Hey guys, as you all know i am always going after unconventional ways of obtaining retarded great HP numbers out of 13B's. From my Blowthrough Weber turbo cars, to me current S#6port 190whp car, to my next 13B half bridge project.
Here are the parts i have put together so far. I will document my build here and post results. I started with a used 13B full bridge I got from a friend took it apart to not be happy with any of the ports. I found a 12A Y plate center iorn that i had ported using a Judge Ito FD Agressive street port by ArmyofOne (Jesus). then I took the R5 brige ported secondaries and cleaned them up as much as I could. I left the runners intentionally small to the bridges to keep velocity up through those ports since they will see soo much timming.







Here are pics of the housings that came with the old BP. I think they open way too early and they don't have any sleves. Any oppinions appreciated.

 

So those are before and after pix, right? Cuz the early pics look like sloppy ports and I know you're not capable of such sloppy work

 

The Bridges are after about 2 hours of fixing them. They were really bad. They need probably another 2-3 hours of shaping to get them close to good. They were in really bad shape. The exhaust ports I havent touched. This is just what i am starting with. Nothing is finished yet.

 

I wish I could have taken better pics, those primary ports look a lot like mine.

I also like the attention to detail given the closing edge with respect to the closing edge/opening edge corner. Those were done "wrong" on my housings when I got them.

 

Its going to be tough to fix those exhaust ports. The sides need to be straightened out and the top edge definitely needs a beveled edge and a little bit of rounding off to allow the apex seal to get back into the slot smoothly. Repairable yes. Finess is a must. Dont worry too much about the sleeves. It helps get a higher HP number with that large a port. Just remember efficiency is going to move up a bit higher in the RPM range.

I just still can't believe that the metal on that Y plate was so soft. I was about to pull my hair out there towards the end.

As for the port runners. I would advise that you open them up at least as far as the opening on the intake side, then give it the venturi treatment on the edge again. You may lose some port velocity down low but it will allow you to make full use of that bridge.

Just my 2€ cents.

 

i would throw those housings in the trash,and start over,not only will it be loud from the port shape,but the they have too much overlap for such a small bridge port.my peripheral port still has the exhaust port sleeves.what did you do with the engine that was in it when you got it fron C.J.?

 

The Pinecrapple (receipt said huge street port pulled off manifolds to find stock port sizes with cleaned up runners)engine is still in the car doing 190WHP now. It was only making 138WHP when I bought it.. > not to mention the car was missing the 4.77 gears and RB sway bars that were advertised... nothing on the car is the same every single mod has been changed. Threw away the Eibach springs and now it rides on RE-speed coil-overs Mazdatrix camber plates and Tokicko Illuminas, Enkies were trashed in favor of much lighter and rarer Weds Bavaria's. Interior is now complete and completely different. The entire fuel delivery system was trashed in favor of a SE tank Holley pump and Mallory FPR all fed by -8AN stainless and Literally the only thing that is the same is the engine. My complete custom exhaust I'm sure you've read about. The intake manifold was ported by myself. I went through the carb and changed every single thing. Nothing in the carb was correct. It had DCOE idle jets in it... Anyway car runs and drives perfectly, but I want 230+WHP hence the 1/2 bridge build. oh and it's got a Mazdatrix wing and IMSA front bumper.

back on topic. I took the rotor housings and compared them to some S5 turbo ones I have and they close the exact same time as the stock S5 housings, but open much earlier. I've been looking for pre85 13B housings for 6 months now and haven't found one outside of new... So I've been considering using these again...

 

that exhaust port is HUGE!

 

No **** huh? LOL! I know its huge. I'm going to clean one up this week and see how it looks.

 

I would throw the whole lot in the bin. You know if you use R5,N or Y front and rear plates you get 32ABDC port open time with 40ATDC closing times. 12A N centre iron has the same 32/40 port timing.

TII plates all round are 50ATDC closing, secondaries 32ABDC opening, with longer duration exhaust ports (4degrees earlier opening and 10 degrees later shutting). Primary port opening is retarded by 13 degrees to drop primary port to exhaust port overlap back down to 3degrees, and secondary port overlap is increased to 15 on ALL turbo rotaries from 12AT right through to final 2001 S8 FD 13BREW blocks.

Now the facts on what porting does.

Extending the duration of the intake port increases reversion in all lower RPM's decreasing filling efficiency. It works at high RPM when there is insuffient time and high runner velocity allows filling to happen with the longer duration.

Earlying the opening of the intake port will destroy idle quality and LOW rpm emissions, improve midrange emissions and power everywhere from midrange up, as well as broadening the powerband.

Taking that on board you are probably better off with using 100% stock 12A N centre plate with or Y or N or R5 end plates. This gives you tall primary runners (a feature the FD has and its because you want the port size to shrink all the way to the sliding face of the engines side irons) and 32/40 timing all round.

You can early the opening without a bridge to about 15 but you increase the chances of the plates being damaged by seals grabbing and ****. Seen plates like that first hand myself. The secondary bridge is still gonna massively increase overlap for not many other improvements. IMHO do an early open extend port with 0 NO NONE ZIP extra duration. You want latest possible exhaust port opening to increase the length of the power stroke, ie 12A rotor housings (NOT 12AT ones) or pre 86 13B housings. This gives you minimal overlap for maximal intake port, long intake duration...


[EDIT] Is your 6port at its limits? 9.7:1 rotors lightened balanced? perfect housings without the stupid NA baffle, worked runners? correct length intake? spot on tune, cold air ECU controlled spark?

 

Well I'm not going to run stock ports in this thing at all. It's going to be a half bridge build with a target peak at 8000-8500 RPM. I'm using the 12A Y center iron with a Judge Ito FD street port. So the port is already done and huge. The End plates night get trashed as they port is really a little more extended than I had planned, but I'll decide that later.
The rotor housings are the only things I'm questioning here.

 

Well you can work out what I was hinting at re the housings.... trash them. You're letting the gas out well before you need to and decreasing the amount of push from each engine cycle.

Well with a HP target peak at 8500 certainly extend duration, you'll want slightly more than TII Height all round, how much more I don't know. RX-8 makes peak up there, and has 65 closing timing on primaries and 80 on secondaries, with a way earlier open.


Primary plate may aswell go full width too then, which is about 2.5mm wider than a standard N is the port like that, something around 11-12mm from the water seal mark. You want abrupt closing of the port especially if using front to rear interfering intake manifold? Which one are you using?

For my project motor I'm working on making everything as efficient as possible with a mixture of designs shown to make the numbers. Nearly all parts will be OEM from various models with gentle mods 'in the right direction' for HP and efficency.

 

I like where this is going! keep us updated!

 

regarding the exhaust ports, i think they are all wrong for this project. for what it's worth, i'm not that crazy about the bridges either, but i'll wait to see what your reworking of them produces. there is nothing that can be done about the exhausts though. you'll have to get new rotor housings and port those.

 

You can theorize all you want but there's only way one to find out if it will work well or not and that is to put it together and test it out yourself. The porting is just a small piece in the big puzzle to make power. But I'll have to agree that those exhaust ports look a little pretty sketchy.

 

^ Agreed. I'm doing a lot of experimenting with my 20b engine and it's not even ported. Once I hit that brick wall then I'll hook them up.

 

I would say the intake ports (although massive) can be put to use with a good external setup. The exhaust ports are as you already stated, really are going to hurt things. The port timing is just extremely early and are past n/a territory. Turbo however might make good use of them after clean up. Keep up the experimenting! Oh, and T-von do you have a thread of your car up and running? or vids? want to see it

 

The only video I have is this one from back in December.

https://www.rx7club.com/naturally-aspirated-performance-forum-220/20b-teaser-audio-video-clip-880165/

Experimenting is very time consuming. I had the engine back together and running a couple weeks ago now it's apart again for some more tweaks. I'm getting closer to having everything working correctly. As son as I get it back together again, I will post a new vid. Should be later this month.

 

spend 10 minutes on one. Pictures of s5 t2 housing cleaned up housing, and what they looked like when I got them.

 

I know they're probably trash, but it's near impossible to fine pre85 13b housings in good shape for an affordable price.

 

cool thread i am doing a 1/2 bridge port also which i will daily drive i am useing 6 port s4 motor wild mild over lap but more porting on the aux ports so i dont hurt my low end power and i will also be useing a ports s5 intake mainfold and running a rb header 3" exhuast and rtek 2.0

do you think i should open the exhaust ports more like you have on yours my goal is to reach 200 hp to the wheels yet have a good power band form at least 5k to 8k

thanks in advance

hope i amd not thread jacking lol lol

 

the HP potential is a function of the port size, and timing as well. with a peripheral exhaust port the area vs location is a balancing act.

it turns out opening later actually helps, as the power stroke becomes longer, but then it needs to stay open later which adds overlap. overlap, quickly adds lots of exhaust gas dilution at low speeds (like a HUGE EGR valve), and at higher speeds needs a very free flowing exhaust.

the factory racing PP housings and the Rx8 actually open the exhaust LATER than the 74-2003 housings. the PP stays open much longer, and the Rx8 has 4 exhaust ports vs 2.

opening early however, will give a larger port size, which is good, with less overlap, which is also good, but loose a little bit as the power stroke is shorter.