ColinRX7

Okay, you can STOP pretending to know what you are talking about, anytime now...

Epitrochoid

I think the renesis would be a cool swap, imo, but just to say you did it. The performance that you will get out of a stock renesis is not that much, the car only puts down like 182 whp and 126 ft/lb stock.



http://www.rx7.com/rx7rx8comparo.html



You could do that with a mild built n/a 13b. Sure it may not be as clean, or get as much mpg, but it would be a lot cheaper.



There are guys pushing out more than 182 with modded 13b's. Look at Kahren: https://www.nopistons.com/forums/index.php?...e=post&id=33473 he is making that much power and I he's running s5 rotors, so pretty much oem compression. If you were to get higher compression you could jack that up even more, look at the difference in power between the s4 and s5 with just a .3 diff in compression ratio.



Go to the dyno section on this website and you will see lots of people with just bolt-ons, porting, and some tuning are getting close or more than the renesis puts out stock.



If you wanna get the renesis just for bragging rites, then do it, it would be clean, and I don't think anyone has done it yet. But if you are looking for 182whp n/a then the renesis is a waste of time, and money.



I do have 1 questions though, what is the highest compression ratio that a 13b can run on 91 octane? I know my 99 civic si that I use to own I bumped the compression up to 11.5:1, but I don't know if a rotary can do that on pump fuel.

deadrx7conv

Sure, you can rebuild/port/tune an NA for more power(up to the Renesis level). But, wouldn't the same make the Renesis even more powerful?? Think of all the extra power in the Renesis with porting, lightening, blueprinting,.......emissions elimination!!!!!!!



Some things to consider:

Any of the aftermarket computers that will work with a rotary should have no problem with the Renesis. Who says you need to have throttle by wire or any other complex trickery???? DUMP THE CANBUS!

Use a normal TB with cable, use RPM switches for the staged intake/6-ports..... running 6 injectors(if even needed) can be controlled with the above computer or RPM based additional injector controllers, and oil injection made easy by premix........



I just don't see why everyone makes it more complex then it needs to be. Its just a f@#$%^& engine. It needs spark, air, and fuel! Hell, you could make it run with a carb if you made a new intake to fit the carb on.



Would I want one in my car, SURE! Is it worth the money for the engine/tranny/mounts/ECU/.....???? NOPE! But, some people live for bragging rights and it would be cool!

i.didnt.do.it

yeah mon, i spent like $10,000 on this motor swap.



how much hp?



oh, like 180 mon. but yo, no ones done it yet mon.

mazdaspeed7

Raising the compression on a rotary isnt like raising it on a piston engine. Any increases in compression ratio adversely affects an already inefficient combustion chamber design. Its long, thin, and flat, and raising the compression makes it worse. The Lemans winning 4 rotor only had a compresion ratio of 10:1, which is the same as the renesis engine. The S5 n/a rotors are 9.7:1, which isnt much of a decrease at all.



Of the 14 hp difference between s4 and s5 n/a engines, nearly all of the hp is from the intake manifold and the higher rpm's afforded by the manifold and the lighter rotors. The compression changed from 9.4:1 to 9.7:1. But just putting a S5 intake manifold on an otherwise stock s4 car will get you 8-10 rwhp, which is damn close to the 14 hp (crank) difference in the power ratings in stock form.





Kahren made 182 rwhp on a stock engine stock ports with a haltech, custom intake manifold, and full exhaust. Thats about what stock RX8's are dyno'ing at. A relatively mild streetport on a customers car did almost 200 rwhp on the stock ecu with bolt-ons and a s-afc.



Personally, I think the renesis will be more limited in its potential than the previous n/a engines. The exhaust ports were moved to the side housings, which decreased port timing. And in addition, there is no longer a straight shot out of the combustion chamber down the exhaust. It has to go into the port, make a 90 degree bend almost immediately to get into the runner. Not to mention there is a considerably higher ratio of runner surface area to the cross section, meaning there is much more surface drag and flow loss. And you have more heat lost into the housings because of the increased surface area, which cools and slows down the velocity of the exhaust gas.



A lot of the hp gains on the renesis came from the intake manifold and the 30% increase in intake port area accomplished by moving the side seals out towards the rotor face. With the increase in port area, the intake ports also open earlier.

ColinRX7

I think Adam and I are on the same page..





I'm building an all peripheral port engine for street use, I'm not making tremendously huge peripheral ports either, I'm looking to keep intake velocity high and tune for a fat power band in lower RPMs



My HP numbers will be lower than a regular peripheral port, but you know what, I'll be a big gob of power higher than a renesis motor. My powerband will be more applied, not shooting for peak power at 10,000 RPM - much lower, that in itself constitutes a better reliability factor, doesn't it?



Alot of peripheral port engines people say idle at 3k, they are totally unstreetable, sounds about right doesn't it? With all that overlap?



I've seen in person a large peripheral port engine running EFI that idled pretty damn smooth at 1200 rpm.. Not bad for the size of the port work. It's all in the tuning (manifolds and all) and, as far as I'm concerned, EFI is the key. It was brapping a hell of alot less than those bridgeport engines you see running carbs, or an SAFC on stock FC ECUs.. You'd imagine a peripheral port would be worse, no?



It's not all about building a ported engine and tuning the EFI.. It's about tuning the intake manifolds, runner length, throttle sizing, dynamic chambers (if applicable), and then tuning the exhaust..



There's much more to it than just dropping something else in and saying, well it's got more power so, that's good enough.



Don't believe me on the port tuning? Look at the differences Mazda made in the renesis intake. How much different is the shortblock intake porting compared to a bunk old S4 6 port? Not dramatic, but different albeit. How about the runners? Length? Dynamic chambers? Throttle body? MUCH MUCH MUCH different. You'd think they would be at a hinderance using side ports for exhaust too, but they aren't. They tried something different, and tuned EVERYTHING, not just slap together some manifolds and dink with the EFI until it runs smooth. The renesis figures are a direct result of maximum tuning, and up-to-date EFI controls.



Imagine what you could do with two (more ideal as far as fluid dynamics are concerned) peripheral ports (intake and exhaust), some math to figure out what type of power band you are looking for (forget the go big or go home dyno queen attitude), and tuning every aspect of the motor? Say smaller peripheral ports, tuning intake runners for a specific powerband, same with exhaust, and then tuning the EFI?



Really now, stop worrying about bolt ons, and design something! Use math! Use creativity! Make an idea, and goto town with it..



You might end up having a car with a powerband that will give just about anyone on the street a run for their money all over the board, and leave that guy with the renesis FC in the dust, wondering how you did it with just 35 more ponies..

j9fd3s

the devil is in the details. the 6 ports are stepper motor driven, that means you need a stepper motor controller, which is not hard, but its needed. yes a normal throttle body would be a good thing, or you can use another stepper motor controller for the stocker, no real challenge there. the injectors are no problem, neither is the metering pump.



none of this is hard, it just needs to be there. i think thats why a lot of the renisis engine installs you see are the 4 port low power motors, none of this stuff is needed