Renesis into FB
 

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. :icon_tup:

This is what I found using the search term REW.

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

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?).

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.

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...

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.

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. :lol: 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?

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

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...

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.

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

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. :)

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.

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?

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

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.

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?

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

2 - Yes, the 6 port version has sleeves.

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.

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

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

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 fucking rocket which is exactly why I wanted to do it but I lost that job and never got the car :(

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

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.

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.

Wouldn't the computer only receive resistance inputs from the sensors for, for instance, the wheel speed. Couldn't you theoretically ground it in such a way that the proper resistance is met whatever the condition? Or do new ECU's not work the same way.

Theortically it is possible to just to replace the sensors with a resistor that would provide a false positive to the PCM. Though, in all honesty you could just as easily set-up the RX8 axles for the FB as well.

The RX8 Subframe has mounting point within the FB's Frame and is a plausible bolt in with minor modification. The problem is measuring where the Subframe needs to be exactly and reinforcing the frame if it needs it, which it probably will in other areas.

It is also possible to use the rear subframe to place the IRS in place of the rear axle as the mounting points also are within the Fb's frame, though doing such a thing is a lot more work than the front subframe due to the construction and purpose of the rear end.

Though you should be able to just fit the spindles in the rear with the RX8 hubs and rotors, which should have the speed sensors in them already onto the existing rear axle.


Another problem that will probably come up is speed, because the PCM calculates evehicle speed differently than our cable powered speedos and the vehicle speed can also be part of other subroutines in the PCM.


Its a bit of work and depending how much of the RX8 and its components you want to transfer over; it can be even more difficult.

Just my two cents...

I would suspect that the ECU is looking for a tach signal as opposed to a constant resistance. This would be the way it can calculate speed.

I really don't know what the ECU is looking for, but if it's comparing transmission speed and road speed to try to sense slipping, you'd also need to make sure you have the same overall tire diameter on the 1st gen as the Rx-8 uses.

I don't know about the front subframe from the rx8, but there was a member on this board that did a thread on fitting the rear suspension of a Miata to his 1st gen. It's not a minor effort by any stretch as the entire rear floorplan had to be removed and redesigned for the suspension arms to clear and for the shock mounting locations to be correct. I'd imagine the effort for an RX8 rear end would be similar.

The HKS V-Pro can handle the Renesis... Much cheaper than Motec. I believe you need to by their engine harness, though...

T2 swap is looking more appealing. :lol:

I'm still gonna keep looking into the Renesis swap, I KNOW it has been done before. How hard can it be? :wallbash:

Seen top gear? That seems to be their catch phrase. and usually its quite difficult lol

I think the reason this isn't done much is because the cost isn't worth the benefit to most people. Like I said above, there isn't much power difference between the S5 street port and a stock renesis (if at all), but it's soo much easier to drop in the S5 engine that the renesis doesn't make much sense. If your power goals were the stock renesis, you don't even need to go with a turbo engine.

That sounds interesting, but here's the drawback that I see:

"Programming is done via the HKS Power Writer software; which only Certified HKS Pro Dealers have access to"

It sounds like you can't do any of your own tuning, meaning they better have it right and it's going to cost you $$$ in labor for tuning or buying their map, which may not be tuned correctly for your specific set-up. I have no experience with the HKS system, but I can tell you from working with my car, the tuning is never quite finished.

yea i had the back asswards, but the point still remains, not a direct bolt together deal.

From the HKS site.

I just wonder if they have the RX8. I imagine disabling some sensor inputs would be much easier on that computer over the factory unit. Still...$1300 for an ECU is awfully steep. :scratch:

Found this, apparently a guy put a Renesis into his plane, which would obviously necessitate a different ECU. Although I do see that he is using individual throttle bodies instead of the factory manifold, which you can easily do for a plane...not so easily for a car.

http://www.rotaryaviation.com/renesis_engine.htm

He is using the EM2, but I'm not totally sure what that is. Anybody know?

EDIT: A little more digging
http://sdsefi.com/prices.html

Looks like they have a unit specifically for the Mazda rotary, and its cheaper than HKS's, although it doesn't say whether or not its compatible with the renesis. I didn't see a throttle by wire facility on any of the listed ECU's :(

$1300 is dirt cheap for an ECU that controls everything that thing does.

You have to buy the harness too, I believe... ~$400 or so.

Also, I'm not so sure about the Street Port S5 making the same power levels as a Renesis swap. The power levels mentioned above on the SP S5 imo are only made with a very open exhaust system. Renesis makes slightly more power than an open exhaust Street Port while choked with modern emissions equipment. A Renesis is more comparable to a mild Bridge than a Street Port with an open exhaust.

And then, unlike a street or bridge, a Renesis would get pretty darn good milage in an FB, especially if you were to use one of the FC, NA transmissions with the .697 5th ratio. I worked out the gear ratios one time for my SE, and the combination -SE rear, -SE wheels and FC NA trans would yeild a much higher ratio than 6th gear in an -8. Add to that, the FB is like 700 pounds lighter, you tune the motor via your standalone to take advantage of not having all the emissions stuff, or tune for an open exhaust and it should do much better than the 22mpg highway the -8 makes.

I don't think you'd really need a TII trans for a Renesis FB swap, the FB is so much lighter than an FC or an 8, and you're only talking 160 lbft of torque... S5 TIIs were like 200 torque and 500 more pounds stock, yes? Unless you really plan on giving it to the car, I think the FC na trans should be fine. And if you swap tailshafts, it's a bolt in on an FB.

And if you can maintain the function of the Renesis intake, the torque would be plenty for an FB, even with the tall 5 th gear. And, you have the potential for an emissions legal swap --even in CA, as long as you could adapt the stock ECU.

I'm working on another engine swap right now (BPT GTR motor and trans into my 323 GTX) but if I ever finish that, (which seems doubtful at times) the Renesis into my FB would definitely be high on the priority list... Be a hell of an all around car...

EM2 does not have provisions for the oiling system or the intake, I believe. You'd need to premix and run a custom intake to take advantage. Also, planes spend most of their time in a very narrow rpm band. The difference between takeoff power and cruise power on a Cessna 172 is ~ 300rpm. Tracy Crooks Renesis setup is optimized for that narrow useful band. Not very good for a street car.

Yeah I noted that in my post, although not as in depth. Part of me wants do this swap purely because its uncharted territory, but then part of me realizes that I'm an architecture major and finding time to work on a project like this in the next 6 years will be very difficult. I think for the moment, I'm going to stick with my little 13b re-egi for a while, as it still runs great with 105k on the clock. It does feel a bit sluggish past 5500 or so, so I'm going to seafoam it when I get the clutch back in, to see if it helps the top end, which I'm willing to bet it does. After that I think it will be full exhaust and maybe an MSD setup, tokiko's, ss brake lines, hawk pads, RB swaybars, and just enjoy it like that. Hell I might skip the Renesis all together and wait until i can afford the 26B-PP + 300 shot fogger, hewland sequential, and full widebody with 315+ rear tires I've been dreaming about. :drool: Be kind of cool to put down over 1000whp with a 2.6 liter and no boost. Race gas most likely. [/dreaming]

My SP is limited to just a little opening of the exhaust ports. I have all my mods listed in the dyno thread, here's the plot (red line):

http://www.nopistons.com/forums/uplo...1083865442.jpg

Here are a couple more with different intakes

http://www.nopistons.com/forums/Stoc...-5-t65787.html

http://www.nopistons.com/forums/Na-S...no-t54928.html

http://phishcave.com/upl/eJAOcR9wBt.jpg

Now comparing that to other dyno runs isn't 100% accurate, but it's probably close enough for our conversation. Here are a couple of dyno sheets from stock RX-8s.

http://www.dragtimes.com/2004-Mazda-...aphs-8792.html

http://www.myrotarycar.com/portal/fo...7_rx8tx800.gif

They are not that different. I'm not saying that there isn't more power in the Renesis to be tapped, but with conservative stock tuning, there's not much difference with a tuned and ported peripheral exhaust.

The Renesis would still probably have better drivability and longevity though, which are two key things I'm looking for. Plus 9500rpm is really cool.

We'll have to see more high mileage Rx-8s before we know about longevity. The S4 and S5 are very stout motors in NA form. The Rx-8 has a lot to live up to there and they didn't start off too well.

As far as driveability, with the right tuning, you'll never know a street port isn't stock. The torque curve is what you should be looking at to tell you how every day driveable and engine is. How broad is the curve and where does it peak. Notice how my toque peak is 1000+ RPM sooner than the Rx-8s!

No dude, please, DON'T!

Please don't what?

Hmm I was thinking the Renesis would put down a little more than that. Was that a 6 port or a 4 port in those dynos?

There are 2 jumps in the curves, so I assume that means they're 3 different runners, which I believe translates to 6 port engines.

But thats nearly 30% drivetrain loss...that can't be right, even if it was awd.

EDIT: They all seem to be about the same though, I guess they are just over-rated factory. Kind of disappointing, considering I can make that power with MY 13b with some work.

The new SAE power rating requirements pretty much negate any chance of underrating from the factory...

i looked at the rx8 swap vs 12A PP

when i really started, the PP setup was cheaper, although a couple years ago finding the expensive stuff (rx8 intake manifolds are in the $3000range new) used wasnt really possible, now its different.

power and redline are similar, PP makes a little more at the fly and revs a little higher, but the rx8 engine will smog no problem, and well its stock!

they both have challenges to implement

1. rx8 ecu is networked, if you look at the JDM FB with the rx8 engine, you'll see they used the rx8 gauges and climate control and stuff, not to be cool, but because its in the loop with the pcm. the best option is either standalone, or a pcm thats reprogammed not to look for that stuff.

2. the rx8 uses a turbo 2 clutch, but the best option is just to use the rx8 trans, its got nice gearing for a high hp rotary

3. mounting in the car; it'll take some custom mounts. not a huge deal

4. the FB rear end should be fine, you're increasing torque from the 130lbsft to 150lbsft...

i'm doing the PP, but its mostly due to costs. ($2000 vs $5000+)