Small vs mild vs large streetport

Force Fed · 05-01-2009, 11:52 AM

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.

vex · 05-01-2009, 11:55 AM

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.

PercentSevenC · 05-01-2009, 02:34 PM

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.

Force Fed · 05-02-2009, 09:19 AM

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.

vex · 05-03-2009, 12:38 AM

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.

Force Fed · 05-03-2009, 06:48 AM

Quote:

Originally Posted by vex

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?

NoDOHC · 05-03-2009, 07:49 AM

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.

RETed · 05-03-2009, 10:30 AM

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

Force Fed · 05-03-2009, 10:50 AM

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?

NoDOHC · 05-05-2009, 10:17 PM

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.

Force Fed · 05-06-2009, 05:32 AM

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

N.RotaryTech · 05-06-2009, 06:19 AM

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.

Force Fed · 05-06-2009, 07:04 PM

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

classicauto · 05-11-2009, 11:51 AM

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

laf_20b · 05-12-2009, 04:14 AM

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

05-01-2009, 11:52 AM	#1
Force Fed Rotary Fan in Training Join Date: Dec 2008 Location: Spartanburg/Greenville area, SC Posts: 45 Rep Power: 0	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.

05-01-2009, 11:55 AM	#2
vex RCC Loves Me Not You Join Date: Jul 2008 Location: Influx. Posts: 2,113 Rep Power: 19	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. __________________ The Official FC Radiator Thread My Project Thread: Cerberus CCVT Virginia Rotary Group Last edited by vex; 05-01-2009 at 11:59 AM.

05-03-2009, 12:38 AM	#5
vex RCC Loves Me Not You Join Date: Jul 2008 Location: Influx. Posts: 2,113 Rep Power: 19	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. __________________ The Official FC Radiator Thread My Project Thread: Cerberus CCVT Virginia Rotary Group

05-03-2009, 07:49 AM	#7
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	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. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

05-03-2009, 10:50 AM	#9
Force Fed Rotary Fan in Training Join Date: Dec 2008 Location: Spartanburg/Greenville area, SC Posts: 45 Rep Power: 0	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? Last edited by Force Fed; 05-03-2009 at 11:04 AM.

05-02-2009, 09:19 AM	#4
Force Fed Rotary Fan in Training Join Date: Dec 2008 Location: Spartanburg/Greenville area, SC Posts: 45 Rep Power: 0	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.

05-05-2009, 10:17 PM	#10
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	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. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

05-06-2009, 05:32 AM	#11
Force Fed Rotary Fan in Training Join Date: Dec 2008 Location: Spartanburg/Greenville area, SC Posts: 45 Rep Power: 0	Okay, what changes the port timing? Changing the length of the port?

05-06-2009, 06:19 AM	#12
N.RotaryTech Home-brew Rotary Join Date: Feb 2008 Location: GooseCreek SC Posts: 552 Rep Power: 18	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. __________________ '89 RX7 GTU, half-Bridge-port S4/S5 NA, E6K, Full RB exhaust, weekend warrior. '83 RX7, The "this might take awhile" project. '87 RX7 GXL, Rest In Pieces. '98 Subaru Impreza Outback-sport, rx7 rescue vehicle, down for repair. '94 Ford Ranger, daily.

05-06-2009, 07:04 PM	#13
Force Fed Rotary Fan in Training Join Date: Dec 2008 Location: Spartanburg/Greenville area, SC Posts: 45 Rep Power: 0	Awesome site, definitely helps understanding the port timing and how the whole engine works really.

05-12-2009, 04:14 AM	#15
laf_20b MADAZ BRA Join Date: May 2009 Location: Penrith Posts: 1 Rep Power: 0	PP or Ext Port Hey guys im new. What do you think is more appropriate for my street rx8? PP or Extended port?