detectiveorange

I've been seeing this a lot. And I know it's associated with the "brap brap brap brap" sound. After doing some searching on google and rx8club, all I could find was stuff ABOUT bridgeporting (i.e. doing it on a renesis engine is a waste because of the exhaust ports). But what exactly is it? What are the advantages/disadvantages?

I've gathered it has something to do with the exhaust ports. And from the sound, it sounds like the engine has more torque just because you can actually hear the individual combustion strokes as opposed to hearing a nice and quiet hum of stock engine. This is all just in hindsight and speculating. I have no idea if any of that is true.

Also, what's the difference between bridgeporting and streetporting? or are the 2 not even related?

Carbon8

iTrader: (4)

Buy this book!

While you wait for it to ship to you visit this site,
Porting

Really the only port work you can do on a Renesis is intake porting, anything more than a mild streetport will yield almost 0 gains and jeopardize the life of your engine. Unlike all post rotory engines the Renesis uses side intake and side exhaust ports, this is why most people hate this engine. Moving the exhaust ports to the side (Irons) you are very limited by the size of the port due to the side seals flexing while traveling over this port and they will degrade and break rather quickly as they are not as strong as the appex seals. All other rotors the exhaust ports where in the housings. You could make these ports quite a bit larger back then.

So now that we understand that you cannot make the exhaust ports larger without expecting to replace an engine every 15-20K miles, you now have to apply that to the intake ports.

What is the purpose of increasing the intake port if the same size exhaust port is still restricting flow?

I believe to this day (and I may be wrong) not bridgeported Renesis has been able to produce much more (I am talking 5 WHP) over a streetported Renesis.
Its really just not worth it, I have also not seen one thread about it that ended well.

Also keep in mind that the "brap brap brap brap" you refer to is not from bridge porting it is from Peripheral Port which is done on race engines only because after about 8 hours on the track the engines are already worn out and must be rebuilt.

Carbon8

iTrader: (4)

Heres one members thread on it,
https://www.rx8club.com/rx-8-discuss...loving-234757/

I believe this member also increased their RPM to 10K RPM which again yields no benefit, this engine lasted a little over a year and needed to be rebuilt.

People just need to face the facts that the Renesis is limited by design, Mazda has tapped its potential NA (and they did a damn good job) and not much can be gained in anyway besides going FI or NO2

Another thread that explains why this is a bad idea (and it has pictures, everyone love pictures)
https://www.rx8club.com/series-i-maj...enesis-174588/

detectiveorange

I see, so you just make the intake and exhaust ports bigger to get a bigger boom, makes sense. So since porting renesis engines is pointless, there's a still a few questions about the 13b.

I'm taking it when you do any porting you have to get aftermarket intake/exhaust manifolds right? to fit the new intake/export holes?

also, that article you linked went over lots of different ports (lots of them I hadn't even heard of) but I didn't see street port mentioned anywhere. I'm assuming it's just another shape of the intake port?

as for the "brap brap brap" sound being attributed to peripheral porting. I noticed that it says "the side ports are actually filled and completely new circular - peripheral - intake ports"

PPRE 6 Rotor RX4 Track Test at the 2013 V 4 & Rotary North Island Jamboree (Onboard Footage) - YouTube


are the "completely new circular intake ports" those tubes that are at the top of the rotary in this video?

it says on that article that bridgeporting "introduces the characteristic lumpy idling" is that the "brap brap brap" noise I hear whenever the car settles down to it's idle? Because I seem to hear that noise in every youtube video titled "bridgeported rotary"

what does "NA" stand for? I see this abbreviation all over the forum and haven't seen it anywhere else.

actually, in that video, that just looks like a weird intake manifold. those are obviously fuel injectors sitting on top. IM VERY CONFUSED!!! hahaha

RIWWP

iTrader: (2)

The circular tubes on top of the engine are individual throttle bodies (ITBs). It's one of the popular and effective methods of increasing throttle response and top end power, although it's comparatively expensive even when compared to other N/A mods. Not possible on the RX-8 without an aftermarket ECU and probably a lot more R+D.

N/A = Naturally Aspirated, as in, no turbocharger or supercharger. Those are "forced induction" or "FI".

Carbon8

iTrader: (4)

"brap brap brap"

Is associated mostly with peripheral ports only, that Rx4 in the video above is peripheral ported.

Bridgeport and "lumpy" idle are just that you get a very rough idle with RPM fluctuation because the car has a very hard time finding the right A/F, so you just get dips and revs this goes away once the throttle is opened.

You only need a new intake for peripheral porting, which means you are not running a Renesis engine anymore.

And streetporting is on the page I sent you its labeled "Mild Port" it essentially just makes the existing port slightly larger ( I mean millimeters larger), the main benefit of this is not increasing the port size but actually smoothing the port elbows and channels thus allowing more air to flow with less restriction.

Mild street porting is what I had done on my engine build, along with other things

detectiveorange

Ya it seems to do a pretty damn good job of increasing throttle response. that thing goes through the RPMs crazy fast. what does R+D mean?

RIWWP

iTrader: (2)

Research and Development.

The costly part of making anything new.



Throttle response isn't the speed of the RPM increase. Throttle response is the momentary lag time between a throttle pedal position change and the engine's response to that change. When the throttle plate opens, the engine doesn't immediately see the air flow, as the air in the intake is already moving at the prior speed. It has to accelerate up to the new speed requested, and this take a bit of time. ITBs significantly decrease this time, as well as being as nearly as unrestrictive as possible for top end air flow. Longer intakes mean better low end torque, shorter intakes mean better high end torque, variable intake length, such as the RX-8 achieves through the intake valving, tries to get the best of both. ITBs ignores low end torque, only carring about high end.

detectiveorange

I see. This is all so new. I didn't know how much modding you could do to a rotary. I thought it was pretty much limited to turbocharging and such. These guys I take my rx8 to (neptune speed garage rx) do bridgeporting and such and there's all sorts of thrashed rotary parts lying around. I saw a few side housings with weird shaped intake ports but I figured they were like that because something went wrong. Nope! Guess not haha.

This is friggin cool!

RIWWP

iTrader: (2)

I edited my response above with the response time clarification.


Keep in mind that there IS a lot you can do to a rotary. Just Mazda already pretty much got all the right choices from the factory for extracting power N/A from this particular engine design, so most of those other options are not going to gain you anything.

ITBs for example, could possibly see a power increase, but you have to go to a completely different tuning method, the factory ECU couldn't handle it, plus the fitment under the hood, etc...

You would probably be looking at $800+ for the ITBs themselves, plus another several thousand for the aftermarket ECU, lots of integration hassle, disabling most of the other RX-8 body control functions, and probably pick up 5-10hp at the top end.

Not really worth it, especially since you would lose 5-10hp across the rest of the range, if not more.

detectiveorange

I can see how that would be a PITA. I associated throttle response with speed of RPM increase because I figure "oh, the RPMs just shot way up, that means the driver just stomped on the throttle" which made sense in hindsight (everything makes sense in hindsight lol) but I didn't think about the fact that the driver could've mashed his foot on the throttle 0.5 seconds before I even heard a change in RPM.

"extracting power N/A from this particular engine design" there's that "N/A" abbreviation again. what does that mean?

Oh, and carbon. thanks for showing me that book. No joke, just bought it on my Nook (too impatient to wait for shipping lol) I've been looking for something with information like this for a while!

RIWWP

iTrader: (2)

I answered the "N/A" question in post #5

detectiveorange

Ah! you most certainly did! Naturally aspirated. derp -_- lol

out of curiosity, you guys both seem to be the ones who comment most here on the threads. Have you guys done anything crazy to your 8s, or have you guys kept them relatively stock?

Carbon8

iTrader: (4)

That book is a must for anyone wanted a good foundation on rotory engines

RIWWP

iTrader: (2)

Mine was mostly stock, just AP and BHR midpipe. I sold it last February, though I'll be looking for another this coming spring.

Lots of mod money in my MSM though.

Carbon8

iTrader: (4)

My sig has my entire build thread on car (or here https://www.rx8club.com/series-i-maj...-build-242275/), I have no idea what RIWWP has done to his past 8 as I believe he sold it before I got involved much in this community. He has a miata that he built and is looking for another 8.

He knows leagues more than I care to know about the mechanics of these engines tho

detectiveorange

your build is friggin sick man. RIWWP, why'd you sell your 8?

GertrudeGrant

i would definitly buy this book, here and it has made me more and more delighted now..

detectiveorange

I bought it as I got done reading a snippet. definitely an awesome book

RIWWP

iTrader: (2)

Life reasons. Looking for another at some point next year, likely an R3

detectiveorange

I'm not a huge fan of the way the R3s look. But better suspension, and BBS wheels? I'll play.... haha

RIWWP

iTrader: (2)

I drove a 2009 R3 immediately after a 2009 Sport. The R3 was hands down the better car. It was remarkable how all the subtle bits made the car as a whole that much better, noticeably.

detectiveorange

That's almost artistic in a way. That's pretty much how every form of art works. Add little touches here and there until it makes the whole thing better. I REALLY respect mazda for that.