Chriz88DX

iTrader: (1)

ok i am about do my rebuild and street port soon i already have a rtek turbo 550cc and s5 intake other supporting na mods.

my questionis is will swapping in a pair of higher compression rx8 rotors and e shaft help to make more na power?

the main purpose of the car will be mountain run track autocross A to B car. i am not lookin to make killer power but just looking for a little more pep on corner exit.

I wanted to make it turbo but i really love the reilably that the s4 na has also i love the fact that i can drive it to the mountain or a autocross track day beat the snot out of it and drive it home. not saying that i ca not do this with a turbo car but i don'w have the money to build this car into a turbo car. (the tranny and diff would be what i would spend on the turbo) if is way cheaper just to buy a turbo 2 chassis with a blown motor really

Thanks in advance guys

diabolical1

iTrader: (3)

from what i've seen around here, the simple answer is no. you're not going to get them to make enough to justify them over some S5 rotors.

SirCygnus

iTrader: (1)

it all depends on porting and tuning and exhaust and everything. the simple answer is no, the complex answer is... who knows?

kevk

just put in a rx8 motor and call it done

afterburner16

I won't comment on the complexity of the swap, but it's a better idea than just using the rotors.

Mazdanowski

The renesis rotors offer higher compression but also more timing. With the side seals moved out 2 mm the intake ports are able to open earlier. Without a degree wheel I am not sure how much more timing 2 mm is worth. I know the renesis opens a lot earlier but I am not sure how much of the earlier intake opening is due to the 2mm and how much is due to more aggressive porting. Does anyone know what 2mm is worth in terms of opening timing?

Then the next question would be what is it worth in hp and where is the next restriction in the system. The stock manifold is designed for a given amount of timing. If you open the intake earlier you may make more power but no longer being optimized it might not make as much more as we all would like. Also if you open the intake sooner you know create more overlap with the exhaust cycle. Just something to plan for.

sen2two

iTrader: (10)

Its been done. By a hand full of people. Many things have to be taken into account when doing this.

Most have seen a loss in power vs. the 9.7 rotors. And these are pro's that do not need to ask if it will work...

Slevin_FD

iTrader: (26)

The small performance gain doesn't justify the cost or complexity of using the rotors. It's not a direct swap as the rotors need to be machiened to compensate for the difference in the apex seal and rotor housing design. Personally I would stick with the S5's, and adjust your timing via port work., add fuel and a standalone.

rotarygod

iTrader: (1)

Just stick to the RX-7 rotors. As has been pointed out you need to have them machined to allow the use of the deeper 13B apex seals which completely offsets any financial savings you were going to have by using them. They have still not proven to make any more power than RX-7 rotors anyways.

Why are you going to use 550 cc injectors on an na? There is no need to go larger with only a streetport. Those who say otherwise need to get an education on fuel systems.

ultimatejay

iTrader: (1)

So far the people that I have talked to using them in N/A motors did not see a "gain" and went back to the 9.7 rotors. They actually saw a "loss", so there is no justification neccessary.

In fact after a certain RPM, even the lower compression rotors made the same power as the 9.7 rotors, this info given to me by RacingBeat. So maybe there combo or timing is not ideal for the Renesis rotors or maybe rotory engines don't need the high compression at high rpm?

rotarygod

iTrader: (1)

From about 9.0:1 - 11.0:1 or so, peak power should be about the same. Out of this range will be lower. BUT, the higher compression side of things will make more power at part throttle, lower load situations. This is why the RX-8 uses higher compression. It isn't for ultimate power production. It is for better part throttle/cruising/mileage. Although no one wants to admit it, the reason the Renesis makes more power has absolutely nothing to do with the compression ratio but everything to do with having no overlap by using side exhaust ports.

diabolical1

iTrader: (3)

i don't have anything to add, but i just thought it appropriate to repeat this in light of the subject of this thread.

j9fd3s

iTrader: (3)

i agree too. i have a P port, i understand overlap now

ultimatejay

iTrader: (1)

Please clarify. The Renesis makes more power than what? The reason I ask is because the most power a Renesis PPort with side exhaust made that I have seen is like 280 or something like that. 13b with pport intake and exhaust have exceeded 350+ to the wheels, so please clarify for me.

diabolical1

iTrader: (3)

well, not to speak out of turn or anything ... but i think he's simply comparing stock for stock (old 13B and new 13B (Renesis)). it would seem (to me) to be pointless, counterintuitive even, to compare a semi-peripheral Renesis to a full peripheral port engine. however, i'm sure he can correct me if i have mispoken about what he meant.

Liborek

I want to add, that it is whole combination of parts, not just side exhaust port. Milder opening characteristics of side exhaust enabled using less restrictive exhaust system. Shortened duration - no overlap enabled opening intake ports way earlier than older engines without sacrificing low load driveability. And of course, Intake manifold is nicely designed

As far as power production goes, internally stock Renesis has been tuned over 220 whp on Mustang dyno - with catalytic converter Still, its all around best naturally aspirated 13B based rotary - good low load driveability, can pass emissions and can be resonably quite, yet produce good numbers

Jobro

iTrader: (2)

Intermediate Side Housing RENESIS / 13B-REW
Primary Intake port opens, degrees ATDC : 3 / 45
Closes, deg ABDC : 65 / 50
Exhaust Opens, deg BBDC : 50 / 75
Closes, deg BTDC : 3 / ATDC 48
Outer Side Housing RENESIS / 13B-REW
Secondary Intake port opens, deg ATDC : 12 / 32
Closes, deg ABDC : 36 / 50
Aux intake opens, deg ATDC : 38 / n-a
Closes, deg ABDC : 80 / n-a

ultimatejay

iTrader: (1)

I don't think the side exhaust ports is the reason why it makes more power than the older 13b's as Rotarygod mentioned. We all know-at least I do- that the pport exhaust ports flow way more than the Renesis side ports, thus making more power. That's why the Renesis N/A engine has only made 280hp. 280 hp is pretty pathetic cosidering most 13b bridgeports make about 300 and full pports make well over 350+. I think the added horsepower, when comparing stock Renesis to stock 13b, comes from better fuel management system and better flowing intake/throttle body and intake porting than the older stock 13b. We are comparing technology from 18 years ago, Hello. Just look how much more power and fuel economy engines have progressed in the last 10 years.

t-von

iTrader: (8)

The side exhaust makes it possible to have longer intake duration. The intake opens earlier and stay open longer than the older 13b's. You couple that with a higher flowing intake? Simply put, because the Renesis is able in injest more air (for any given rpm), it's gonna make more power at said rpm. You should know that already. With the Renesis, it isn't always about power. The fact is the older side port pp exhaust 13b's will never equal the Renesis in terms of power AND emissions. There's no comparison. However, the total power advantage will always go to the older 13b's.

ultimatejay

iTrader: (1)

And that's all that matters to me and all the other racers out there. If you want fuel economy, go buy a Honda.

t-von

iTrader: (8)

???? Uhh no one said anything about fuel economy. To each his own!

diabolical1

iTrader: (3)

why do i get the feeling this is going in a direction of an argument? anyway, i'll try to clarify what i was saying before, and whether i succeed or fail, i'll hope to leave my side of the argument here.

when i quoted Rotarygod earlier, i was merely taking what he wrote (as it was written) and emphasizing it because i see (and hear) so many people attributing the power difference between the last production older 13B and the current MSP to the higher compression rotors, if not wholly, then mostly. i simply disagree with that and that's why i highighted it. when i responded to your question to him, i was just trying to point out that comparing the stock Renesis to older bridges and peripherals is pointless because you're using a different context. what's the use of saying older race ported engines make more power than Renesis engines that go through what i'd oversimplify as calling a "retune" (to go from 230-ish to 280). as far as i'm aware there's no change in the engine itself to facilitate this. the older race engines having more power is the result any logical mind would expect. if comparisons must be made, why not leave the comparison limited to an older 6-port with similar porting?

i realize racing is quite important to you, but for the majority of Rx-8 owners, and the handful of people that put Renesis engines in older Mazda, how many of them have racing in the forefront of their minds and would furthermore be willing to daily drive an obnoxious car? that's all i'm trying to point out. using a 6-port block (or even a turbo block with 9.7s) if you were to reach 280 (on stock or streetports) you'd have something prohibitively expensive, no emissions, and just bloody LOUD! Logan (GtoRx7) eclipsed 230 (wheels) on an RE block, if my math is right, that's on par with high 200s at the flywheel. so it is possible. however, how many Logans do we have out there?

280, pathetic? would you call an older streetported engine making 280 pathetic? again, keep the porting similar and then make the comparison. look, i'm not misguided enough to feel the need to compare the old to new. i have both. i enjoy both. i see each for what it is and that's where i leave it. however, your comparison is decidedly lopsided and with all due respect, to me, invalid. sorry.

first of all, you are absolutely right, you're comparing two different eras of rotary engines, and that's kind of why i see it as being pointless. i am not so out of touch that i don't realize there are many factors at work to make the Renesis do what it does. it's not just the zero overlap/side port exhaust or intake setup or electronics, or porting, it's the combination of everything. i realize that, and if it sounded like i was simply saying it was zero overlap or whatever, then i guess that's on me. maybe i should have taken the time clarify better.

for racing applications i am well aware that the older engines have an edge. they have decades of development and on-track experience, plus they can now benefit by modern electronics to shine even brighter. whether Mazda chooses to address the Renesis' shortcomings through time, we all have yet to see.

i don't know if i'm any clearer than i was before, but essentially i'm leaving the all-out, no-holds-barred stuff aside (i.e. radical porting) when i say the uses the side-port exhaust (and what it brings with it) to make more power than a comparable older 13B. surely, you can see that the sideport exhaust is the fundamental difference between the two, so electronics, rotors, intake, ignition, and the like would naturally get second billing even though they contribute to the overall package.

diabolical1

iTrader: (3)

oh and this ... i simply don't get this. i'm not sure where it was directed.

diabolical1

iTrader: (3)

see? this is what i'm talking about. everything in context ....

lastphaseofthis

iTrader: (8)

https://www.rx7club.com/showthread.p...timing+degrees

if given the chance to put rx-8 rotors in an n/a build, i would, and then go hog wild with timing and make my own judgement, b/c this thread is about rx-7 vs rx-8 rotors right? not porting, or side exhausts and pps. i'm betting theres more to the rx-8 rotors then just the compression ratio and weight.

lets not let this thread end like that one did.