rotarypower101

iTrader: (1)

I would like some advice as to feasibility of adding a metal substrate cat into my system.

Hoping for some feedback about the changes I should be concerned with, and hopefully some advice on if the location of the items are going to be OK and logical.

System: GT35r > 3” SS DP > WB bung ~ 2-3” from end Vband > 6” SS metallic cat > resonated MP > RB catback

I can elaborate on anything that would be helpful.

Any things I should worry about and be aware of by adding this component to the system?

Is there a better location arrangement for the components?

The MSC now sits in the position where the original mid cat resided, so I am hoping that the heat developed will be mitigated by the original insulation and shielding.

Is there any sense in putting the cat downstream further?

Assuming it would be OK to move the cat further back in the system and still develop the heat required, would there be an advantage placing this device in a different position?

Is there an optimal temperature range the metal substrate cats like to see, and if so any ideas where that should be?

Does the location of the wide band need to be changed?
What is a desirable distance from a MSC that would be safe for the WB?

I have the issue of wanting to keep the WBO2 close to the end of the DP, but not too close to the MSC...

Is heat from the MSC going to be a factor for the WBO2 sensor?
I am guessing NO, but am concerned about the issue.

Would there be any sense in installing a WB bung downstream of the MSC just to see its effectiveness?

Any advice, tips or helpful concerns?

j9fd3s

iTrader: (3)

i've learned that you do want the cat under the factory shielding, if something goes wrong, (i have this t shirt), that heat shield actually will save things like the carpet.

second, arghx has posted some info on cat temps before, and with the metal cat you should ask the manufacturer. with the stock ceramic cats, the cars are basically tuned to keep cat temp under 650-700c. i'm not sure if they are measuring precat, or post cat (the reaction in the cat adds heat).

i did put an EGT in place of the o2 sensor, on an S5 NA, and the highest i could get EGT's to go was 710c.

in summary, put the cat under the heat shield, and find out what temp the cat is rated for.

arghx

iTrader: (3)

I wouldn't worry about what nominal temperature the cat can tolerate, because I can guarantee you will exceed it on a regular basis. There's a reason why conventional turbo engines run AFR's in the low 9's to high 10's at WOT when they are stock.

rotarypower101

iTrader: (1)

Thank you for the help guys.
Even just having a rough idea what should be happening is very helpful.

Any speculation or advice on the other issue I posed about the wide band?
Are these issues I should be at all concerned about?
I was running a SS shroud and copper finned heatsink as was recommended at the time for the LM1 sensor, but I have not really read/noticed anyone having temperature issues with these sensors even when neglecting to shield the sensor.


Would anyone have a link to the catalytic converter thread mentioned?
Was the thread specifically about cats, or just an aside to a different topic?
Having trouble locating it.

Is there any knowledge out there on MSC efficiency of operation VS temperature?

TIA

rotarypower101

iTrader: (1)

Also wanted to say I searched through the last 10 pages of Raymonds posts that it is allowing me to, (has there been a change in how the search here works?) but not seeing anything .

And I have contacted the manufacture of the metal substrate cat, but have not received anything back as of yet.
Performance Weaponry

I dont think these will be issues (and there is likely something more important I am overlooking) but before I weld all this assembly together, I thought it prudent to ask in advance instead of learning what I had overlooked down the road at significant cost and time misspent.

Seriously, thank you guys!
Its hard to convey the amount of appreciation for your time spent informing and helping some of us along all these years.

j9fd3s

iTrader: (3)

Raymond knows more about catalysts than anyone else, basically. the thread was in the 3rd gen section, but other than that i don't recall, nm found it https://www.rx7club.com/3rd-generati.../#post10813488

this too https://www.rx7club.com/2nd-generati...lained-874626/


the O2 stays ahead of the cat, i've never seen an OEM car with the o2 after the cat...

neit_jnf

iTrader: (17)

I dislike aftermarket metal substrate cats... I had a very nice setup from a reputable shop (Australia's SMB) and the metal cat lasted about 10k miles and melted.

The interesting thing is that when inspected from both sides it looked new, it melted from the middle out and spat the second half out the exhaust!

j9fd3s

iTrader: (3)

the its a catalyst, so the reaction between the hydrocarbon/nox's and the metals in the cat actually create heat, so the cat will actually add heat.

the Rx8 has two bricks in the cat, and its pretty common for the second brick to just be missing but the first is fine.

conclusion is that the first brick input temp is ok, but the output temp is too high for the second brick

rotarypower101

iTrader: (1)

Thank you for the links j9fd3s



So then assuming one would like the thing to last a little longer than just as a preliminary test, I am going to need to find out a decent operating range for the unit, and somehow try to estimate operating temperature.

Any good ideas or methodology to find a acceptable way of determining operating temperature? EGT probes before and after?

Would it be a safe assumption that the position of cat shouldn't really make significant difference in operating temperature?

I am unconcerned with startup/cold operation, so quick warm up is a non issue.

The entire goal was to see if I could remove the hydrocarbon smell that can enter the cabin at times.

ArmyOfOne

iTrader: (12)

So is that why the air pump normally feeds between the two bricks? Makes total sense now. A nice corvette electric pump would do nicely!

rotarypower101

iTrader: (1)

Yes I think it is pumping in extra air, specifically oxygen , to combust the excess hydrocarbons, and of course this reaction is where all the extra heat is coming from.

My guess is that with the amount of hydrocarbon that is coming into this cat I am tying to install, the temperatures may be unmanageable, and a very short life will be the verdict.
At the time of purchase I was concerned with throughput and not requiring the airpump, hoping that it would reduce the “stink” that passengers are not very fond of, let alone the driver.

Doesnt the rx8 have a electric airpump...keep it all in the family

moehler

iTrader: (12)

I'm going back to a cat as well with my new set-up. Going with a smaller turbo (from my GT40R), BWS360, for good response, but wanted to keep the higher end power around 400 rwhp - with a cat. I plan on running pre-turbo WI (just bought the wannaspeed kit) to get the boost to 20 psi or so. I hope this setup gets me the response I want, plus the power. The WI should also lower my exhaust temps a bit as well for the cat.

After researchning a lot of cats over the years (and trying a few of them, bonez, smb, vibrant), I decided to try out the random tech cat. It's plug-and-play for FDs (PN 141-30038), and flows very well. Should work pretty good too with 300cells per sq inch. I hope to have the setup completed in the next month or so...

j9fd3s

iTrader: (3)

well a metal cat should be able to run hotter before it melts, although the manufacturer should know this, and be able to supply this kind of info.

for operating temps, i think you could take the info that Raymond posted as the low end, IE if you can keep cat temp under 700c, i think you would be totally fine. the thing with the metal cat is that i am under the impression it can withstand higher temps than this, which is nice on a rotary.

further back = colder, but it needs to stay under a heat shield (voice of experience!).

yes, but the side ports the Rx8 has allows it to run 14.7:1 AFR's at idle, so it only uses the air pump on cold starts for about 30 seconds.

the previous engines won't idle that lean, and so they inject extra air into the exhaust ports.

the split air pipe on the cat is kind of a red herring, its only used on transitions between accel/decel.

Speed of light

iTrader: (8)

On a FD, The split air air pipe is used during cruise and most o2 feedback conditions; port air at startup and idle. The 93 service highlites has a good chart on this. During high speed conditions, no air is injected.

In my experience, midpipe seems to be a good location for the cat. I agree with the poster who said to use/put it under additional shields.

What I've found will destroy cats fast is a misfire or rich misfire condition where there is a lot of excess air (and fuel) available.

j9fd3s

iTrader: (3)

i skipped the stories, but it needs the stock shield at least

rotarypower101

iTrader: (1)

Please enlighten us,no judgments, just gratefulness for your hard learned lessons passed on, sometimes being the pioneer comes with hard knocks for being the first to learn.
Was it simply omitting the heat shields? DP&MP or still using the cat?

Perhaps you can help me as well as others not make a similar mistake.


I am trying to find the best position that does not decrease stock vehicle clearances,reduces complexity of bends and adjusting angles but also maximizes the distance away from susceptible components, ie transmission and floorpan.

There are a few points to the front of the MSC that don't leave much more than 1-1.5” at best to a heat shield, but does open up quickly because of the wide berth left for the stock mid cat.

I would like to move it back a few inches and increase my air buffer on the front of the cat, but I believe I am at a good compromise ATM, and have a easily replaceable 12” strait section that will plug right back into the space leaving ample room for Vbands and easy threaded clamp section accessibility and clearances for movement.

rotarypower101

iTrader: (1)

Really metal has a higher usable range than the ceramic substrate cats?!?
Not that its implausible, just surprising.

Thats what I am hoping for something in this range would sure help if not a bit cooler, been looking around for hard numbers, and hoping that the manufacturer will mail me back about the specific setup within the week or I will mail them again and call if it becomes an issue.

j9fd3s

iTrader: (3)

ok the quick one, is this one time, i bought a GSL-SE, and it had a full RB exhaust with no heat shield on it, and to smog it i just put a stock exhaust on it, with no heat shield.

it seemed ok, on the street, but it got hot enough during the test to trip the exhaust overheat, which actually makes it go rich, dumps air pump air, and well fails the test.

so next time i fixed that by tossing the exhaust overheat sensor over the roll cage. it passed the emissions test but the carpet was steaming.

the other time was on the 3 rotor FC, which had a cat, and i was driving to work one day and the Haltech decided to drop leading ignition or something* on the freeway. eventually the car stopped running, and i was able to pull into a parking lot. the cat was about 1/2 from being under the heat shield, and everything from the end of the heat shield back was either red hot or smoldering, carpet, seat belt bolts....

on tear down the cat had turned liquid, and actually poured itself into the muffler.

contrast this with a stock FD, where you can drive it hard, and get the exhaust hot enough that its glowing all the way back to the muffler tips, and its fine.


*the E11, when it worked it was really nice, but it was was always locking up, and or going into boot mode.

rotarypower101

iTrader: (1)

Good to know, so often we just HOPE that we understand everything, and that everything we believe is true...until it isnt.

Reassuring to know the underside of the FD is fairly resilient to precipitous amounts of heat energy.

rotarypower101

iTrader: (1)

I have a question about soot, as I see a heavy buildup inside the existing tubing and components.

How will this affect a cats ability to do its job?
Will the heat level change the amount of buildup on the catalytic reactive surface?