Falken

Kind of ashamed to ask this at this point. I keep hearing terms like "street ported" and "race ported" engines. I know that it probably refers to modification of the exhaust/intake ports in the engine but that's about all I know.

In regards to the Renny, what does porting envolve and what does it improve?

Also I heard that 20B users have seen 70hp gains from porting their engines. Can someone explain that to me as well?

Thanks,
-Falken

09Factor

http://www.yawpower.com/

He dosen't have any of the Renesis port timings. However the info is still revalent to your question.

mysql

the rx8 intake ports are the size of street ported intakes on rx7 engines. This is one of the reasons why the 8 has more power than a NA 7.

the exhaust can be ported a little bit, but the way the housings are cast, there isn't much to remove.

rotarygod

There is so little that you can do on the exhaust ports before you hit the water jacket that it's best to do nothing at all.

Falken

So porting is done to improve flow?

I still don't get the basics of this.

dillsrotary

::simple answer::

Porting drills the inside of either the intake or exhaust hole making them larger, a larger hole allows more air and fuel in, or in the exhaust side more exhaust out.

rotarygod

In a very simplified manner, porting is to rotaries as new cams, and larger valves are to piston engines. When we port an engine, we modify the ports themselves, which are the openings that the air flows into the engine through. We can either open them earlier, close them later, or do both. Each has a different effect. Each changes the usable powerband too. Then end goal is to get more air into the engine so we can make more power. However the ports in the Renesis are just about as large as they can get so we can't do much to these engines.

Falken

I suppose I CAN ask this because you know RX-7s. What was it about the ports in the 20B that allowed for huge gains? And what type of modifications were done to achieve this? Shape/size? Location? I should probably ask this on the 7 forum but hey, I'm already registered here.

bse50

definitely both size and shape.
As far as i know a bigger size doesn't always mean better flow (or better timing) so instead of making them simply bigger you need to modify their shape a bit. the peripheral exhaust port helps as well with power increase.

I think that pineapple racing sells 13b porting templates, which are not usable for our engine but you can get an idea from them.

Falken

I'm not planning on porting my renny. I'm just trying to understand the concept.

Now to be more specific, I would like to use the 20B-REW as an example, because it sees 70hp gains N/A from porting alone. Can anyone talk about how shape and size are modified, and how specific modifications affect power/power curve?

What I don't understand is what exactly mazda was thinking when they designed the 20B, considering it could have been much more powerful just by reshaping ports.

rotarygod

20B's were turbocharged. There are many ways to see 70 hp gains on a 20B. Bridge or peripheral porting can do it to one naturally aspirated but any mild porting when turbocharged will really be highlighted. I wouldn't put any faith in the person that said the 20B gets 70hp n/a from porting. There's no detail there that's useful and I could argue that all day.

There is more to porting that just size and shape. Port timing is determined by the size and shape. There are certain things you do and don't do with port timing when it comes to emissions, powerband, rpm limit, etc. No manufacturer is going to give you the most powerful thing that they can. The reason for this is because it'll affect emisisons, mileage, and drivability among other things. It's just not that simple.

You need to keep in mind that the 20B and all the other 4 port engines don't have ports as big as they could have. This limits flow and potential power. Since the 20B, 13B-REW, 13BT came turbocharged, they relied on the turbo to make power for them. By keeping porting mild, you didn't sacrifice emissions, mileage, etc. 6 port engine have much more port area. Historically there was still room to go but again it would adversely affect mileage, emissions, drivability, etc. The Renesis moved the exhaust ports which affected port overlap and how much porting could be done before you encountered any. It allowed for more with no ill side effects. Mazda has pretty much built in as much as they could now. The Renesis has ports that are larger than most ported 13B engines. It's easy to pick up power when you are nowhere near your potential. A big gain from porting doesn't have to mean that the engine is better. It could mean that it wasn't as good as it could have been. The last non turbo rotaries were rated at 160 hp at the crank. Even a poorly tuned low compression Renesis can beat that at the wheels which is less than at the crank! The fact that you can't do much to a Renesis doesn't make it a bad engine. It makes it nearly fully optimized.

To answer questions in specific detail would take pages and pages and has all been written before anyways. Go look for it. The info is out there.

Here's a start. In fact just go ahead and read all of the rotary engine specific topics on this page first:

http://www.yawpower.com/techindx.html

After you understand all of that, then go look at these topics. These explain everything about porting. Well mostly. The little bit on flowbenches couldn't be more wrong if someone purposely tried to write an incorrect article on the subject but aside from that the rest has relevance.

http://www.rotaryengineillustrated.com/porting/15.html

Almost all of your questions can be answered by studying these topics.

Falken

LOL! Thank you, I will read these today. It's just funny, I got the same exact links when I asked on 7club, in the same order.

09Factor

Because that's where you should start reading if you want to know how porting effects the timing and flow of a rotary.
At least I'm using the same info RG does.

rotarygod

I've written so much on the topic already that you could easily search for more advanced info on it here. However, you'll be able to learn about it in a book later this year.

paulmasoner

iTrader: (1)

OOOHH!! very nice RG! more reading i can do while i'm in honduras!!

Motomouse

iTrader: (1)

A BOOK this year ??? Did I miss something RG ?

rotarygod

I'm not writing one. Someone else is. I have had a hand in it's content editing though. There are a few well known rotary people that have. I'm not sure if the book will be out by SSXI as the final draft is due at the end of this week but the author will be there. I am planning to be but I'm not 100% sure. There may be a 2nd book as a more advanced follow up to this one later on as the last 2 intended chapters aren't even going to make it into this one. I do have alot of tech info I'd like to put into an advanced follow up. We'll see. It's not my project. I'm just one of several people helping.

Easy_E1

iTrader: (2)

Oh boy new reading material. Can't wait RG.
And you better be at SSXI! Don't make us come and get you.