put a few bolts through the upper intake manifold and make sure the same thing doesn't occur. Once you're satisfied that the gasket is in the right position and tapped off such that it won't move, assembly the sandwich. Take a small 3/32 or 1/16" drill bit and drill through the Upper intake mani, the gasket and into the LIM. Remove upper intake. Place drill bit through hole in gasket and into hole in LIM. Mark with whatever what needs to be ported. Port Place drill bits through UIM and gasket and mark with whatever what needs to be ported Port Clean throughoughly Place drill bit through UIM, place gasket over drill bits, place gasket, UIM, and bits over LIM until bits fall into previously made holes on LIM. Bolt UIM to LIM. Remove drill bits. PayPal me some form of compensation and go touch yourself repeatedly infront of the mirror while your neighbor watchs. __________________ -The Angry Stig- DGRR 2009, 2011, 2012 & 2013 - Best FC DEALS GAP!! WOOHOOOO!!!!! 2015 Audi S4 - Samantha - Zero Brap S4 2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter 2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins 1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle 1988 'Vert - In progress 1988 FC Coupe - Gretchen -The attention whore BEAST! I'm a sick individual, what's wrong with you? I'm pure Evil I'm still insane, in the best possible way. I think Brian's idea of romance is using lube. Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion. You win with your thread. Most everything It's a truck with a steel gate on the back. Just a statement of fact Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff.... No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon. *-Angry Motherfcker Mode ENGAGED-**

11-14-2010, 06:52 PM	#2
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	I think you understand this issue better than most already. The purpose of port matching is to avoid any steps in the intake runners (where the ports do not match) which impede flow. There are various factors that can impede flow, one of which is a step in the pipe. Bad flow results in a loss of power (pressure drop in the intake runners will reduce the pressure in the chamber when the intake port closes, thus decreasing the volumetric efficiency of the engine) The air must flow at a certain velocity in the pipe in order to acheive a certain flow rate. Losses are related to velocity (slightly greater than the 2nd power). Larger diameter pipe will result in a lower velocity (fewer losses). The effective diameter is what I call the center portion of the intake runner that is able to carry air (not effected by the boundary layer). The boundary area is determined by surface roughness of the material. Polishing the runners will decrease the boundary layer, increasing the effective diameter of the runner. Bear in mind that increasing the size of the runner has it's own implications. Larger runners will help high end and hurt low end (due to fuel mixing problems and lack of energy for inertial or resonance tuning). Please remember that with any intake-injected engine, it is not all about air flow, but fuel mixing and mixture distribution are equally important. On a DI engine, it is only air, so make it flow as well as you can. On no account should the intake port be larger in cross-sectional area than the runner (unless this is a track-only engine). This will result in a poor low end performance and excessive fuel consumption as some of the fuel will fall out of suspension in the runner as it expands. If a runner diameter can't be maintained constant, it should decrease area as it goes toward the engine as this will keep the fuel in suspension. I wish I could explain this simply, maybe Vex can help me out: Any step in the wall of the pipe disturbs the flow of the air, so does any change in cross-sectional area (as it requires a change in the velocity of the gas). Turns also create losses. Basically, any time the air changes velocity (magnitude or direction) it requires energy to do so. This energy is absorbed from the incoming air as a pressure drop in the intake runner. To make a long story short, what you say is true. If you gasket-match the intake manifold to the block without addressing the cross sectional ares of the intake runners or the block, it would probably have been better to have left it alone. If you gasket-match the intake and then make sure that the runners also match the cross-sectional ares of the intake manifold gaskets, you should have a very good flowing engine. It is completely acceptable to polish the exhaust ports to a mirror-like finish. This will do no harm to the engine. It will have two effects: Nominally better heat reflection (less exhaust heat absorbed by the inserts). Slightly louder exhaust note (less sound energy absorbes by the exhaust ports). Exhaust ports should increase in size as they leave the engine. sharp steps are a no-no, but the gas is expanding and cooling, so it will need more cross-sectional area as it moves away from the port. My friend who taught me to port always said "If you think bigger is better, leave the exhaust port alone." I hope this helps. It helped me when it was explained to me. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic) Last edited by NoDOHC; 11-14-2010 at 06:55 PM.

11-14-2010, 07:32 PM	#4
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	The issue that we have with your runners is that we have to worry about both fuel suspension and air flow. The good news is that changes in area and steps will both hurt both. I wish that I had dyno'ed my engine before the intake maifold modification, but I am reasonably sure that it helped. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

11-15-2010, 07:21 AM	#5
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	Agreed..... to a certain extent... Smooth transitions are key. I had to open up the RE mani's to the point where I had to cut the gasket. To make sure they were always the same, I built a template out of some 1/4" AL so that I can quickly and accurately trim the gaskets. I then smoothed the runners and tapered them as much as possible. This was on the UIM to LIM. The LIM to the block was closer, but still a little off. __________________ -The Angry Stig- DGRR 2009, 2011, 2012 & 2013 - Best FC DEALS GAP!! WOOHOOOO!!!!! 2015 Audi S4 - Samantha - Zero Brap S4 2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter 2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins 1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle 1988 'Vert - In progress 1988 FC Coupe - Gretchen -The attention whore BEAST! I'm a sick individual, what's wrong with you? I'm pure Evil I'm still insane, in the best possible way. I think Brian's idea of romance is using lube. Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion. You win with your thread. Most everything It's a truck with a steel gate on the back. Just a statement of fact Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff.... No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon. *-Angry Motherfcker Mode ENGAGED-**

11-15-2010, 12:18 PM	#6
t_g_farrell Waffles - hmmm good Join Date: Aug 2008 Location: Huntersville, NC Posts: 757 Rep Power: 0	Just poking my nose in here for a second but what about reversion? Isn't that supposed to be preserved when porting the intakes on a rotary? __________________ 1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs Project Fat Nikki Budget 12A rebuild Video setup < $30.00

11-14-2010, 07:20 PM	#3
JustJeff RCC Contributor Join Date: Mar 2008 Posts: 505 Rep Power: 18	^NoDOHC Makes perfect sense to me and helps solidfy what seemed logical in concept. Explaining it in terms of energy spent follows right along with what I was thinking. My thoughts were that if you suddenly give pressurized air MORE space it's going to create "turbulance" as it expands. Then when the chamber/runner constricts back down it requires more energy to press the air back into the smaller area. You're pressing the air against an angled surface and the suspended fuel is going to hit the side and come out of suspension. That scenario seems equally damaging to the process as having a lip exposed.

11-15-2010, 01:14 PM	#7
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	That's port timing, not port matching __________________ -The Angry Stig- DGRR 2009, 2011, 2012 & 2013 - Best FC DEALS GAP!! WOOHOOOO!!!!! 2015 Audi S4 - Samantha - Zero Brap S4 2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter 2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins 1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle 1988 'Vert - In progress 1988 FC Coupe - Gretchen -The attention whore BEAST! I'm a sick individual, what's wrong with you? I'm pure Evil I'm still insane, in the best possible way. I think Brian's idea of romance is using lube. Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion. You win with your thread. Most everything It's a truck with a steel gate on the back. Just a statement of fact Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff.... No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon. *-Angry Motherfcker Mode ENGAGED-**

11-15-2010, 01:22 PM	#8
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	It's definately a good discussion to have but it's a whole different can of worms that's been opened a few times before. However, you're right, and it should be preserved. It's one of the reasons I believe that when it comes to port timing, less is more when porting. For example, I never touch the closing of the exhaust or the opening of the intake...... __________________ -The Angry Stig- DGRR 2009, 2011, 2012 & 2013 - Best FC DEALS GAP!! WOOHOOOO!!!!! 2015 Audi S4 - Samantha - Zero Brap S4 2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter 2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins 1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle 1988 'Vert - In progress 1988 FC Coupe - Gretchen -The attention whore BEAST! I'm a sick individual, what's wrong with you? I'm pure Evil I'm still insane, in the best possible way. I think Brian's idea of romance is using lube. Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion. You win with your thread. Most everything It's a truck with a steel gate on the back. Just a statement of fact Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff.... No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon. *-Angry Motherfcker Mode ENGAGED-**

11-15-2010, 10:08 PM	#9
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	It's the little details that make an entire package perform at it's peak. Take mine for example And FWIW, I'm an OCD perfectionist as well. __________________ -The Angry Stig- DGRR 2009, 2011, 2012 & 2013 - Best FC DEALS GAP!! WOOHOOOO!!!!! 2015 Audi S4 - Samantha - Zero Brap S4 2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter 2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins 1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle 1988 'Vert - In progress 1988 FC Coupe - Gretchen -The attention whore BEAST! I'm a sick individual, what's wrong with you? I'm pure Evil I'm still insane, in the best possible way. I think Brian's idea of romance is using lube. Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion. You win with your thread. Most everything It's a truck with a steel gate on the back. Just a statement of fact Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff.... No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon. *-Angry Motherfcker Mode ENGAGED-**

11-16-2010, 12:04 AM	#10
scotty305 Rotary Fan in Training Join Date: Mar 2008 Location: Culver City, CA Posts: 84 Rep Power: 18	Cool thread. I have occasional access to a flow bench if people are interested in before/after testing or comparisons. There are some rough assumptions that must be made: mainly that the engine doesn't suck a smooth steady stream of air like the pump in the flowbench, there are quick pressure (vacuum) fluctuations as the engine 'gulps' air in while the intake ports are open. It will probably be a while before I get around to testing intake manifold porting or modifications on my car, but if anyone local wants to stop by and measure their setup(s) feel free to send a PM.