OK - I just picked up an '04 RX-8. During the test drive, I noticed very low power and torque until I got up to around 35 mph.

Oh, did I mention I bought an automatic? (I can hear you all out there groaning - stop!)

It was advertised as having the engine replaced under 5000 miles ago, so I thought I was getting the deal of the century. Of course, I was not. They replaced the old engine with 130,000 miles on it with a used engine with 60,000 miles on it. No maintenance records, seller bought the car used and had just graduated high school. He bought the replacement engine used also. I figure the last 5000 miles were probably HARD miles.

I bought the car anyway, because I backed myself into a corner and then I felt like I HAD to buy it. I told the guy I would only buy it if he knocked $1000 off the $5000 price AND threw in the old engine/transmission combo. He agreed. It DOES have a 3" exhaust mod and, I gotta say, sounds MEAN AS HELL. Also, everything inside the car is immaculate and functioning.

Drove 60 miles back to my house and by then it was having trouble just pulling away from a light or stop sign. Seemed like it was flooding.

Here's my plan -
Rip open the old motor and verify it is rebuild-able.
Perform my first ever rebuild of a rotary engine (I can do ANY piston engine you throw at me, provided you don't hit me. Then I need recovery time)
Rebuild the tranny with new friction and steel discs
Swap motors
Rip open the second motor.

Here are my questions:
Any tips on why it may be sluggish at low RPM? I intend to do a compression test on the engine currently in there, so if that comes back bad it will answer this question
Has anyone used this mod ( https://www.rotaryaviation.com/store..._Adapters.html ) and, if so, was it worth it? It is supposed to inject additional 2-cycle oil in the housing.
What kinds of things should I look for on teardown that will disqualify my motor from being rebuilt?

 

Oh, also the transmission does not appear to be slipping. In fact, it grabs tight and I would have expected it to be smoother.

 

I also own an automatic RX8. It's really not that bad and does keep up with the 6 speed manual. These cars sound amazing with an exhaust kit dont they? Definitely wait until you have a compression test done before you start tearing into the engine. Is it showing any engine codes? Also wouldn't bother with OMP mods. They aren't worth the trouble and it's not difficult to just premix.

 

I have one code - secondary air pump failure (smog pump) No codes indicating bad compression, but no test done yet.

 

Any hot start issues? I know you said it stalled and wouldn't start back up. But were you able to deflood it and get it going again? Could just need new plugs and wires. Coil packs generally throw a code if they are bad. There are no codes for low compression.

 

Oh, and if the compression test is good, I may not tear into the second engine. The first engine (the one on a skid in my garage) was diagnosed with bad compression, likely bad apex seals. I'm getting NO SMOKE from the engine currently in the car, but no low-end power either. If it is a CAT issue, I would think it would be more noticeable at high rpms (more gasses flowing) than low rpms. I'd really like to get some direction as to why there's little to no low-end. I nearly got in an accident crossing a busy road from a side street because it felt like it was gonna die mid-way. Feathered the throttle and kept it running, but damn!

 

It never actually stalled, but I do notice I can hear it rotate about 10-15 times before it fires. It has a high-torque starter in it, that's one thing the kid was able to confirm.

 

You should inspect your spark plugs. You can get a lot of information just from that alone. Also, if they are in bad shape that would also cause power issues. Ultimately, the compression test will confirm whether you need to tear into the engine or not. Sounds like you are on the right track. With the spare engine a rebuild is more likely to succeed.

 

There's a bunch of stuff to verify on a new to you RX8. Might want to read the New/Potential Owners of rx8help.com
Ignition, vacuum leaks, any prior mods especially in the intake tract, cooling components, etc.

 

THANK YOU!!! I LOVE the compression chart included here. Very helpful.

 

I prefer the manual but that's me, honestly I care much less about it than I did back in the days. Realistically I would think the automatic is actually slightly faster at lower speeds due to the torque multiplication effect from the torque converter when it's not locked up.

And ignition coils as well. That's a known weak point for the car.

 

Coils, plugs and wires are always good to replace if they are in unknown condition. Usually if a coil is really bad it will throw a code, but it could just not be performing well and won't trigger any codes. The Mazda Rev C coils are really good. I've run them on every RX-8 and have had no issues. One car has had them for over 25k miles and still runs like a top.

 

The auto is actually pretty good. It keeps up fine with the 6 speed.

 

My compression test indicates the engine is failing, but I should be running better than I am. Getting average 6.5 BAR. I'm leaning toward a rebuild and I think I'm gonna get torquey with it. Thinking about street-porting. So, all I need is a 4-port template, grinding tools, and a steady hand? Also, and I think it's obvious but I will ask anyway, do I need to widen the exhaust ports if I widen the intake?

Yeah, I know it's not 'simple', but I'm pretty damn good with modding and customizing. And, I do have an extra engine if I mess up.

 

Not really worth it to port out the auto. You'll not see any real HP increase and it will mess with your idle. You could rebuild it though and with 6.5 bar on average, that engine does have some reduced power life to it. If you rebuild now you will likely have less issues with the irons, housings and rotors (hopefully reusable). Unless this is a race build (which I wouldn't really recommend on the auto) you won't see much benefit from port widening/mods and the car will require a tune at that point to make use of the extra flow.

Maybe just try to do a really good job on the rebuild. Use new seals and really clean it up.

 

Personally I think nothing short of a turbo will make a rotary be considered torquey, but then again, everyone has a different definition for it.