Starfox07

I think I've decided that I'm going to do a Renesis swap at the end of next summer. After considering the 20B and 13B-rew, I think my heart lies with the Renesis. I know it has been done before, but has anybody on this forum specifically done it? I have a feeling it would be quite an undertaking, but it seems to be the most reasonable as far as cost goes out of the 3 options. I would be keeping the engine completely stock aside from exhaust, so I'm not looking for huge power, just a reliable 200whp would be fine with me and I think i can get at or near that with the mostly stock Renesis. I do have a few questions before I commit myself however.

Will the stock SE transmission bolt onto the Renesis with a custom bellhousing? Can I use the clutch I JUST bought? Will the transmission handle the added torque of the engine?

Will the rear end sustain the extra torque?

Will I be able to use the instrument cluster that is in the car? Or do I have to go custom or use a factory RX8 unit retro-fitted in?

Will the stock subframe work? If not, will it work with modifications or would I need a whole new (probably custom) one?

I plan on using the stock ecu and its associated wiring harness, which doesn't seem to me like a big deal. Am I missing some massive headache in this approach? I can do megasquirt or something similar if I have to.

These are the biggest questions for me, and I think the rest of the things can be solved/figured more easily. I have plenty of experience with doing engines, although not specifically with rotaries but I don't see that as a problem since I won't be delving inside of it.

Any answers or advice would be appreciated.

Rx-7Doctor

iTrader: (13)

This is what I found using the search term REW.

https://www.rx7club.com/showthread.p...&highlight=rew

PercentSevenC

If you're only looking for 200 WHP, it's a lot easier and cheaper to attain with a TII engine. But to each his own.

People tend to forget that a Renesis is just a 13B like any other. Thus, your tranny will bolt up and your current clutch/flywheel setup is compatible. So is the tach, but the water temp will likely be off (there's things you can do about that if you care). I believe the Renesis is rear-mount like the 13B-REW, so the same issues apply.

There might be some difficulty with the stock ECU for a couple of reasons. First, it'll be missing a number of sensors present in an RX-8 (wheel speed, etc.). Second, it controls the throttle position on the stock throttle body. You'll have to rig something up so it can read pedal input (or possibly modify the throttle body to use a cable?).

Jeff20B

iTrader: (13)

The oil pan is longer than a 13B so you could use two 12A pans and splice them together. There are lots of other differences though. Somebody on another forum actually succesfully messed with a Renesis. I'm not sure if I can mention the forum name here anymore, but it rhymes with snowpistons. Check there.

sen2two

iTrader: (10)

easieast way to do this:

bare renesis core
12a front cover
any 12a/13b timing geard besides rx8 one
2nd gen CAS or 1st gen dizzy
custom oil pan, or two 12a oil pans
stand alone ECU
custom headers/exhaust
custom intake manifold, or modified stock ones

your pretty much done.

12a front cover gives you motor mounts and a way to get easy ignition.

yes to the SE trans
sub frame? what do you mean?
custom gauges will be needed
the rear is over 20 years old. it might break

im doing this. not easy. but not hard.

4 port gives 198 flywwheel. 6 port gives 238 i think... btoh equal too or better than a TII. with no lag...

Jeff20B

iTrader: (13)

I understand the RX-8 omp gear is backwards so you need any previous one, like you mentioned.

I like what rotargod says about the stock intake manifolding, and how all the numbers apparently match up so velocity and all that Sterlingesque stuff (sorry, lol) makes for a snorting good time in the end, like natural supercharging at its finest, or something. Anyhow I'd like to keep as much of that stuff as possible while changing the die by wire motor/servo throttle plate opener thing to a more traditional cable operated throttle body and of course an aftermarket ECU.

Starfox07

My reason for the Renesis.

I have a friend who is pretty good with megasquirt so I think that will be how I do it, with his help. I don't know why I said subframes. I meant motor mounts or however the engines are contained in these cars. In any case, I figure it will be much easier than a 20B and will make the same power with less weight stock (the 20B being n/a of course) You can score a bare, rebuilt renesis core for around $2000 right? Quick question. Why do I need a custom intake manifold? I understand the exhaust, does the intake just not fit within the engine compartment physically?

FirebirdSlayer666

iTrader: (3)

No it's not that, he just has no idea what he's saying really. Most of the hp and tq numbers with the Renesis are gained thru the DEI intake. If you eliminate that then it's just the same as S4 and S5 13B's really. No need for a custom header, Racing Beat is just about ready to release their Renesis header, and you can do a little fab work to make it work with a First Gen RB exhaust. It's definitely an interesting swap, I just don't think it's going to be cheaper than a 20B swap in the end. Keep all your receipts and keep us updated on progress. I think a Renesis 1st Gen would be a great daily driver

sen2two

iTrader: (10)

actually. i do know what im talking about there buddy.

to many people are in love with the factory intake manifold. at the end of the day, its a factory manifold. oriented towards driveabilty with everything being stock. not top performance. as soon as you start chainging things. an aftermarket manifold is usually needed for best results.

you dont need a custom manifold. but it would be better. it could be designed for what your trying to do with the car. i also stated that you can modify the stock one. and the OBX headers are only 200 and made pretty nice.

im not sure if the megasquirt can handle the tricky RX8 ignition control. so thats why i suggest the 12a front cover and FC CAS.

i picked up a low milage 4 port in good condition for 300. the swap will cost wayyyy less than a 20b swap. i already did the numbers...

posting on the internet (of things you read elsewhere on the internet) does not make you smart. working on your car and sharing actual exspierences dosnt either. but its a start...

Whizbang

i was talking to Kevin Landers about this similar idea, but the front iron is thinner and the front cover thicker on the Renesis plus the water pump housing is cast into the front cover. The 12a cover would need machining to be flush with the e-shaft.


from the stand point of using the oem mounts, i think it would actually be easier since they aren't too off base of the FC stuff. Running an FC sub frame inst that crazy (and very cheap in comparison to making manifolds and what not). Then making a mount piece to attach to the FC mount locations would work out pretty good i think.

Then you can just run mostly all of the stock rx8 components.

sen2two

iTrader: (10)

the front and rear irons are thicker. this is why the renesis is 2 inches longer.

Jeff20B

iTrader: (13)

As I was saying I wouldn't want to try to figure out all the ins and outs of engine mounts with a 13B Renesis, but this 16X is the same length so now I don't know what to think.

FirebirdSlayer666

iTrader: (3)

Well apparently you don't understand how the DEI intakes are supposed to work with a proper 6 port set up. If you change the manifold, you will lose power and torque unless you go crazy with ITB's and a custom built intake of proper length. You got a 4 port cheap cause no one wants the 4 ports, they want the 6 ports because they make more power. The only way he could get the full benefit of the Renesis is to use as much of the stock equipment as he can or it's pointless. It's like swapping in an S5 NA motor only to ditch the intake for a carbed intake and lose 25hp. The reason the Renesis makes the power is does is due to the ignition set up and intake set up in combination with the rotors it uses. You take that away and you're back to a basic 6 port 13B only is has side exhaust ports instead of peripheral. And I'd like to see your "numbers" seeing as nobody that I've seen on this board has succesfully completed a Renesis swap in a 1st Gen.

purple82

I'm curious, what kind of torque numbers are we talking about here? The S5 can make 200 whp with porting (Mine's at 170 with a very minor street port, in CO), but it's not going to be especially fuel efficient. In a 2400 pound car, it's 130 or so pound feet are plenty torquey. So is there more torque to be had from the renesis or is there some other benefit that makes it worth the effort?

FirebirdSlayer666

iTrader: (3)

The current Renesis is rated at 159 lb/ft of torque at the flywheel so it's about 135lb/ft to wheels when you factor in drivetrain loss. But it will make a few ponies less than 200 to the wheels with a sweet 9k redline

purple82

So there won't be much difference in power or torque between a street ported S5 and a stock ported Renesis. The Renesis will have 1000 RPM redline increase and probably cleaner emissions.

I assume that you'd need a motec600 to run the renesis as it can run a drive by wire throttle body, ignition, and handle the stock dynamic intake features. But at a cost of about $2-3k in the CPU.

Jeff20B

iTrader: (13)

There is a chance you can open the throttle body too quickly with a throttle cable.

Here is a stupid question, and has probably been answered before, and I should know the answer but for some reason it escapes me at the moment. Ahem. Does the Renesis have aux port sleeves?

purple82

1 - The fuel injection system shouldn't have any problem with a fast throttle opening.

2 - Yes, the 6 port version has sleeves.

sen2two

iTrader: (10)

why would anyone go through the trouble of creating a manifold and not design it to be most efficient for what the car is being used for???

ok, i will not waste any more time explaining to you. beleive what you do. and move on.

FirebirdSlayer666

iTrader: (3)

So you would spend the time and effort creating an intake manifold that would be identical to the stock intake seeing as it's the one designed for the most efficiancy for the Renesis? Intelligent. Thank you for pointing out your own stupidity

jones75240

iTrader: (1)

...........and oh so silky smooooooth I have a MT 8. The Renny is quite capable. Be sure to get the "6 port" though.

MazdaMike02

iTrader: (4)

Throttle body is controlled by an electronic servo therefore its fly by wire, just use an rx8 pedal with the throttle servo. Don't use the SE tranny....use a TII tranny. I was originally going to do this swap but with the FE 6 speed into an SE. To use the FE tranny you need to make a custom tranny mount (because RX8s use powerplant frames). Rear end you'd need to upgrade..obviously. You would need an electronic speedo because the RX8 uses one. Custom exhaust obviously...OBVIOUSLY a brake upgrade unless you want to die..220 hp in a 2700 pound car? It'll be a ******* rocket which is exactly why I wanted to do it but I lost that job and never got the car

Starfox07

Would there be anyway to use the factory ecu with a piggyback? It seems like the biggest problem is the ecu.

BlackWorksInc

There shouldn't be any problem using the Renesis PCM to replace the current unit in our car. Though, there will be a lot of cutting and electrical diagrams that will need to be looked through tor make sure you do it properly.

Secondly, you will most likely have to have someone reprogram or trick teh PCM for anything that is missing as it is an OBD II unit and will throw codes at you.

(As an example, the computer goes through its checks and can not find a component that was orginally installed on the vehicle; like say an EVAP unit in the gas tank, it will throw a code and possibly affect engine performance even if you hooked up the fuel injection and EVAP properly.)

Those are all things you need to consider in such a swap.

purple82

I remember reading that the ecu looks for front and rear wheel speeds for traction control. I suspect adapting the ecu to a 1st gen would be a pretty big job, if it's possible at all. Maybe it can be reprogrammed to ignore some of the stock sensors.

Reprogrammimg an ecu can be upwards of $1000. You might think about an aftermarket ecu at that point.