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 Post subject: 13B aux port inserts
PostPosted: Mon Nov 13, 2017 10:31 am 
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Joined: Sun Oct 08, 2017 2:58 pm
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All right, starting an EProd build of an RX-7 - and I'm wondering if it is permitted to modify (adding material or other stuff to smooth the transition) the rotating sleeves used to actuate the 5th and 6th ports, and if so under what rule. Under 9.1.5.E.1.b.8 it seems like it's illegal to call the rotating sleeves part of the intake manifold, and in general, the rules seem to frown on almost anything where you're adding material... but I'm pretty sure that I've seen reference to builds where it was done. Tech shed legal, or is there a rule I missed?


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 Post subject: Re: 13B aux port inserts
PostPosted: Tue Nov 14, 2017 5:44 am 
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Location: Topeka, Kansas
Dan I'm not going to dig and find the exact rule but you can't add material for one. I've seen it done before and it's great but totally illegal, save that for NASA. You can remove those auxillary port sleeves for sure. After that all you can do is porting. Don't overthink it, it's a simple rule. There's a link somewhere with pictures showing the street port rules for EP.

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 Post subject: Re: 13B aux port inserts
PostPosted: Tue Nov 14, 2017 6:41 am 
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Location: Wauwatosa, WI
SCCA Street Port Definition
If I remember correctly the info included was prepared by Jesse Prather and Dave Lemon, Thanks guys.

https://dk1xgl0d43mu1.cloudfront.net/us ... 1432140723

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David Dewhurst
CenDiv Milwaukee Region
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 Post subject: Re: 13B aux port inserts
PostPosted: Tue Nov 14, 2017 7:14 am 
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Thanks gents, digging through the GCR I thought that was the case - it was more of a "if anyone is running reworked sleeves, what rule says you can?" than trying to find rules that say you can't. I have enough variables to play with on the dyno as is and I did not want to have to duplicate the heavily reworked sleeves I saw some years back to have competitive power. Works of art, but it looks like there was probably at least five-ten hours of welding and grinding into each one.


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 Post subject: Re: 13B aux port inserts
PostPosted: Tue Nov 14, 2017 5:44 pm 
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Joined: Sun Aug 18, 2002 6:52 pm
Posts: 2142
Location: Topeka, Kansas
You bring up a good point.
The rotating sleeves that come stock are allowed to be removed. What says you can't modify those and retain them? I'm not sure. They're not part of the engine, they actually are retained by the intake manifold and in all EP rotary engines you can port the intake manifold. Still, you can't add material to the intake manifold either so that might throw that out. Good discussion.
I'm quite sure they're very restrictive so even modifying them I wouldn't think would help. Thanks for the thought process though!

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 Post subject: Re: 13B aux port inserts
PostPosted: Wed Nov 15, 2017 7:34 am 
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I suppose if I run out of things to try on the engine dyno, I'll try building a set and writing a letter - that's the end authority right? I'm still learning in Midwest Council so it'll be a while before anyone asks to open my engine anyway. ;)


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 Post subject: Re: 13B aux port inserts
PostPosted: Wed Nov 15, 2017 10:56 am 
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Jesse Prather wrote:
You bring up a good point.
The rotating sleeves that come stock are allowed to be removed. What says you can't modify those and retain them? I'm not sure. They're not part of the engine, they actually are retained by the intake manifold and in all EP rotary engines you can port the intake manifold. Still, you can't add material to the intake manifold either so that might throw that out. Good discussion.
I'm quite sure they're very restrictive so even modifying them I wouldn't think would help. Thanks for the thought process though!


Question on the modification part.. (caveat: I don't even know what these thingies are or do, other than rotate and pass air).. are these things of such dimension that you could rotate them to expose another side that's not machined, and then remove material to get the shape you want, without machining through to the other side of it? that would eliminate the need to add material to get the desired shape, but might not be physically possible... just curious.

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 Post subject: Re: 13B aux port inserts
PostPosted: Wed Nov 15, 2017 11:13 am 
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Location: Topeka, Kansas
In a stock engine they're closed off until a certain load. Then they spin and open up the extra 2 ports. Nobody runs with them in the engine in EP. I can't imagine they would help even if you modified them as they choke the port size down a bit.

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 Post subject: Re: 13B aux port inserts
PostPosted: Wed Nov 15, 2017 11:44 am 
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The stock ones are a tube with a hole in one side, a flat cap on one end, and a pin near the intake manifold mating surface to rotate it. As Jesse says they're used basically on the same concept as variable valve timing - close the second port at low RPM.

What I'm talking about... the best easy comparison is the Atkins ones here: http://www.atkinsrotary.com/store/84-92-13b-rx7-atkins-designed-six-port-actuator-valve-kit-are113-.html?category_id=1315 where it's shaped at the end to have a smoother flow from the port to the combustion chamber. Obviously the Atkins ones aren't stock but if you're industrious you could form that shape with welding and grinding. And if you're OK with them being open all the time, you could remove that pin protruding into the air flow, add a little material to the outside diameter (very little) and press them into place.


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 Post subject: Re: 13B aux port inserts
PostPosted: Wed Nov 15, 2017 12:37 pm 
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Joined: Thu Nov 12, 2009 6:01 am
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Dan DeRosia wrote:
The stock ones are a tube with a hole in one side, a flat cap on one end, and a pin near the intake manifold mating surface to rotate it. As Jesse says they're used basically on the same concept as variable valve timing - close the second port at low RPM.

What I'm talking about... the best easy comparison is the Atkins ones here: http://www.atkinsrotary.com/store/84-92-13b-rx7-atkins-designed-six-port-actuator-valve-kit-are113-.html?category_id=1315 where it's shaped at the end to have a smoother flow from the port to the combustion chamber. Obviously the Atkins ones aren't stock but if you're industrious you could form that shape with welding and grinding. And if you're OK with them being open all the time, you could remove that pin protruding into the air flow, add a little material to the outside diameter (very little) and press them into place.

As soon as you weld material to them you are illegal. No material may be added is absolute. We did some testing once with some modifications to them and made no more power. Spend your time on exhaust system and port shape.


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