MintyFresh

would i be right in assuming that if the cat is on the way out then the emissions would increase , so you could simply get the garage to stick the hose up the exhaust and check it.

Aseras

sounds like a simple fix, drop the cat, shove a broom stick in there and fsk it up, then call mazda and have it towed in....

ranger4277

So if I were driving down the highway for an hour doing ~70 in 6th gear and got on the gas to accelerate and instead of speeding up the car slowed down to 68... then suddenly it "woke up" (about 10 seconds later) and quickly got up to speed, would opinions here support CAT problems? My mileage was crap (5mpg lower than normal highway) plus the CAT area is making a lot of nasty rattling noises when at a stop. Is my CAT about to catch fire?

It would rattle around and appear visibly blocked possibly if it were bad, correct?

BlueRenesis82

i dont think you could see if your cat was blocked, but from what i have heard you would def. know from performance loss and other stuffs

turbine

Do your drinks get hot in the cup holders? Does the trunk area stay hot? Does your power decrease after driving over an hour? Get down on the ground and look at your CAT after driving. If you see big thermals, you have CAT issues. Do not park your car over grass, it will catch fire. The CAT is the lowest spot in the ride, besides the tires. The CAT system will fail in this car, unless Mazda repositions the CAT further back. The ECU is pouring fuel in the intake to cool down the block. This adversly affects the CAT. In turn the CAT turns into an afterburner instead of a CAT.
I have put on at least 1500 miles without the CAT, no CEL. In fact the car runs like a scalded dog. I don't get a bad smell that often, like others say it will. I am getting 20+ miles to the gallon in the city. How bad can it be hurting the enviroment. A Harley Davidson has a bigger motor than this car. No CAT there. My thinking is this: Unconvetional engines do not need to use conventional ways to to burn unburned emissions. Mazda figure it out!

BlueRenesis82

thank you for your input.

DOMINION

dude you are like a god. So do you think I should get the hi-flow-cat?

turbine

Do the Throttle Body Bypass as well. There is no way to get cold air in the intake with the coolant running through the throttle body. It does not make sense why they are doing this. It makes a huge difference when you bypass the coolant from the intake. The intake on my Typhoon was getting scalding hot. Now it runs warm to hot, but not scalding hot.

turbine

I would run a midpipe in place of stock CAT. Then I would fab a CAT behind the rear wheels before mufflers. That’s what I am shooting for. My car does not seem to be emitting too much unburned fuel. I can not get my car to shoot flames. I extended my tips past my plastic bumper. Went to 3.5 inch chrome tips. Did that first. I knew it was going to get hot, if not shoot flames. I think the temp inside the pipes are enough?
Most of the threads I read on high flow converters. They seem to fail often as well. That’s why I think we are looking at a design flaw.

When I get a chance at the end of the summer, I am going to fab a new system from midpipe back. Try a Magnaflow converter or something with no o2 sensor hole. I will be looking for a muffler that will give me enough room to put converter and muffler behind rear wheels.

This is would keep heat from building up so close to the header. This will prevent the ECU from making the mixture rich; to overcome heat increase it sees from coolant temps. Damage to the converter will be minimized. I think it is a matter of time for all 8's. Most people will trade theirs because they think the engine is blown. I would have done that if I had bought a 350Z.

The EGT is sufficient to support a CAT behind the rear wheels; it’s just a matter of placement. You want to keep the Converter in mind of heat exposure to adjacent parts. Dynamat makes some heat shielding that acts as sound proofing too. It has that foil on it. Some people think I am crazy when it comes to my car. I just tell them "I am just not the type to sit on my *** and wait for a someone else to figure it out". That seems to work.

Raptor2k

i'm assuming that was directed at me? I still have the rattle, dealer says it's normal (but they cant explain why)

turbine

I don't comment on other members like that. I am talking about people I know.

turbine

Abbid, thats what I saw. When I took it off there was no sign of damage from the front end of the CAT. When you shake it, you can hear stuff inside. It sounds like it is coming from the area that has dents and scratches on it. You are going to be amazed how heavy the stock converter is? It is massive. Its a piece of ****.

turbine

I have been on this issue for 2 years. I have gone through a bunch of mods trying to run down the problem. I thought I had it patched until last week. After all the mods before that did reduce symptoms dramaticly. The one mod that made things worse was the flywheel. As long as you keep the rpms at a higher range while using the AC. The flywheel's reduced weight put strain on the system if you were in a low rpm. This normally happened while in cruise or start ups. I would disengage the AC at starts and some cruise speeds. Helped a ton. But more importantly was the last mod I did, which helped the most of any changes I have made. That is the vaccum line from the intake to the oil system. Most are putting catch cans inline with the vaccum. On the K an N intake, you have to consider that the vaccum is much stronger on this neck than the stock neck. It is smoother and free flowing, thus creating more vaccum than the designers had. What is the purpose of this line you ask? After doing some reading, my research led me to believe that the system cycles any unburned gasses back through for emisions and to release any condinsation inside the oil pan. If there is alot of emisions coming through the intake, this will reduce the octane in the fuel. It runs like you put cheap gas in it.
I went down to Autozone and bought a breather kit for 9 dollars. It looks like a mini K and N filter. I slapped it on the oil stem to allow the system to breath without getting dirt in the system. I capped off the vaccum line with a stopper, so that if something goes wrong I can reattach stock setup in less than a minute.
No rough idle anymore. Runs very smooth. Most guys are putting the catch can on. I believe that this will clear up carbon deposits, but not the octane issue. There is more force coming out of the oil system, than going into vaccum at idle. I don't know about high engine speeds.

MadDashRX8

Turbine, can you post some pics of this breather kit you speak of, and where it's installed on your engine? Sounds like a quick and easy fix to a irritating problem. Thanks!

MD

Josche

This is an interesting thread. In your first post you were hoping to see 275-300 miles per tank. What have you actually observed in terms of mileage the last couple of months?

Any chance you could do some sort of DIY for diagnosing cat problems?

turbine

Just got back from DC last week. On that trip I was putting 5 to 8 gallons in every 160 to 175 miles. That is going up and down big hills in the middle of the summer. I kept it under 85 most of the way. From Nashville to Memphis, I bumped it up to 90. Like I thought, the gas mileage increased at that higher speed. I don't know how much I got on that last tank because I drove it to work for several days before I could put fuel in. The car gets it best gas mileage around 90.

I am going to take a bunch of pics of my car this weekend. The breather just fits on the oil stem that you pour oil into. That vaccum line is where the breather goes. The end that you pulled off, just put a plug or bolt in it. Everyone just try this and see what happens. This is no butt dyno. The engine really smooths out, like it is suppost too.

As far as your CAT goes. I hate to speculate, but this may help. If your cup holders are getting so hot that you can only put hot drinks there. I had a lot of back pressure coming back out of the intake. You could hear it from the drivers seat. There was some scrapes on the bottom of the CAT that concerned me. I could hear minor leaks. Thermals would pour off the CAT. It is a POS.

My advice is to buy a midpipe from rx7store.net. It is the bomb. Just put your o2 sensor back. I get no CEL. I am around 3 to 4k miles with the pipe. It picked up some serious power. Especially standing at a clogged CAT standpoint. I just discovered sliced bread. Why not try a midpipe? Worst case, you have a midpipe and a good CAT. Switch them around as fit. If this CAT fails so will all the others.

Midpipe=swollen head
CAT=scratch head

Does anyone know what the EGT is on the 8? I am going to wrap the whole exhaust system with heat tape and dyna mat heat sheilds. I want to keep the heat in the pipes all the way back from the header. I believe that this will increase power and have a better chance of burning emisions. Not to mention it will make the exhaust note deaper. No resonance.

Josche

Which product exactly? There are a few different ones on the site. Are these bolt-on, or is professional installation required for an idiot like me?

turbine

Sorry no pics yet. Email jason@rx7store.net. Tell him you want the midpipe with no resonator. You will need a air socket to do this.