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MrJoshua
MrJoshua UltimaDork
4/6/22 10:44 a.m.

Title says it all. Can a Renesis be reliable? 

I find myself wanting a fun small car again. I pestered Paul about his totaled NB and chased an MR2 Spyder or two on marketplace, but they all are really impractical for the fact that I frequently drive the kids around. My son now drives so I am down to 2 kids needing transportation, Now a 4 seater works. Since I grew up on first and second gen RX7's, challenged and daily drove several Miatae, and the RX8 is said to drive like a 4 seat Miata-here we are. 

fatallightning
fatallightning Reader
4/6/22 10:47 a.m.

You'll want  one with receipts for a recent build and ideally deleted oil injection pump and running on premix. 

Mr_Asa
Mr_Asa PowerDork
4/6/22 11:04 a.m.

Does it have to be a Renesis motor?  Plenty of RX8s with bad engines out there, nice amount of room under hood, could have a lot of engine swap options. 

j_tso
j_tso HalfDork
4/6/22 12:35 p.m.

Lately I've been wondering if anyone has been crazy/foolish enough to spend the big bucks on ceramic apex seals in a relatively stock engine.

They're supposed to be more durable and high revving yet easier on the rotor housings.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/6/22 1:19 p.m.

In reply to j_tso :

That isn't what is failing, by my understanding.  The side housings warp at the exhaust ports, and the side seals wear heavily as a result.

BoxheadTim
BoxheadTim MegaDork
4/6/22 1:21 p.m.

In reply to j_tso :

Ceramic apex seals like detonations even less than the regular ones, though.

One of the big longevity issues on the RX8 is the lubrication for the apex seal, as that had to be reduced again for emissions reasons. The two early years (04 & 05) had the least amount of oil injected and thus are the ones most likely to go pop.

Definitely run premix in them - I ran Idemitsu premix with the original oil feeds in place, that seems to have worked. 

Also, especially the automatic ones don't tend to get driven hard enough and thus go pop for that reason. Like most rotaries, if you drive it like it owes you money, they last longer.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/6/22 1:26 p.m.

In reply to BoxheadTim :

You should not be running into detonation with a naturally aspirated engine, though.

BoxheadTim
BoxheadTim MegaDork
4/6/22 1:31 p.m.

In reply to Pete. (l33t FS) :

Good point. These also suffer from ignition coil issues that probably aren't helping.

My understanding is also that the exhaust port situation is a bit of a mess and the ports don't flow well. That's probably going to put more heat in the sideplates, too.

MrJoshua
MrJoshua UltimaDork
4/6/22 1:33 p.m.
Mr_Asa said:

Does it have to be a Renesis motor?  Plenty of RX8s with bad engines out there, nice amount of room under hood, could have a lot of engine swap options. 

No-not in the long run, but it feels foolish to pony up the coin for a rebuilt motor example in the hopes it will last a couple of years until I get to the swap. It feels like I either buy a cheap dead one, a semi expensive one that's soon to be dead, or a perfect example that might last a couple of years for stupid money.

Its a different world for me. I'm spoiled by the abilty to buy old beat stuff that just keeps working with minimal upkeep.

Flynlow (FS)
Flynlow (FS) Dork
4/6/22 2:55 p.m.


My buddy had a very similar situation.  He loved miata's but wanted a 4-seater one now that he has a family.  Drove the renesis for ~2? years until it started going downhill, then fixed the glitch:


 

Now he has both a 4seat miata, and a 4 seat Corvette.  

dean1484
dean1484 MegaDork
4/6/22 3:27 p.m.

In reply to Flynlow (FS) :

That almost looks factory!!!

I have always wanted to put a Mazda k series motor in a Rx8.   If for no other reason the sounds that motor can make are amazing.  I would argue that Mazda should have continued the platform but gone to one of their other motors.  The motor from a speed 3 would be a fun package. 

SV reX
SV reX MegaDork
4/6/22 3:34 p.m.

Rebuilt Renesis motors are surprisingly cheap. 
 

I'd look at a cheap blown motor car and drop in a rebuilt. Then you know the entire history, and can document it well for resale. 

SV reX
SV reX MegaDork
4/6/22 3:59 p.m.

Banzai Racing does Renesis rebuilds with their Level 1 rebuild starting at $1500. 
 

Banzai rebuild price list

dyintorace
dyintorace PowerDork
4/6/22 4:48 p.m.
dannyp84
dannyp84 Reader
4/6/22 6:20 p.m.

It can be a lot more reliable than the internet would lead you to believe but still not as durable as the older versions of the 13b with exhaust ports in the housings not the irons/side plates.

79rex
79rex HalfDork
4/7/22 8:12 a.m.

premix, High RPMs often, a manual trans, change the coil packs to something reliable.  RX8s got a really bad rap.  but if you start with a known good motor they can last you a reasonable amount of time

Hungary Bill (Forum Supporter)
Hungary Bill (Forum Supporter) PowerDork
4/7/22 8:40 a.m.

Absolutely. 

Case and point:  Every RX8 build thread on here with a Renesis is mind-numbingly boring and uneventful (Mine Included).  You buy these things and expect the awfulness implied by the memes and get.....  nothing.

I changed the ignition coils, made a couple "reliability mods" (oil pressure regulator, cooler t-stats, and the like), added a Racing Beat gauge pod and started attending track days.  The dang car has been as reliable as the sunset, and I can hit the track and do the school run all in the same day.  A coworker of mine bought one about the same time I bought mine and uses it to commute.  No issues there either.

Besides, if you're coming from RX-7's then you already know all the talking points and all the arguments.  I haven't seen anything about the RX-8 that was any different from my experiences with my NA FB or FC.  In short, 5-stars.  Would RX-8 again. wink

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/7/22 8:58 a.m.

High RPM is not what rotaries like.  High LOAD is what makes them happy.  I upshift at 2000-2500 and I get no carbon deposits.

This with 60:1 premix.

rslifkin
rslifkin UberDork
4/7/22 9:01 a.m.
Pete. (l33t FS) said:

High RPM is not what rotaries like.  High LOAD is what makes them happy.  I upshift at 2000-2500 and I get no carbon deposits.

This with 60:1 premix.

Yup, high load = higher combustion temps and that's what keeps most engines clean. 

dannyp84
dannyp84 Reader
4/7/22 9:58 a.m.
rslifkin said:
Pete. (l33t FS) said:

High RPM is not what rotaries like.  High LOAD is what makes them happy.  I upshift at 2000-2500 and I get no carbon deposits.

This with 60:1 premix.

Yup, high load = higher combustion temps and that's what keeps most engines clean. 

Can either of you explain this? Not that I'm disagreeing, I've just not heard this before and would like to learn.

j_tso
j_tso HalfDork
4/7/22 10:05 a.m.

In reply to Pete. (l33t FS) :

I remember side seals being an issue in Grand Am Cup, don't know if Speedsource found a solution before moving to the 20B PP in the Rolex series.

CyberEric
CyberEric Dork
4/7/22 10:38 a.m.

You guys have got me reconsidering RX-8s. This is such a terrible forum.

BoxheadTim
BoxheadTim MegaDork
4/7/22 11:23 a.m.

In reply to CyberEric :

And we're proud of it

fanfoy
fanfoy SuperDork
4/7/22 5:29 p.m.

There are a 3 guys that run RX8's with 100k+ engines in them in my local auto-x / track clubs. One is a 2004, the other is a 2006 and the other one is an S2 (2009 probably?). The 2004 is the one with the most mileage. They all use the same formula:

- Run it as Mazda intended (5W20, stock coils, no premix, etc.)

- Never been flooded

- They hit redline at least once every time they use them

Two of them have removed their cats, but one still has his in.

This is anecdotal, but it's the recipe I'm using on my 47k miles original Renesis. Still has perfect compression and is as reliable as any Japanese car.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/7/22 5:49 p.m.

In reply to fanfoy :

j9fd3s on teh forums has opined that being on forums is what leads to problems, people who aren't online in car specific groups don't seem to have issues smiley

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