So how do I keep my engine healthy?


For this, we have to go back to the article in Before You Buy: The Engine Failure Story. Remember that list of failure methods? That's the list we have to address and keep addressing. If you address all but one failure method, guess which one is going to be the one that will be the cause of your failed engine? Right. That one. They ALL matter, and there are no exceptions. Even the ones that you have no control over matter.

Things to keep in mind while you read these solutions:

  • 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. Everything in moderation.
  • These are fairly basic concepts. They can get far FAR FAR more involved. Pursuing ANY of these should be preceded by proper research.


Failure Methods, and how to help prevent them:

  • Excessive carbon buildup accelerates seal wear, causing compression loss
  • Excessive carbon buildup unseats the apex seals, causing compression loss
    • Cause: Carbon exists in the gasoline, and as long as gasoline is the fuel of choice, then carbon buildup will be a problem. Note that GASOLINE is the primary source of carbon build in the engine, NOT the burning oil.
    • Solution: High RPM at full throttle: Commonly known as "redline a day", this 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. Note: This will NOT prevent all carbon. Carbon will exist because it's in the gas. Other solutions should still be used as well.
    • Solution: 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 is a bit easier to remove.
    • Solution: Seafoam / Decarb / Steam Cleaning. See the article in Understanding Your RX-8 about decarbing, where I tested several methods for how effective they actually are, including borescoped pictures inside the engine before and after.
    • Solution: 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 yet 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. Auxiliary injection also gets the intake valving that none of the other treatments do.
    • Solution: E85 fuel conversion. This basically wraps alcohol injection with a significant reduction in how much gasoline is being burned, the primary source of carbon build up. Of course, you will pay through the nose in fuel mileage, highway mileage would drop to around 14-15mpg, MAYBE a bit higher with the consistently superior sealing you should be able to maintain.
  • Excessive heat buildup warps the housings to one degree or another, preventing the apex seals from sealing, causing compression loss
    • Cause: 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. (This is separate from the oil injection. Oil injection rates shouldn't ever produce oil smoke from the tailpipe, which oil control ring failure usually does). This can be a sudden failure from any single cooling system component.
    • Solution: Remove the catalytic converter 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. I believe that my engine failed due to housing warp from a failed cat.
    • Solution: Upgrade your cooling system Do not rely on your factory coolant temperature needle in the gauge cluster. The needle won't move until 235F, and you can suffer damage as early as 220F. See the section on cooling for details on how to improve the hardware you have.
    • Solution: Lower the trigger temp for the radiator fans The OEM trigger temp is almost 'too high' already, at 207F. That's only 13F of headroom before failure temperatures. There are a few kits you can buy, as well as it is built into Mazdamaniac's AccessPORT base tune. MazdaEdit can also adjust the trigger temperature, same as the AccessPORT. So your fan runs more, but your system stays cooler.
    • Solution: Flush radiator fluid periodically Already part of regular maintenance, but more critical for our engines than piston engines.
    • Solution: Replace everything after engine replacement I continue to see more and more cooling system failures between 5,000 and 10,000 miles after installation of a dealer-installed reman engine. The pics and evidence from several different builders all point to the excessive sealant used at the Mazda reman facility that breaks free and floats through the cooling system until it clogs something. Flush as much as possible (using regular water is fine for short durations) after the engine is replaced, and by 5,000 miles, you should plan on replacing at least the radiator and thermostat, if not the lines as well.
  • Excessive exhaust temperatures overheat the side seal springs
    • Cause: This is a failure that most of us don't have to really worry about. It's a common 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). It is a scale though, it's likely more about how much "increments of energy" the spring takes, and a lower power level can get away with more time at high load than a higher power, etc...
    • Solution: High efficiency exhaust Increasing the efficiency of the exhaust system will also help reduce exhaust port temps. A more efficient exhaust dumps heat more rapidly, reducing buildup.
    • Solution: Tuning for EGTs Keeping EGTs low is mostly a matter of tuning.
    • Solution: ??? The only 'known' hardware 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.
  • High lateral G left turns with low fuel
    • Cause: The fuel tank is separated into two halves, with a hump in the middle. At approximately 1/4th of a tank of fuel left, the gasoline from one side of the hump is separated from the other side, and a high G turn can push the fuel from one side to the other completely. In a high G right turn, this pushes the fuel onto the side with the fuel pickup, so there is no problem. On a high G left turn however, it pushes the fuel to the right side of the tank, without the fuel pickup. Fuel starvation is then inevitable. When the ECU expects fuel to be injected, and suddenly it isn't, there is going to be a massive lean spike, which can easily cause knock/detonation, and destroy the seals.
    • Solution: Take turns slower at 1/4th of a tank and lower It's about that simple. Keep the fuel above 1/4th of a tank if you want to sling the car through the curves all the time. If you go lower, back off and take the curves slower.
    • Solution: Baffling or Swirl Pot RX8Club.com member Brettus pioneered a change to the pump assembly that helps trap fuel around the pickup. It's not a lot, but it's enough to make it through most high G left turns
  • Fuel Pump Failure
    • Cause: The OEM fuel pumps are prone to failure, starting around 50,000 miles. They may last much longer than that, but plenty fail early. When the ECU expects fuel to be injected, and suddenly it isn't, there is going to be a massive lean spike, which can easily cause knock/detonation, and destroy the seals. I personally know a couple members that lost engines in this manner, including one who also had the replacement get destroyed within a mile of the 2nd engine being installed because the dealer hadn't noticed the first cause.
    • Solution: Replace the fuel pump ...if there are any signs that it might be failing. Watch for stumbling or studdering 15-20 minutes into a drive when cruising at a stable speed. Longer cold starts can also indicate a problem building fuel pressure. If the engine suddenly shuts off and won't restart for 15-20 minutes, where it restarts just fine, it's probably the fuel pump.
  • Caalytic converter failure
    • Cause: A catalytic converter clog causes localized heat and pressure buildup that overstresses the seals and breaks down oil viscosity, leading to various issues
    • Solution: 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
    • Cause: 4 Stroke oil is dirty filthy stuff, and there are lots of various sludges and breakdowns possible depending on what brand and weight you use. (See the What Oil section for a link to a Russian study showing the various ways oil can break down) Over time, this crap will get sucked into the oil injection lines and slowly clog them up, preventing oil from being injected, leading to excessive apex seal wear and side seal overheating, leading to compression loss and/or catastrophic failure (depending on which fails first). 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, as in: more miles between each added quart.
    • Solution: Clean the OMP lines 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.
    • Solution: Install a SOHN adapter 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
    • Cause: Low starting compression accelerates any other issue. Unfortunately, this is one that you can't do anything about. Some remans are just terribly built, and you won't know until it your engine eventually fails early and every other solution has already been addressed. This is the point I made earlier about "no exceptions". Unfortunately, it really doesn't matter if you can't do anything about a bad reman build, it will eventually be the reason for your engine failure, one way or another.
    • Solution: Better Rebuild It's not a pleasant solution, but starting with a good engine from the beginning is the only way to solve this problem.