Jastreb's 2009 Mazda Rx-8, "Isabella"

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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby Squint » Tue Apr 07, 2015 9:54 am

AHTOXA wrote:My experience is also limited, but yes, rotary motors do need much more frequent overhaul. Their biggest issue are the apex seals, which will wear out far sooner than, say, piston rings.

The rest of the maintenance isn't lower, either, as it doesn't really get much lower than nothing but oil changes on modern timing-chain driven motors. Even if you have a timing belt/waterpump to be done around 100k miles, it's still cheaper than apex seals.

Plus, a few RX-8 owners run pre-mix (oil and gasoline) when filling up, so that adds into the cost. It's not required, through, as the RX-8 has an oiling system, but forums have claimed better gas mileage with pre-mix.

Interesting. Especially since with the Le Mans win in the early 90s, the Mazda Wankel rotary-powered had the reputation of being reliable. I guess reliability and the more intensive maintenance schedule aren't mutually exclusive, though somehow, in my mind, they are related.
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby AHTOXA » Tue Apr 07, 2015 10:57 am

I think it's a question of reliability vs. durability. Will the motor be reliable to get you to work and back for 4-5 years or so? Yes, because it isn't likely to break down within that time. Is it durable in comparison with a piston engine? No, because you'll need an overhaul around 80k miles.

Reliability is mechanical longevity within a defined parameter (time, mileage), while durability is mechanical longevity beyond those parameters. The two, of course, are highly intertwined.
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby theholycow » Tue Apr 07, 2015 12:00 pm

I see durability as "If I take it off any sweet jumps is it gonna break?", reliability as "Do I need to worry about whether or not I will get to work tomorrow morning?", and longevity as "Will it need to be replaced in 100,000 miles?". Among those attributes, the overhaul falls into longevity since it's so extensive and expensive.
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby Rope-Pusher » Wed Apr 08, 2015 12:08 pm

I'm thinking that if they made the seals out of "Unobtanium", they could last forever, but prolly cost a femur and a humerus. In racing, that would be a no-brainer decision, but the same can be said for the decision not to go that route for volume production vehicles.
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby Jastreb » Wed May 27, 2015 10:06 pm

Lot's to post about here, but I'll start with this funny video. Also I'm getting a reman engine courtesy of Mazda. Also a new clutch is going in, since the engine is out of the car anyway. I think the old engine would have gone another 20k miles before serious drive-ability problems, but compression was a bit below spec, so...

https://youtu.be/bUBhJM2An34
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby Squint » Thu May 28, 2015 9:27 am

Jastreb wrote:Lot's to post about here, but I'll start with this funny video. Also I'm getting a reman engine courtesy of Mazda. Also a new clutch is going in, since the engine is out of the car anyway. I think the old engine would have gone another 20k miles before serious drive-ability problems, but compression was a bit below spec, so...

Getting the engine for free from Mazda? If so, why?
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby Jastreb » Fri May 29, 2015 6:14 pm

So many engine failures on Series I RX-8s (2004-2008) that Mazda extended warranty coverage on the engine core (rotors, housings, bearings, eccentric shaft) to 8 years/100,000 miles in order to prevent an RX-8 owner riot and to re-assure future buyers. The extended engine core warranty also applies to Series II RX-8s (2009-2011) even though Mazda made a number of changes to the engine to improve durability. They added a 3rd oil injector for each rotor, new electric metering oil pumps, increased the oil pressure, revised oil filter, larger oil sump, among many other things. This decreased the failure rate of Series II engines, so now instead of apex seals lasting 60k on average it looks like you can get to 100k without additional "extra" maintenance. Not many Series II RX-8s have rolled over 100k yet.

The common failure mode is carbon buildup on the rotor housings that gradually wears down the apex seals. Carbon can also get behind the seals and unseat them. The problem is that injecting 4-stroke oil is not the best solution for keeping things clean, it was a compromise for the sake of user-friendliness (though some people still bitch about having to add a quart every 1000 miles or so). A better solution would be to inject 2-stroke oil from a separate tank. Hence why the video recommends premixing a little 2-stroke oil into the gas. They also probably compromised on the amount of oil injected for the sake of emissions.

My car was displaying subtle symptoms of low compression (occasional hot start issues and occasional rough idle when hot), but otherwise running well. I wanted to make sure I had good compression before I was out of warranty and before I started doing some mild performance mods. As compression deteriorates, symptoms would have gotten worse, progressing to stalling at idle, real difficulty hot starting, misfires, loss of power, flooding. A reman engine from Mazda is about $5k out of pocket these days, and I believe a custom rebuild from a shop can run north of $6k.
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Re: Jastreb's 2009 Mazda Rx-8, "Isabella"

Postby AHTOXA » Fri May 29, 2015 10:58 pm

Good to hear that Mazda has stepped up!

As much as I loved your car specifically, every time I see an RX-8 in the wild, I wonder if the owner knows what they have gotten into and how many miles are on the car. Surprisingly, not many of those owners outwardly look like car enthusiasts.
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