The Rotary Engine (Renesis 13B)

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

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So What Is This Engine Anyway?

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. (Wikipedia) 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

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 (Wikipedia)

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?

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 (initially advertised as 197hp, later revised), and the 6 port automatics produce around 212hp. (Wikipedia)

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

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 community estimates suggest that around 50% of RX-8s have had at least 1 engine replacement in its lifespan. (RX8Club)

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. (Wikipedia)

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

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. (Foxed.ca)

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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

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	Assessment
8.5+	Exceptional engine! Rare. Scores that are too high may indicate excess oil in the housing.
8.0–8.4	Very good engine. Good power, should last a long time with regular maintenance.
7.5–7.9	Acceptable engine. Most new engines fall in this range after break-in. 40-60k additional miles possible.
7.0–7.4	The engine still has life, but start looking for replacement options. Compression loss is accelerating.
6.5–6.9	Officially failing. The engine doesn't have much life left. Accelerated compression loss from blow-by.
6.0–6.4	Significant failure. Very sensitive to flooding even with a new starter, battery, and ignition. Difficulty hot-starting.
5.5–5.9	Severe failure. Extremely sensitive to flooding. Nearly impossible to maintain hot idle. Significant power loss.
5.0–5.4	Starting probably only possible by towing. Daily driving nearly impossible.
< 5.0	How is this engine still running?

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

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. (RX8Club)

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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Testimonials: It Can Last — High Mileage Engines

The picture painted above may seem discouraging. Yet, some owners achieve very high mileages on the original engine. The common thread: rigorous and proactive maintenance.

Owner	Mileage	Engine	Key to Success
u/coolbeanzguy123 (r/rx8)	148,000 miles (~238,000 km) + 85,000 miles (~137,000 km)	S1, original engines	Regular decarbonizing via maintenance ports (seafoam), Rotella T6 5W40, premix 2 oz/tank, new coils/plugs
u/kraln (r/rx8)	150,000 miles (~241,000 km), 17 years	Original engine	Regular maintenance, adapted driving style
u/Downtown-Scene-5154 (r/rx8)	190,000 miles (~306,000 km)	Original engine	Drove Florida west → east without issues
u/FuJa-TsuNaMi (r/rx8)	165,000 miles (~265,000 km), 75k on the engine	S1	Cooling upgrades (aluminum radiator, rerouted oil lines), raised coils with heat shield, permanent OBD2 monitoring
u/djfreon (r/rx8)	146,000 miles (~235,000 km), 1st owner since 2003	OEM replacement engine at 96k	Öhlins coilovers, lightweight flywheel, S2 starter, proactive maintenance

(r/rx8)

Common Patterns Observed

1. Fresh oil is more important than oil type — frequent oil changes, always above half on the dipstick
2. Ignition is replaced proactively — don't wait for symptoms (misfires, power loss)
3. Cooling is monitored — OBD2 constantly to know the actual temperature
4. The engine is driven high in the revs — "redline a day" clears carbon
5. Premix is used — even in small amounts, it keeps carbon softer
6. Failures are addressed immediately — an untreated small problem cascades into catastrophe (coils → fouled plugs → destroyed cat → overheating → engine)

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Decarbonizing via the Maintenance Ports

The rotary engine accumulates carbon in the housings, particularly on engines that don't frequently reach high RPMs (city driving, automatic). Mazda provided maintenance ports for chemical cleaning.

What are the maintenance ports?

There are 2 rubber plugs on the passenger side of the engine block (on the rotor housing). When removed, they provide direct access to the inside of the engine. The engine creates a vacuum when running, which allows a cleaning liquid to be drawn in.

:::info Mazda Reference Mazda published an official TSB describing this procedure with a proprietary Mazda product. Seafoam is the recognized community substitute. :::

Seafoam Method

1. Start the engine and let it reach operating temperature (needle in the middle)
2. Remove the 2 rubber plugs from the maintenance ports (passenger side of the block)
3. Insert an aquarium tube into each port
4. Let the engine slowly draw in the Seafoam through the vacuum (do not flood the engine — go gradually)
5. Replace the plugs
6. Shut off the engine and let it soak for 15-30 minutes
7. Restart — expect a large cloud of smoke (carbon burning off)
8. Let it run until the smoke dissipates
9. Change the oil immediately after — the Seafoam ends up in the oil pan

:::warning Caution

• Do not perform this procedure with the catalytic converter in place — the smoke and residue can destroy the cat more quickly. If you still have the cat, remove it first or be very careful.
• Never use carburetor cleaner in the ports — too aggressive, destroys the oil film inside the engine and contaminates the crankcase oil.
• Detailed procedure (in English): Seafoam for Newbies - RX8Club :::

Alternatives to Seafoam

Method	Description	Advantage	Disadvantage
Distilled water ("steam cleaning")	Drawing distilled water through the ports	Free, very effective at high RPM	Hydrolock risk if too much water at once
Flammable washer fluid (alcohol)	Drawing alcohol-based washer fluid	Good cleaning/safety compromise	Not as effective as water at high temperature
Mazda cleaning (official TSB)	Proprietary Mazda product	Manufacturer-validated procedure	Limited availability, cost

Distilled water ingested at high RPM is considered by many to be just as effective as Seafoam, and 100x cheaper. See the reference video: Steam Cleaning Rotary Engine

:::caution Controversy Some owners and mechanics advise against steam cleaning, fearing that moisture accelerates internal corrosion. Discussion on RX7Club: Dangers of Steam Cleaning. As always with the rotary, opinions differ. :::