Stinky FD exhaust with resonator pipe!!
 

I've recently rebuilt the 13B in my 1992 RHD FD. Its a stock motor aside from:

• Street ported housings and super seals
• Replaced the original cat for a resonated straight pipe (removed and blocked off emissions stuff)
• Stainless exhaust

Without the cat when I run it in my garage the exhaust looks good (no smoke etc) but is very stinky, the sort of stink that sticks to your clothing. It does seem to be running a little rich so I hope the Power FC I ordered can cut that down a little and smooth it all out.

Anyone have tips on reducing that stink, I thought about replacing the straight pipe for a high-flow cat but I really don't want to hook up all the emissions stuff (air hose) again since I've already blocked it all off.

Any input is greatly appreciated!

I hate to say it, but I have yet to see a non-smelly rotary. My eyes tear up when I'm near the car, my friends never want to drive behind me, and I hate taking my car to work since I wear shirt and tie and I don't want to pay for dry cleaning all of the time.

https://cimg9.ibsrv.net/gimg/www.rx7...1a12757824.jpg

I'm actually curious if there's anything other than putting back the factory emissions..

I think you can just put a cat in without hooking up the emissions stuff.

My friend has passed etest with everything blocked off, no airpump and just by tuning it with the PowerFC.

I do believe a high flow cat will reduce most if not all of the stink. However, WO the airpump, I suspect it will burn out the cat faster, but not 100% sure on that claim.

^ when you guys say stink,, do you just mean the smell of unburnt fuel and a touch of 2-stroke? If so, that's part of the charm! What kind of annoys me is the bit of smoke on start up and over-run while driving.. would a high-flow cat fix that at all? No pollution gear or air pumps on mine.

You might call it "charm." My wife would politely disagree with that assertion. She can tell everytime I arrive home if I've been with "the mistress" (my FD), based on how my clothing smells. It requires a shower before bedtime :)

I'm guessing you would still get some startup smoke WANKfactor, but what exactly do you mean by "over-run"?

By over run i basically mean lifting off the throttle.

Your charcoal canister line in the rear may have come off. If filters out gaseous fumes from the tank.

A high-flow cat will all but eliminate the stink and you'll probably be surprised on how little it reduces power. You might also like the sound better. I've been running a BONEZ cat without emissions for over 10 years and it's still going strong. It won't miss the air pump and you don't have to worry about boost creep on the twins either.

Embrace the petrol fumes, let them become one with your pores.

I've run a quality high-flow cat for years, it cuts the stink WAY down and you do not need to run the air pump/emissions with it. A good high-flow cat will be VERY little restriction.

If your car is running richer than normal it will make more stink. If you have a stock ECU and no air pump, it will run much richer and of course be stinkier. The air pump messes up the O2 sensor readings, the factory ECU compensates for this, but if you remove the air pump the ECU doesn't know and it compensates the wrong way. Makes the car idle crappy and it's jerky on/off throttle. Easily fixed with a PowerFC.

If you get REALLY poor fuel economy that's a sure sign of being too rich. Bad plugs, bad o2 sensor are common culprits.

Dale

^^ listen to him. Solid advice as always Mr. Clark

Yep, switching in a high flow cat really improved smells/emissions with really no downside for me, definitely a worthwhile switch to make.

Thanks for the feedback all, I did a little more research after reading your suggestions. I think I'm gonna go with a Metallic Substrate HighFlow Catalytic Converter and have it welded into my downpipe, apparently they work great and don't ever clog etc.
Magnaflow 59956 | 200cpsi | 2.5"in/out | Metallic Substrate HighFlow Universal Catalytic Converter
I mocked up a quick image of what I'm thinking:
https://cimg4.ibsrv.net/gimg/www.rx7...559c3b2a0b.png

Good, bad, ugly?

No need to mess with the downpipe/precat. Just replace the main cat or your midpipe with a Bonez or equivalent. :icon_tup:

EDIT: Yeah. What sarge said.

Good points Sgtblue/Natey! I've heard tho the stock mount high flow cats can clog or overheat without the air pump hooked up, I wonder if anybody sells a bolt on cat that's intended not to have an air pipe installed, do you guys know of anyone selling a cat like that?

Just get a RP/Bonez cat and run the air pump. I don't understand why don't you want to run the pump? You have stock twins based on the downpipe, so turbo clearance isn't an issue.

When I tune/log I disconnect the air pump plug and the exhaust gets waaayyy stinkier. Also, when I run my air pump I get better exhaust pops on decel and off throttle. I guess that's from the added oxygen allowing unburned fuel to combust. Win/win IMO...

High flow Bonez main cat and air pump FTW.

Sgtblue you've convinced me, stock mount high flow cat it is. I'll just block off the air pipe inlet.
alexdemin, I'm planning to install a single turbo in the near future so I'm slowly checking off things like blocking off the emissions etc..

It's pretty easy/cheap to buy and rig up an RX8 electric airpump, and wire it to the original plug to trigger it (you may want to actually draw power from a more direct source), and you have a lot of flexibility with where you place it.

Or remove it if you don't have emissions testing, are moving to a standalone ECU and want to simplify. The only thing you should consider since you're also going single is a Pineapple idler pulley.

I've read on here that people have had luck running the SMB metallic substrate cats with no air pump without it clogging, etc. I was thinking of running one to just cut down on the smell (I have no air pump so didn't know how long the HFC that came with my car would last). SMB's are crazy expensive but there are some other places that sell similar ones, I believe.

My SMB Metal cat melted, probably caused by bad HKS TP misfiring though

https://www.rx7club.com/3rd-generati...p-pics-668417/

^ doesn't matter. SMB is defunct now. Which is a damn shame. Best rotary mufflers on the market (if you were local)

That is a shame, I have an SMB high flow cat. Ran it for at least 10 years, solid as a rock.

Ignition problems can kill most any cat.

Rigging up an RX-8 air pump would be a BIG pain. They are not designed for continuous use, they only run for a short time on startup on the RX-8 and that's it.

I think the air pump could cut down on stink some MAYBE, but it's a pain in the ass. It's always in the way, there's a lot of plumbing with it, you need to have the air control valve....

On a stock/near-stock car, keep it and run it. As stated you do need a PowerFC to properly remove it, the car runs SO crappy on a stock or chipped ECU with no air pump.

You could totally go with an aftermarket weld-in cat but you'll be doing your own experimentation. Had to dodge the guts of a friend's 1-month-old high flow cat at Deals' Gap one year as it ejected out the back. Also, the mid pipe is typically the best spot for a cat, the downpipe is too close to the engine and REALLY hot and as stated way more work to get to.

As always, you can pave your own path and pioneer a new way to do things but it's worth listening to the experience of others.

Dale

Did you read higher in the thread?
My BONEZ high-flow cat was in the car when I bought it 16 years ago. I don't have testing where I'm at so 10+ years ago I removed emissions with a PFC. No air pump, no split-air bypass plumbing, halved the number of solenoids and vacuum lines and just blocked the cat's air inlet with a section of hose, a bolt and a couple of clamps. I bought a Garfinkle idler pulley to replace the AP at the same time. I also began pre-mixing at half-rate WITH a working OMP. About once a year when it's up on the lift I drop it and look inside. Despite the extra oil and no AP, the matrix has always been clean and as far as I can tell, it flows just like it did 16 years ago. I also don't put up with the eye-watering stink and I prefer the sound.

I'd read previously from multiple people that the SMB cats run fine w/o air pump. I had not read that the Bonez do--in fact, in my foggy memory I feel like I remember reading of people's Bonez cats clogging w/o air pump, but I could be mistaken. Therefore, reading one success story was positive but not enough to move me from my interest in getting an SMB (that is not apparently not possible as they are now defunct). If more people come out of the woodwork with positive, similar stories as yours with the Bonez with no air pump, then that will be [happy] news for me. Detailed account of your experience is appreciated, that is much more helpful than a lot of posts.

:dunno: OK...go for a metallic cat. SMB? Post up a WTB in the parts section here...and wait. There's also an Australian FD forum (not sure putting a link up is Kosher) that you could check for someone willing to sell one. Shipping will be a killer though. Or you can go with a generic, which again, isn't likely to stand up long to the higher exhaust temps of the rotary.
I can't remember off-hand if the stock cat is metal or ceramic. If it's metal it might be an option. I see those come up from time to time. One last option for you if you're not easily convinced is to start your own thread looking for other anecdotal stories from people NOT running an AP with a cat and see what they use. I'll stay out of it. :)

I have had both cats on my 94'. First I replaced my stock system with a Bonez cat back in 2004. I lasted a long time(8 or 9 years), the smell was tolerable, and it lasted until my air pump failed and then it began to clog slowly. I then switched to the SMB metal cat and the smell was again tolerable but not as good as the Bonez ceramic cat and this cat partially melted at some point in the 3 years I ran it. Also, it was a 100 cell which is why it was smellier than the Bonez and other metal cats. I now have a Vibrant high flow racing cat that is a 300 cell, is OBDII certified for emissions, and has virtually no backpressure, will not melt until around 1600-1800 degrees F, and is good up to 500rwhp for race cars. It has not melted yet, no smell, and much better spool-up of the turbos but some people could have problems with boost creep. I am still twin sequential but only ran the car for a few weeks with the Vibrant before I started a major rebuild for super high efficiency fresh air/ram air induction, WI injection, new suspension, brake rebuild, U-type intercooler with complete CO2 nozzle spraying,etc. The only major problem with the Vibrant is it is very expensive at around $400, but it should last for years.
Mike

That's funny. You think 400 dollars is expensive for a cat.

You are right Raymond. $400 is not expensive for the cat but to have it rewelded into the SMB pipe, which is made at a very funny angle, required 10 hours of work with a special jig made and an additional $450. So all together it was $850, which is not cheap.
Mike

Jesus christ..and I thought the whole Prius cost $1800

Mind sharing the link to the Vibrant cat?

I did the UHO for the least backpressure and highest flow. I see the retail was over $500, but I searched out the best deal which was around $400 at the time around 2.5 years ago.

Part # 7530 correct?

https://cimg8.ibsrv.net/gimg/www.rx7...0b25b6e0e9.jpg

I did the #7830. It is 3" inflow and outflow pipe but has a 4.5" diameter center which allows more flow and less back pressure. It is only around $40 more. Mine was welded in where the stock converter was so there is plenty of room since this is still a smaller in diameter than the stock.
Mike

Yes you could. I have a larger bellow SMB 3.5" to 3.0" downpipe. Then the Vibrant cat in a shorter pipe. Then clamped to a SMB small muffler that quiets the car down some. Both of these make up the mid cat section and is all 3" and was made this way originally by SMB, when their cat was in there before it partially melted. Then an older 3" pipe dual tip RS*R catback from around 2004. No smell or very little with the car idle tuned to about 13.1 to 13.4 AFR. The car is definitely louder than stock but not so loud as to not be able to listen to some quieter music. The exhaust tone I think is pretty nice.
Mike

There's also this -

http://www.srmotorsports.com/sr93xhst.html

They put what looks like a metallic cat in the DP. Very curious how well this works. As far as I can tell, it's the last direct fit metallic cat on the market for our cars.

SR Motorsports' page hasn't been updated in 15 years, I'm not sure if any of their products are truly still available or what capacity they are in any more. They used to be active on the old mailing lists back in the day and had some nice products then pretty much went silent.

That may be worth someone calling them up and seeing if it is available.

Dale