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Peripheral port with factory ports

Old 02-08-18, 10:23 PM
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Peripheral port with factory ports

I know it's possible to make a 13b to have the stock intake ports used with a peripheral port, but I'm more curious on how the engine will run.
I'm expecting fairly well or really bad
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Old 02-09-18, 11:46 AM
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Your kinda describing a semiPP. Really why would you want to? Your already pulling tons of air from the PP, why add MORE air from the stock ports? Unless you got really fancy and made it idle on the stock ports, and had the PP act as a secondary kinda like a 5th/6th port
But i'm sure the air velocity would be horrendous and wouldn't help much
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Old 02-09-18, 11:50 AM
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I wasn't planning on making this a thing, was just curious on what the outcome would be, thanks for the information though
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Old 02-09-18, 02:33 PM
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It should run just like a peripheral port of the chosen port timing runs when it has the wrong intake manifold on it.

Meaning, a bit worse running than a standard peripheral port.
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Old 02-18-18, 10:04 AM
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the standard peripheral ports run just fine, if you tune them, would not bother with a hybrid setup
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Old 05-30-18, 08:13 AM
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Originally Posted by j9fd3s View Post
the standard peripheral ports run just fine, if you tune them, would not bother with a hybrid setup
Is there a disadvantage to running a SemiPP over just a PP setup? I'm planning to run a SemiPP setup on my 13B, that's why I was asking.
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Old 05-30-18, 10:23 AM
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If you use side intake ports and a smaller peripheral port versus a regular peripheral port alone you do have some disadvantages.

Disadvantage 1
There is more runner surface area relative to runner cross section. This means more drag on the inlet charge and thus lower velocity/less chamber filling capacity per engine rpm.

Disadvantage 2
There is a smaller peripheral port and therefore less of the intake area available to the affects of overlap which create more torque.

-----------------

There is one scenario that I would like to employ where the semi- peripheral port engine has some advantages over full peripheral port and that is in a turbo application.

You can close off side intake ports (it gets sealed off by the corner and side seals unlike a peripheral port where the apex seal is smaller than the port). Mazda did this with the aux ports in the 6port NA rotaries.

So, if you ran your small peripheral port as a primary port with early intake closing, but early intake opening (so, a narrow D shape with flat on top) it would help spool the turbo (like the Alfa reverse vtec system where they run the rowdy cam down low to spool the turbo with overlap). The small runner area would also aid in torque and throttle response (both from higher intake velocity).

Then for higher rpm you would have the big side intake port open with later closing timing to keep the torque from dropping on the high end.
The small peripheral ports wouldn't close, but they would reach choke flow with the majority of additional turbo flow going through the larger low overlap side ports.

Yeah, the opposite way that a normal semi-peripheral port turbo motor works. I know, I'm a weirdo.
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Old 05-30-18, 11:08 AM
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Originally Posted by BLUE TII View Post
If you use side intake ports and a smaller peripheral port versus a regular peripheral port alone you do have some disadvantages.

Disadvantage 1
There is more runner surface area relative to runner cross section. This means more drag on the inlet charge and thus lower velocity/less chamber filling capacity per engine rpm.

Disadvantage 2
There is a smaller peripheral port and therefore less of the intake area available to the affects of overlap which create more torque.

-----------------

There is one scenario that I would like to employ where the semi- peripheral port engine has some advantages over full peripheral port and that is in a turbo application.

You can close off side intake ports (it gets sealed off by the corner and side seals unlike a peripheral port where the apex seal is smaller than the port). Mazda did this with the aux ports in the 6port NA rotaries.

So, if you ran your small peripheral port as a primary port with early intake closing, but early intake opening (so, a narrow D shape with flat on top) it would help spool the turbo (like the Alfa reverse vtec system where they run the rowdy cam down low to spool the turbo with overlap). The small runner area would also aid in torque and throttle response (both from higher intake velocity).

Then for higher rpm you would have the big side intake port open with later closing timing to keep the torque from dropping on the high end.
The small peripheral ports wouldn't close, but they would reach choke flow with the majority of additional turbo flow going through the larger low overlap side ports.

Yeah, the opposite way that a normal semi-peripheral port turbo motor works. I know, I'm a weirdo.
I feel like I may have lead you astray on this one LOL.. I guess I should have mentioned that I plan on running a BW S475 on the engine. I was hoping that the engine would be as efficient as possible so that it will help in spooling the big turbo.
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Old 05-30-18, 01:38 PM
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Well shoot!
Feel free to try my idea. I can let you know the intake manifold parts I was planning on using.

Or go the "traditional" semi-peripheral port direction using one of the available intake manifolds that tie the peripheral ports into the 2ndary intake port runners.

These work well, just typically mushier throttle response/worse driveability because-
1) you either "block" the 2ndary and peripheral port flow at low throttle input/low rpm which gives you all the full exhaust contamination of overlap under a closed throttle plate and no benefit (when "blocked").
2) open primaries, secondaries and peripheral ports all at once, which works better- but because of the big runner area intake velocity is low so throttle response is soggy.

With the size of the turbo you have chose you probably don't care what happens below 4,000rpm anyways.

In a turbo application the bridgeport or semi peripheral port is preferred over the full peripheral port as
the rotor flank (bridge port) or rotor face (semi peripheral port) obstructs flow through the intake port when not in the intake phase.

Full peripheral port is large enough that flow is not obstructed by the rotor as the rotor face depression is exposed to the port and intake flows into the exhaust stroke more easily. This can cause very high EGTs, turbo overspeed, reduced peak power potential on a given turbo (loss of compressor flow to exhaust), and poor throttling driveability.
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