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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 12:19 pm 
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thanks again guys.

i had a bit of a look and measure on my plates last night..

seems quite obvious where the side seal is running and i have measured this as 4.5mm from the outer edge of the port.

so i think it is safe to widen the existing port by 2.5mm leaving 2mm to the wear line of the side seal.

i think i will have a play without a template... i'm not pushing the boundaries with a massive extended bridge port so i think i should be able to come up with something reasonable without making too much of a mess.

i like the idea of more torque throughout the rev range so maybe lean towards the curved shape at the top of the port as i intend t o keep the nikki to maintain some originality to the car so i will need more broad power curve than a high rpm peak.



if i fuck it all up then oh well, plates cost me nothing and i will have learnt what not to do.

will post some pics for comment before i butcher it !!

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 12:33 pm 
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What Dazz is saying certainly has some merit, and the person who said it was no doubt an absolute wealth of knowledge, however I haven't personally found the same to be true. I'm sure there are too many complex variables at play to give hard, fast rules.

You will most likely find that lengthening your intake runners will reap better mid-range results than the shape of the top of your port. Top curved or not, my point was to keep in mind the interaction between the side seal and the closing edge of the port.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 12:59 pm 
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I think the other thing to remember is that the runner shape and the transition from runner to main port has a big effect on the whole deal.

Some people get the port shape right but the transition from runner to port edges are shocking. Air doesn't like to make sudden direction changes, not does it like a sudden change in cross section, so keep all of this in mind and pay attention to the "whole port" from runner face to inlet port face.

Also the opening edge of the port does have a big effect on things, make no mistake there. Getting the port timing and shape right so that the exhaust pulse is creating a partial vacuum which then assists in early chamber filling is where gains will be made, as you can only make the closing edge of the port so high. The key is keeping the air speed up so that as the port is closing you get that last bit of squeezing into the chamber.

Lengthening inlet runners will increase mid range if there is a deficit for sure, BUT, it will potentially reduce the top end power. So it makes little sense to have an inlet port that will peak at 8,500rpm then an inlet system that will peak at 7,500rpm to try to gain back some artificial mid range. What you are doing is restricting the porting chosen, for exactly the opposite reason of choosing the porting style!

On top of that you need the right exhaust port and exhaust to all work in harmony together to get the best from it all.

Aspirated motors are a real balance, and very few people get it right, as there is no way to artificially compensate for poor porting styles.

I dare say if you are sticking to a std Maazda inlet manifold, even if match ported, choosing a top end style porting shape will not give you the best results overall as the inlet manifold jut cannot flow the amount of air for the port.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 2:07 pm 
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my starting point...

bit of permanent marker with some scatches.

guess it is similar to dazz port but still undecided on the shape of the top part... maybe i should flatten the curve a bit more.

any thoughts on this backyard scribble ??

( note: this is for a 12a n/a with a stock modified carb)

Attachment:
brown hornet extend port 1 - reduced.jpg
brown hornet extend port 1 - reduced.jpg [ 146.22 KiB | Viewed 8419 times ]

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The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 2:46 pm 
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Looks pretty good to me, the only thing I'd do is bring the outside line back towards the main port so it starts where you have it at the bottom after it comes out towards the housing at the bottom, but taper it in from there so it hits the top left corner of the std port and continue the radius from there.

Hard to show but the port I have comes back to about that std top left original port corner which gives a bit more assistance to the corner and side seal. As well as that the air will typically be moving towards the other side of the port so that short turn radius area at the top left of the std port is not where huge amounts of extra flow are coming from anyway.

What you do want to do though is make sure that that area is nicely flowed to aid the flow up into the newly ported area. You can see in my pis where the dark shadow starts in the runner area at sort of upper middle left or the port, that whole part there needs to be nicely flowed in so it's all a smooth radius, not a sudden direction change. You also don't want the port to be too smooth, no bumps and lumps, but it does not need to be polished.

Be very mindful of the water jacket behind where you extend the port up as you do only have a certain amount of metal there.

Image

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Last edited by Dazz on Sat Mar 16, 2013 3:06 pm, edited 3 times in total.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 2:48 pm 
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This is my motor, a stage2 from Glenn Munro.. seems to have heaps of torque. The ports are fat, real fat, down to the oil ring tracing line. The port runners are big and centre plate is very tall, almost as tall as the port itself (see my avatar)..
Image


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sun Mar 17, 2013 10:47 pm 
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front and rear plates almost done....

need a longer tool to finish off smoothing the deeper parts of the runners that i can't reach..

anyway this is a pic of my first go at an extend port..

Attachment:
front plate bloke ep1 - reduced.jpg
front plate bloke ep1 - reduced.jpg [ 114.2 KiB | Viewed 8375 times ]


Attachment:
rear plate bloke ep1 - reduced.jpg
rear plate bloke ep1 - reduced.jpg [ 104.8 KiB | Viewed 8375 times ]


original port for reference..
Attachment:
stock port.jpg
stock port.jpg [ 93.42 KiB | Viewed 8375 times ]

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The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Mon Mar 18, 2013 11:18 am 
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They look great, really nice job on getting a nice radius from the runner to the opening edge of the port.

With a std carby they will work very nicely I think.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Mon Mar 18, 2013 8:47 pm 
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thanks dazz,

i am pretty happy with them so far... i'm even a bit surprised how they look, guess its all cosmetic until i put them in a motor.

bit more shaping the curves at the top so they are the same and as i said some cleaning up of the runners

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My RX7's - ..
The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 23, 2013 7:28 am 
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brown hornet wrote:
thanks dazz,

i am pretty happy with them so far... i'm even a bit surprised how they look, guess its all cosmetic until i put them in a motor.

bit more shaping the curves at the top so they are the same and as i said some cleaning up of the runners


Leon i mean Dazz :lol: :lol: knows what goes into making a good engine, i dont believe he has given you all his secrets :bounce3: :bounce3: he is a dark horse with lots of knowledge.

geeeeez the rotary world misses Leon, i wish he was around.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sun Mar 24, 2013 10:04 pm 
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Epitrochoid Shaped Head

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so.. how close can you go to the water seal when bridgeporting..

i initially did my own extend port, then decided to have a play with adding a bridge.

after widening the original port by 2.5mm i then left a bridge of 5.5 to 6mm (bridge metal) then did the extra port at 5mm wide which leaves me with a massive 1mm of metal to the water seal location... or 2mm into the housing.

this is on a set of N series 'practice porting' plates..

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My RX7's - ..
The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Wed Mar 27, 2013 10:29 am 
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I'll just leave this here...

Image

Please note, this is a j-port, not a bridge port.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 29, 2013 9:42 am 
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i'm new to porting but isn't the problem with that port above that the bridge is in the wrong place and it isn't supporting the end of the side seal, it should be closer to the centre.

changing the port shape to suit that white line is going to make it worse as the side seal will be coming up a square edge instead of a gradual curved edge...

as i said i'm new to this but everything in this thread says that the problem is that the end of the side seal isn't supported.

making the top of the port more 'square' wont fix this.... correct ??

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My RX7's - ..
The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 29, 2013 8:56 pm 
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No not right

Post above with pic is spot on. Look at the side seal and imagine it contining it's cylce. With that port shape the tail end off side seal catches port first. If you square it off the seal will come up gradually starting at the inside top of port and finishing at outside top of port.

Mark up a plate and do a seal trace with a rotor and shaft. Start with the rotor past port and spin backwards. You will soon see what is going on


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 29, 2013 9:15 pm 
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Mr Rota wrote:
No not right

Post above with pic is spot on. Look at the side seal and imagine it contining it's cylce. With that port shape the tail end off side seal catches port first. If you square it off the seal will come up gradually starting at the inside top of port and finishing at outside top of port.

Mark up a plate and do a seal trace with a rotor and shaft. Start with the rotor past port and spin backwards. You will soon see what is going on


yeah ok, i see what you mean about the seal coming up over the top of the port better with that more square shape so yes i can see where i was wrong there.

but the first part of my post....
what i was getting at is if the bridge was closer in then the end of the side seal wouldn't get caught at all as it would be supported all the way through its path and you wouldn't have this problem.

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My RX7's - ..
The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100


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