tt2323

I'm sick of my main cat. I'm looking to replace it while still passing emissions. What is my best bet?
1) highflow with airpump hole already?
2) welded in cat with custom airpump line hole?

Is there something that will last w/o the airpump

I was thinking about getting a stainless ebay midpipe cutting it in half and installing a cat/airpump line is this a good setup?

rynberg

You have your best chance of passing smog by buying a hi-flow cat from RX-7.com or Gotham Racing with the air pump tube. The new metallic substrate cats may pass smog without the air pump hookup but no one has tested that AFAIK. I'm torn between which way to go at the current moment, and I have my smog test due in July.

tt2323

rynberg, i've searched and came up with this:

regular weld in cats are made for piston motors not hot running rotaries so they don't last/clog.

metal substrate will last, but will they pass emissions? regular cats run the airpump line into the center, where would you weld in a line for the substrate? Even though its said they don't need it would you pass emissions easier? is there any drawbacks using your airpump with a metal substrate cat? someone stated it'll heat up the exhaust is there any truth to this?

insomniac

iTrader: (5)

you can use the catco cats from Summit Racing. I had it on my car for six months, with a single turbo, so no smog pump. I then took it off, and check it, the inside was still very clean, when I thought it might be clogged up by then.

7racer

I'm a couple parts away from getting my car back on the road and will do a Metallit cat smog here in Dallas. I did a "before" with the stock cat.

DaiOni

I vaguely remember metallit claiming that their products = better emission levels

of course, product promotion and reality are often two very different things

John Magnuson

Don't you need the airpump to pass smog anyway?

I've got the bonez cat now and I'm happy with it. Havn't tried smog with it yet though.

tt2323

Can you run an airpump with a metal substrate? Where would you plumb it? cleaner emissions? any downsides?

7racer

Knightsport makes one (I have this one) that has a airpump pipe prewelded right before the cat.

https://www.rx7club.com/forum/showth...nightsport+cat

alberto_mg

here is a good thread about metal substrate cats
https://www.rx7club.com/showthread.p...etal+substrate

and another
https://www.rx7club.com/showthread.p...etal+substrate

i think the consensus is the bonez is one of the best out there that has been proven to work.

OC94Rx7

Last August '04, I passed the smog test with my KS metallit cat. I did have pre- smog test problems with my air pump (magnetic clutch was not working correctly with my PFC, had to use the stock ECU so the pump clutch would engage/disengage correctly to pass) and ran a few test without the pump. With the air pump disconnected, I remember my lamda was perfect but the Co was way off. The test numbers below were taken here in Denmark at my local Madza dealership during after hours (free of charge I might add) it was done quickly and this is what my notes read. It would be nice to compare with some of you in the States...I'm sure it vary's from FD to FD, mods, etc....

KS Cat with air pump (pass) - 2 runs

co- 0.064 / 0.058
hc- 19ppm / 18ppm
o2- 1.38 / 0.95
co2- 15.3 / 14.7
lamda 1.046 / 1.048

KS Cat without air pump (failed Co)- 2 runs

co- 0.933 / 3.74
hc- 8ppm / 347ppm
o2- 0.94 / 0.01
co2- 14.6 / 14.2
lamda 1.000 / 1.003

Regards
Oliver

dubulup

with yen to USD, KS is over $850 right now.

7racer

hey Oliver! thanks for posting the results!

tt2323

Alberto thanks for the links, but i've already read them. My most important thing is passing emissions and it hasn't been stated if those work or not..

tt2323

Anybody? I'd like to get more information

7racer

tt2323,

was oc94rx7 data on the knighsport cat above what your looking for??

tcb100

I bought the Random Technology high flow and it lasted about a year. Not happy. Shopping myself right now.

RotorMotor

iTrader: (5)

i passed the CA ****-dyno smog with a knightsports HF metalit cat. my airpump WAS hooked up. passed first time.

however, id like some more info on how i would do without the airpump, as im building up another FD (20b) where i will not have enough room for an airpump. also, the plan (as of now) is to run 2 metal substrate cats in parallel.... however, i dont know if not using an airpump will work out.... not to mention wether ill be able to get BOTH cats hot enough to scrub the air if i split the exhaust flow. hmmmmm wish there was more info out there on these metal cat cores.

i dont assume anyone has compared the other various brands of cores out there? the only one i have experience with is the metalit.

Mazdabation

iTrader: (9)

Im bringing this back from the dead. Any more new info on comparisons between Bonez and a metal substrate??

Also do either of these come in 4"?

t-von

iTrader: (8)

You do know that if you do the engine steam cleaning method (water with vacuum nipple to clean the engine carbon) that it will also steam clean out your exhaust system including the cat if it's slightly clogged? Ever since I started doing this, I've noticed that I don't get the black smoke out my tail pipe under WOT anymore. Now the color is a greyish white. If your car is nearly stock, it makes more since to clean out the system than to spend the money on a cat that you might not need. Anyways, I would rather have the greyish smoke than black smoke before an emission test.


Edit: Never mind my post, I just realized how old this thread was.

alberto_mg

my random technologies metal substrate cat is still working well. ~8 months now.

moehler

iTrader: (12)

To answer the topic title question, N-Tech claims that their cat will work with out an airpump. You wont pass a smog test, but you wont clog the cat either. I ran the n-Tech cat for 2 years with no airpump and the thing never clogged or melted or anything like that. It controlled smell pretty good too.

I am running the SMB cat right now and I'm pretty impartial about it. My main concern is with smell, not with passing smog, so I am running it without an airpump (SMB reccomends that you do use an airpump with it). The cat doesn't really control smell too good without the A/P... in fact I just bought a midpipe because I don't even see the point of running this cat.

Bad_Karma7

Any one know for sure if the cats can be "clogged" and not show any signs of damage as far as the honeycomb is concerned?

7racer

not sure....but wasn't there a link to the rx-8 forum about melting of these cats?