Why not 13b-MSP?

So bear with me here. I'm semi familiar with the differences in the working theory and most of the technical details behind the Renesis and the S6 motors (Rotors, side ports rather than peripheral exhaust ports, and different side seals, etc) I'm trying to suss out if I want to investigate going down this road.

So the RX3 needs an engine. Prices for S4, S5, and S6 have become insane, its like Ebay sellers have decided that they're going to compete to see who can charge the most for a motor and caused the rest of the market to follow along. I may as well buy a running FC TII at that point and part the thing out.

Anyway, the goal for the RX-3 is fair weather cruiser. I'm not going to be able to get a ton of tire under the thing without removing the rear seats and putting in tubs, which I don't really want to do, so that limits the tire/wheel choices to something in the 205/14 area maybe a 15 inch wheel (I need to measure but it has GSL-SE wheels on there now so I know 14's will work.) Realistically I'm not going to be able to put down huge power, keep the interior intact, and keep it streetable so I was looking at 250 to 300 hp max and in all likely hood probably less.

It appears PAC Performance was able to coax 200hp to the wheels of a S1 RX-8 and, with a turbo system, put out over 400 on the stock seals, rotors, and transmission. Renesis motors are also shockingly cheap for running and even cheaper for imported pull outs (assume rebuild.)

VersaTuner appears to have cracked the S1 RX-8 ECU so tuning and engine control won't be an issue.

I'm pretty much assuming I'm going to need to run premix if I change the ECU for a turbo system but for the NA motor I'd probably just use Versatuner.

Is there some reason not to consider the 13b-MSP? Is the internet just locked in an endless loop of mutual masturbation over big numbers with the S5/S6 motors so it won't consider the MSP?

The only issue I can see is potentially the timing cover as I'm unsure if I can swap it with a TII cover to easily mount the engine with an off the shelf RX3 13b swap kit.

Running is better than an indefinitely stalled project. So any insights?

I've got nothing for you on motor selection, but you are relatively close to Rhinehart's, which is where I bought all my spares/replacement parts when I had the FC rally car.  He probably won't sell you an engine for scrap value, but I would bet he'll be better than the eBay prices if you give him a call.

In reply to ¯\_(ツ)_/¯ :

Awesome I'll give them a ring. I've been having some trouble just finding one since it seems like most salvage yards don't want to touch a rotary and Craigslist is also full of eBay sellers (Literally same pictures and watermarks.) I'm under no illusions I'm going to pay scrap price for engine + trans but prices for a 13b have better than doubled in the last two years. I could deal with 25% or 30% more but 100%... I can't imagine the demand has increased that much for them but I could be wrong.

Bump.

Sorry. I really am interested to know.

I'd be cautious of getting a 2004, as those are likely to be scored beyond use due to the earlier oiling issues, but I'm a big fan of the engine overall (I have one in my Rx-8).  

I know, the plural of anecdote is not data, but so far my 2007 Rx-8 has gotten me 78,000 trouble free miles with routine maintenance.  It was still well within compression numbers right before the engine warranty ran out, and that's with numerous autocrosses and 4 or 5 track days on it.    The engine is stock except for a cat-back, and I run premix on the track.

The power is very usable, and it feels like my old S4 engine with more low end torque and a hundred or so extra ponies in the mid/high range.

I'm not sure about the electronics as a standalone, but it sounds like you've got it figured out with VersaTuner. I didn't realize they cracked the 2009+ ecu, that's cool!    I have a Cobb that seems pretty feature complete, so I'm sure those guys are at least comparable.  It's on my list to do some dyno tuning at some point just to see what we can get without raising the EGT too much.

RX-7 front covers will bolt on, but then the water pump won't because Mazda changed the bolt/stud pattern, and the OE pump housing is cast into the Renesis front cover.

And even if I trusted a remote water pump set up, I'm not sure about the oil pan fitment.  So I think it's better to fab the mounts.

There are intake adapters to fit older style 6 port manifolds on to a Renesis as well, I've wondered how well they would would work with a 4 bbl manifold and EFI system.

They're perfectly fine motors. I would avoid the early years for the issues quoted as recommended. The internet doesn't like them because they can't be easily modified for more power like the older engines. People forget the RX8 makes similar power while naturally-aspirated as the first generation FD (S6). I know some people have stuffed them into FBs and had fun. You'll need aftermarket engine control, obviously. Note the RX8 uses the larger flywheel and clutch diameter as the turbo RX7s so you'll have to figure out a transmission solution.

Personally, I'd love a later model RX8 or a Renesis-swapped RX7 as a daily driver. Maybe my next project will be a 13B-MSP swapped late model FB.

Thanks for the info and technical clarifications everyone. I was figuring on using the RX-8 transmission and that I'd have to fabricate the engine mounts/cross member but I was hoping to get off easy.

So follow up.

Was it only the 4 port autos that had the issues or did the 6 port manuals also have problems with scoring the housings?

I was under the impression it was a problem with the 4 port autos because the manner in which the auto transmission's ECU was programed it didn't rev high enough to prevent a carbon build up. Or is that just an internet folk tale? I should find that GRM buyers guide on the RX-8.

I know Mazda switched to only six port motors for 2006+ but if the motor is a pull out how can you tell the difference between the the 2008+ with a middle oil squirter and one without?

I should probably just call Rhinehart and pay whatever they're asking for an 09 - 11 manual because this path sounds pretty appealing for my application.3

Edit: Or I could just not be an shiny happy person and look it up because GRM's website is awesome

The0retical said:

So follow up.

Was it only the 4 port autos that had the issues or did the 6 port manuals also have problems with scoring the housings?

I was under the impression it was a problem with the 4 port autos because the manner in which the auto transmission's ECU was programed it didn't rev high enough to prevent a carbon build up. Or is that just an internet folk tale? I should find that GRM buyers guide on the RX-8.

I know Mazda switched to only six port motors for 2006+ but if the motor is a pull out how can you tell the difference between the the 2008+ with a middle oil squirter and one without?

Paying for an 09 up is the easy button. 

There were problems across the board for 2004, both 4 and 6 port.  For emissions reasons, they didn't inject enough oil.  Once they started scrapping engines, the fix was to cycle the oil injectors more on the earlier cars (04-05) and I believe (note, I can't remember 100% and don't' have time to look right now, so don't believe me!) that the 2005.5+ have slightly larger orifices for the injectors in addition to longer cycle times.  Whatever they did, it apparently worked as if you craigslist a large net for Rx-8s, you're going to find the majority of blown-upped ones are 04/early 05s.

You don't want a 4 port for the lower compression, power & redline, which was the real reason for their problem.  With the lower redline and higher propensity for an auto-driver to not get heated up & wound out, that's why they had carbon issues.  Same as the auto FCs and (probably?) the FDs. 

I'm not sure how to tell the difference between an 04 and an 07 keg, though, sorry.  The good news is that most of the 04s have been replaced under warranty by now.

In reply to WonkoTheSane :

Thank you. It looks like it's possible to coax 09+ engines out of LKQ with less than 80k miles if you know what combination of words to use (not 13b) so it appears I can get a engine, harness, pedal box, fuse box, transmission, gauge cluster, ECM, and solid mounts shipped to my door for about 2500 dollars. Which is less than the cost of a 13b-REW long block with a sketchy history.

I'd preferred to have kept, and refurbished, the RX-3's gauge cluster but that probably won't be possible with the MSP engine since everything seems to be electronic on the RX-8. That's fine as it looks like I can unload the cluster pretty easily for a couple hundred dollars. This thing is going to stay with me for a long time so the criteria is that I enjoy it.

Looks like this is the route I'll be going down after some of life's little (and major) problems are dealt with. Thank you again to everyone who chimed in.

The0retical said:

I'd preferred to have kept, and refurbished, the RX-3's gauge cluster but that probably won't be possible with the MSP engine since everything seems to be electronic on the RX-8. That's fine as it looks like I can unload the cluster pretty easily for a couple hundred dollars. This thing is going to stay with me for a long time so the criteria is that I enjoy it.

It's just the speedometer that's mechanical, right?  There are a bunch of people who make boxes to drive those with electrical VSS signals.

You may be able to find a way to keep your RX3 transmission and in return, the stock speedometer. In RX7s it's not uncommon to swap transmissions between turbo and non-turbo models. My understanding is the clutch, flywheel and starter are tied to the transmission being used. The issue is the flywheel. In RX7s the rear counterweight is integrated into into the flywheel and must be paired with the engine rotating assembly. In the case of aftermarket flywheels the separable rear counterweight from automatic cars are used. I don't know if the RX8 has a separable flywheel from the factory. I've seen aftermarket flywheels but no counterweight options so maybe it is. If that's the case, you should be able to swap the smaller clutch and flywheel (w/ rear counterweight) combination on the back of the Renesis and be able to keep your current starter, transmission and driveshaft.

That still leaves the engine mounting question as I think all those older rotaries were front-mounted and, as mentioned before, you can't swap front covers. The tachometer should be fairly easy to figure out. Just find whatever coil is being used now and hook it up. For engine control you're probably better off with an aftermarket unit. I think there are several that work with drive-by-wire throttles.

In reply to codrus :

I could do that with the speedometer, the secondary problem is the tachometer since the it tops out at 8k on the RX3. If it's accurate I don't see an issue but I tend not to trust gauges at their extremes. I could add a secondary tachometer in but I find those, for the most part, to be pretty tacky. I bet I could add a nice hud into the dash pretty cleanly though... hmmm.

In reply to infernosg :

I'll look into if the smooth case transmission I have will mate, and hold up to, a MSP. I keep forgetting I have one because I was planning on putting in a Turbo II transmission initially as it they supposedly mount up pretty easily to the RX-3. Also it's in the rear hatch so I don't look at it often. Stuff you don't pay attention to when you buy an engine-less car.

I've considered the aftermarket ECU's but I'm not sure it'd be a huge benefit from a price/performance standpoint. For the time being I'm planning on running relatively stock and the ECU is about 100 dollars. At that point all I need is the accelerator pedal. I do need to look into if the ECU will freak out if a bunch of sensors are missing because that would put a damper on things.

VersaTune seems to be able to handle most of the tuning on an NA motor pretty well. For a turbo application no question I'd put one in.

Mounting still remains the biggest question at the moment but not having a turbo system will free up a bunch of room.

The0retical said:

I could do that with the speedometer, the secondary problem is the tachometer since the it tops out at 8k on the RX3. If it's accurate I don't see an issue but I tend not to trust gauges at their extremes. I could add a secondary tachometer in but I find those, for the most part, to be pretty tacky. I bet I could add a nice hud into the dash pretty cleanly though... hmmm.

Hm.  Is there a peg at 8K, or is that just where the markings end?  If it's just the markings then it'll probably happily spin to another thousand RPM's worth of degrees, it'll just be hard to read.

You could also rescale the tach signal electronically so that 9K (or whatever max speed you want) displays on the existing tach at 8K.  The markings would all be off at that point, but that might or might not matter to you.

Mazdatrix shows aftermarket flywheels with bolt-on counterweights just like RX-7s.  I think the actual counterweight itself is a different piece though.  http://www.mazdatrix.com/8flywheel.htm

For the speedometer, I'd look into the classic speed gps box.  They're a grm/classic advertiser and I'm pretty sure Tim used one of those in his truck after the engine swap with good results.  Keep the old cluster for sure!

Their website is classicautoinnovations.com.

For the tach, perhaps a nice 3 led sequential shift light somewhere unobtrusive would do it for the 8-9-9500 range where you don't trust the old mechanical one?

In reply to The0retical :

A Turbo II box will definitely handle whatever the Renesis can throw at it. All you would need is a RX8 rear counterweight, Turbo II flywheel, clutch and starter, and a custom driveshaft to mate to your RX3 rear end. I don't know how different the tail housings are between the RX3 smooth case and the Turbo II unit. I'm guessing the Turbo II is longer so you'll have to figure out shifter location.

How integrated with the chassis is the RX8 ECU? Don't modern ECUs control everything from the engine to the ABS, traction control, climate control, etc? Will the RX8 ECU still control the engine properly without all those other inputs?

In reply to codrus :

I was looking at Mazdatrix's site and somehow missed the RX8 rear counterweights. In that case he could grab an aftermarket flywheel for the older 215 mm diameters, pop on a RX7 rear counterweight and use the existing drivetrain from the clutch back, correct?

infernosg said:

I was looking at Mazdatrix's site and somehow missed the RX8 rear counterweights. In that case he could grab an aftermarket flywheel for the older 215 mm diameters, pop on a RX7 rear counterweight and use the existing drivetrain from the clutch back, correct?

I think the RX8 counterweight is a different balance than the RX7 one, and I believe that weight is set based on the rotating internals, not based on the flywheel (AIUI the aftermarket flywheels are balanced on their own).  So I would think you would need to use an RX8 counterweight with any Renesis motor.  Whether or not you can bolt an RX8 counterweight to an early flywheel I don't know.  I'm a long way from an expert on this, I only knew about the RX8 counterweights because I ran across them when hunting Mazdatrix's site for flywheel parts for my FD a couple months ago. :)

I would call up Mazdatrix and ask, they've been pretty helpful when I've called them with questions before.

Doesn't the rx8 throttle body use dbw? 

For only $600 I'll let you pull the stock motor, transmission and wiring out of my 87 RX7. Haven't attempted to start the car since owning it but previous owner couldn't get it to run properly. May just need a rebuild. I can't recoup more than $600.  

Because this thread is worthless without pics. Forgive the grossness of the car I literally pulled it out of my buddies barn in California and had it shipped to PA.

In reply to codrus:

There doesn't appear to be a pin so that would be an option. Aviation does weird things to your brain when someone start talking about taking things to their upper limits. I'd probably trust it more if I sent it out for overhaul. Side note mileage is correct, probably, as it was listed on the CA title as 33549. This thing is a real survivor so I don't want to cut it up too much.

In reply to WonkoTheSane :

I'll look into that. I think I saw something in GRM about them but it didn't cross my mind to use one. I was trying to avoid falling into the "Use Torque" trap because I'd like to keep things looking as period correct as possible. That would be a pretty seamless option.

In reply to infernosg :

Thanks for the info. It appears the RX-8 transmission is about 3 inches shorter than the TII transmission. It appears from some cursory searching that I'll need flywheel, clutch, pressure plate, and starter from a RX-7 to adapt a TII or smooth case to it. Like codrus stated it's probably better to call Mazdatrix up and make sure though because the internet... well it's the internet. Using a smooth case or TII trans actually appears to simplify the transmission mounting as well which was a concern.

As for the ECU that's still the big unknown. The RX-8 uses a drive by wire throttle control I'm not sure how nicely a Haltech would play with one. I know with my Mazdaspeed 3 that my Cobb Accessport will allow me to turn off a number of sensor inputs to the ECU to prevent it from freaking out about various modifications and completely defeat SWAS. I have a email into Versatune to see if their software is granular enough to turn off stuff like ABS and TCS so it doesn't freak.

In reply to yupididit :

It is DBW which is why I was looking at doing the pedal, harness, and stock ECU with some tomfoolery from Versatune rather than a Haltech. Apparently MSP transplants have occurred, there's videos of them and some forum posts but they're all very light on details about how they made it happen.

Andy Neuman said:

For only $600 I'll let you pull the stock motor, transmission and wiring out of my 87 RX7. Haven't attempted to start the car since owning it but previous owner couldn't get it to run properly. May just need a rebuild. I can't recoup more than $600.  

Tell me more... TII or NA? I'd be happy to zero your budget and you're not that far off.

I don't have big power dreams so I'm a bit more open than I was a few months ago. Rebuild's don't scare me that much.

Picture time since we all love them. Forgive the quality I took them at 10:30pm last night.

My chasm of sadness:

Neato center cluster:

Awesome steering wheel with dual horn buttons

Cool artwork details on the door cards, rear hatch card, and head rests (all the rubber need to be replaced after 45 years)

Car when I got it home and off the dolly. Prior to pushing it into the garage just after I bought the new house.