Hey everybody, I have a black 1980 First-Gen RX7, and I'm going to keep the chassis until I'm dead or it's wrecked (maybe both at the same time... not a bad way to go) and I've been thinking about putting a RENESIS into it as soon as I can get my hands on one. With the 250 horsepower, potential for modification, and the light chassis I have, I think it would be ridiculously cool.

I'd heard that a RENESIS is basically the size of a 13B, is this true? I know some first-gens had 13Bs, so I doubt it would be too hard to put in if so. Also, could the headers I've been using on my 12A fit? Would increasing the airflow with headers and removing the cat make a very substantial difference given the RENESIS' higher intake? Also, what kind of job is it to switch from a carbureted engine to a fuel-injected one with a computer? I've also heard that the only reason a turbo wouldn't work with the rx-8 is that the exhaust gas would be too cool and thus wouldn't react properly in the catalytic converter, resulting in bad emissions. (I'm not going to have a cat, who cares?) Would it be possible to turbocharge this beast? Would you need a turbo specially made for it? (Probably.)

Thanks for your time in answering these questions and making suggestions as to the actual swap-in job and possible modifications, hopefully other rotary enthusiasts could get excited about this.

 

Yeah but this is an engine that was made to function with emissions. Don't take it the wrong way but I think that's a crazy idea and not worth the money or time. You can get 300 plus HP by turbocharging an older 13B. The RENESIS IS a 13B, actually. Turbocharging a RENESIS is nearly impossible and costly. The 12A headers will not work either. What's a RENESIS engine cost anyways, like $10,000 new? They aren't even out yet. It was hard enough to cram a 3rd gen engine into a 1st gen, ask Mike. It's nice to dream, but it'll probably always be just a dream. Oh well.

 

heh ya never know... ya never know.

 

The advantage of a Renesis is 250 HP with a new, factory-warranty engine. Whether or not turbocharging is 'impossible' remains to be seen - the main difference is side, rather than peripheral, exhaust ports resulting in lower emissions and better fuel economy PLUS 250 HP without the added plumbing and overheating potential of a turbo.

Yes the Renesis as a crated unit is costly (nowhere near $10,000 though ) but so is 300 HP worth of mods, with no warranty. As with any swap it comes down to what the person wants for his/her car.

 

That's what I'm all excited about, I think putting one in my SA may be almost as easy as a 13B. I'll probably have to use an rx-8 tranny and put in a computer, etc., but right away I'll have 250 hp in a new engine that will, with luck, last me a long time. I'm going for a street car that's fast and fun to drive, and this will give me great reliability too. Like I said, I want to keep this chassis forever and a Renesis might outlast the chassis.

I live at home, going to community college preparing to transfer to the U of Minnesota, and I'm a pizza delivery driver. That translates to a lot of disposable income, and with some saving I think I can do this.

P.S.: My car's had some weight reduction done to it, but I haven't gotten around to having it weighed and dyno'd, I guesstimate it may be around 2100-2200 lbs since I think stock SAs are 2300. How much do 12As weigh in comparison to a renesis, assuming 360 some lbs on the renesis (which is what I read in some mag)? Even if it weighs 100 lbs more, at 2200-2300 lbs total with 246 horsepower, the car would have a power/weight ratio of 4.07-4.25 kg/hp. Does anybody have some comparison power/weight ratios of some other sports cars handy? I think ~4.1 is pretty good w/ an unmodified engine swap.

 

I figured they probably wouldn't. I might know somebody who would buy them from me, though.

3rd gen engines were turbocharged. Turbos take space. If a renesis is just a more powerful 13B, I don't see any problem getting it to fit.

 

im sure the engine mounts are way different, it would take alot of fabrication but for the right amount of money anything is possible!

 

The engine mounts on a TII are way different and that doesn't stop people

 

Go for it, and post pics and stuff when done. It may take time, but the time spent will be worth it, being the mods that will soon hit the market for that engine.

 

its a good idea, and would be original, but there is ALOT of stuff youll need to look into.

1.) in order to put a 13b into a 12a car, you need the 12a front cover along with the racing beat mount. im not sure if the renisance will hold the 12a cover since its "redesigned".
2.) WIRING WIRING WIRING! did i say wiring? dude, its a brand new motor, you know how many systems are bound to be in that car? no question youll need an ecu, especially since your going from a carb'd motor to a EFI. it will probably be the same computer ways as a 20b, the cosmo ecu has a lot of "features" since it is a luxury car, since the rx8 is a 'family ' car... you get the point. there will probably be 23423344567456345345345236 million hours in wiring
3.) 250hp probably would destroy the tranny(dont hold me to it) but if you plan on modding, it definatly wont. i see.. new tranny, driveshaft, u-joints, diff., axles.. ect.
4.) like people have said, getting the motor. im sure its going to be a bitch to actually get your hands on one.

other than that.. im sure it would be like any other 13b swap. but i think youll need to know your **** with electronic.

good luck though

 

eh, if you're gonna get the renesis, ya might as well steal the 6-speed form that car too, right?

 

You act like that's hard or something? Diagrms are easy to follow, You can mount the ECU where ever you like... I don't see anyhting hard about wiring...

The fabrication of mounts would be difficult, but that's just me... I don't know how to weld, nor do I own a welder. Ditto with the fabrication of a driveshaft. Rear axle will probably have to be a Ford (Shudder) unit.

 

that's the plan.

 

i'm looking at the renisis for a couple of reasons.
1. bridgeport power on a stock engine
2. it might pass smog without a cat
3. you dont have the wieght penalty of a turbo, or the heat
4. better gas mileage

hopefully its easy to mount in the car...

mike

 

Its all speculative at this point, but the feasiblity of dropping a renesis into a 1st gen is relative to several things...

1) does the 12A or SE 13B 6PI front cover attach to it, if so then the actual "fitting" of the engine into the car would probably be no different than any other 13B.

2) ECU: the renesis meets the requirements of a ULEV (ultro-low emissions), that means you would have to have the multitude of sensors in the exhaust, and probably several cats just to keep the ECU a happy camper, and that is not even mentioning the actual wiring and install (which in my opinion would be well worth it). You could go stand-alone, but as there is no one qualified to tune it (and I hear the A/F ratios are quite different), what are the chances you'll get the rated 250 hp out of it. Of course going stand-alone you make the turbo-charging very possible.

The renesis may or may not like turbocharging as much as the older 13B's. The PP exhaust makes the kick from the opening of the ports a force to behold. The SP will not have as powerful of a kick. What this means is the older 13B's will probably be able to have higher A/R ratio turbine housings than the new renesis. But the renesis has no overlap, so a smaller A/R ratio may not have as adverse effects that it has on the older 13B's.

3) exhaust and intake: the exhaust will obviously be a challenge, it is unlike any other rotary out there, the headers not only won't fit because they're for PP exhaust, and the renesis is SP, but the tuning lengths are bound to be significantly different. The intake may not even fit under the hood, it appears to come up fairly high.

Getting one for a while may be the hard part. The costs are bound to be high, but would probably be worth it to somebody to transplant it in... who knows?

 

well they had a renisis in a star mazda car at sevenstock. they run a motec ecu and put 240hp to the ground. i dont know much more than that though

mike

 

One of my car came with 3 cats and a ULEV rating. I don't have any left, and while it definitely won't qualify for that rating any more, but I've never gotten so much as a whisper from the ECU about it. If the new engine DOES have a few cats and O2 sensors all over the place to make sure everything is good, IME, they can be replaced with resistors, or a clever exhaust design.

I'm wondering if the the best way to go with the ECU (at least to start with) is to get an engine with harness and the ECU, and just throw the ECU somewhere. You can run the stock ECU to control everything that isn't engine related, and the new ECU to control the engine. It may sound like a lot of wires, but it shouldn't be too bad, since so much is mechanical in the first gen.

Anyone have any thoughts on the potential for that setup?

 

Well maybe not $10,000 for the engine alone, but well over $20,000 for the engine and everything to make it fit right. The engine would only be under factory warranty if it remains STOCK, so he can't risk turbocharging. That's if he buys the motor from the factory, and not off the first junkyard that houses a rear ended RX-8, etc. I'm not against this project at all. By all means I think it can and should be done, if not attempted. But it's not a feasible idea for some college student to go out there and spend that kind of money on something that hasn't been done yet. Debt and maxed out credit cards can be the result. Sit back, relax and wait for the engine swap to be done first, by a company like Mazdatrix for example. Then you could at least have an idea of what you're going to need to buy. Don't screw up a first gen past the point of no return unless you have a decent blueprint of what you're doing.
Oh yeah, even if you could turbocharge it, why would you turbocharge a 6 port?

 

looks like the renesis motor is about to get a workout

http://www.starmazda.com/mazda04/2004FM.htm


2004 FORMULA MAZDA SPECIFICATIONS




Engine
240 HP Mazda “Renesis” rotary engine with encrypted ECU including rev limiter, pit speed limiter, traction control, ignition trim, fuel trim.

Tub
Carbon fiber composite built to FIA standards with 17 U.S. gallon fuel cell

Transmission
Six-speed sequential with no lift shift

Optional (subject to testing and rules review)
Data acquisition, including paddle shift on steering wheel, traction control defeat, ignition and fuel trim controls on steering wheel, pixel screen display, auto blip downshift

Suspension
Pushrod, inboard with two-way adjustable shock absorbers, adjustable rear sway bar, cockpit adjustable front sway bar. Front suspension tethered.

Bodywork
Fiberglass

Aerodynamics
Front wing and quick adjustable flaps of aluminum, rear wing two upper and one lower element of aluminum with composite end plates.

Brakes
Cockpit adjustable bias, 4-pot alloy calipers, vented, floating steel discs.

Cockpit safety
Anti-intrusion Kevlar panels, FIA headrest/side head restraint, compatible with HANS device.

Wheels
Front 9”w x 13”d, rear 11’w x 13”d, magnesium, center lock

Dimensions
Front track 61.5”, rear track 58.5”, wheelbase 101” and weight 1050 lbs.

 

well actually the ecu problem is easy, just buy the star mazda engine package =)

mike

 

How do you figure $20,000 to make it fit right? And with FD power right out of the box more than doubling 12A power, why does everyone immediately want to slap on a turbo? Mazda avoided selling 12A turbos due to reliability issues, the FD had turbos and reliability issues, and the N/A Renesis overcomes this. With a custom crossmember and a few plumbing tweaks the engine should fit just fine, and while it won't be cheap and easy I can't see $20,000 USD - that's approaching the cost of a base model RX-8

 

There are allot of long posts here I am feeling lazy and don’t feel like reading them... I think the engines would run about 12k... they WILL NOT WARRENTY THEM I do not believe... at least not for a while when they start mass producing them for replacement in the rx8... but just the price that it would run you for the motor ecu and all that crap go do a turbo motor... with 10k+ you would have spent on the rx8's power plant you could build a NICE 400 hp turbo motor with a ford 9 in in the rear of your car...

 

To repeat what Manntis said, why does everyone want to slap on a turbo?

And why wouldn't you be able to get a warrantied motor? You can buy 12As with warranties, and you can buy 13Bs with warranties. Why wouldn't you be able to buy a Renesis motor with a warranty?

And just out of curiosity, where did the 12k figure come from?

 

Manntis, i think your the only one here who is making sense. Ill agree with what you said also.

 

I'm sure it'd be warrantied if you put it in an RX-8. I'm also sure they would NOT warranty it in a 20 year old first gen with a home made wiring harness.

I've sat down on the can a few times and thought through what it would take to do a renesis swap, and came up with a few ideas, but it is dependant on how the renisis makes it's power --which leaves a few questions:

How much difference does the side-port exhaust make? If most of the power is made here, could you buy side-port plates and build a custom motor using them? If so, could u fabricate a manifold and bolt up a carb? Or possibly use an adaptor and bolt up an older 6port efi system. (The renisis is 6port just like all 84 up na 13bs, though much different in design)

Is the spark timing different? Can an older ignition system be used instead of the one on the renesis? This presents a small problem. All Vehicles made after 95 have at least an OBD 2 computer. And the ignition on the renisis is electronically controlled like all 86 and newer 7s. This computer will kick into limp home mode if your fuel cap is loose. If you think you can figure out how to wire the stock computer (because following a wiring diagram is Soooo easy) than be my guest.

A better option would be to use an aftermarket ECU and go through the expense of tunning it. Probably a haltech or something would be best. The motech is like 10k, so it would be out of the question.

How much power is based on an increase in rotor compression? The highest compression rotors to date were in the 89-92na (9.8 to 1, or is it 9.4 I forget) This car (like all NA rotaries to date) was designed to run on reguler gas.

The renesis runs on premium. I know if I'm going to have to put premium in my 7, it's gonna have a turbo. So I would want lower compression rotors, which leads us back to the first question.

The renesis is high HP, but low torque --only like 160foot pounds. Could the 1st gen drivetrain hold up to it? My guess is maybe --depending on the driver. A similar hp output turbo motor would be puting out a lot more torque, and would be much harder on the drivetrain --and there are people doing it.

So to sum up could it be done? Yes. Would it be worth it? Maybe. Would it be fun to try?