Building a 13B FC motor

Technical info not specifically 1st gen RX7 related.

Building a 13B FC motor

Postby TOOL » Wed Oct 08, 2014 9:53 pm

Just for you Ghost ;)

Get yourself a 13B from an FC:

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Hope it doesn't look like this one:

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Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Wed Oct 08, 2014 10:01 pm

Pull the motor apart and work out if you can use it again.

Housings.

Plug the water jacket with core plugs:

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Open up the ports to your liking:

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MAKE SURE THEY MATCH
Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Wed Oct 08, 2014 10:08 pm

Source an appropriate intake manifold for your application (4 port, 6 port) if you want to go carb or Injection Perfection set-up.

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Port your plates to your liking (nothing too radical here):

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Lap the plates to your liking taking care not to eat through the nitride layer:

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Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Wed Oct 08, 2014 10:17 pm

Choose your rotors.

Not this one. It dropped a tip and suffered detonation. Notice the dent. This will move all the seal grooves in the vicinity. Everything will be out of alignment.

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NA rotor vs Turbo rotor:

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Turbo rotor has a deeper bathtub. In the S5 engine 9.0:1 vs 9.7:1 ratio.

I am running the 9.7:1 ratio rotors.

The other good thing about the S5 rotors is that they have the same mass as FD rotating assembly so can be used with FD counterweights which are easy to find. More on this later.
Now with 3 rotors
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Re: Building a 13B FC motor

Postby Ghostkls » Thu Oct 09, 2014 8:56 am

Thanks Tool!!

Just a random idea I have been thinking about recently with porting..... When I think about air flowing in and out of the motor. For intake ports, the best would be to use the rotor as a guide and optimise flow into the motor when the port is at the halfway point in the transition and for exhaust ports sharpen off the bottom of the port allowing the port to open as fast as possible will tapering off nice and smoothly at the top. In my opinion this would allow gases to escape as fast as possible but still protect the apex seal by allowing it to be "slowly" slid back into the apex seal slot.

The down side to this exhaust port would make the exhaust rather loud as the gases would most likely go super sonic as the port opens to maximum really early in the rotation.

This is obviously just my thinking of how gases flow and could be completely wrong..... But if I don't ask.... :?: :?: :?:
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Re: Building a 13B FC motor

Postby TOOL » Thu Oct 09, 2014 8:02 pm

How about these beauties?

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Rice Racing I believe.
Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Thu Oct 09, 2014 8:21 pm

Remember that this is where the exhaust ports started:

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They were designed to keep the noise down, not support the apex seal. Still very effective even when they're this tiny.
Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Thu Oct 09, 2014 8:29 pm

Hopefully people are aware of this great book:

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It contains all sorts of great stuff........

Adjustable rear pressure regulators:

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Although, you can press the stock FB rear pressure reg to increase the preload, thereby raising the oil pressure.

You can also get adjustable pressure regulators out of twin dizzy motors as these were fitted as standard.
Here's one installed:

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FD rear pressure regulator is 110psi iirc which would be loads and bolts straight in. I'm toying with the idea of fitting one.
Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Thu Oct 09, 2014 8:53 pm

Sump baffling to keep the oil at the pick up:

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Sump brace to prevent the block twisting:

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Pretty much unnecessary for an NA motor cos it won't produce enough torque. It might help with getting the sump to seal properly though.

You can also add a thin plate between the sump and block to slow the oil down on it's return, allowing more time for the air bubbles to come out.
Now with 3 rotors
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Re: Building a 13B FC motor

Postby TOOL » Thu Oct 09, 2014 9:00 pm

Carrying on with the oil system theme, oil pumps:

Fit a turbo oil pump, not an NA pump.

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Mazda also does a 17.5mm hardened gear set oil pump (aka MFR) for the 12A.

Three window bearings for the stat gears:

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I would only bother to fit that in the rear stat, as that is supplying all you oil up the eshaft to feed the rotor cooling. Put a multi window bearing in the front one imo.

See here:

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You can also swap out the rotor oil jets to flow constantly but you'll suffer low oil pressure at idle:

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Now with 3 rotors
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