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New Engine?

Old 08-08-2015, 09:53 PM
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Question New Engine?

Hey guys! I'm new to the forum (and also new to the rotary world). I just bought an 05 RX-8 with what seemed to be a dead engine. Owner said compression failed, etc. etc. Well, as I was planning on getting a new engine, I got a phone call from my mechanic and told me to get a new battery cause mine was dead. He said he was able to turn on the car the day before, but after hours of trying to charge the battery and countless tries. So I bring in the new battery, and in like 5 tries, the engine turns on. It's all nice and well, he takes it out for a spin, takes me in it as well (nearly had a heart-attack, RX-8s are AWESOME). Then the engine dies on us and we push the car back to the side where we took it for the joyride.

Now, my mechanic said the car can't last in normal idle RPM's and it needs to be kept at 1k or so, otherwise it dies. At first, one would think it's the MAF sensor's fault (or MAP idk yet the difference). But the previous owner said it had a new OEM sensor, and yes that was a true statement. My mechanic said the problem COULD be some other TC-something or TP-something sensor that has to do with the RPM's.

Could this be a slight possibility? Do I have a chance to actually get away with this engine for another year? Seals haven't been replaced in God knows how long, that's for sure. Failure to start usually means bad compression, but once the car is running, heck, it runs. I personally went to hell and back, soooo
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Old 08-08-2015, 10:32 PM
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Welcome aboard.

Unfortunately, since it cannot maintain at idle, that's a bad sign. The only way to know for sure is a rotary specific compression test. This will measure the compression of all three rotor faces. Any Mazda dealer can do it, should cost you about a hundred bucks, less than two hundred. Ask them for the printout, you should have six numbers and an rpm. Come back to us and we can help you interpret it.

Just out of curiosity, is it a six speed or an automatic? The automatics were lower powered, and that particular engine was only made for two years. As such, they are harder to find. A rebuild by a competent mechanic (new seals, new housings if needed, etc) will cost between three and five thousand. Less than that, you should be careful.
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Old 08-09-2015, 01:30 PM
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It's a 6-speed manual. I mean, compression tests can be done at home too. I know how to, and so does my mechanic. He even has the tools for it. I was just wondering if there may still be a SLIGHT possibility of going on this engine another year. As I have stated, it turns on cold (a little bit harder), but once hot, can't turn it on, and it can't idle properly. As for the rebuild and such, yeah, it would cost a lot, but lower than $2k. My mechanic is very good and very cheap, I have full trust in him. He wanted to hook up the ECU to his PC to see if he can detect anything else that may be wrong electronically. After that, we'll try the compression test. Of course, first conclusion is busted APEX seals, but you never know, and that's why I posted on this thread
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Old 08-09-2015, 02:06 PM
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Unless you or your mechanic owns a rotary compression tester, he cannot do it, and nor can you. A conventional compression test will not work. Has your mechanic rebuilt a rotary engine before? 2k is quite the bargain. Oh, and while apex seal failures are common, there are other things that can cause a rotary engine to go bad.

Last edited by BigBadChris; 08-09-2015 at 02:10 PM.
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Old 08-09-2015, 03:08 PM
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I mean, I saw some videos of how people tested compression. You just need a gauge with PSI capabilities and other small hardware. You unplug a sparkplug and then take all these other safety measures and you turn the key. You are supposed to see the needle bounce three times (for each apex of the rotor), and based on the numbers you see there, you will know. I heard 70 or 75 PSI is acceptable. Failed seals usually do 20-30, and you can easily tell from that alone. No, he hasn't had much experience with rotaries, but he did his homework. He told me how the rebuild process works long before I even knew what apex seals are and how they work. He warned me of what I would get myself into, and I was prepared
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Old 08-09-2015, 03:13 PM
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No offense, Eirulisse. You seem like a nice guy, you obviously enjoy the car. But this is not a good plan. The specific test is much easier and much more accurate, and it is weighted by starter speed which is directly related to compression. (Faster moving rotors can compress air better than slower moving ones). Your method is the mechanical equivalent to pissing in the wind and hoping you get it in the cup.

Also, do you really want someone to rebuild your engine knowing they have never done it before? Experienced engine builders are hard to find, and they command a price premium for their services. Why? Because its as much art as it is science. Its very different from a piston engine.

Best of luck with your car
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Old 08-09-2015, 03:41 PM
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Oh, yes, I do agree that a test done at the dealer is probably my best bet, and I might actually end up doing that. As for trusting the mechanic, this is of course something you can't confirm as you have not known the person, but I do. Guy's been working on cars in shop and private for most of his life. He has a mechanical engineer degree. He HAS worked on rotaries before, just not sure about rotary rebuild. As for other rebuilds, he has done plenty.

I will reply back on this thread when news comes up in regards to compression test results or other things. As for now, is there anything else I should expect or do in advance?
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Old 08-09-2015, 03:55 PM
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Here is the RX8Club recommended maintenance schedule. The coolant can react with the heater core, which starts to dissolve, and then you get crap in your coolant passages. Obviously that is less than good, so regular coolant flushes are highly recommended. Unfortunately, ignition coils are considered "wear items" on this car, and they need to be replaced every 30k. Otherwise, you get misfires, which clogs the catalytic converter, which leads to backpressure, which kills the engine. Its a domino situation. Overheating can literally kill your engine in minutes, so watch that temp gauge.

RX8 Club’s recommended maintenance schedule, more comprehensive and proactive than Mazda’s schedule.
30,000 miles:
- Replace Ignition coils
- Replace Plug wires
- Replace Spark plugs
- Clean MAF (mass air flow sensor)
- Clean ESS (e-shaft sensor)
- Reset ESS profile
- Clean power steering connections
- Clean battery terminals and clamps
- Replace transmission fluid
- Replace coolant (Mazda FL-22 is highly recommended)
- Replace air filter
- Replace brake fluid (fluid in the brake lines AND the clutch line)
~$300 USD in parts if you shop smartly.


every 60,000:
...all 30,000, plus...
- Clean all chassis electrical grounding points
- Replace accessory belts
- Clean OMP lines
- Replace rear differential fluid
- Replace thermostat
- Clean / Straighten AC condenser fins
- Clean / Straighten oil cooler fins
- Inspect catalytic converter
- Clean / Inspect intake valving
- Consider / inspect all points in 90,000+ as well, many items fail early
~$130 USD in parts if you shop smartly.

90,000:
...all 30,000, plus any 60,000 not yet done, plus...
- Replace coolant bottle
- Replace radiator hoses
- Replace radiator
- Replace front O2 sensor
- Replace motor mounts
- Inspect clutch pedal assembly for flex / weld breaks
~$900 USD in parts if you shop smartly.
At 100k, anything original in the cooling system is really suspect and failure prone. It represents the biggest threat to your engine.
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Old 08-09-2015, 04:09 PM
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Other stuff to know

Some people pour 2 stroke oil into the gas tank. This is referred to as "pre mix". The idea is to add extra lubrication to the engine seals. Some 2 strokes are better than others. Some people do it, some dont. Its up to you.

You can run synthetic oil in the engine, even though the owner's manual says not to. Its all personal preference. The crankcase gets extremely hot, and revs to very high rpms, which is a hard environment for any oil.

Oil changes every 3k are a must. Also, the engine literally burns oil every time there is combustion. As such, your oil level is continuously dropping. Keep a quart of your favorite oil in the trunk, and check the dipstick every time you get gas. While we are on the topic, your dipstick may appear to have cappucino foam on it. This is normal, it happens. If it really really bugs you, there was a TSB for it, and you can install a crankcase ventilation kit. This helps, but doesnt eliminate the problem 100%.

The engine is pretty close to its maximum performance from the factory. You can get more from a tune, but it is hard. The off the shelf tuner boxes will not work, the ECU will eventually "relearn" and overwrite what you did. If you really want more, you can get it via a complete reflash, search the Cobb or Mazdaedit. Likewise, most "bolt ons" wont do you any good. Cold air intakes are mostly garbage, and most improvements on the exhaust system come from removing the catalytic converter.

Lastly, a word about cooling. The rotary runs hotter than a piston engine. It sheds heat through the water pump/radiator, and through the oil coolers in the front bumper. If your oil coolers get bent or clogged, you will have a problem getting temperatures in line. If you plan on tracking the car or going to high performance driving events, you will want to look into more drastic cooling measures.

Lastly, enjoy the car. The engine wants to be flogged, it wants to be revved, and it wants to be pushed to its limit. If you dont hear the shift warning beep, you are shifting too early. Mazda told the first time owners "a red line a day keeps the mechanic away". The shift warning beep is just that, a warning. If you exceed it, the car will cut fuel and rev back down. You arent hurting anything by going that high, thats where the motor makes good power (and a fantastic noise!)
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Old 08-09-2015, 04:35 PM
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Thanks for the tips, will keep this in mind as well. Yeah, I was considering looking into some better coolant and oil cooling. As for enjoying it, oh, every moment of that brap will be enjoyed all right XD
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Old 08-13-2015, 08:46 PM
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One more easy thing to try. With the car cold. start it, do not touch the gas pedal. Let it warm up all the way. Just let it sit. You may notice that towards the end, the RPM will rise, then settle down.. Then go for an easy driver, shut it off until it cools completely, like overnight, then repeat.

The engine has to learn to idle. sucks, but it does. The dead battery likely lost all the existing data.

If you really want to rush it, sit in it hot and try to keep it running. But, a PITA, and takes longer. The auto learn process is best. If it is having problems, I found that turning the AC on helps things. The extra load seems to help sort things.
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Old 08-14-2015, 01:38 PM
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you are onto something. I might try it. I dont really have time to go to my mechanic's place because of work. But the day before yesterday I dropped by so we can try some diagnosis with his computer. Funny thing is, the car actually had some errors. He was able to clear all of them (except the airbag, which apparently has a shortcircuit or open circuit). My honk doesnt work either. The REAL mindblowing thing is that the reader cant connect to the ECU while.the.car is running. My mechanic suspects that maybe all my headache could be from the ECU. He is gonna do a compression test soon, and I'll drop by the dealer for a diagnosis. Maybe an ECU reflash might fix a few things. As for the idle, this time it dropped to 800, and it kept revving itself to 1.2k when it was about to die. It eventually died though. Hot start took like 15-20 seconds of cranking, but it actually worked.

Now my question is this: what does.the.big blue fuse from the FUEL do? Im not talking about the fuel pump fuse, just plain FUEL. I was looking around the engine.bay and.decided to open the fuse box. Lo and behold, the FUEL fuse was taken out and resting on the side. I put it back yesterday, but didnt get a chance to crank cause I had to help with my dad's car.
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Old 08-15-2015, 12:29 PM
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Update: ok, so the inevitable has settled upon me. It's either new engine or rebuild. Compression fails. Once the car gets warm, it loses power in 2nd gear, not to mention 3rd and 4th. I tried looking for engines, but hard to find. Guess I need to look further. But rebuild doesnt sound like a bad idea. Anyone here can give me any link for rebuild kits? I saw something on racingbeat's website.
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Old 08-15-2015, 12:34 PM
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With engine components, you get what you pay for. Do you need race ready stuff, with ultra fine tolerances, designed to be run at high rpm for long periods? Probably not. But I wouldn't buy the cheapest rebuild kit out there, either.

If you want to pay someone else, you can ship your engine off. Rotary Ressurection is a sponsor here, several members have had success with his work

Mazdatrix also sells complete engines, and you ship back your broken engine core.

Last edited by BigBadChris; 08-16-2015 at 11:23 AM.
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