In the midst of another project, I was playing around with some 6-port style housings that I had sitting around; converting them to an E-Prod style streetport (IE, into a 4-port) and it kind of struck me how goddamned huge that ended up. And to smooth out the top edge, well, it seemed like it was closing awfully late.

So, just wondering, is there a finite limit to what's useful? On the 12A stuff, just going to the metal seems to work pretty well but... that's a lot of port on the 6-port stuff.

 

apparently, Judge Ito wrote about the siamesed ports on the www.nopistons.com board. i have not read the writeup myself yet, but you could check it out to see whatever he said.

 

I have a VERY late closing six port semi-combined seconeary / aux design with nearly all the opening timing I can get before the side seals lose support, and beveled rotor edges on top of that. It idles at 750 rpm, gets 23 mpg as of last week, and ******* rips! I need to take it to the drag strip after I ditch the stock ECU, because it is seriously faster than it was last year with a milder port when it ran 14.7@96. All this with stock cat still on, which I really need to get rid of.

 

actually, there is a section of This Discussion that might interest you, too.

 

Yeah, poked at that one a bit. Currently trying to find the one where Ito talks about the things... I've got this funny idea about using (modified) 6-port end housings and a 12A middle housing to take advantage of the 12A having so much more meat around the primary ports. On a 12A, by the way.

 

Answer to your question is YES. My motor was ported too high which pinched a corner seal which then makes you loose compression and get blow by.

 

ErnieT: I just meant in terms of the effects of late port closing on the powerband, though going big enough to lose seals is, I admit, not a good thing.

I suppose I should mention that this would be done with a fabricated intake manifold anyway, so I'm not concerned about the transition from 2 runners to 1 port hurting flow.

 

There is an old post on this forum in which the owner of Mazdatrix (Dave Lemon) chimes in about the siamesed 6 port that they developed for the E-prod car. NA, of course. They had a hard time making the intake and exhaust manifolds right to get torque to peak below 10,000rpm because that is where they started getting enough velocity to work the timing in the larger volume port.

I suspect 88integrals has left some port runner in the side housing to preserve velocity before the port face or his motor would suffer. Probably just took out the 2ndary to aux divider so he could port for early opening and drop the upper sideseal into the port.

There is a point in timing duration where the upper and lower (well, leading and trailing at this point) outer track edge converge and that stops you from being able to drop the leading seal without droping the trailing seal and recover it in a scissor action. You can so it non-scissored but the sideseal can pinch at lower rpms. These overported EP motors were idled at much higher rpm so the sideseals wouldn't drop into the port, but now they can't port for early opening in that class.

I would think with a turbo the large port/runner volume causing such a high powerband shouldn't be such a problem as the turbo will provide velocity in the larger volume MUCH sooner- but before the boost comes on the car will be SOOO slow. If you port for more and more duration on a turbo car you just need more boost to overcome the reversion- it will be slower in the lower boost ranges/rpm.

This could be fixed by going w/ a Lysholm SC and basically being Miller cycle rotary- right 88integrals?

 

I saw the results of some dyno testing of various 6 port configurations, they tried everything on the 6 port, and would have to agree with Mazda trix's summary of the 6 port, they are almost better left alone than screwed with, the more they were ported, the higher the rpm peak got resulting in less power in the rpm band the engines internals could handle...
The only real power gain came from a polish job of the primary and lower secondary, outside of that there was nothing spectacular.. They then bridged it, then made did a monster streetport, then they bridged the monster streetport. The goal was to see if they could make huge n/a power using the stock n/a intake setup and manifolds, bottom line, those manifolds are for low rpm power and response and are simply wrong for top end airflow, which then contradicts the added porting. A streetported n/a 4 port 13bt with T2 manifolds made about 75 more hp on its first pull...
There is alot of science built into the 6 port motors, and mucking with the port timing seems to throw it all off..Max

 

BLUE TII: Ahh, thanks for going into more detail; didn't know all of that about how the side seals have to move... will have to watch for that. The class I'm looking at building this for doesn't have the restrictions on adding material that EP does, so I was planning on building up parts of the port with Devcon in order to smooth the airflow (since the aux ports aren't shaped that well) but it sounds like reducing port area would be really helpful too. Boost would be a nice solution but... not legal to race a boosted, heavily ported rotary. (why no mr. tech inspector, that thing on the exhaust is just a muffler! )

Maxthe7man: The key point in all of that was "using the stock n/a intake setup and manifolds". I don't have an FC, I don't have the stock manifolds, and the 6-port plates might not even end up on a 13B... so the fact that the stock NA 13B manifolds kill any effect from porting doesn't really bother me.

 

Most of my port runners as well as the aux port sleeves are still in, the port just closes very late with a very "different" shape compared to what I've seen done by others. I just ground down 5mm from the divider between the two ports, so as to retain a secondary port bowl and keep the runners fairly small.



^this was before I ground down the divider a little, for side seal purposes. Ignore the scratch on the corner seal track, it's my signature.


But it remains to be seen how this my little lysholm supercharger project pans out:



If I don't get it done the end of summer I'll go crazy. The Megasquirt ECU is hopefully almost done, then I'll start making the oil lines, intercooeler pipes, bypass valve, and throttle cables.

 

wow I have never seen a 6 port motor with a port job........I always thought a 6 port was useless...........

 

Give me your useless six port end plates please.

 

Yes the stock manifolds kill all porting effect, even with a T2 lim adapted to the mix it still doesnt perform as well as a 4 port for over all power production, the 6 port is very good at throttle response and emissions tuning, above that, its not worth the effort... Use an FD block with 9.7:1 rotors...Max

 

We are having a misunderstanding here. Again, I am not doing anything at all related to any of the stock manifolds, or to retaining the aux ports for low end throttle response or emissions or whatever. I am looking at creating something like http://www.yawpower.com/146.jpg which is a larger street port than is possible with FD irons, fabricating an intake manifold, and putting it in a car that will never see street use.

 

No misunderstandng at all, all I am trying to tell you is porting a 6 port plate is like polishing a turd...

 

Give me your 6 port plates please, I'll dispose of them for you.

 

Well, so far the only anecdotes you've provided are about the things on stock manifolds... whereas I can look at the things and see how the port area is larger than is doable on other irons, how the runner area is huge, and how the E-Prod motors are making in the neighborhood of 240hp through undersized carbs... well. I'm still waiting for evidence that they're turds, let's say.

 

Yes the manifold sucks for a ported 6 port, and yes I'd loooooooooove to delve into fabricating a custom RX8 style six runner manifold tuned for my ports. Hmmmmmmm, RX8 features six ports and makes 240 hp too. I see a pattern.

 

If you want to waste your time with it, thats fine.. But all I am trying to tell you, is there is a easier and better way to go..
Here is a streetported 9.7:1 13bt with FD intake n/a, notice the afm, its still passes the sniffer in Japan...It made 255 rwhp, and is daily driven, idles at 750, amazingly still on the stock turbo ecu with an ITC.
I have pics of an fd with the same setup, but power fc, I missed out on the final tuning of that car, but it broke 250hp n/a on its first dyno pull through full exhaust with a cat in place and the expected 275-280 rwhp out of it.. Its becoming a favourite swap for rx7 owners in Japan who dont like thier fuel bill...
I also have a collection of pics and the dyno chart somewhere of a 13bt 4 port miata, that with a bridgeport, made over 300 rwhp...still with full exhaust..
I havent seen a fc series six port make it past 215 without nitrous on a dyno yet...I have ridden in a true 250rwhp rx8, and that was the absolute ceiling for that motor in tractable street n/a form..

 

Right, so a smaller street port with EFI ends up making about the same power as a modified 6-port restricted to not adding material to smooth or reduce area of the ports makes with a specified (too small) carb. So what happens when you smooth the 6-port runners out, reduce the area for better velocity, have larger primary ports (though that's kinda unrelated to the issue at hand) and have an EFI setup without any restrictions on minimum size?

Besides, FD intake manifold won't fit either... this ain't for a 13B.

 

No a smaller streetport efi ends up making more power with far better driveability and probably twice the mileage...
About the same place as you started in a nutshell, feel free to waste your time, I am done wasting mine...Max

 

Driveability? Mileage? WTF?

This is for a race motor, which I thought was obvious. Close ratio transmission, lightweight car, no having to give a damn about what happens below 7000ish RPM.

Ah, bugger it... I got some other useful responses.

 

I guess I'll throw out my gas mileage and quarter mile times: 26 @ 75 mph on the freeway and 14.78 @ 95.6 on a 90 degree day at ~250 feet above sea level with a 2600 lb car (with driver). Only mods beside the port was a RB header, cone filter / cold air intake, and ported S4 NA intake manifold. The quarter mile time was on a very early version of my ports that started to lose torque at 6500 rpm. My latest setup has beveled rotors and similar ports as shown on the first page, and pulls uniformly to 7.8k where my stock redline is.

I don't have dyno data yet and probably won't as NA as I'll be going supercharged in the near future. But yeah, it would be a dream to fab up an RX8 style intake manifold for this engine, full collected exhaust and get an EMS on it. There is definately potential with six port engines that apparently few people want to explore.

 

the major oversight here, or at least what no one has mentioned is that extending the aux port higher up is not usefull because its too late in the intake stroke to draw in any mixture. Thats why its not worth it. Sure, join the secondaries with the aux, thats fine but don't use the na manifold and hope to get power, its not made for that.

You would be best in your application to combine the aux and secondaries and also add a small bridge. Give the 12a intermediate plate a street port. Just don't raise the aux port timing, concentrate rather on shaping the top of the port to increase airflow.