Small vs mild vs large streetport
 

What are the pros and cons of each, what's the idle like on each, etc. I did some searching but couldn't really find anything to answer me to my satisfaction. I'm thinking to street-port my S4 TII when I rebuild it, and am wondering how large to go. I will street drive the car a lot, possibly even DD it. I will probably keep all accessories except maybe the air pump. Also it is a 5-spd.

Let me see if I can dig up that site that explains it...

http://www.rotaryengineillustrated.com/porting/15.html
http://www.rotaryengineillustrated.c...t-port-14.html
http://www.rotaryengineillustrated.c...t-port-14.html

That should give you a basic understanding.

I'm daily driving a fairly large streetport. It's not quite an Ito port, but the secondaries especially are pretty big. It's quite well-mannered and had plenty of low-end even while it was NA.

What about supporting mods? Like, when would I need to upgrade/replace the turbo? Will a stock turbo keep up w/ a large streetport? Will the injectors need to be replaced for a small streetport? That's kinda what info I'm looking for. I know most people have no problem w/ a large SP, but what mods are needed for each level is what I want to know.

Check the site. It all depends. You can only make as much power as you have fuel for (hence why you tune with a wideband). If you start going lean you run significant chances of pre-ignition. Remedying this you can switch to a rising rate FPR, bigger fuel pump, or bigger injectors. Having means to control the fuel is what is really important. If you can't adjust fuel either by piggy back, ecu, or another means you have no *real* reason to port the engine.

I know this, I will get what is needed to tune it.

So, I guess a large SP is not that bad to live with on the street, so that's probably what I'm gonna do. I'm thinking to use Pineapple Racing's templates, unless there's better ones out there? Anybody about what size injectors would be needed for this? How about the turbo, stock one work fine? Compressor need upgrading? Is there an Rtek chip for this?

If you go too big with the street port, your intake manifold will become your primary restriction. If you go too small, the engine can't breathe. From what I am told, you want the intake tract on the engine to remain the same cross-sectional area throughout. If anything, the port should be slightly smaller than the intake runner.

Basically street manners are completely determined by port timing. If you extend the port downwards too much, it will not idle well. Upwards hurts your starting and low-end torque.

The minimal street port that I have on my 4-port was designed to leave port timing completely stock, but to close the port more abruptly (better dynamic tuning) and allow for additional cross-sectional area to support my 1.42" primary and 1.68" secondary intake runners.

It idles rock-solid and does not stall at launch (110 Wlb-ft at 1000 rpm by g-tech). It really doesn't start to pull until 3500 (pulls the tires loose) and it comes alive at 5500 (weeee).

I will post power numbers when I get a chance to go to the dyno.

Porting isn't just about taking a die grinder and changing the port shape...
I think it was Judge Ito said it best when he called it a 3D process.
Good porters can actually keep the stock intake port shape and get it to flow better just by redoing the contour within the passage!
Think about it!
If the entire intake path was straight, then changing the port shape will change airflow dramatically.
Because the intake path takes a very abrupt bends to get into the combustion chamber, there's a lot more voodoo that just grinding metal away here and there...
It'll take tons of fluid dynamics theory to hash all this out...

In general, a smaller port will give you better (port) velocity.
Velocity is GOOD, especially for low end.


-Ted

Cool, good info. Yeah I read that you don't really want to drop the port abruptly, like basically end up w/ a wall at the end I guess? Which is basic common porting sense, but is there a specific angle it like the best? I need to find some pics of what I'm talking about. I think it's the big end of the port.

Are there better intake manifolds out there for the 13B? I don't recall seeing much in the way of aftermarket intakes.

Edit: Here's what I'm talking about on the ports. In this post the guy says you shouldn't cut straight down at the big end of the port (like he did in the 1st 2 pics to find the water jacket). Does his porting look right?

http://rotarycarclub.com/rotary_foru...88&postcount=6

I couldn't seem to find any good pics of streetports, anybody have some they can post up?

I think that it is easier to lay a rotor and housing on the iron and figure out your port timing and adjust it to what you want. I wanted a good idle and a tame street machine, so I did not change port timing at all. The larger intake runners did hurt my low end quite a bit (but they make up for it between 7,000 and 9,000 rpm).

I agree with ReTed, there is a lot that can be done for the ports without really changing the port opening at all.

I think I posted pictures of my intended port modifications in a previous thread.

The templates are cool, but they kinda ruin the fun.

Okay, what changes the port timing? Changing the length of the port?

Its length and width I believe.

Here is one of my favorite pages of the rotary eng. ill. web site:
http://www.rotaryengineillustrated.c...-ports101.html
This has helped me alot with understanding these concepts.

Awesome site, definitely helps understanding the port timing and how the whole engine works really.

The longer I do rotaries, and the more ports I've played with - I've found that stock ports are actually pretty damn good. Aside from some obvious casting issues, they can make a tonne of power....and I'd recommend looking at torque on dyno's vs. stock/small/large street ports - you'll be surprised with what you see :)

PP or Ext Port
 

Hey guys im new. What do you think is more appropriate for my street rx8? PP or Extended port?

street car? not a PP then :)

Length for timing, width for volumn.

If you want it to be somewhat drivable then not PP. Great if you just want something that makes a lot of noise and goes bloody fast and really doesn’t work well at low speed then go for it. PP is best for all out racing.

As to port size, larger is not necessarily better. Ask Paul Yaw. He is one of the few if the only one that has used a flow bench to figure out porting. In the old days we would just make the holes as big as possible thinking that was the way to go.
There is a lot to be found in the earlier motors, 15/20%, pre 93. (84 to 91 13B not so much, six port he found you really had a hard time making them flow as well as the four port)

93 on Mazda has made a lot of improvements in flow characteristics. When Paul was in Tucson I was able to use his flow bench to develop the ports and intake for my FD package. It was the first time he had seen an FD housing on the bench. He saw the readings and wondered what porting I had done, he was impressed. It was a stock housing that I was using to get the base line. The stock FD housings flowed as well as ported early housings. I was able to get the steel plates to flow 98% and rotor housings 100%. Was also able to improve the flow in the FD intake which actually flowed better stock than early modified manifolds. Could only find 8 to 9 % though. But as he found out the increase in flow in the intake usually equated to same % increase in hp.

So if I SP it, should I focus more on the timing or the volume? Like, leave the timing stock and open it up for more flow, try to stuff as much as possible in w/ stock timing? Or will longer timing work better, like make it spool quicker? Should I just buy a template from someone and follow it, or just do it myself? $35 a template, seems I could save a good bit if I do it myself, just need to know what to work on.

Getting the template will save you a lot of time and effort. You will be getting holes that are proven and work. Most of the other flow characteristics are from what is done before the port and there are not any templates for those. This is where the flow bench really comes into play. Many of us have our own templates and will actually vary the ports to specific applications.
If you have never ported a rotary before and you are building a street car, a template is the most cost effective way to go and will yield you good results.

Any particular template better than the others? Who all sells templates?

Other guys on the forum probably have a better idea on exactly who sells them now and who's they like since I use my own. Racing Beat I know sells them and I believe Mazdatrix, Gotham, and Pineapple also sell them. RB was the standard for many years.

I can't seem to find the Racing Beat templates. I think I'm going to get the Pineapple template.

Extending the closing edge of the port does not change port overlap. It gives more time for the combustion chamber to fill up which affects the higher revs. The torque curve will be simiar to stock but extended to higher rpms with less affect at the lower rpms.The Racing Beat Street secondary ports are like this. Think of a cam with later closing and higher valve lift.

Inceasing the opening edge of the port also increase overlap which decreases low rpm torque but increases higher rpm torque more than just extending the close. PineApple primary and secondary ports are like this. Think of a cam which sooner opening, later closing, and more valve lift. The RB primary port is also like this.

The RB street port and PineApple medium ports idle about the same and are similar to stock ports with a smooth idle.

I have done them all and I must say 100% stock ports, make the best power band for a street car, have the broadest power range, and with a turbocharger fitted any power loss compared to a mega ported engine is not ever important as it can be made up with only a couple of PSI difference in boost pressures............. and you give up nothing else, in fact you end up with a far better street motor (read more tolerable to back pressure, wider power band, more economical, faster acceleration, faster on track, and perfect match for stock 5 speed box).

Moral is don't waste your time porting your engine unless its an all out race car with 6 speed dog box attached. :beatdeadhorse5:

Further to this post (stock V's street port)

Two RX7's both weight checked prior to running, both dyno's *varying methods* alone with vastly varying estimates of engine power! one matches reality (read other cars) the other is optimistic to say the least!

Stripped track car (13B-REW street port) Garrett single turbo 1.3bar
1> 1180kg (432rwhp DD! owners dyno shop estimates 509bhp!!!!!!!)
100kmh-200kmh = 8.3 seconds

Road car (13B-REW stock) Garrett single turbo 1.3bar
2> 1380kg (275rwkw "real power measure!" owner estimates honest 430bhp in this test)
100kmh-200kmh = 8.2 seconds

(same number of gearshifts, same OEM gearbox, same shift points.........) *both at sea level and std temp and pressure day* You do the maths :beatdeadhorse5: power curve on one is far superior, but also some dyno figures are not worth the paper they are printed on :rofl:

Unless those dyno's are certified accurate and the paper they print out shows not only the peak power and torque, but everything else such as the torque curve and what not. :lol:

Any dyno can certify what ever it likes @ the end of the day. I see sheets from all over the world from all types and most of them count for shit in my books, especially when you see what kind of "factors" people slap on to estimate the engine power.

Best Reference you can have is reality.

It's commonly available to almost anyone hundreds of cars (legitimate ones) from OEM sports car makers and you can find at least a dozen well known cars in your class all of which have been tested on proper electronic scales before the test, along with the OEM engine dyno rating and low and behold some "500rwhp" 300kg less Mazda's with hektik power bands still can match the figures of much less specified cars running normal manual syncromesh H pattern shift conventional gearboxes :o11:

Most if not all the figures you see from performance shops are BS, most of the engine "enhancements" especially to do with porting are a liability rather than any type of asset, making the cars louder, and much more peaky as well, all for the sake of making the same power on 1 or 2 psi less peak boost and 600rpm higher engine speed............ problem they all forget is you loose out so much mid range and upper end power before your normal red line of 8k. A stock ported 13B-REW even when fitted with a full catalyst exhaust will make usable power to 8k rpm, unlike its ported cousins it will make a shit load more power in the mid range and upper revs especially 5k to 6k rpm (where you spend a bulk of your time).

It's a great question, one lots don't really give much thought or proper on road/track analysis.

Maybe I should have qualified that statement? I'm used to certificates of accuracy being given for instruments such as pressure transducers, thermocouples, etc, etc. The one's that usually cost a good 12k+ to get certified with a %error of +/- 0.01% (exaggerated, but you get the point).
I think the best reference you can have is a statistical analysis of other cars based on specific dyno's. You can have multiple readings from the same car but different effects on the engine resulting in large discrepancies of the car. If the effects of the run time and environment can be accounted for the statistical analysis can give a more realistic understanding of the car's power profile.
Agreed.
Of course. There's a bunch of trade-offs when it comes to porting, but at the end of the day you need to know how much air is going through your system and what velocity you want that air to hit the combustion surface.

http://i594.photobucket.com/albums/t...Comparison.png

This is a comparison of a stock-port 6-port and a very mildly streetported 4-port. I only compared the torque curve as it is a good measure of charging efficiency.

Please note that while the 6-port is considerably lower, it is a much flatter torque curve than the 4-port. You can see that even a tiny bit of porting will hurt the low end torque.

** The 4-port is ignition energy limited past 7000 rpm, otherwise the curve would probably be flat to about 8500

I take it that was taken at the wheel?

Yeah, Mustang chassis dyno.

I took the data off the actual sheets and combined the three graphs on a single chart in Excel.