FAQ and everything you want to know about the RX8
So you are thinking about buying a Rx8 and cannot find a good/quick helpful guide about them. You already own a Rx8 and want to upgrade its performance. Or Maybe you just bought one for cheap because its not running. What can you do? Who can you ask? Here at Defined Autoworks we have been servicing the Rx8 for over 11 years with many engine rebuilds under our belt. My number one subject in emails is about the Rx8. I'm going to go over common questions and also shed light on this platform.
#1 Your car runs great, has power, but will not start back up if it is warm. What’s wrong?
8 times out of 10 this is a indication of poor compression. What causes poor compression? A few factors. Most of them I assure you are not your fault. When the Rx8 was produced, Mazda was held to strict emissions and also a very tight budget. As a result Mazda had to use very thin coatings inside the motor. The rotor housings and side housings (essentially the cylinder walls) do not wear long compared to the previous generation rotary motors. 80-110,000 miles is the normal amount of miles before this wear is seen. First step is to check compression by removing one spark plug from each rotor housing. with a good charged battery and accelerator on the floor while cranking, you should see no less than 70 psi. If its under that you will need a rebuild.
#2 I need a rebuild how much does it cost?
I list starting rebuild costs of $2400 for rebuilding the motor only. If the entire car is brought in, it is $3800 for rebuild, labor of removing and installing the powertrain and fluids/spark plugs. STARTING price is listed for a reason. Many Rx8 suffer from excessive wear. These worn components can be "resurfaced" but that will no help much. If the coating is already gone, how is removing more of it going to help? The cold hard truth is new parts are required. Mazda parts for the motor are not cheap. A new rotor housing is $890 each and the side housings are $580 each. 7 times out of 10 the Rx8 motor will need at least two new housings. Now you are looking at $5580 to rebuild your Rx8 if dropping off the whole car. This is just an example
#3 My car is running poorly I just need the apex seals replaced. I found the seals online cheap, how much to install them?
The Rx8 actually has no issue at all with apex seals. They take the blame due to many reasons but none of them are legit. Referring to question #1 the issue with the Rx8 motor are the COATINGS not the seals. If you have poor compression, the WORST thing you can do is tear down the motor and replace just the apex seals. I promise it will not make any more compression and often times have worse compression. A excellent comparison is disc brakes on a car. If you replace brake pads, but leave the old warped/ribbed rotor, will the brakes work right? No the disc needs replaced as well. Rotary engine housings are just like cylinder walls. They need to be true and smooth for the seals to ride on correctly.
#4 My Rx8 runs perfect, I want to make it faster. Can I turbocharge it?
Yes and no. The Rx8 motor already has limited life in stock form. Adding a turbo to this will only shorten it further. Boost pressure adds horsepower but also stress on all internal components. Horsepower also increases heat. The motor CAN be turbocharged and will make more power. Just realize its lifespan will be cut in half best case scenario.
#5 Ok so the Rx8 motor is not good for turbo. What can I do safely to make it faster?
Much like other high RPM naturally aspirated motors, the Rx8 is kind of hard to get more power out of. The best power adders are a complete header, and cat-back exhaust. If you are racing or off-road use only the cat can be deleted to gain some more power. A good cold air intake will add a bit more. Do not expect big gains here. 15-30hp is average.
#6 I want to add on a rotor and make it a 3-rotor 20b.
Short answer, no. While on the surface it seems like the rotary is stackable, and extra rotors can just bolt on, that is not the case. A three rotor can only be achieved by importing one from Japan. These engines are getting rare and cost $6500-9500 just for a old, used, not great shape motor. Then this old motor will need rebuilt. a 20b is very expensive to swap in. See #7
#7 I know now you can bolt on extra rotors. How much to make my Rx8 a running 3-rotor?
Long story short, if you drop the car off at Defined Autoworks or another shop that has actually performed complex work like this before... $35-45,000. Yes that is not a typo. Unlike other motor swaps, just the engine is highly expensive. It was produced in VERY limited numbers from 1990-1995. There is multiple series- Number series, A, B,C, and D. C and D feature stronger blocks and will go for the most money. After the motor is sourced, a rebuild will need to be performed. Most likely you would want to do some porting inside the engine along with other performance mods. After this is done, getting it into the RX8 is A LOT of work. Custom motor mounts, different stronger transmission, custom transmission mounts, custom driveshaft, custom exhaust manifold setup to the aftermarket single turbo system, stand-alone computer system will need wired in, custom intercooler setup, custom radiator system for the extra heat, custom oil setup, new custom exhaust, ignition coil system, the list goes on and on. So there you have it.
#8 Lets play with the big boys, I want to swap in a 4-rotor!!
Yes you can put a 4-rotor into the Rx8. It is even more expensive than the 3-rotor. Way more expensive. Why? The 4-rotor does not exist. Mazda produced 4-rotor engines strictly for pro-level racing in the 80s and 90s. Nobody has access to buy these thoroughbred motors. And if they do, the price tag would be far higher than what most want to afford. Luckily shops like Defined Autoworks can make a 4-rotor from scratch. These engines use components shared in the 13b along with many custom made parts. Due to all the unique pieces and time to build a 4-rotor, the price starts at $28,000 for just the short block. Now to put it into the car, add all the custom external parts, you would be looking at $60-95,000.
#9 Is there anything I can do to extend the life of my Rx8 motor?
The best thing to extend engine life, is oil changes. Make sure to stay loyal to every 3,000 miles. Also replace spark plugs every 15k miles or less.
#10 My Rx8 has good compression but still has a hard time starting up.
This is usually bad spark plugs. Many people forget about this item for maintence but it is very important. Change spark plugs every 15k miles or less. The Rx7 spark plugs from 1986-95 NGK units can be used to save a lot of money. If it still has issues, replace all four ignition coils and spark plug wires. This is a weakness in the Rx8.
#11 I have a 4-port engine and want to swap in a 6-port motor.
Basically this should not be done. It is far easier to sell the car and buy a 6-port model. Mazda Changed many things between the 4 and 6 port. The ECU is different, the wiring harness is different, the fuel system is different. Since the chassis harness ties into the engine harness a swap is very complex to do.
#12 I heard you can put in seafoam to help breakup all the carbon and restore compression.
Seafoam will not help restore compression. If compression is low, most likely the motor will need rebuilt. In some rare cases I have seen motors that came from japan "dry up" and produce low compression numbers until started. In this case, adding ATF and rotating the motor without the spark plugs will help pump out nasty old fuel and additives. This is the only exception to the rule I've seen.
#13 Is the series 2 Rx8 better than Series 1? What does series 1 and 2 even mean?
In the Rx8 crowd, they refer to the Rx8 as a series 1 or 2. The series 1 are 2004-2008 and series 2 2009-2012. The series 2 did significant changes. They added another oil metering oil nozzle (making a total of three per housing instead of two) Remade the complete fuel map in the computer and also the oil system was changed. Many say internally the clearances were changed to be tighter and possibly better coatings. The series 2 does seem to be consistently going to much higher mileage numbers vs. the series 1. But Series 2 is also much more expensive to purchase vs. the series 1.