Linguo415

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Is there a way of knowing if my engine has been ported without taking anything apart? Any tell tale signs?

rx-7 obsessed

idle sound. a ported motor will run rough at lower rpm....large ports wont idle below 1000 rpm and will have a very different sound from a stock rotary.

Linguo415

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Oh cool. Thanks.

Aaron Cake

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Unless it is ported quite large, there won't be much change in idle. And a rougher idle could easily be due to any number of other factors.

Mild porting also won't effect vacuum.

Only way to know for sure is to pull the intake and exhaust manifold, unless you have a boroscope.

jjwalker

I left my intake alone (the stock 6 port flows pretty damn well) and only ported and removed the diffusers in my exhaust during my rebuild, and it changed my exhaust tone rather considerably.

Linguo415

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I know that bridge, P port and others are big ports, Are thre different sizes in street port?

Aaron Cake

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There are an infinite variety of street ports. It will depend on the person doing the porting.

Linguo415

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Do they all do generaly the same thing are there benefits to some and not others?Is it possible to request a large street port from the shop? Is there such a thing?

datz

you can only streetport so much, right above the port the cornerseal glides, a little bigger and you need a bridge for the cornerseal to glide across on.

Linguo415

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Is that what a Bridge port is?

jjwalker

Yep.

Pic for posterity....

http://www.rotaryheads.com/porting/i...ter-bridge.jpg

Oh, and here is a link that explains everything...

http://autospeed.com/A_111123/cms/article.html

Aaron Cake

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In general, most street ports end up about the same. Roughly 20% gain in NA applications. When they start to go too big, they emphasize the high end and lower low and midrange torque. Not what you want in street applications. So in most cases, going conservative on an NA street engine is the best way.

The 6 port block already has HUGE port area. Generally the best porting is to make the primaries a bit taller, open them a little earlier. Then open the secondaries and aux ports a little earlier. Exhaust should go down a few MM, up a few MM, and widen a bit.

jjwalker

Porting my exhaust during my rebuild is the best thing I have done for the car...well besides the rebuild. We left the intakes alone because as you said, they are huge anyway.

Linguo415

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Cool pic. Is this some sort of bridge port?

Linguo415

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That's cool. What does it mean for us T2 kids though?

Aaron Cake

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Sorry, I'm an idiot. I didn't see that you had a TII.

Whenever I street port a TII, I do the following:

-primaries: Mazdatrix 6 port NA template primaries, moves the port up and down
-secondaries: Racing Beat "streetable" 4 port turbo template, moves the port up and towards the housing
-exhaust: Racing Beat "streetable" turbo exhaust, moves the port down quite a bit (oh noes!!!) and widens it a little

This combination maintains great drivability due to the smallish primaries, but also carries top end to 8K or so. Boost response is very nice.

FC_fan

iTrader: (2)

^great info on what templates to use, I assume because of the "great drivability" that reliability is close to stock, assuming only cold air intake and turbo back exhaust are done? would/could you run the stock ecu, piggy back, or full standalone? and would it be worth it after all that to keep using stock injectors or upgrade. your statement got me curious.

Linguo415

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So you get the template from all of these places? Do you the porting yourself?

Linguo415

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How much power can you get out of this combination and make on top of that with mods?

Aaron Cake

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I originally bought my templates from the places I listed, yes.

The port shape is actually the easiest part when porting, just grind it out to the template. It is all the other stuff such as transitions between the runner and port that takes skill and experience.

Depends on the turbo. With the stock turbo, you are limited to 250-275HP regardless of what you do.

jjwalker

I get your "Oh noes!" quote as most say that is bad.

I am curious as to whether or not opening the exhaust port earlier is all that bad. I am not sure in which direction RP extended and opened my exhaust port. Since the rotor face has such an elongated combustion area, I always thought the flame front propogation is somewhat slow thus it requiring a longer combustion cycle to achieve complete combustion. Moving it down some I don't see an issue with, but you said it extends it quite lower, so do you worry about the combustion cycle ending too soon? I also realize going upward can cause too much overlap as well.

I am just curious on your thoughts on the matter Aaron, as I am not a rotary porting expert.

Aaron Cake

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Opening an exhaust port earlier is supposed to cut into combustion a little and reduce torque. But in my experience it doesn't do this at all. Combustion has already taken place and peak torque is far earlier in rotor rotation. It is actually cutting into blowdown and I find that the extra exhaust energy spools the turbo, resulting in more boost sooner. The RB template moves the exhaust down quite a bit...4MM or so as I recall.

Linguo415

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Ok cool. I'm going to have it done when I rebuild my engine though. I don't have the tools or the know how to do it myself. Haha