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intake manifond for 3 47mm tb's

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Old 10-29-07, 10:52 PM
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intake manifond for 3 47mm tb's

so i am going to run a half-bridge n/a race engine with extended street ported primaries, i am planing to fabricate a manifold that has a shared throttle for the primaries and 2 additional tb's for the secondaries which will open after 4,000- 4,500 rpm.

i am recycling some 47mm carbs from an out-board engine that i will convert to itb's
i will use the aluminum throttle plates and each runner will have an oil fitting for the OMP. as for the manifold im still working on the runner lengths and other crucial features but this is basically what i am planing to build.
Attached Thumbnails intake manifond for 3 47mm tb's-manifold.jpg   intake manifond for 3 47mm tb's-itb-003.jpg   intake manifond for 3 47mm tb's-itb-004.jpg  
Old 10-30-07, 03:43 AM
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sounds interesting. what sort of injector setup are you thinking about?
Old 10-30-07, 09:24 AM
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Interesting. Keep us posted. Definitely a little different than the Hayabusa route some of us are going. Good luck!
Old 10-30-07, 09:39 AM
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I'm planning on going individual tb pretty soon and am running half bridge as well.. May I ask the reasoning behind staging the secondaries?
Old 10-30-07, 12:09 PM
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this is to help out with low end power and better throttle response

as for injectors i haven't calculated what i need yet but 750/1200 is probably enough without runing them too high a duty cycle i also wanna set-up the ecu with a 93octane map and one for e-85 < poor mans race fuel lol.
Old 10-30-07, 02:42 PM
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If I were you, I'd run smaller injectors with higher fuel pressure. This will help atomization a ton... We run 460/720 at 75psi making 250+whp, duty cycles in the high 40's..

The bridge will still be working even with the throttle plates closed on the secondaries. Even though the plates are closed, exhaust gases can still enter the port and fill the intake runner. To reduce the effect of the bridge, the throttle plates need to be as close to the motor as possible. You can still gain the benefits of a runner effect even if the plate is near the end of the runner rather than the opening of the runner.

I will be running prolly some gsxr tb's and get them as close to the engine as possible. I plan on removing the secondary tb butterflies in the primary tb's, but leave them in the 2ndary throttle bodies to let the motec control when they open. I'm just hoping to make my car more driveable under part throttle.
Old 10-30-07, 03:08 PM
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Originally Posted by 2a+RoN

The bridge will still be working even with the throttle plates closed on the secondaries. Even though the plates are closed, exhaust gases can still enter the port and fill the intake runner. To reduce the effect of the bridge, the throttle plates need to be as close to the motor as possible. You can still gain the benefits of a runner effect even if the plate is near the end of the runner rather than the opening of the runner.
i thought about this but these old carburetors have no gap between the throttle plate and the wall do you think this will be a problem? BTW, i will be welding the idle holes in the butterfly shut and all other holes, i will control idle with a bypass valve.
Attached Thumbnails intake manifond for 3 47mm tb's-itb-006.jpg   intake manifond for 3 47mm tb's-itb-005.jpg  
Old 10-30-07, 03:36 PM
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Originally Posted by Bluem
this is to help out with low end power and better throttle response

I'm glad you have an understanding about this. Most people here don't and always wonder why they loose so much low end. The Rx8 uses the exact same principle.
Old 11-04-07, 04:35 PM
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Originally Posted by t-von
I'm glad you have an understanding about this. Most people here don't and always wonder why they loose so much low end. The Rx8 uses the exact same principle.
It's no secret. Mazda has been doing it for YEARS prior to the RX8. What made the RX8 different is the extreme differences in runner lengths for the intake manifold.

Tuning an intake system for a rotary is more simlar to tuning an intake on a two stroke motor. The key to the game is port air velocity. the faster you can get the air moving early on the better. you don't want a large volume of slow moving air. Think of it like trying to use a stop sign to control cars merging on to a freeway rather than a yeild sign.

If you tune your exhaust correctly and acheive adequate scavenging you should also be able to tune your intake runner length on the primary runner to supply the ports with enough air velocity that exhaust back flow can be minimized.

To achieve greater port velocity on the primary runner you will want it to be long. I can't tell you a specific length because it matters on MANY factors. Port Timing, Port cross-sectional area, Port CFM and Port Turbulence. This is all further complicated by tuning for resonance. The engineers on the RX8 did a MASTERFUL job of tuning for resonance on the RX8. If you can take advantage of the energy released through sound waves moving back from the port towards the ITB and reflect those sound waves towards the port at a specific rpm range (power band) then you will be able to achieve some serious power and torque numbers.

Ray
Old 11-05-07, 02:30 PM
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plan b (constantly adjustable runner length)

if i can find u bends or rings with the proper i.d. and o.d and same radius that will fit one inside another like a telescoping bend i will go with plan B and use a step motor to control runner length with the ecu
Old 11-05-07, 03:23 PM
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here are some solid works pictures of the assembly
Attached Thumbnails intake manifond for 3 47mm tb's-13b-intake-cut.jpg   intake manifond for 3 47mm tb's-telescoping-manifold-assembly.jpg  
Old 11-05-07, 03:39 PM
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small but powerful step motor, i lifted 25lbs. with this little sucker quite quick with a faster gear ratio than i will use with the manifold, if its too slow i have another one that is about twice as powerful that i scavenged out of an old copy machine.

bi-polar 1.8 degree/step motor and the Ericsson micro electronics dual step controller
i will use (pbl3775/1)

i love picking up e-garbage lol!
Attached Thumbnails intake manifond for 3 47mm tb's-itb-009.jpg   intake manifond for 3 47mm tb's-itb-010.jpg  
Old 11-05-07, 11:52 PM
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Originally Posted by GTRay
It's no secret. Mazda has been doing it for YEARS prior to the RX8. What made the RX8 different is the extreme differences in runner lengths for the intake manifold. Ray

I know what you mean but I was comparing to the Rx8 because of the electronic delay of the secondary's that open at a specific rpm. The older rotarys had the mechanical linkage to the secondary throttle plates that did the same thing (exept they opened much sooner).
Old 11-05-07, 11:57 PM
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Originally Posted by Bluem
small but powerful step motor, i lifted 25lbs. with this little sucker quite quick with a faster gear ratio than i will use with the manifold, if its too slow i have another one that is about twice as powerful that i scavenged out of an old copy machine.

bi-polar 1.8 degree/step motor and the Ericsson micro electronics dual step controller
i will use (pbl3775/1)

i love picking up e-garbage lol!

Damn I like how you think. I've been looking for stuff like this myself. You think it will hold up to the engine bay heat?
Old 11-06-07, 01:42 AM
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i don't know but i am thinking of machining a heat sink for it and insulating it somehow maybe glue the heat sink with that super thermal adhesive they sell at Comp-usa.
Old 11-06-07, 01:47 AM
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anyone here an electronics expert?
Old 11-08-07, 07:49 PM
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Not me! I just know how to solder and follow board building instructions.
Old 11-08-07, 08:09 PM
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Originally Posted by t-von
I know what you mean but I was comparing to the Rx8 because of the electronic delay of the secondary's that open at a specific rpm. The older rotarys had the mechanical linkage to the secondary throttle plates that did the same thing (exept they opened much sooner).

I guess the main point is that port air velocity is CRUCIAL at low RPM's - it pays dividends later. After low rpm port velocity comes tuning for the effect of sound in the intake. This is where the VDI of the NA FC comes into play. Mazda did some VERY smart things with this intake system and if you can mimic it then you will make a LOT of power. The key will be to tune your manifold for both low rpm velocity and high rpm harmonics.

Ray
Old 11-09-07, 11:27 AM
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Originally Posted by t-von
Not me! I just know how to solder and follow board building instructions.
same here lol
Old 11-09-07, 06:46 PM
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Loctite makes a thermally conductive ceramic cement for applications like this. The stuff at comp usa for computers just transfers heat, it doesn't actually bond the parts.
Old 11-09-07, 08:13 PM
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thanks for the tip

i am still figuring out how to control the position of the motor via a programmed rpm table.

anyone have any ideas?
Old 11-10-07, 08:19 AM
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Originally Posted by Bluem
plan b (constantly adjustable runner length)

if i can find u bends or rings with the proper i.d. and o.d and same radius that will fit one inside another like a telescoping bend i will go with plan B and use a step motor to control runner length with the ecu
This is what mazda did to their Le Mans winning race car. This is the technology that was specifically banned after they won. The adjustable manifold technology allowed Mazda to significantly broaden the effecive range of their peripheral port race motors. This is also the same technology that lead to the development of the VDI intake manifolds for the FC and later imprved for the RX8. A fully functioning variable runner length intake manifold is just too expensive and potentially problematic for OEM level equipment.

If you are going to do this then there will be more variables involved in tuning than just RPM. it will have to be a combination of load(manifold pressure), throttle position, and RPM. I would try to find a stepper motor control unit that can accept a PWM input and translate that into step position. Most standalone ECU's have PWM outputs that can utilize those parameters.

This can be a complicated project but certainly not impossible.

Ray
Old 11-10-07, 08:33 AM
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here's a cheat sheet on intake manifold theory for rotary engines.

http://www.rotaryeng.net/intake.html

Ray
Old 11-10-07, 08:50 AM
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Originally Posted by GTRay
This is what mazda did to their Le Mans winning race car. This is the technology that was specifically banned after they won. The adjustable manifold technology allowed Mazda to significantly broaden the effecive range of their peripheral port race motors. This is also the same technology that lead to the development of the VDI intake manifolds for the FC and later imprved for the RX8. A fully functioning variable runner length intake manifold is just too expensive and potentially problematic for OEM level equipment.

If you are going to do this then there will be more variables involved in tuning than just RPM. it will have to be a combination of load(manifold pressure), throttle position, and RPM. I would try to find a stepper motor control unit that can accept a PWM input and translate that into step position. Most standalone ECU's have PWM outputs that can utilize those parameters.

This can be a complicated project but certainly not impossible.

Ray
i have some handy info on the Telescopic Intake Manifold System (T.I.C.S.) from S.A.E. paper#920309

thanks for the input but i am still blank on a step motor driver with a P.W.M. input or how to put one together, i was told it had to be a home made closed loop system meaning the step control needs to know the position of the intake runner in order to determine action taken, don't want to seem rude here but the runner length is dependent only on engine speed.




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