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Naturally Aspirated Performance ForumDiscussion of naturally-aspirated rotary performance. No Power Adders, only pure rotary power!
From the "12A" to the "RENESIS" and beyond.
Hey all, just wanted to know how high in the powerband peak power can be on an NA 13b 4 port with a large streetport, s5 rotors, 55mm ITBs, an ECU, and a good tune?
How high in the rpm range peak power will occur will largely be a function of intake manifold design.
The HP limit will be around 250rwhp peak at whatever rpm your intake manifold is working best at.
Power under the curve will vary greatly by intake manifold design and basically the more money you spend on parts and time you spend on a dyno the more power you will make below whatever peak rpm power.
You specify ITBs which means individual throttle bodies.
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A 4 barell Holley style manifold is cheapest form for a rotary and can run a carb or a 4 barell throttle body. A 4 barell throttle body has a throttle plate for each intake runner. Is that an ITB engine or an ITP (individual throttle plate) engine?
You only need the 2 primary injectors if you size them for your peak power (so anything over 1,000cc injectors?), the manifold, an injectorless 4150 TB, a boost hat and a stand alone ECU. SpeedMaster makes the least expensive new parts (~$250 manifold and ~$150 TB).
This style manifold/TB also typically makes the highest peak power out of your choices by a small margin at the expense of power under the curve.
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Four TB off of a motorcycle sized correctly for your desired (rotary) power (so, you need more airflow and fuel for the same hp as the bike) on individual runners would be a more traditional looking form factor of ITB and will provide better power under the curve than the holley style and very nearly the same peak power with the hood open on the dyno.
If you then build an airbox to contain the 4 throttle bodies with an inlet to draw ambient air outside of the engine bay it will make more power under the curve as before and will also make the same peak power as the above holley style intake.
But you will again have to explain to people its ITBs because unless you remove the airbox, it wont look like it.
You are on your own as far as making it, so its either nearly free if you have skills or skys the limit of you are paying someone. This includes additional tuning time synching the TBs airflows at idle and under load over the holley set-up.
I am speaking from the experience of s9meone who helped a friend set-up and instal ITBs on his S2000.
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The final option is by far the best option that is called ITBs, but t is not ITBs.
That is to use the MazdaStar (factory race intake manifold) or other side draft style or down draft carb manifold and two throttle bodies.
This intake manifold combines the primary port and 2ndary port of each rotor and provides a TB for it.
In this way, you not only use helmholz frequency wave tuning supercharging to improve lower rpm power like the previous two manifold designs, but also dynamic wave tuning like the factory Mazda manifilds use.
That is, using both the positive and negative wave forms for the inertial supercharging to broaden the power band.
For best power with the hood shut this will also require an airbox over the two TBs as a recent video by the rotary hacks the vargas brothers demonstrates (hey, they got something rigjt).
So, again- you will have to explain to people that you have ITBs and this time you will be lying since there are only 2 throttle bodies with 1 throttle plate each. But you can justify the lie by explaining that there is 1 throttle body per rotor so its still ITBs.
And that is some good justification because this combination jas been shown to provide the best power under the cirve with no sacrifice to peak power which is obviously why Mazda chose ot for their 4 port na factory race cars (MazdaStar, Formula Rotary, whatever).
Cost is not too bad, couple thousand for manifold and TBs and aorbox and then the same injectors, ecu etc that you need for the holley set-up.
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Whatever ITB you choose, when you want more than ~250rwhp peak all you have to do is bridge port or semi-peripheral port or go full peripheral port.
With the cheap holley style manifold you can bridge port and just change your tune and gain peak power and power under the curve.
Or if you are using the semi-peripheral port holley style, you can add the semi-ports to the engine.
Or you can build the engine with the semi-p ports initially and just leave the gasket between the intake manifold and engine and just run the 4 side ports till you are ready to re-tune and make more power.
Logan of Defined Auto built his first 3 rotor this way (albiet with a bespoke intake manifold. He made 360rwhp on the street ports alone and then when he got around to fabricating the intake manifold for semi-peripheral ports and rwmoving the gasket blocking them he made 480rwhp. You can over lay his two dyno charts to verify no power was lost under the curve by uncorking the already built peripheral ports.
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The motorcycle and side draft or down draft ITBs can also just bridge port and re-tune for more power, bit semi-p port is a more involved option with them.
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The full peripheral port engine is by far the king of power inder the curve and that is why Mazda used it for all racing classes that allowed it.
They were originally banned in the early early '70s for production class racingin Japan, so Mazda developed the bridge port to use the production rotor housings. Soon Mazda was making more power on the bridge port engines than the initial peripheral port engines and the sanctioning body relented and allowed peripheral ports again on the condition that they were available to the public to buy and use.
This was the birth of the "sports kit" engines and orgin of Mazda Motorsports program. Anyone can buy Mazda Factory Race dry sump oil systems and periheral rotor housings and all the other parts to make a full MFR race engine as well as dog ring race transmissions race bodywork and anything else Mazda has used in club racimg (sorry, not many 4 rotor Lemans parts that I have seen) up to today (baring discontinued parts).
Pretty soon Mazda developed the 13B and put that in the RX-3 and it was game over for the previously dominating (prince) nossan skyline GTR.
This little shitbox rx-3 with an engine anyone could buy if they stiffed their kids of allowance (production racing) absolutely dominated the Nissan GTRs (with their unobtanium S20 all aluminum OHC inline six that nissan bought prince motor company to obtain) down Fuji speedways 1 mile straight in front of the packed grand stands and could just keep it together enough through the banked tirn at the end and following corners with their shitty leaf sprumg rears and poggo stick front struts to be within passimg range of the GTRs the next lap to win all the races.
The price of that fat lip humiliation to nissan and japans national treasure skyline GTR was the end of all production car racing in Japan for the next several years with the excuse of the oil shortage caused by opec.
Wouldnt be prudent to race right now with the high cost of gas.
Once nissan got a leg up again and the 2nd generation skyline GTR (r32) was in full swing they were probably feelimg pretry good again battling closely with the FC rx7.
Sadly mazda fucked them again by introducing the FD rx7 and m9ved on to humiliating the porsche 911 while the GTRs made due with being fast for a sedan.
When Mazda retired from factory backed racing a shitty little cluttered shop called RE Amemiya took over the reigns amd campaigned the aging FD against the factory race teams with fairly good success in production racing JGTC.
It was harder to compete now against the factory race teams now that JGTC allowed cutting up the firewall to move engine back and basically tube frame cars, but Amemiya san soldiered on with a shoe string budget and over 20yr old na peripheral port 20b production engine restricted to 300hp to fit the class rules with most usable power under the curve and as close to a race car chassis as he could manage.
That is Takeyari spirit and Amemiya san should be recognized and enshrined as the true national living treasure.
And Mazda should get a little more support from the japanese government for their contributions to national prestige.
But what do I know?
Oh yeah.
Buy the Mazda peripheral port rotor housings and make 250rwhp with the most power under the curve.
That is what I know.
If you eant to learn more, read a book.
I recommend the 1971 book "the wankel engine" by Norbye because absolitely nothing has been developed for the rotary engine since then.
Direct injection, aluminum rotors, ceramic apex seals, 3 lobed rotor housings (liquid piston cough) and the fraud that all production rotary engines are compared to Wankel's real genius rotary engine is all in there.
Nothimg new has been developed since 1971 and you will learn how and why Mazda settled on the rotary as they produced it.
It was hard to soldier through all those cursing epithets. It’s one thing to say those things another to write them where you can see it straight up in front of your own face. Not sure what is wrong with people these days other than just being ignorant. Will probably get the effu response for pointing it out I suppose.
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Hey all, just wanted to know how high in the powerband peak power can be on an NA 13b 4 port with a large streetport, s5 rotors, 55mm ITBs, an ECU, and a good tune?
Will your engine be based on Turbo II housings and NA rotors?
A 4 port 13B seems to max around 200-220 at the crank. 13BT, RE, and REW engines can make a lot more.
You could not port a 4 port's ports out to T2 size without hitting water all around.
Four 55m throttles is crazy, you are better off with 45s or 48s at most.
I was planning to get an EFI Pro-Series IDA kit with two throttle bodies 55/53/50mm tapered bore. Is that still overkill for wanting to make peak power close to 8.5k rpm?
Hey all, just wanted to know how high in the powerband peak power can be on an NA 13b 4 port with a large streetport, s5 rotors, 55mm ITBs, an ECU, and a good tune?
Hmmmn, now to answer the question.
Peak power on an NA 4 port 13B with large streetport can be as high in the rpms as you want it, but it wont help you make anymore power than the ~250rwhp I estimated above.
If the set-up flows poorly at low rpm not only will low rpm power be bad, but it will take many rpms to get intake velocity high enough to fill the chamber and make the ~250rwhp.
Example-
Mazdatrix highly developed EP 13B.
6 port ported to 4 port had a hard time getting peak power under 10,000rpm where engine ("minimal" mods allowed) would stay together. I think made peak ~250rwhp (290 engine dyno) and was run at 280 flywheel hp spec to get peak power under 10,000rpm for reliablity.
At 10,000rpm you are going to find a lot more rear wheel horsepower in the transmission, driveline and rear end than by increasing the engine flywheel hp a bit. Talking frictional losses here.
Ah yes I read about Mazda doing that in another thread, but a bit different from what I meant to say, sorry! By "NA 4 port" I meant using turbo 4 port plates in the setup and keeping it naturally aspirated, not porting 6 port plates to make them 4 port. I'm honestly trying to base the build off of the orange FC guy that had his car tuned by Angel Motorsports, he wound up hitting around 260 whp with what sounds like a large streetport, the EFI IDA set up, and their airbox. Link here:
Ah yes I read about Mazda doing that in another thread, but a bit different from what I meant to say, sorry! By "NA 4 port" I meant using turbo 4 port plates in the setup and keeping it naturally aspirated, not porting 6 port plates to make them 4 port. I'm honestly trying to base the build off of the orange FC guy that had his car tuned by Angel Motorsports, he wound up hitting around 260 whp with what sounds like a large streetport, the EFI IDA set up, and their airbox. Link here: https://www.youtube.com/watch?v=IcSViKc6TsQ&t=279s
He makes peak power at 8.3k rpm which I personally wouldn't mind at all, but if I can hit it at 8.5k that would be ideal.
OK cool. When I think 4 port 13B I think of '74-78 engines. These used the same side housings as contemporary 12As. The later turbo engines had significantly larger ports than those old engines.
I have a bridge ported 4 port right now but I really liked my street ported 13BT un-turbo engine. I have 90% of the parts to put another one together with a S4 NA intake manifold. I learned too late that the S4 NA manifold flows way better than the T2 manifold. I only ever ran the T2 engine as a street port with the T2 intake manifold.
and only made 5 more whp (175 vs 170) but 1000rpm lower. I modded a 6 port lower to port match to the T2 engine and the power shot up dramatically, everywhere. Gained low end and top end. I never dynoed it that way but I gained almost a half second in the quarter mile, running the injectors static.
I really do want to know what I could do with a street port T2 engine with the S4 N/A manifold....
I've been curious about how a street ported 4-port compares against a street port 6-port lately. So much so I 'd almost wait about going turbo until after I can put one together instead of turboing my 6-port.
I think for me though if possible and if it made sense I'd like to keep peak power around 8k or less. I plan to use a 3rd gen. UIM so it will be what it is I guess.
My EFI hardware ida taper bore tb 4port 13b s5 na rotors. Standalone ECU ign1a coils makes 192hp. Have since improved the tune so it makes more but haven't had it on the Dyno. Pulls hard 5k to 8k. This is a 4port made from my old 12a street ported using rb templates. Very limited choices for intake manifolds for the early 4 port 13b. I wouldnt waste your time with modifying a 6port. Only reason mazdatrix used the 6 port was because of the rules in scca. More useable power with the 4 port. I prefer the early housings with the water jacket in the housings not the irons. I couldn't find any good turbo2 irons when I went that route.
07-05-22, 05:46 AM
