Cutting grooves in intake manifold?
11-21-06, 08:42 PM
#26
Reversion can also have advantages, i.e., think dynamic intake charge. This is where the 'bounce back' helps fill/pre-charge the other housing. That is a good portion of the hp gain between the S5 over the S4 engines. The redsign of the intake makes better use of this.
Fwiw, the exhaust ports need to be as smooth as possible, even polished. Adding grooves will only provide an additional place for carbon deposits to build up, making flow even worse.
Fwiw, the exhaust ports need to be as smooth as possible, even polished. Adding grooves will only provide an additional place for carbon deposits to build up, making flow even worse.
11-21-06, 08:49 PM
#27
Airflow is my life
Very true. Also wave tuning/Hemholtz chambers can also have a "supercharging" effect. Its a very complicated deal on a wet flow intake. Check out ENDYN and www.theoldone.com for some interesting reading. While they develop piston engines, the theories about flow are universal and theres still much to be learned. 
On noes! One more post and Ill have a scary number.
On noes! One more post and Ill have a scary number.
11-21-06, 09:03 PM
#28
Respecognize!
so for my future 12 BP project, i was original planning on running a 1/2 BP. now could i perfect this a bit, and run a full BP or a larger streetport in conjunction with the 1/2 BP than i originally could given a set desired driveability?
11-21-06, 09:39 PM
#29
Originally Posted by Jeff20B
... I added a channeled spacer to my REPU's unchannled manifold and it produced similar results to a channeled manifold ... Those channels are where it's at!
Now I'm curious about cuts in the runners. I'm interested in anything that boosts ultra-low RPM performance ...
Now I'm curious about cuts in the runners. I'm interested in anything that boosts ultra-low RPM performance ...
i will probably put some cuts in mine after the engine gets broken in so i can maybe get some comparative data.
Originally Posted by vxturboxv
I noticed what feels like a small gain up top too 6-7500 rpm were the car would die down before it seems to pull clean through to redline now. But i'd assume this is just because of the port job.
11-21-06, 10:53 PM
#33
Originally Posted by Rx7carl
When the intake port closes, the charge in the manifold runner is still moving towards the chamber. Well when it hits the closed port it compresses (like a spring). Well once this packed charge (think compressed air) has enough energy to overcome the downward moving charge (which is also slowing down since theres no "pull" on it), the charge reverses direction and starts moving back up the runner. Well when the port opens again it takes considerably more energy and time to reverse and accelerate the charge back in the right direction. Net result is less fuel/air charge to fill the chamber before the port closes again which means less power and efficiency. This is critical at low RPM's when the port is open (and more importantly closed) for a longer duration of time. At hi rpms the time for reversion to occur is short because the port is closed for a much shorter period of time. So its not as big a factor. The intake is almost pulling in a forward direction all the time. Overly simplistic explanation but you get the idea.
i see the points made, but how come no one has brought up the turbelence effect from doing groove cutting on the intake side as well? sure it'll help intake reversion, but how about the turbelence created by the uneven cut channels?
i'm still skeptical...
11-21-06, 10:55 PM
#34
The General RE
Everyone seems to agree that grooveing the intake runners when using a carb sounds like it should work. No one tried to apply the second technique mentioned to rotaries and get the extra MPG promised. Increase turbulence in the combustion chamber with cuts too. But how to do this with a rotary? Can't groove the housings. The rotor seem like the only other choice. It may do something, it may not.
11-21-06, 11:02 PM
#35
The General RE
Originally Posted by d0 Luck
so could this also mean that a full aggressive BP will benefit from this (since it is laggy low-end)? wouldn't it also be disadvantageous at the same time since it is creating turbulence... kinda like a double edged sword i think.
i see the points made, but how come no one has brought up the turbelence effect from doing groove cutting on the intake side as well? sure it'll help intake reversion, but how about the turbelence created by the uneven cut channels?
i'm still skeptical...
i see the points made, but how come no one has brought up the turbelence effect from doing groove cutting on the intake side as well? sure it'll help intake reversion, but how about the turbelence created by the uneven cut channels?
i'm still skeptical...
Last edited by 13BT_RX3; 11-21-06 at 11:22 PM.
11-21-06, 11:42 PM
#36
Originally Posted by 13BT_RX3
Everyone seems to agree that grooveing the intake runners when using a carb sounds like it should work. No one tried to apply the second technique mentioned to rotaries and get the extra MPG promised. Increase turbulence in the combustion chamber with cuts too. But how to do this with a rotary? Can't groove the housings. The rotor seem like the only other choice. It may do something, it may not.
11-21-06, 11:49 PM
#37
Grooving the rotors may not help flow at all. What it will do is create hot spots at the tops of the ridges and places for carbon to build up in the grooves. The combustion chamber, i.e., housing/iron faces and rotor faces, need to be smooth to cut down on those 2 issues.
As far as how to improve laminar flow, I will defer to Purple82, as that is part of his occupation.
As far as how to improve laminar flow, I will defer to Purple82, as that is part of his occupation.
11-22-06, 02:24 AM
#38
Lives on the Forum
I agree. Any sharp points added to the combustion "chamber" will result in hot spots. These can cause early detonation of the fuel/air resulting in, um, "detonation". lol. Blowing up your apex seals is typically frowned upon... 
11-22-06, 08:17 AM
#39
The General RE
OK so that makes 4 of us that lack the vision to to risk an engine on this idea. Cutting grooves may not be the right fit for this aplication, but there may be something else that would work. It might be interesting to compare stock rough surface rotors to polished rotors. Maybe golfball dimples would do somthing to keep fuel suspended in the combustion chamber. Fuel suspension through turbulence is the goal right?
11-22-06, 08:46 AM
#40
Respecognize!
why not make the grooves start just inside the intake manifold and become increasingly aggressive into the intake port on the iron? that why the combustion chamber remains smooth but the desired turbulance occurs all the way until the edge of the intake tract.
11-22-06, 11:19 AM
#42
humm ... another thing that would happen with cutting grooves on the rotor slightly less compression (i might be wrong but would you not be increasing the space that it can be compressed into hence lower compression or do i have to hit the books again about that one)
The one that I've always thought about is cutting grooves, in a "spiral" shapes, to create like a "hurricane" wind in there, this would increase turbulance a bit, and make it act like a little longer due to the spiral effect ... this could all be bs ... but this is my theory on it.
The one that I've always thought about is cutting grooves, in a "spiral" shapes, to create like a "hurricane" wind in there, this would increase turbulance a bit, and make it act like a little longer due to the spiral effect ... this could all be bs ... but this is my theory on it.
11-22-06, 03:32 PM
#44
If one looks at the changes in rotors from the early ones to the REW rotors, one will notice a steady progression towards smoothing/machining of the bathtub combustion chamber. This is twofold. One, better manufacturing, two, to reduce detonation from carbon deposits.
If one were to groove the intake tract, I would be inclined to take it all the way from the top of the intake to the inner face of the iron. Spiraling may help, don't know. The inside of housing chamber itself must however remain as smooth as possible.
When one tears down an engine, they become acutely aware of how insidious carbon deposits can be and how tiny of an spot that it can begin to build up in. Cutting grooves in the rotor only allows for a greater build up and, in the long run, a greater danger to tossing a seal when one of these larger than average carbon chunks breaks loose.
If one were to groove the intake tract, I would be inclined to take it all the way from the top of the intake to the inner face of the iron. Spiraling may help, don't know. The inside of housing chamber itself must however remain as smooth as possible.
When one tears down an engine, they become acutely aware of how insidious carbon deposits can be and how tiny of an spot that it can begin to build up in. Cutting grooves in the rotor only allows for a greater build up and, in the long run, a greater danger to tossing a seal when one of these larger than average carbon chunks breaks loose.
11-22-06, 03:50 PM
#45
Watching how air reacts on a flow bench and knowing how to find 'dead' spots in the intake tract leads me to believe that a spiral would do nothing. Air with the velocities involved couldn't be 'steered' with grooves this small. One of the things I've heard from turbo guys is that they want to STOP the spinning of the air as it comes out of the turbo. You can actually get good flow from a banjo type exhaust manifold right after the turbo.
Grooves can be used in select areas to help air flow, or, if you have a high volume intake tract you can make it act smaller at low velocities and big at high velocities. The higher the air speed the less it is effected by the grooves. Driveability is all about air velocity.
I can't think of any advantage to grooving a rotor but I agree with all the negatives.
Grooves can be used in select areas to help air flow, or, if you have a high volume intake tract you can make it act smaller at low velocities and big at high velocities. The higher the air speed the less it is effected by the grooves. Driveability is all about air velocity.
I can't think of any advantage to grooving a rotor but I agree with all the negatives.
11-22-06, 04:50 PM
#47
The General RE
The spiral cuts would need to go one way in the northern hemisphere and the other in the southern hemisphere to harness Coriolis like when I flush my toilette.
11-23-06, 02:48 AM
#50
I agree with the carbon deposits being a problem.
But is it not possible with the cheap WB02 technology of today to run our cars lean and clean enough that carbon build up wouldn't be a problem?
I know I had zero carbon build up in my boosted "boinger" motors. This is ususally because I moniter and control my A/F ratio's. Usually 15ish:1 cruise and high tens low 11:1 wot. Also I use alcohol/water injection. I swear the motor I just pulled apart looked almost new and it has 120k on it... Even the heads and valves look extremly clean for a high mileage motor.
Is it possible to have a "clean burn" rotary? I'm definatly out of my element here but I don't see why not? Unless the oil injection causes it?
Either way the same thing could be said for piston motors. Why don't the grooves increase areas for carbon to build up in and cause hot spots/detonation as well??
But in all honesty I doubt much benefit would come from it... maybe a little better gas mileage and a little less detonation under boost? Not like we can bump our NA compression up to 11:1.
Not worth it IMO.
Interesting stuff though... Wish I had the money, time, and patience to groove some rotors. It would just be nice to know.
But is it not possible with the cheap WB02 technology of today to run our cars lean and clean enough that carbon build up wouldn't be a problem?
I know I had zero carbon build up in my boosted "boinger" motors. This is ususally because I moniter and control my A/F ratio's. Usually 15ish:1 cruise and high tens low 11:1 wot. Also I use alcohol/water injection. I swear the motor I just pulled apart looked almost new and it has 120k on it... Even the heads and valves look extremly clean for a high mileage motor.
Is it possible to have a "clean burn" rotary? I'm definatly out of my element here but I don't see why not? Unless the oil injection causes it?
Either way the same thing could be said for piston motors. Why don't the grooves increase areas for carbon to build up in and cause hot spots/detonation as well??
But in all honesty I doubt much benefit would come from it... maybe a little better gas mileage and a little less detonation under boost? Not like we can bump our NA compression up to 11:1.
Not worth it IMO.
Interesting stuff though... Wish I had the money, time, and patience to groove some rotors. It would just be nice to know.