Le Moteur Rotatif (Renesis 13B)

Source : RX8Club.com - New and Potential Owners START HERE! Auteur : RIWWP

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So What Is This Engine Anyway? — Présentation du moteur rotatif

You may have heard that this engine is not a piston engine. This is correct. The RX-8 is powered by a rotary engine, based on the principle design developed by Felix Wankel, from whom Mazda bought the exclusive rights to develop. The rotary engine is very hard to describe with just words, so here are a few pictures:

Exploded view of the engine and it's component parts

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All put together:

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The total package is quite small compared to piston engines: (That is one rotor, housing, and the eccentric shaft)

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So how does it work?

Basically, the combustion sweeps the rotor around the e-shaft in an off-center looking wobble. (This is actually an RX-7 engine, but the basics are still the same)

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Here is a YouTube video of the components and motions of the engine:

Rotary Engine - YouTube

Dramatic difference from the traditional piston engine.

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So, as you can see, we have 3 combustions per rotor for every full rotation of each rotor. However, due to the gearing reduction around the e-shaft, each rotor spins at 1/3rd the speed of the e-shaft. So when you are at 9,000rpm, each rotor is only spinning at 3,000rpm, however each rotor is producing 9,000 combustions per minute, for a combined total of 18,000 combustions per minute. This is most of what produces the buttery smooth power delivery of a rotary engine. You can also see that the motion is already rotational in nature, rather than the continual start/stop of pistons in a piston engine. This is the other main contributor to the smoothness of the engine.

Our "lack of torque" is also a byproduct of this. Each combustion is quite small, and there isn't much leverage provided by the e-shaft angles.

So what makes our engine different from prior RX-7 engines that are also listed as 13b engines?

Primarily, the difference is the location of the intake and exhaust ports.

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RX-7 engines had their ports on the rotor housing, so the apex seals sweep across them.

RX-8 engines, the Renesis, have the ports on the end plates and center iron. This means that the apex seals do not sweep across them at all. This enables unburnt gasoline in the exhaust post-combustion to be more likely to stay in the engine to be burnt the next time around, rather than getting swept out into the exhaust system. This improves emissions and fuel economy.

The other primary different from the RX-7 engines is that the Renesis has higher compression rotors, also in the name of power, emissions, and fuel economy.

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4 Port or 6 Port — Les différentes versions du moteur

At first release, there were two different basic engine designs. The 4-port and the 6-port. (In Europe and some other regions, the 4-port is referred to a "192hp" or "197hp", depending on the transmission, and the 6-port is referred to as "hi-power", "232hp", etc... i believe all of these had the 6-speed manual in those regions.) The difference is essentially that the 6-port has 2 more intake ports than the 4-port. This allows a higher amount of air flow into the engine at high RPM. A 4-port beyond 7,500rpm is being choked by difficulty flowing enough air. The two additional ports in a 6-port provide enough air flow to overcome this problem.Like any other intake flow change, allowing more airflow at higher revs means a shift of airflow optimization away from low revs. The 4-port actually has a few ft/lbs of torque more than the 6-port as a result

2004-2005 4 speed Automatic transmissions (North America): 4-port engine, Series1 design

2004-2008 4 speed Automatic transmissions (Europe): 4-port engine, Series1 design

2006-2008 6 speed Automatic transmissions: 6-port engine, Series1 design (combination was not sold in Europe)

2004-2008 6 speed Manual transmissions: 6-port engine, Series1 design

2004-2008 5 speed Manual transmissions: 4-port engine, Series1 design (combination was not sold in North America)

For 2009~, the engine design was updated in many subtle but significant ways:

2009-2012 6 speed Automatic transmissions: 6-port engine, Series2 design.

2009-2012 6 speed Manual transmissions: 6-port engine, Series2 design.

Swapping between engines:

Of the 3 designs (4-port Series1, 6-port Series1, 6-port Series2), each design is directly swappable into RX-8s that had that same design. So you can use a 6-port from a 2008 Automatic directly in a 2004 6-speed manual with zero modifications, and vise versa.

The Series1 and Series2 engines can be physically installed in each other's vehicles, however the OMP and electronics differences are considerable. Swapping between Series1 and Series2 will involve replacing every electronics module in the car, even the ones not engine related.

The 4-port and 6-port can likewise be physically installed in each other's vehicles, but there are significant electronic differences that will require replacement or re-coding of at least the ECU, likely additional components. If the 4-port to 6-port swap also includes a change of transmissions then there are additional hardware components that need to be converted as well.

Swapping between any of the different engine designs becomes a long and costly process.

How do I quickly tell which one a car has?

The easiest method is to look for the Upper Intake Manifold (UIM). It's the large curved section of black plastic that curves from the center right side of the engine bay to the back left (from a perspective of standing in front of the car looking at the engine bay). Look for the presence of the two intake runners that lead to the two extra ports. The runners you are looking for are to each side of the main runners, and are positioned lower

This is a 6-port. The front lower runner is circled in red

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This is a 4-port. There is no extra runner where I made the red circle

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So How Much Power Do We Have Anyway? — Puissance réelle du RX-8

Officially, the RX-8 produces somewhere between 228hp and 238hp, depending on what publication you look at. Mazda kept revising the numbers, but the engine's actual output never changed. This is for the 6 port manual transmission engines. The automatics produce less power, because of their lower redline. The 4 port automatics produce around 192hp, and the 6 port automatics produce around 212hp.

This is all measurements at the crank. The actual power put down at the wheels is significantly lower. Completely healthy 6port MTs put down about 180whp and 130wtq. The auto's are correspondingly lower.

Now, what does this actually mean?

Well, first take a look at the numbers. Notice how they are lower than an Evo's 300hp rating. And they are lower than a Mustang's 260hp-340hp.

This means the RX-8 is SLOWER in a straight line.

If you buy an RX-8, do NOT be shocked that you won't win at the drag strip. If you want to win there, buy a different car. If you buy the RX-8, don't come crying to us later on. We bought the car knowing full well how much power it produced. Those of us that want more do something about it. We don't create threads to whine about it. You can join us in flaming the people that do create threads whining about it, because you were smart enough to learn first. They weren't.

Our engine, when every single part of the powertrain is healthy, is at a bleeding edge of performance. It doesn't take much at all in the way of something not ideal for power and efficiency to fall off. The engines all typically fall to around the same point, ~170whp (6 port MT), and from there it takes a ton of problems or huge failures (like excessive carbon caking or cat failure) to really kill the engine. Maintaining it on that razor's edge is the difficulty.

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The Engine Failure Story — Les défaillances moteur

RX-8 engines don't have a very good reputation. Unfortuantely, the reputation is well deserved. Fortunately, the general public at large has it ALL WRONG, while at the same time as generally being right.

Back in 2004-2005, reports of RX-8 engine failure started to pop up, alarm was generated, and the reputation was born that these engines don't last 30,000 miles. Part of this was that engines were actually failing. The early ECU flashes weren't injecting enough oil, and things were wearing out fast and/or breaking. MSP16 was the final iteration to try to solve this. However, this was only part of the problem. MOST of the problem was simple mis-diagnosis. Owners would feel misfires or power loss, they would change their spark plugs, and the problem wouldn't go away. They would take it to the dealer, who would poke around trying to find a problem, and not finding one, decide that the engine needed replacement. They would order an engine, put it in the customer's car, and send them on their way. It wasn't until years later that dealers started realizing that the IGNITION COILS were failing around 30,000 miles. There are no hard numbers, but many of us believe that a large portion of the original "engine failures" were nothing more than simple ignition coil failure, and were replaced needlessly.

Now, add to that problem that Mazda's engine reman plant that would take the 'dead' engines and rebuild them into remanufactured engines was bad. REALLY bad. The quality control was nearly non-existant, skilled workers were no where to be found, and the result was that a rather large number of engines from the plant were far worse than the original factory engines. These reman engines were popping very quickly as well from their own issues. Yes, this means that a customer could have had a great engine, had it erroneously replaced by a dealer not realizing that it just needed new coils, and get a terrible engine put in as a result.

This is how many of the original 2004s and 2005s went through multiple engines. Replace something that isn't broken with something that is and yeah, things aren't going to go well. Reman quality is significant better than it was, but certainly not perfect still.

Now, if you remove those problems from consideration (the original ECU flash and the reman quality problems), then the engine is very reliable. There are still several major design flaws that tend to hurt the lifespan of the engine, and there are other failure methods where you can destroy a perfectly good engine REALLY fast through in-attention. Most RX-8s DO get a 2nd engine within 100,000 miles, so yes, engines are replaced all the time on the forum, but not for the reasons that the general public likes to believe.

How many are replaced?

Well, that is still mostly guess work and theory, though there is some indication from outside sources and leaked Mazda information that around 50% of RX-8s have had at least 1 engine replacement in it's lifespan.

How about the newer RX-8s though? Shouldn't they be good to go?

In 2009 they introduced some subtle but significant engine changes correcting several things, the most critical of which was an increase in oil pressure to RX-7 ranges (they dropped it for the 2004-2008 years for some reason), and re-introducing the center oil injector (they deleted it for the 2004-2008 RX-8s for some reason, all prior rotories had the center injector). This doesn't make them immune to engine failure however, for example a failed thermostat could kill a perfectly good engine, but it helped to reduce the wear-related failures a bit.

A compression test should be standard before anyone buys an 8 though, just to be on the safe side. Most dealers charge $120 to $250 to do a compression test. I go more into the compression test itself in a post further down.

You might be wondering why it is that we have such a poor outlook. The problem is that there are so many different ways for an engine to fail:

• Excessive carbon buildup accelerates seal wear, causing compression loss (particularly a problem in automatic RX-8s)

• Excessive carbon buildup unseats the apex seals, causing compression loss (particularly a problem in automatic RX-8s)

• Excessive heat buildup warps the housings to one degree or another, preventing the apex seals from sealing, causing compression loss (particularly a problem with older RX-8s that haven't had a cooling system overhaul)

• Excessive exhaust temperatures overheat the side seal springs, warping them until the side seal pops out of it's location, clips the exhaust port and shatters, throwing shrapnel through the engine (particularly motors that are turbocharged, supercharged, or see nearly 100% track time)

• Fuel pump failure or high lateral G left turns with low fuel causes fuel starvation under load, creating a lean spike that causes detonation and shatters seals (particularly a problem with older RX-8s that haven't had a fuel pump replacement)

• Cat failure (even more common than engine failure) causes localized heat and pressure buildup that overstresses the seals and breaks down oil viscosity, leading to various issues (particularly a problem with new owners that don't know to replace their ignition)

• Clogged oil injection lines prevent oil from being injected, leading to excessive apex seal wear and side seal overheating, leading to compression loss and/or catastrophic failure (particularly a problem with long oil change intervals)

• Subpar reman engine quality, starting with low compression that accelerates any other issue (reman quality has improved over the years, but bad apples are still reported)

These are just the common failure methods. There are uncommon ones, and/or freak ones, like a transmission issue snapped one guy's e-shaft somehow (probably a defective e-shaft that was too weak), or issues that are entirely owner caused, like too low octane or not keeping on top of the oil level.

Any single preventative measure you can find only addresses at best a couple of these, maybe just one method, and maybe none at all (but people think it does). And since you don't usually know how well the engine was put together in the first place, it's largely a roll of the dice on these engines.

Short answer: If possible engine failure makes you that uncomfortable and/or paranoid, then this is not the car for you. You have to accept the issues or ownership will turn into a nightmare. It still could anyway, but your mindset going in is far more important than statistics. The more prepared you are, financially and mentally, the less of a problem any of this will actually be for you.

Yes, I paint a bleak picture. However, it really isn't much worse than any other sports car. Every sports car out there has had it's share of problems. Why do we still love the RX-8 anyway? We love it because of it's ability to plaster a grin on your face. More on that later.

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Compression Test — Le test de compression

Yes. And it can not be done with a standard analog compression tester for piston engines. A typical cheap analog tester just plugs into a spark plug port and as the engine cranks, the needle moves, and you can easily see where it's swinging to every compression stroke. 1 spark plug, 1 cylinder, 1 compression number.

The rotary however is 1 spark plug, 3 rotor cavities, 3 compression numbers per revolution. There is no way for a simple analog tester to record each face of the rotor independently as it spins, updating each number correctly as it compresses.

Piston engines also have relatively the same compression number regardless of how fast the engine is pumping. If there is a loss of compression due to a seal or whatever, there will be some loss as it compresses, and a slower RPM will read slightly less as it allows slightly more time to leak. Rotary engines have plenty of 'gaps', and there is a very real and measurable difference in compression depending on engine cranking speed. The faster it spins the higher the compression. You can even remove the apex seals completely, and it gets enough compression at 9,000rpm to stay alive, though not much below that it won't. (incidentally, this is an often over-looked dynamic of how the engine produces it's power curve, and how it doesn't have severe drop-off in power the higher you go in RPM the way piston engines do, and one of the reasons low rpm torque is so poor. Not the only reason, but a contributing factor). So, in addition to the 2 sets of 3 numbers for each of the 3 faces of each of the 2 rotors, you need the crank RPM for the test. A normalization chart based on RPM determines if you are pass or fail.

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Many dealers also obtain a BARO voltage reading test to determine vacuum as another method of determining pass or fail. Vacuum is related to compression, but it isn't the same thing, and is possible for them to differ more than expected. There have been quite a few reports of Mazda techs returning BARO numbers that clearly fail and stating that they pass, so if it fails compression but passes vacuum, I'd question the techs quite a bit about making sure they did it right.

Originally Posted by omgitsdomie

1. While i've been searching around for rx8's there are some at different dealers. EX: an rx8 at a Nissan dealer. How would you go about asking to get a compression test since usually most dealers wont let you take a car somewhere without a representative, and usually they only go with you only for test drives, and test drives only?

Only Mazda dealers will be able to do a compression test, unless you happen to live near one of the bare handful of non-Mazda owned rotary compression testers.

Your best bet is to simply ask the dealer if you can take it to get a compression test. If they decline, they ask if they can do it. If they still decline, then they probably have something to hide and you should immediately cross that 8 off your list, no matter how much surface appeal it has.

No reputable dealer will object to having one of their cars checked over by a 3rd party, ESPECIALLY when it's a particular check that only Mazda dealers can do. A 129 million point inspection means nothing if they don't have a rotary compression tester to check the most critical part. Or convince them to cover the engine with an extended warranty on THEIR dime. "Hey, if you can't check the engine, I'm taking a risk buying it, and you need to cover it in case I'm buying a time bomb."

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Compression Test Numbers — Interprétation des résultats

You should have gotten numbers in a format something like this:

Rotor 1: 7.5, 7.6, 7.5
Rotor 2: 7.2, 7.3, 7.3
250 RPM

• The 6 numbers, 3 for each rotor, are your compression scores, one for each face of each rotor in the engine.
• If you don't have all 6 rotor face scores and at least 1 RPM number, your compression scores are going to be vague and hard to interpret.
• You may also have your compression scores in a different scale, such as PSI.
• The RPM is the speed at which the test was done.
• The RPM is critical to interpreting the numbers, as rotary compression changes with engine speed, especially at low RPM.
• Since the engine is spun by your starter, this is ALSO a good indication of the health of your starter!

The general guideline for how good, or bad, the scores are, WHEN NORMALIZED TO 250 RPM AT SEA LEVEL:

Score	Évaluation
8.5+	Moteur exceptionnel ! Rare. Des scores trop élevés peuvent indiquer un excès d'huile dans le logement.
8.0–8.4	Très bon moteur. Bonne puissance, devrait durer longtemps avec un entretien régulier.
7.5–7.9	Moteur acceptable. La plupart des moteurs neufs sont dans cette gamme après le rodage. 40-60k miles supplémentaires possibles.
7.0–7.4	Le moteur a encore de la vie, mais commencez à chercher des options de remplacement. La perte de compression accélère.
6.5–6.9	En échec officiel. Le moteur n'a plus beaucoup d'espérance de vie. Perte de compression accélérée par blow-by.
6.0–6.4	Échec significatif. Très sensible au flooding même avec starter, batterie et allumage neufs. Difficulté à démarrer à chaud.
5.5–5.9	Échec sévère. Extrêmement sensible au flooding. Presque impossible de maintenir le ralenti à chaud. Perte de puissance significative.
5.0–5.4	Démarrage probablement possible uniquement par remorquage. Usage quotidien quasi impossible.
< 5.0	Comment ce moteur tourne-t-il encore ?

Caveats:

• If the test was done incorrectly, this can skew the numbers up or down.
• If the engine has excessive oil inside the housings, the compression numbers will be reported as higher than they actually are when the engine is running.
• If the test was not done at 250rpm and at sea level (neither of which is likely), the numbers you have will need to be normalized to 250rpm at sea level. Use Mazda's calculator here: Foxed.ca - Rotary Compression Calculator
• This is largely my opinion, based on seeing hundreds of compression scores on the site over the years. I am not using anything scientific to back it up. As always, your mileage may vary.

The black line is the failing line. Any 1 rotor face at a 6.9 or lower is failing.

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Making Your Engine Last — Prolonger la vie du moteur

For this, you have to understand that each different failure method has to be addressed individually. Some solutions help more than one aspect, but if you ignore one, it's probably going to be the one to bite you.

First Note: There are some "solutions" presented which conflict with causes listed. Example High Load High RPM helps carbon, but hurts side seal and cooling. It's the excess that gets you into trouble. Don't stay high RPM all of the time for carbon, because you are dramatically increasing the chance of heat related failures, but don't avoid high RPM either because it is increasing the chance of carbon related failure. Dip your feet in both pools...

Second Note: These are fairly basic concepts. They can get far far far more involved. Pursuing any of these should be preceded by research.

Excessive carbon buildup accelerates seal wear / unseats apex seals

It is nearly impossible to prevent all carbon buildup in our engines. But some things can help make an impact:

A) High RPM at full throttle (commonly known as "redline a day") produces lots of heat and energy along with high air/exhaust velocities, which can help is breaking down the carbon and blowing it out of the engine. An engine that only sees low RPM and low load (as many automatics do) has been shown to have significantly more carbon buildup than one that is rev'ed hard often. This will NOT prevent all carbon.

B) Premix. Premix is largely a benefit for apex seal wear, however it has been shown on engine teardowns that the carbon in an engine that was premixed is 'softer' than carbon in an engine that wasn't, and seems to lend a slight benefit in this area to decarbing.

C) Seafoam / Decarb / Steam Cleaning. See my testing thread here for the effectiveness of it: Decarbing Before and After Rotor Pics

Soaking with seafoam simply doesn't remove any appreciable carbon. The only way to really strip carbon periodically is with ingestion while the engine is running. And in this circumstance, seafoam is just as effective as distilled water. Seafoam is also ~100 times more expensive per unit of measure, so there isn't much of a reason to actually use seafoam. It is also more benefitial to ingest the water at higher RPMs, and to feed both rotors at the same time. This will indeed strip away carbon. However, it is a VERY slow process. Do not expect a single gallon will do it. 1.5 gallons of water, 0.5 gallons of washer fluid (it's a water/meth mix), and the carbon near the seals was less than half gone. Removing carbon is always a good thing, however don't expect stellar results, and don't think that it's removing all of the carbon, or even that it's removing carbon where it needs to. If you do this, you will need an oil change immediately after at a minimum. If you have a cat installed, the cat can start glowing, so you will need to take breaks to let it cool down. May kill the cat and/or reduce it's life span. See the testing thread for details.

D) Water/Meth injection. W/M injection is usually targeted almost entirely for forced induction as a safety margin by increasing the effective octane rating of the fuel. However it does have side benefits of producing remarkably clean engine internals. If you want to learn more, read up on this opening post on RX7Club: Making The Case For The Rotary Powered FD: The Fix - RX7Club.com. He largely talks about methods of failure for the RX-7, and it has a slightly different application and goal that the writer was going after, but still valuable nuggets in there for our engine's long term health and how effective it is at removing carbon. However, note that W/M is not legal everywhere, many racing organizations prohibit it, it usually requires some sort of tuning, and kits are usually set up to deliver under boost, which an N/A engine won't have. I don't know of anyone running W/M on an naturally aspirated Renesis for the purposes of cleaning only. W/M injection solves a few of the steam and seafoam treatment weaknesses, namely the inability to deliver either with the engine under full load while the car sits in your driveway. Injection also gets the intake valving that none of the other treatments do.

Excessive heat buildup warps the housings

This can be caused from a few different sources. Probably most common is a coolant system overheating, followed by a cat clogging. Most housing warp failures end up leaking coolant and/or oil directly into the housing because the seals and rings can no longer seal properly. The greater the warp, the faster the oil and coolant leak.

A) Remove the cat, install a midpipe. This isn't kosher with the EPA, environmentalists, federal government, most state governments, emissions inspection stations, your spouse's nose, or your rear bumper paint. However, aside from the power increase it will give you, removing the cat removes the possibility that it will clog on your car, which can cause significant localized heat within your cat, header, and back up into your engine. I believe that my engine failed due to housing warp from a failed cat.

B) Upgrade your cooling system. Do not rely on your temperature needle. By the time it starts to move, the engine is already hot enough to be able to start warping. Damage is almost guaranteed. You have to understand what each component of your coolant system does, don't just go upgrading willy-nilly. The radiator is what transfers the heat out of the coolant. An upgraded radiator means a faster heat dump from the coolant it sees. However, the thermostat is what controls what coolant gets to the radiator, and if the coolant temp drops to a certain point, it won't even send the coolant to the radiator to dump heat from. So if you have a 200 degree thermostat, and your coolant temps sit at 200 degrees, upgrading your radiator will do nothing to drop this! It will only increase the rate of temperature drop when you are ABOVE your thermostat temp. Upgrading your thermostat to a lower temperature is what can allow your radiator to bring temps down. If you are getting an engine rebuild, there are improvements you can have done to your coolant passages to aid their heat transfer from the block to the coolant. There is also the water pump, which pushes the coolant through the system. It's speed is based on RPM speed, and the OEM water pump can have quite a bit of trouble moving coolant at high RPM. Upgrading the water pump can help reduce heat-spotting in the engine.

C) Lower the trigger temp for the radiator fans. The OEM trigger temp is almost 'too high' already. There are a few kits you can buy, as well as it is built into Mazdamaniac's AccessPORT base tune. So your fan runs more, but your system stays cooler.

D) Flush radiator fluid periodically. Already part of regular maintenance, but more critical for our engines than piston engines.

Excessive exhaust temperatures overheat the side seal springs

This is a failure that most of us don't have to really worry about. It's the number one failure method in race engines, and I suspect most turbo'ed engine failures that don't involve a sudden lean spike detonation. Lots of exhaust heat builds up exhaust port heat, leading to the side seal spring deforming until it gets to the point that it pushes the side seal out of place, the seal catches the exhaust port and shatters. This is usually only a problem in cars putting down ~220whp or more, AND spends most of it's life at high RPM and high load (like a race engine).

A) The only 'known' solution for this is using the side seal springs from the FD engine. I have nothing to prove this, and you can find race teams that swear there is nothing to do about it and other race teams that swear they no longer have the problem. If you are getting a rebuild and want to reduce this risk, there is likely no harm in going with the FD side seal springs, and it very well may help.

B) Increasing the efficiency of the exhaust system will also reduce exhaust port temps. A more efficient exhaust dumps heat more rapidly, reducing buildup.

Fuel pump failure / fuel starvation

This is an all-too-frequent failure seen. If you expect frequent full throttle hard left curves, it is recommended to not let the tank get under 1/4 remaining. The OEM fuel pumps can start failing around 60,000 miles (for 2004-2008, the 2009-2012 should be better), though can certainly last far longer. Most fuel pump failures are due to overheating of the pump, and will suddenly stop pumping, which suddenly shuts off the engine inexplicably. Letting the car sit for a while and then restarting should get it started just fine as if nothing happened. If this happens to you, stay low load, low RPM and get it where you can park it for a fuel pump replacement. Going full throttle with a fuel pump failing is dangerous to your engine.

Cat failure

I've covered the issues with cat failure, so this is largely a redundant point. If you can remove it, do it.

Clogged oil injection lines

This is one of the 'silent killers'. The only real symptom of clogged oil injection lines is when oil consumption drops below the 1qt / 1,500miles rate.

A) You can run seafoam through them using engine vacuum as a good cleaning method. There is no set recommendation on how often to do it, but the longer you go between oil changes, the more likely you are to need it more frequently. No shop or dealer will have any idea on how to do this, or even what you are talking about, so just do it yourself for free.

B) If you run the SOHN adapter, this becomes largely negated, as the clean 2-stroke will not be prone to clogging.

Subpar reman engine quality

There isn't anything you can do about getting a reman engine that has poor seal clearances or overly worn parts. So, cross your fingers.

For a specific thread on further steps to take, read HiFlight's excellent thread: My Sneaky Plan to Extend Engine Life - Series I

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Temoignages : ca peut durer — Moteurs haute kilometrage

Le tableau dressé ci-dessus peut sembler décourageant. Pourtant, des propriétaires atteignent des kilométrages très élevés sur le moteur d'origine. Le point commun : un entretien rigoureux et proactif.

Proprietaire	Kilometrage	Moteur	Cle du succes
u/coolbeanzguy123 (r/rx8)	148 000 miles (~238 000 km) + 85 000 miles (~137 000 km)	S1, moteurs d'origine	Décarbonnage régulier via ports de maintenance (seafoam), Rotella T6 5W40, premix 2 oz/plein, bobines/bougies neuves
u/kraln (r/rx8)	150 000 miles (~241 000 km), 17 ans	Moteur d'origine	Entretien régulier, conduite adaptée
u/Downtown-Scene-5154 (r/rx8)	190 000 miles (~306 000 km)	Moteur d'origine	Parcouru Floride ouest → est sans problème
u/FuJa-TsuNaMi (r/rx8)	165 000 miles (~265 000 km), 75k sur le moteur	S1	Upgrades refroidissement (radiateur alu, durites huile reroutées), bobines surélevées avec shield thermique, monitoring OBD2 permanent
u/djfreon (r/rx8)	146 000 miles (~235 000 km), 1er propriétaire depuis 2003	Moteur de remplacement OEM à 96k	Öhlins coilovers, volant allégé, démarreur S2, entretien proactif

Points communs observes

1. L'huile fraîche est plus importante que le type d'huile — vidanges fréquentes, toujours au-dessus de la moitié de la jauge
2. L'allumage est remplacé proactivement — ne pas attendre les symptômes (ratés, perte de puissance)
3. Le refroidissement est monitoré — OBD2 en permanence pour connaître la température réelle
4. Le moteur est mené haut dans les tours — le "redline a day" chasse le carbone
5. Le premix est utilisé — même en petite quantité, il garde le carbone plus tendre
6. Les défaillances sont traitées immédiatement — un petit problème non traité cascade en catastrophe (bobines → bougies encrassées → cat détruit → surchauffe → moteur)

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Decarbonnage via les ports de maintenance

Le moteur rotatif accumule du carbone dans les logements, particulièrement sur les moteurs qui ne montent pas souvent dans les tours (usage urbain, automatique). Mazda a prévu des ports de maintenance pour effectuer un nettoyage chimique.

Qu'est-ce que les ports de maintenance ?

Il y a 2 bouchons en caoutchouc sur le côté passager du bloc moteur (sur le logement de rotor). Retirés, ils donnent un accès direct à l'intérieur du moteur. Le moteur crée une aspiration (vide) quand il tourne, ce qui permet d'aspirer un liquide de nettoyage.

:::info Reference Mazda Mazda a publié un TSB officiel décrivant cette procédure avec un produit Mazda propriétaire. Le Seafoam est le substitut communautaire reconnu. :::

Methode Seafoam

1. Démarrez le moteur et laissez-le monter en température (aiguille au milieu)
2. Retirez les 2 bouchons caoutchouc des ports de maintenance (côté passager du bloc)
3. Insérez un tube d'aquarium dans chaque port
4. Laissez le moteur aspirer le Seafoam lentement par le vide (ne pas noyer le moteur — y aller progressivement)
5. Replacez les bouchons
6. Coupez le moteur et laissez tremper 15-30 minutes
7. Redémarrez — attendez-vous à un gros nuage de fumée (carbone en cours de combustion)
8. Laissez tourner jusqu'à ce que la fumée se dissipe
9. Faites une vidange immédiatement après — le Seafoam se retrouve dans le carter d'huile

:::warning Attention

• Ne pas faire cette procédure avec un catalyseur en place — la fumée et les résidus peuvent détruire le cat plus rapidement. Si vous avez encore le cat, retirez-le d'abord ou faites très attention.
• Ne jamais utiliser de nettoyant carburateur dans les ports — trop agressif, détruit le film d'huile dans le moteur et contamine l'huile du carter.
• Procédure détaillée (en anglais) : Seafoam for Newbies - RX8Club :::

Alternatives au Seafoam

Methode	Description	Avantage	Inconvenient
Eau distillee ("steam cleaning")	Aspiration d'eau distillée par les ports	Gratuit, très efficace à haut régime	Risque hydrolock si trop d'eau d'un coup
Lave-glace inflammable (alcool)	Aspiration de liquide lave-glace alcoolisé	Bon compromis nettoyage/sécurité	Pas aussi efficace que l'eau à haute température
Nettoyage Mazda (TSB officiel)	Produit Mazda propriétaire	Procédure validée constructeur	Disponibilité limitée, coût

L'eau distillée en ingestion à haut régime est considérée par beaucoup comme aussi efficace que le Seafoam, et 100x moins chère. Voir la vidéo de référence : Steam Cleaning Rotary Engine

:::caution Controverse Certains propriétaires et mécaniciens déconseillent le steam cleaning, craignant que l'humidité accélère la corrosion interne. Discussion sur RX7Club : Dangers of Steam Cleaning. Comme toujours avec le rotatif, les opinions divergent. :::