Hello guys,

I’m new to forums and this is my first post ever. I would really appreciate it if someone could give me advice on how I should move forward with my current project.

Let's start with some backround information:About two years ago, at a party, I had a conversation with a friend about cars. Somehow the topic turned to rotary engines, which I had never heard of before. My friend told me many things about them and really sparked my interest. Right after that day, I started reading and learning more about rotary engines. I decided that I wanted to buy a non-running or poorly running RX-8 and restore it together with my brother.

After searching for maybe two months, I found a bad-running but starting RX-8.

The previous owner told me that he and his friend had also planned to rebuild it, but due to unexpected life changes, they didn’t have the time anymore. Before he bought it, the car had apparently been sitting unregistered in a garage for seven years.

It’s a 2004 RX-8 231PS manual with 92,000 km (57,000 miles).

He said they had started the engine several times. When I went to look at the car and started it myself, I noticed the engine sounded bad (knocking) and had cold-start problems.

Because the chassis and most other aspects of the car were in good condition, I decided to buy it for €1,800, with the mindset of rebuilding the engine. I trailered it home and started stripping the engine bay to check for leaks, rust, and any broken or suspicious parts. It looked like a regular 20-year-old car to me. Over the next few weeks, I bought all the necessary tools for removing and tearing down the engine.

Before stripping it, I started the car one last time, hoping the knocking sound would fade as the engine warmed up. I uploaded this start to YouTube if you want to hear it yourself — the knocking remained:
Link:
When we started disassembling the engine, we found that the entire cooling system was clogged and muddy. Many pipes were rusty and in poor shape.



After tearing it down, we discovered that the front stationary gear and front rotor gear were damaged, with several teeth broken off. The front rotor and its side housing also had deep dents and scratches on the surface. Apart from this damage, the rest of the engine looks mostly fine to me. I knew I’d be rebuilding it, but I didn’t expect the internal damage to be this severe.







Links to videos of the components: (More detail, every housing/iron and rotor)
1. 2. 3. (the dark line is engine oil)
4. (Rear rotor)
5. 6. (the dark line is engine oil)
Questions:

1. Can someone explain how such damage could occur?
   
2. Based on the videos/images, which parts can I safely reuse?
   I think the irons, center housing, rear rotor/housing, and eccentric shaft are fine, but I haven’t checked if they’re still within Mazda spec.
   

Now to the reason why I am writing this thread. I want the car to get back on the road and therefore need a working engine.
I think I have several options to continue this project:

1. Buy a new engine from Mazda
- will run
- no headache

- expensive (6-7k?)
- won't learn to rebuild and I don't do it myself

2. Buy a used running engine from a scrapjard or other
- will run (hopefully)
- semi-expensive (1-2,5k)

- won't learn to rebuild, can't do it myself

3. Buy a used engine from a scrapyard or other with no information about condition (running or not), tearing it down, combining the best parts and rebuild one working engine
- cheep
- will learn to rebuild and do it myself

- headache
- risk -> not running engine (maybe also internal damage)

4. Buy seperate good parts to replace my damages ones
- probably good base to rebuild the engine
- will do it myself and learn

- expensive

5. Buy a rebuild engine from Rotorshop.eu
- semi-expensive
- will run for a bit

- won't do it myself
- probably won't run very long. I read a few threads about this, which lead to my conclusion that these rebuild engines often die around 10k miles.

Thank you very much if you’ve read this far!
I would really appreciate your opinions and advice on how to continue this project and get my RX-8 back on the road. Keep in mind I’m a 20-year-old student from Germany and can’t spend huge amounts of money.

Question:
3. Which route would you pick in my situation?

Thank you for your help!

Best regards,
Leo

 

Hey Leo, welcome to the forum, congratulations on your rx8 project,

I was in your boat about 5 yrs ago, i went down the 2nd hand engine,
as for yourself i would go the 2nd hand engine and slowly buy the parts you need for your broken engine, to rebuild it and get the lesson your looking for. while driving your car.
why i say this is so you have time to rebuild and mod as you go to get your dream engine, porting, supercharger/turbo ect.
i would stay with the s1 engine so your not changing all of your electrics.
engine swap (piston, rew 13b, 20b) i would go with a aftermarket computer.
as for the parts replacement in the engine, i will leave that to someone else in the fourm with more exp.

hope this helps.

 

I can't diagnose parts based on shaky video, but given the engine's history, I wouldn't reuse any of it. Do it right or do it twice.
If you can get an engine from Mazda, I would do that. Don't know about Rotorshop.eu but you could try Ryan Rotary or more reputable shops in europe. There's no reason a good rebuild shouldn't last a long time... IF it's a good rebuild.

There's nothing more disappointing than putting in the work to replace an engine only to find that it's a dud, You'll enjoy the rest of the restoration a lot more if that's not the case.

The parts in the video are waaay too clean and clearly something grenaded in one rotor. Was it overheated? The steam from the coolant might have had a cleaning effect, or these are new parts that were assembled incorrectly and self-destructed.

 

@CarbonRX Thanks a lot for your reply and advice!
I think I’ll go with a second-hand engine as well, but I’m still not sure whether I should just get a running one from a scrapyard and use it until something goes wrong, or if it’s better to open it up and rebuild it right away to make it last longer.
I’m not planning to mod it or swap in a different engine

 

@Loki Thanks for your opinion on the engine parts.
Why wouldn’t you reuse the parts that aren’t obviously damaged, as long as they’re still within Mazda specs?
Some of the parts in the videos look very clean because I cleaned them to make any damage easier to see.
I don't know if it was overheated.

 

When engines fail catastrophically like rotor 1 there, metal flakes travel everywhere with the oil and compromise every surface they touch. What is left not obviously damaged anyway? The rear end plate and housing? Everything at the front is a writeoff. I'd be skeptical of the eccentric shaft given the broken stationary gear damage. Something bad happened to this engine... Oil starvation, overheating, overrevving... I wouldn't reuse any of it.