Custom built intake questions
Thread Starter
Ooooooh, custom.
Joined: Oct 2006
Posts: 618
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From: Corona, CA
Custom built intake questions
Okay, this is for my current motor build. It will be a couple(x10) paychecks before this has a chance to see fruition, but my hope is something around, at, or above 200hp while staying naturally aspirated.
I am in the process of porting a 6 port NA motor, with a pineapple racing large street port template. Theres about a 1/16th of material between the 5th/6th port caves on the rotor side. Here's where the questions start:
Because I want to make my own short ram aluminum intake with a throttle body /or bodies for each rotor (I have all the tools needed to do so, fabrication knowledge included) what would happen if I were to remove the partition between the 5th/6th port (from the manifold side, where you would insert the 6th port actuator), up to the point where it has the hole drilled between the two, and then knife edge it? Does anyone know of any issues that this would cause? It kinda seems to me that it acts as support for the surface the rotor rides on...though it doesnt seem like it would have a whole lot of pressure there, since its the intake corner of the engine. Has anyone done this? And if so, good or bad results?
Question 2. Pineapple racing makes some 6th port actuator pieces to smooth out the airflow into the engine...but does anyone make a shaped piece for just the hole where it would go?
Link to what im talking about: http://www.pineappleracing.com/index...PROD&ProdID=11
Question 3, I have a general idea on how I want the manifold I would make to look/how it would enter the engine, but does anyone have specific details on what they have done, and how well it works? Most importantly, runner length and diameter.
I dont build engines for a living...but my RX7 is a fun project, and like all projects, I want to have fun, and try different stuff. That, and I sure as hell cant pay someone to do all this for me.
Thanks for any input.
I am in the process of porting a 6 port NA motor, with a pineapple racing large street port template. Theres about a 1/16th of material between the 5th/6th port caves on the rotor side. Here's where the questions start:
Because I want to make my own short ram aluminum intake with a throttle body /or bodies for each rotor (I have all the tools needed to do so, fabrication knowledge included) what would happen if I were to remove the partition between the 5th/6th port (from the manifold side, where you would insert the 6th port actuator), up to the point where it has the hole drilled between the two, and then knife edge it? Does anyone know of any issues that this would cause? It kinda seems to me that it acts as support for the surface the rotor rides on...though it doesnt seem like it would have a whole lot of pressure there, since its the intake corner of the engine. Has anyone done this? And if so, good or bad results?
Question 2. Pineapple racing makes some 6th port actuator pieces to smooth out the airflow into the engine...but does anyone make a shaped piece for just the hole where it would go?
Link to what im talking about: http://www.pineappleracing.com/index...PROD&ProdID=11
Question 3, I have a general idea on how I want the manifold I would make to look/how it would enter the engine, but does anyone have specific details on what they have done, and how well it works? Most importantly, runner length and diameter.
I dont build engines for a living...but my RX7 is a fun project, and like all projects, I want to have fun, and try different stuff. That, and I sure as hell cant pay someone to do all this for me.
Thanks for any input.
Do not remove that wall. There's more to the 6 port engines than just flow. There's pressure. The 6 port engines have a unique phenomenon that allows them to develop roughly the same potential horsepower as a 4 port even though in static flow tests they don't do as well. It's because it's not only about that. Flow is important but it's not all there is.
On the 6 port engines, as the rotor turns and starts closing the intake ports, it closes them from the bottom up. I'm going to ignore the primary port and only concentrate on the side plates. The bottom port which is the secondary, gets closed off completely before the auxiliary port even starts to close. When this happens, the air in the intake runner has to go somewhere. Air has mass and velocity. This air doesn't just stop flowing instantly when the ports close. Further up the runner it is still moving and trying to compress the rest of the air ahead of it into something. It's only when there is nowhere to go that flow stops and the pressure wave reverses.
On the 6 port engines, when the secondary port closes this air in the runners is still moving towards the engine. It only has one place to go and that is the auxiliary ports. The air compresses itself into this runner as the auxiliary port is closing which forces a bit more air into the motor. If you remove this wall, you have killed velocity when the secondary port closes. It also increases area in the port runners in the plates which slows velocity down. That's a bad thing. The same phenomenon does not happen as all you are doing is effectively showing the intake runners a single large port even though they still have a wall at the port opening. Larger is almost never better yet everyone always wants larger. It is very easy to get 200 rwhp on a 6 port 13B with a stock intake manifold yet everyone makes the same mistakes over and over again. do not do auxiliary bridgeporting. It's a waste of a good engine. Do not go as large as you possibly can before dropping in a seal. FWIW: Even the Pineapple sleeves only add about 1 cfm of airflow at 28" H2O measured but remember it's not all about flow.
Build the engine conventionally. It's the best way. Port it according to the template port shape. Don't try to improve it. concentrate on the transition inside the port from the runners to the engine. Also don't get too carried away on real short intake runners. You'd be surprised at how long you really want. The length better be into the double digits inches wise. Start long and then shorten as needed. Not the other way around.
Above all else, remember what you try and take note of what works and doesn't. You'll learn alot this way. Have fun with it but don't repeat the mistakes that everyone else thinks they can somehow fix but can't.
On the 6 port engines, as the rotor turns and starts closing the intake ports, it closes them from the bottom up. I'm going to ignore the primary port and only concentrate on the side plates. The bottom port which is the secondary, gets closed off completely before the auxiliary port even starts to close. When this happens, the air in the intake runner has to go somewhere. Air has mass and velocity. This air doesn't just stop flowing instantly when the ports close. Further up the runner it is still moving and trying to compress the rest of the air ahead of it into something. It's only when there is nowhere to go that flow stops and the pressure wave reverses.
On the 6 port engines, when the secondary port closes this air in the runners is still moving towards the engine. It only has one place to go and that is the auxiliary ports. The air compresses itself into this runner as the auxiliary port is closing which forces a bit more air into the motor. If you remove this wall, you have killed velocity when the secondary port closes. It also increases area in the port runners in the plates which slows velocity down. That's a bad thing. The same phenomenon does not happen as all you are doing is effectively showing the intake runners a single large port even though they still have a wall at the port opening. Larger is almost never better yet everyone always wants larger. It is very easy to get 200 rwhp on a 6 port 13B with a stock intake manifold yet everyone makes the same mistakes over and over again. do not do auxiliary bridgeporting. It's a waste of a good engine. Do not go as large as you possibly can before dropping in a seal. FWIW: Even the Pineapple sleeves only add about 1 cfm of airflow at 28" H2O measured but remember it's not all about flow.
Build the engine conventionally. It's the best way. Port it according to the template port shape. Don't try to improve it. concentrate on the transition inside the port from the runners to the engine. Also don't get too carried away on real short intake runners. You'd be surprised at how long you really want. The length better be into the double digits inches wise. Start long and then shorten as needed. Not the other way around.
Above all else, remember what you try and take note of what works and doesn't. You'll learn alot this way. Have fun with it but don't repeat the mistakes that everyone else thinks they can somehow fix but can't.
Thread Starter
Ooooooh, custom.
Joined: Oct 2006
Posts: 618
Likes: 0
From: Corona, CA
Do not remove that wall. There's more to the 6 port engines than just flow. There's pressure. The 6 port engines have a unique phenomenon that allows them to develop roughly the same potential horsepower as a 4 port even though in static flow tests they don't do as well. It's because it's not only about that. Flow is important but it's not all there is.
On the 6 port engines, as the rotor turns and starts closing the intake ports, it closes them from the bottom up. I'm going to ignore the primary port and only concentrate on the side plates. The bottom port which is the secondary, gets closed off completely before the auxiliary port even starts to close. When this happens, the air in the intake runner has to go somewhere. Air has mass and velocity. This air doesn't just stop flowing instantly when the ports close. Further up the runner it is still moving and trying to compress the rest of the air ahead of it into something. It's only when there is nowhere to go that flow stops and the pressure wave reverses.
On the 6 port engines, when the secondary port closes this air in the runners is still moving towards the engine. It only has one place to go and that is the auxiliary ports. The air compresses itself into this runner as the auxiliary port is closing which forces a bit more air into the motor. If you remove this wall, you have killed velocity when the secondary port closes. It also increases area in the port runners in the plates which slows velocity down. That's a bad thing. The same phenomenon does not happen as all you are doing is effectively showing the intake runners a single large port even though they still have a wall at the port opening. Larger is almost never better yet everyone always wants larger. It is very easy to get 200 rwhp on a 6 port 13B with a stock intake manifold yet everyone makes the same mistakes over and over again. do not do auxiliary bridgeporting. It's a waste of a good engine. Do not go as large as you possibly can before dropping in a seal. FWIW: Even the Pineapple sleeves only add about 1 cfm of airflow at 28" H2O measured but remember it's not all about flow.
Build the engine conventionally. It's the best way. Port it according to the template port shape. Don't try to improve it. concentrate on the transition inside the port from the runners to the engine. Also don't get too carried away on real short intake runners. You'd be surprised at how long you really want. The length better be into the double digits inches wise. Start long and then shorten as needed. Not the other way around.
Above all else, remember what you try and take note of what works and doesn't. You'll learn alot this way. Have fun with it but don't repeat the mistakes that everyone else thinks they can somehow fix but can't.
On the 6 port engines, as the rotor turns and starts closing the intake ports, it closes them from the bottom up. I'm going to ignore the primary port and only concentrate on the side plates. The bottom port which is the secondary, gets closed off completely before the auxiliary port even starts to close. When this happens, the air in the intake runner has to go somewhere. Air has mass and velocity. This air doesn't just stop flowing instantly when the ports close. Further up the runner it is still moving and trying to compress the rest of the air ahead of it into something. It's only when there is nowhere to go that flow stops and the pressure wave reverses.
On the 6 port engines, when the secondary port closes this air in the runners is still moving towards the engine. It only has one place to go and that is the auxiliary ports. The air compresses itself into this runner as the auxiliary port is closing which forces a bit more air into the motor. If you remove this wall, you have killed velocity when the secondary port closes. It also increases area in the port runners in the plates which slows velocity down. That's a bad thing. The same phenomenon does not happen as all you are doing is effectively showing the intake runners a single large port even though they still have a wall at the port opening. Larger is almost never better yet everyone always wants larger. It is very easy to get 200 rwhp on a 6 port 13B with a stock intake manifold yet everyone makes the same mistakes over and over again. do not do auxiliary bridgeporting. It's a waste of a good engine. Do not go as large as you possibly can before dropping in a seal. FWIW: Even the Pineapple sleeves only add about 1 cfm of airflow at 28" H2O measured but remember it's not all about flow.
Build the engine conventionally. It's the best way. Port it according to the template port shape. Don't try to improve it. concentrate on the transition inside the port from the runners to the engine. Also don't get too carried away on real short intake runners. You'd be surprised at how long you really want. The length better be into the double digits inches wise. Start long and then shorten as needed. Not the other way around.
Above all else, remember what you try and take note of what works and doesn't. You'll learn alot this way. Have fun with it but don't repeat the mistakes that everyone else thinks they can somehow fix but can't.
True that it isnt all about flow, there's velocity and actual mass/ratio of the Air fuel mix that you have to get in there, etc.
The ports are clean, I tried to transition them very smoothly from the runner to the rotor surface. I dont want to run a bridge or aux bridge, that just seems a bit too much work/headache for what im looking for...which is a fairly reliable, low (ish) cost, high RPM (7-9k), decent horsepower track motor.
I really dont want to run 6th port actuators, I dont want all the vacuum gizmos hanging off of there...call me crazy but I like when I dont have to rely on other systems to work properly (even well designed ones) for my engine to function correctly. Would it be alright to leave those out and then make something like pineapple did for just that hole? Again, even if it doesnt clean up a whole lot, or improve flow, it has to get rid of a little turbulence at the very least.
Another question...should I still run the manifold to the engine as 6 ports, or would it be fine as 4, and then knife edge the leading area of the split on the block? This is my first build...and I really dont know the standard mistakes...which is why I am here asking first, and doing second. Youve explained everything I was curious about so far...thank you for that. I found a company out of canada that makes an aluminum 6 port flange...seems like the ticket, only 45 dollars+shipping last time I saw it.
To test different runner lengths, could I just change the bell on top of the throttle body (extend/shorten it) to provide the proper length, or would it be better to do that AFTER the throttle body?
Again, thanks for the info.
If you can, you want to keep the manifold runners in the 6 port configuration rather than one large one with a knife edged housing.
Most of the flow issues are actually due to the auxiliary port actuator rods and not the sleeves. The rods take up lots of area relatively speaking and also disrupt flow. With the rods in place, the turbulence is so bad through the upper ports that the Pineapple inserts don't do much. Without those rods in place however flow is improved and the benefit from the inserts is greater. An even better suggestion is to not use the sleeves but rather add the radius directly to the runner itself. This way you aren't losing the area of the sleeve thickness. If you go this route, epoxy is the easiest method. You must be very careful to have the runner cleaned and roughed up for the epoxy to adhere good. I've used this method on 2 different cars over many years and have never had a problem.
Runner length is runner length. At full throttle with the throttle plates open all the way, it doesn't matter where your intake runner length is or even where a plenum is in the system as the plates are effectively invisible. At part throttle however you may see some tuning differences due to the throttle plates effects on air flow. You'll just have to experiment with this one. If you have the time and it isn't too much trouble, devise a setup that would allow you to try each design. You may find the results interesting and fun.
Most of the flow issues are actually due to the auxiliary port actuator rods and not the sleeves. The rods take up lots of area relatively speaking and also disrupt flow. With the rods in place, the turbulence is so bad through the upper ports that the Pineapple inserts don't do much. Without those rods in place however flow is improved and the benefit from the inserts is greater. An even better suggestion is to not use the sleeves but rather add the radius directly to the runner itself. This way you aren't losing the area of the sleeve thickness. If you go this route, epoxy is the easiest method. You must be very careful to have the runner cleaned and roughed up for the epoxy to adhere good. I've used this method on 2 different cars over many years and have never had a problem.
Runner length is runner length. At full throttle with the throttle plates open all the way, it doesn't matter where your intake runner length is or even where a plenum is in the system as the plates are effectively invisible. At part throttle however you may see some tuning differences due to the throttle plates effects on air flow. You'll just have to experiment with this one. If you have the time and it isn't too much trouble, devise a setup that would allow you to try each design. You may find the results interesting and fun.
Thread Starter
Ooooooh, custom.
Joined: Oct 2006
Posts: 618
Likes: 0
From: Corona, CA
That I can do. Like I said, that aluminum flange is set up for the hole pattern for the 6 port. From there it would just mean I would have to get slightly more creative with how to make the runners...I have a couple ideas, Ill try to mock each one up and get some pictures going.
How rough are we talking here? I have carbide cutters, and some 40 grit...would that be enough, or do you have another recomendation? What kind/style of epoxy?
Another thing that just occured to me...if I were to buy those pieces, or make some that were a slightly better fit (or just weld the pineapple ones into the actuator, cut it shorter, bevel it, and then drop that in there) Could I drill through to the coolant jacket, tap it, and then put a set screw in there with some sealant or pipe tape on it, and then weld up the drilled hold on the radius, as well as use some epoxy for more of a double redudant type thing? I just dont trust glue around hot metal parts, especially when some of them are spinning.
Thank you again.
How rough are we talking here? I have carbide cutters, and some 40 grit...would that be enough, or do you have another recomendation? What kind/style of epoxy?
Another thing that just occured to me...if I were to buy those pieces, or make some that were a slightly better fit (or just weld the pineapple ones into the actuator, cut it shorter, bevel it, and then drop that in there) Could I drill through to the coolant jacket, tap it, and then put a set screw in there with some sealant or pipe tape on it, and then weld up the drilled hold on the radius, as well as use some epoxy for more of a double redudant type thing? I just dont trust glue around hot metal parts, especially when some of them are spinning.
Thank you again.
