I have a similar setup to Max Cooper for a hi-flow cat followed bt a Magnaflow muffler.
Due to space restrictions, the cat is about 2-inches from the front flange, thus close to the DP end flange.

Unfortunately, I noticed that while the boost patterns were fine 10-8-10, it took longer to spool and the flow from the muffler was low.

Dropped the hi-flow cat/resonator combo, and low and behold the cat is MELTED.

I have a DP, 850cc injectors all around, a PFC tuned by Steve Kan, and a TRUST cat-back.

I also had the air pipe connected just before the cat.

Any reason why this melted (I do track the car for 30-minute sessions) ?

Should I try another metallic cat ? Any suggestions on brands ? Would a ceramic one be more heat tolerant ?

I'm running rich and the DP is coated by SWAIN TECH.

I do hate the smell without a cat.

TIA,
:-) neil

PS: you may have to zoom

 

The cat' may actually have been doing its job well and it could be a result of another problem. On my CRX a while back I went through three cat's and two were Random Tech' (not cheap) and it ended up being a bad distributer which caused alot of unburned fuel to exit the block and then burn up in the cat' but way more then it could handle. After it was fixed I replaced it with a weld in Magnaflow/Car Sound hi flow cat'. I haven't had the chance to drive my 7 with my metalic cat' so I can't say how well it holds up yet.

 

If you want something that's going to last, get a Bonez cat. Expensive, but they do last.

 

...I guess you didn't see the exhaust heat warning light under your right elbow.
...I agree with Mahjik, the Bonz cat is pretty durable.

 

People have been experiencing problems with those Metallit cats....you are another one in a growing list. I do not think they are suitable for rotary use.

 

Chris Carlisi and me went single the same time and purchased two metal cat's at the same, and "low and behold" melted our cats at the same time. I was told by the engineer at Dynatech, the only cat's that will deal with the rotary EGT's and rich a/f's are the ceramic ones.

 

-gasp!-

I got one that's also a year old (only about 5k miles or less but a couple track sessions, autox's and drag strip runs)! I'll drop it down and take a look asap!

ha! and they said the metal cores could handle more heat! I hope mine's still ok...

 

I think that guy is full of crap. Knightsports and other Japanese companies have been testing and selling Metallic cats over there for a few years. Now, the metallic cats being offered over here currently may not hold up, but I think Dynatech is speaking a little too much out of their **** on this one.

 

I never had issues with my Random Tech metal cat either. The Random is constructed slightly differently than the Dynatech so you can't over generalize.

What basically kills cats is overly rich fuel mixtures. Mixtures in the 10s and even 11s will kill basically any cat. Especially if your flaming the cat on decel.

 

just run a midpipe with no cat.

 

Hmm, 3 failures and a growing list? ...sounds the same as the 3 failures and 1300cc injectors are crap theory. btw, Random does not make a bolt on met cat for the FD.

I had two ceramic random cats fail on my CRX. What does that mean? Nothing, it wasn't the cat. It did it's job but there was too much unburned fuel and it melted. After 3 cats in a row, I knew I had to look elsewhere for the actual cause and not blame the cat for the result. I'm not saying Dynatech is good. I have a different brand of met cat that I beleived was better. I'm saying a couple burned out cats does not disqualify all metalic cats. How many people from the Corksport Knightsport's group buy have had failed cat? Ask the guys in Japan how popular the metalic cat is there (Knightsport, autoexe, RE-A, etc).

 

Any turboed rotary will be running in the 10s and 11s. Hell, stock cars run in the 9s. Stock cats seem to last a very long time, provided the pre-cat doesn't fry it.

I've heard of 4-5 others not included in this thread. Given the small number of people running these in the US and the short amount of time they've been doing so, I think that constitutes a concern.

 

Observation: the stock pre-cat looks a lot like the aftermarket metallic cats. I am not suggesting that the aftermarket cats will have the same problems that some have had with the stock pre-cat, but I think it is interesting that the construction appears to be similar.

My cat experiences:
My stock pre-cat was still in reasonable shape at 70K miles (replaced with a dp). My stock main cat was damaged (cracked substrate) when I removed it at ~90K miles. I had an N-Tech HF cat that looked fine when I sold it after a few years (sold because I wanted both a cat and muffler in the middle). I have a Random metallic cat now that still looks fine, but it only has ~3K miles on it.

-Max

 

I would consider whether your injectors might be dumping a little too much fuel. Running rich = major afterburn and exhaust heat.

 

Max, are you running a PFC, and do you hear "pops" during downshifts and/or letting off the throttle ?

I had the car tuned by Steve Kan (PFC w/800cc injectors all around; SR Motorsports SMIC; DP; Trust cat-back), and I asked him to tune it really conservative, so I know it runs a little rich.

FWIW, with the original PFC tune (non-dyno, but gave the tuner my setup), she rarely "popped" off-throttle. However, according to Steve, it was a little too lean for his comfort.

Hence, I'm wondering if it is too rich, hence the melted cat.

Oh well, I'm running just a resonated mid-pipe now, and she's so much more responsive/eager to rev and powerful.

The smell isn't offensive (e.g., rotton eggs) and my eyes don't water standing behind, so perhaps I'll just keep the resonated mid-pipe.

I really need to get her back on a dyno and measure her A/F ratio!

:-) neil

 

FWIW, I'm also experiencing less "popping" off-throttle now that I'm running the resonated mid-pipe, and I still have the air-pump connected. This would tell me that the HOT catalytic element which had the air-pump (more oxygen) directly in front of it, was just too HOT, hence the numerous popping.

Perhaps, I should install another metallic cat AFTER the Magnaflow resonator, which would be very down-stream of the air-pump as well.

What do you guys think ?

:-) neil

 

Let me tell you my experience about the air-pump.A working airpump doesn't mean that it is really working.I have an KS metallit cat and lately the smell of the fuel was becoming more and more "Smelly".
I was seeing 16:1 mixture at the wideband during idle with my old airpump connected.I then replaced it with a low mileage airpump and the afr went to 19:1.No more smell during idle.I have disassembled an air pump and from what i can understand,the way the air pump works is identical to the ROTOR+HOUSING.There are three apex style seals that get deteriorate because of the rotation inside the housing.After many thousand miles,they dont seal very well,thus the drop in air efficiency.

 

So what's the outcome of your inspection ?

I have a spare air-pump, that I'm going to install.

:-) neil

 

This is what i posted on your other post.

From the looks of the pic it does not look like your air injection is working. The inside of the cat is suppose to be clean. It looks black in your pic. It also looks like the metal substrate is off centered like there was a big back fire in the cat. I have something that looks like a metalic cat but its ceramic. I have been running it with the air pump hooked up in front of the cat for over a year. I even took it to a track day at Button Willow. The inside still looks clean and still intact. When i first ran my cat without the air pump, the insides were black like yours. I was thinking about getting a metal cat to see if i can get a little more power out of my car with a metal cat. But i guess i will wait.

And are you sure the air is actually getting to the cats. You need a properly functioning air control valve for the air to be directed to the cats.

 

I want to add one more to the melted cat list! I also want to warn all of you using metal core cats that mine LOOKED LIKE NEW from both ends as it melted at the center of the core!! A simple visual inspection is not enough!

How did I find out the cat had melted? Well, the core's rear section flew out of the tailpipe and the melted center blocked flow enough to cause the car to stall and leave me stranded. I took out the midpipe and looked at the front section of the cat and lo and behold it looked fine! I still removed it and saw that the center section had melted!

Mine is the 3.5" resonated metallic core cat from SMB...

 

^^It only took another three years to die, sounds like you had a good run

 

well I don't think mine lasted too long.... not even 10k miles I think

I found out the hks twin power was bad, could ignition misfires melt a cat converter? or water injection?

 

Yes, any ignition misfire will result in excess oxygen (and fuel) in the exhaust and can/will result in a meltdown, so to speak.

In the absence of oxygen, excess fuel, i.e., rich mixtures/low AFR's, are not particularly harmful to the cat.

The water injection should have negligible effect.

These pics show what a persistent misfire at idle can do with a ceramic cat. This was due to an ignition problem on the rear rotor. In less than 10 or 15 minutes, the cat basically self-destructed due to obvious overheating. It did not melt; rather, it lost its effectiveness, cracked and the catalyst eventually broke up and was ejected out the tailpipe on a hard run, resulting in a midpipe.

And yes, the oft overlooked "exhaust overheat" warning light did illuminate!

 

That's not true, Random Technology does make a bolt on metal cat for the FD, because I have one. I had my FD smogged almost 2 years ago, and I passed with this cat and a working A/P. From the research iv'e done, Metal cats will withstand higher temperatures, have a higher flow, and last longer then traditional ceramic cats. The downsides to using a metal cat, are: (1 they are more expensive (2 I hear they don't filter as well as ceramic cats when it comes time for smog (but don't quote me on that)

True RX7's do have hotter EGT then most cars, but I agree with everyone that there must be another issue causing that problem

 

The stock FD cat is a metalic cat.

"The main portion of hte 2-stage, 5-bed oxidizing, 3-way catalyst system is a monolith metal-carrier type, possessing extremely low flow resistance."

RX-7 Jack k. Yamaguchi 1992 pg 84

So, I don't think there is an inherent reliability issue with metalic cats and the rotary.

A quick Google search of metal-carrier catalytic does turn up a host of round Chinese metalic cats looking for a market though. That does point to a reliability issue to me