192 vs 231 reliability

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daniel_esp
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192 vs 231 reliability

Post by daniel_esp »

Hello,

Quick introduction: I'm Daniel and I'm writing to you from Southern Spain. I'm thinking of buying an RX8 as a weekend car.
Have been reading this forum for a while now, but I haven't found a topic discussing overall reliability differences between the 192 and the 231.

For one, the consensus seems to be that the 5-speed gearbox is more solid than the 6-speed, so that's 1 point for the 192.

Also, the 192 doesn't rev as much as the 231, so that makes me think it will overheat less and also wear less in time. However, since we're talking about a Rotax engine, is the lower revving a disadvantage instead of an advantage? Is the 192 more prone to carbon build-up?

I'm also interested in the reliability of all other components like clutch, drivetrain, suspension, etc.

Thank you.
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Re: 192 vs 231 reliability

Post by warpc0il »

All parts other than the engine, clutch and gearbox are the same, other than a few that aren't related to reliability.

The 192 has a design flaw that makes it significantly less reliable than the 231 - as it was originally expected to only be used with an automatic transmission.

This means that the rear stationary bearing was never specified to resist the end thrust of a clutch.

It's possible to retrofit the 231 bearing to a 192 engine, which is standard practice by most specialists during a rebuild. Some also offer in-situ replacement.

Other than this there are too many variables to determine if any specific 192 is going to be any more or less reliable than a specific 231.

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Re: 192 vs 231 reliability

Post by 13Black »

The main bearings don't control any thrust forces.
That's entirely the job of the needle bearings in the front stack.
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Re: 192 vs 231 reliability

Post by warpc0il »

That's correct for truly axial thrust forces but clutches aren't that entirely perfect and give the rear stationary bearing a much harder time than an auto 'box.

I had this discussion with the Mazda powertrain guys at a meeting in Merkenich back in 2006, where they admitted that they had raised the concern, after marketing forced through the production of 192 manual for the UK and same other markets. At the time it looked like their concerns were unfounded, and then the failures started...
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Re: 192 vs 231 reliability

Post by mzivtins »

+1 on the 5 speed being better, you wont see 7 guys pushing 400whp through the 6speed anymore, endless gearbox failures starting with sh*t synchro's are common place when you bolt that 6speed to anything that revs high and makes good power.

A 5speed rx8 gearbox on a 7 is a GOOD way to the achieve a reliable drive train in a 7.

Also speaking from experience, that standard 6speed cannot take near 11,500rpm shifts without extreme patience, needless to say, mine shat its synchros very quickly and a 5speed was considered.
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Re: 192 vs 231 reliability

Post by daniel_esp »

warpc0il wrote:
Wed Sep 25, 2019 11:27 pm
and then the failures started...
How many miles we talking? Ballpark.
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Re: 192 vs 231 reliability

Post by daniel_esp »

mzivtins wrote:
Thu Sep 26, 2019 8:16 am
+1 on the 5 speed being better
In all my previous cars, the gearbox / drivetrain always failed before the engine. Hence my prioritization.
That being said, the rotaxness of the engine makes it a much closer call. Is that still the case with the RX8?
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Re: 192 vs 231 reliability

Post by mzivtins »

daniel_esp wrote:
Thu Sep 26, 2019 9:45 am
mzivtins wrote:
Thu Sep 26, 2019 8:16 am
+1 on the 5 speed being better
In all my previous cars, the gearbox / drivetrain always failed before the engine. Hence my prioritization.
That being said, the rotaxness of the engine makes it a much closer call. Is that still the case with the RX8?
stock rx8 with have a 6 speed usually outlive 2-3 engines :lol: as soon as you increse the power by 30-50% (well torque actually) that gearbox will only live for a few months to a year at best.

The guys who used to run the petit supercharges were getting through 6speeds every summer, before sticking a 5 speed in.
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Re: 192 vs 231 reliability

Post by daniel_esp »

mzivtins wrote:
Thu Sep 26, 2019 10:35 am
stock rx8 with have a 6 speed usually outlive 2-3 engines
I see a lot of RX8s here in Spain with over 60k or even 80k miles on the original engine. I'd say most of them are like this, both 192 and 231.
All of them are stated to "start well both cold as well as hot". I haven't seen them in person yet to confirm this, but it does seem that keeping the car 100% stock does wonders for engine life.
Can anyone confirm this?
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Re: 192 vs 231 reliability

Post by warpc0il »

The primary killer of the 231 gearboxes is use of the wrong oil. The synchromesh in these boxes require GL-4 oils only, not GL-4/5 or GL-5.
A few miles with the wrong oil and some damage is done, even if the correct oil is then fitted.

Few oil companies supply a true Gl-4 transmission oil any more and you can pretty much guarantee that what dealer workshops have "on tap" with be GL-5 - lots of previous discussion on the forum and way lots more within the Members Only areas.

Regarding the 192 rear bearing, it was 2008 before we started to recognise a pattern in these failures, so the cars concerned would have been between 1-4 years old at that time, and there's been a constant drip since. There were and still are too many other variables to make even a ball park estimate regarding mileage before failure, especially as the bearing is often one of the contributors to a wider engine failure as it allows the E-Shaft to move.
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Re: 192 vs 231 reliability

Post by mzivtins »

warpc0il wrote:
Thu Sep 26, 2019 10:55 am
The primary killer of the 231 gearboxes is use of the wrong oil. The synchromesh in these boxes require GL-4 oils only, not GL-4/5 or GL-5.
A few miles with the wrong oil and some damage is done, even if the correct oil is then fitted.

Few oil companies supply a true Gl-4 transmission oil any more and you can pretty much guarantee that what dealer workshops have "on tap" with be GL-5 - lots of previous discussion on the forum and way lots more within the Members Only areas.

Regarding the 192 rear bearing, it was 2008 before we started to recognise a pattern in these failures, so the cars concerned would have been between 1-4 years old at that time, and there's been a constant drip since. There were and still are too many other variables to make even a ball park estimate regarding mileage before failure, especially as the bearing is often one of the contributors to a wider engine failure as it allows the E-Shaft to move.
Maybe its just the synchros that are crap for high power/rpm application? i agree with the general consensus that in stock form, especially R3/MX5, these are some of the finest feeling gearboxes out there. I bet a nice r3 would even make some lotus owner a bit jealous :D
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Re: 192 vs 231 reliability

Post by Ryan Rotary Performance »

warpc0il wrote:
Thu Sep 26, 2019 10:55 am
The primary killer of the 231 gearboxes is use of the wrong oil. The synchromesh in these boxes require GL-4 oils only, not GL-4/5 or GL-5.
A few miles with the wrong oil and some damage is done, even if the correct oil is then fitted.
We sell Motul 300 which is a GL4/5 oil, personally used for about 5 years, used on track and with customers for 3 years never had a single issue.

I know some have had issues with pure GL-5 oils but the evidence to support issues with Gl4/5 is pretty thin, although I do know of the [edited] titan oil issue a few members had, so I personally wouldn't use that.

I think a blanket GL4/5 "ban" while prudent does not take into account all the different variants of GL4/5 Oil
Last edited by Ryan Rotary Performance on Thu Sep 26, 2019 12:38 pm, edited 1 time in total.
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Re: 192 vs 231 reliability

Post by PeteH »

warpc0il wrote:
Wed Sep 25, 2019 8:41 pm
The 192 has a design flaw that makes it significantly less reliable than the 231 - as it was originally expected to only be used with an automatic transmission.

This means that the rear stationary bearing was never specified to resist the end thrust of a clutch.
This is often quoted but, as Nick says, the bearing isn't a thrust bearing, so I think it deserves a bit more thought.

Firstly, note that the front and rear stationary bearings are the same. So the 192 gets a pair of bearings to a particular design, and the 231 gets a pair of bearings to a different design.

The 192 stationary bearing is 0820-10-502B. It is the same bearing as was used in all RX-7s from 74 to 91, and in all 4-port RX-8s. It is a simple plain bearing with a single oil way. Interestingly it only comes in one size, which means it must be designed to suit the largest e-shaft, and will therefore often have to run with slightly larger clearances than might be ideal.

The 231 stationary bearing is NF01-10-E##, where ## is a number that represents the size. This is the same bearing as was used in the 93 to 95 RX-7. It is a more complex bearing, and has multiple oil ways. It comes in many sizes, from 1.980mm to 2.000mm, and is therefore designed to run with optimum clearance on the e-shaft. The design of this bearing closely follows the "race bearing" that was supplied for earlier 13B race engines. Mazda clearly learned... But this bearing retails at about twice the price of the 192 bearing.

It therefore seems fairly clear to me that Mazda knew it needed a high performance stationary bearing in the FD and in the 231, but could get away with the lesser (earlier type) bearing in the 192. This just looks like a cost saving measure on the 192 (and there's nothing necessarily wrong with that). Bearing design is always about two things; speed and load. A 231 reaches 9000rpm, and the rear stationary bearing has to carry the radial load of the flywheel and clutch (as well as all the other radial loadings from the e-shaft and combustion forces etc). A 192 auto reaches 7500rpm, and the bearing only carries the load of the counter weight (plus e-shaft etc), so the bearing has a much easier time. But when you put a manual gearbox on a 192 you add back that extra loading from the flywheel and clutch. Is this enough to tip the bearing over its design spec? Maybe. If you've raised the rev limit on your 192, then certainly....

The nearest equivalent loadcase I can think of for the 192 bearing is the FC turbo. That has similar power to the 192, more torque, fewer revs, and a similar manual gearbox. I assume it uses the simple "0820" bearing. I wonder if FC turbos get rear stationary bearing failure....

If I was rebuilding a 192 I'd definitely put 231 stationary bearings in. There isn't going to be a downside, and the 231 bearings are a clear upgrade. The small extra cost seems worth it.
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Re: 192 vs 231 reliability

Post by Ryan Rotary Performance »

PeteH wrote:
Thu Sep 26, 2019 12:36 pm
If I was rebuilding a 192 I'd definitely put 231 stationary bearings in. There isn't going to be a downside, and the 231 bearings are a clear upgrade. The small extra cost seems worth it.
FYI for everyone - We only use 231 6 Port style bearings in all our builds regardless of whether its a 192 or 231, a nice little upgrade along with an up-rated Oil pressure regulator means there is no reason why a 192 cannot redline at 9K just like the 231. :D
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Re: 192 vs 231 reliability

Post by mzivtins »

daniel_esp wrote:
Thu Sep 26, 2019 10:44 am
mzivtins wrote:
Thu Sep 26, 2019 10:35 am
stock rx8 with have a 6 speed usually outlive 2-3 engines
I see a lot of RX8s here in Spain with over 60k or even 80k miles on the original engine. I'd say most of them are like this, both 192 and 231.
All of them are stated to "start well both cold as well as hot". I haven't seen them in person yet to confirm this, but it does seem that keeping the car 100% stock does wonders for engine life.
Can anyone confirm this?
I would say the opposite. a good rebuild give you the opportunity to improve on many things.
better apex seals (depending on application)
Changing oil pressures
adding dry sump
using a seperate OMP tank to run 2 stroke, leaving engine oil out of the combustion chamber has to be one of the best.
Lowering the rotation mass of the engine internals always increases the reliability at higher engine rpms (done correctly etc)
Even going for R3 housing for that 3rd oil injector.

Im sure most would agree?
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Re: 192 vs 231 reliability

Post by PeteH »

I was thinking that the OP meant keep it 100% stock, as in, don't add dodgy "performance upgrades". Some aftermarket intakes, some ecu retunes, some turbo installs, and lots of "home maintenance" can drastically reduce engine life.

I agree that a properly done rebuild, with suitable modifications, can help engine life. Although, in the end, we are all fighting against housings that eventually wear through their chrome.

(Dry sump.... :shock: :lol: )
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Re: 192 vs 231 reliability

Post by mzivtins »

Oh! yeah, totally stay away from snakeoil stuff, ebay turbo and tuning chips haha!

Someone should do a sticky in FAQ of the utopian 13b Reni, that would be great and maybe people might follow that.

You committee guy could probably come up with a really good checklist in no time!
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Re: 192 vs 231 reliability

Post by Juey »

Totally anecdotally -

My 04 231 from new went pop at 35,000 miles and 3 yrs old. New engine from Mazda - went pop again for new owner I believe. Probably running original/A coils mind....

Current 192 05 plate, now at 56k miles and no issues. (pre mixing and C coils, 6 speed box, remap to rev higher, standard bearing)
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Re: 192 vs 231 reliability

Post by daniel_esp »

mzivtins wrote:
Thu Sep 26, 2019 12:58 pm
I would say the opposite. a good rebuild give you the opportunity to improve on many things.
I was just reading the Engine Survey topic earlier and noticed an alarming number of owners are at their 2nd or 3rd rebuild. And the interval between rebuilds is considerably lower than the interval until the first rebuild.
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Re: 192 vs 231 reliability

Post by mzivtins »

daniel_esp wrote:
Thu Sep 26, 2019 3:02 pm
I was just reading the Engine Survey topic earlier and noticed an alarming number of owners are at their 2nd or 3rd rebuild. And the interval between rebuilds is considerably lower than the interval until the first rebuild.
Thats a good point. Data never lies, maybe just some rebuilds not respecting the tolerances laid out by mazda?

Its hard to ever come to a concrete reason why. People will defend the reliability of these engines and rebuilds as if their life depends on it, again the data just proves a catastrophic failure rate every 50k miles growing to almost certainty at 75k miles.

The reliability of rotaries doesn't need to be defended, I think they are all atrociously unreliable, does that stop me throwing 70k of hard earned cash into a rotary car? no....

next question would be... what sports car engine is reliable? porsche 911? lambo? loads of owners have rebuilds of those, its just a feature of a engine engineered for performance as its primary function
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Re: 192 vs 231 reliability

Post by Ryan Rotary Performance »

So I think I can add some value here :)

so after 3 years of providing engines we are yet to have one fail (touch wood), now bearing in mind some of our builds are for purpose track cars, so while miles covered is low they do get a hard time and engine revolutions per mile is high! we now have engines (full Bridge-Port) that have covered over 40K miles.

I think is down to many factors which include:

1. Appraisal of Reused Engine Parts which can and should be reused. We are very selective on the plates and especially rotors that we re-use in our builds, you would be surprised at the amount of rotors we throw away and plates we have in our store awaiting lapping and re-nitriding. some of these are within Mazda minimum specification.

2. The Rebuild Kit - We only use genuine Mazda OEM, No Atkins, No Goopy, No Ceramics. I think the only exception here are water and oil seals, some are better or just as good as OEM. key thing here, dont srimp on anything, change EVERYTHING!

3. Upgrades - Not really an upgrade but when rebuilding engines 90% of the time we use refurbished rotor housings which provide a better start in life for apex seals and generally help with the bed in process. Upgraded Oil pressure regulator is also high on the must do's and finally our serviceable Oil injectors. you'd be surprised at the amount of injectors failing even AFTER cleaning. basically they are impossible to clean fully without taking apart.

4. Oils controversial subject I know, but the oil we have found to provide very good protection for the plates and bearings while burning cleanly is the Motul 300v Fully Syn 5W-30. (which is why we stipulate this oil on our warranty).

5. Coils normally overlooked on an engine build but poor coils can kill an engine very quickly! Do I really need to say what I recommend #-o
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Re: 192 vs 231 reliability

Post by New Duke »

Ryan Rotary Performance wrote:
Thu Sep 26, 2019 4:05 pm
4. Oils controversial subject I know, but the oil we have found to provide very good protection for the plates and bearings while burning cleanly is the Motul 300v Fully Syn 5W-30. (which is why we stipulate this oil on our warranty).
Is that the ester base 'power racing' oil? That stuff costs 4X more than the Shell 10w-40 I use (I'm sure with good reason). Track days and oil changes are going to get pricey post rebuild :pale:

Thanks for your insight Carl, that was all really interesting info.
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Re: 192 vs 231 reliability

Post by Ollie »

Note to self, rebuild not as expensive as oil required to be used post rebuild. #-o
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Re: 192 vs 231 reliability

Post by warpc0il »

Fit a sohn/Cofs and there's no need to top-up engine oil between changes.

I check mine but the level never moves.



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Re: 192 vs 231 reliability

Post by Ollie »

To be fair its not like my car currently burns a lot of engine oil but a COFS is on the to do before a rebuild happens ideally.
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