I am looking at a 2008 rx-8 and was wondering if I could get someone's opinion. This guy claims the car has a clogged catalytic converter, said due to that it won't start. Also he thinks it's misfiring because of the cat. He then claims other then that no issues. I am just wondering if this car is worth a look at or just a waste of time.

 

Unless it's under $2k and you have money for a quality rebuilt engine, don't waste your time. Always have an accurate compression test before considering buying any rotary. One with good compression is a lot of fun though.

 

The guy wants 1,800 for the car. How much would a good rebuild cost me. And if I'm having it rebuilt does it pay to have it bridge ported

 

1800 pretty reasonable if it’s clean inside and out. Salvage title is concerning. Bridge porting a Renesis is not necessary, only needs to have the ports polished. Rebuilds vary in price depending on what’s needed. Could go between $3,000 - $5,500. That being said, try to get it for less than $1,800, there is a chance the engine is not actually damaged but just flooded.

 

If the cat is actually damaged enough to
prevent it from starting, then I would guess the engine has been damaged.
Bad cats can cause misfires, but it's usually misfires that kill cats in the first place.
Usually bad coils are the reason.

Misfires kill cats, bad cats kill engines.

If you need a cat for inspection, then you'll have to spend an additional $1K minimum for a cat that can take the rotary's heat.

Add to that the salvage title and no starting, I'd pass.
There are plenty of running 8s out there that you could buy for the potential cost of this one.

 

True but too early to say in this case. Only a compression test could determine that. Could be possible ignition system failed first before engine damage was done. In this case, would only need new ignition parts (easy to install) and gut the cat.

 

Nothing to gloat about, but I got my rx8 for $1300 with no engine codes clean title. Mine had minor body damage/rocker rust, but the engine still lasted me 20k hard miles of spirited driving.....I had bought it knowing that it was in essence a rolling shell. IMO at $1800 you are looking at doing the same thing at that point. From what you describe if the cat is bad, that could mean you have issues all throughout the ignition system and damaged engine internals. So not only might your engine be bad(could know with a compression test), but other systems around the engine may be bad. This means look into the pricing of a rebuild+ Freight shipping+ ignition coils(LS upgrade kits most likely)+ Sparkplugs ($80) + New cat (or midpipe) + O2 sensor ......and so on.

When it comes to doing a rebuild, changing from the stock renesis intake port design is near useless. If you read up on all the theory threads for hybrid engines where people compare engine components from other rotary engines, the renesis engine already has the largest intake ports while still maintaining "good" fuel economy and a balance between low/high end power. A bridge port would destroy your fuel economy, idle, and low end power for little Hp gains at peak. The renesis really only has issues on the exhaust side....and even then it doesn't entirely have to do with the port shape being restrictive. The sleeves have their own issues with flow and heat buildup, which is why having a clogged cat leads to premature engine issues. Excess heat building up at the sleeves/ports leads to issues with the side seals on the rotors having premature wear/failure. Generally the shape of the exhaust port only changes to open slightly sooner to help alleviate this restriction. Again doing anything to the ports will affect Hp/torque/mpg at different regions high/low rpm. At the very least on a rebuild most people just clean up the ports and touch up on common trouble areas that build up carbon.

For seal kits, the only reason to go away from mazda oem rx8 seals is if you want to go to deeper rx7 apex seals to potentially turbocharge in the late future...even then for a newer owner I'd say to just do a plain rebuild first and enjoy the car. Doing to many changes at once during the rebuild process can also lead to headaches. If possible the best thing would be to go from a no engine code running car > rebuild internals > running car again > external upgrades(injectors+ exhaust+ intake+etc.). There are plenty of stories of people doing everything at once after just buying the car, doing a rebuild, and have random issues>>> then wanting to get rid of the car after dropping $5k+