Catalytic converter retrofit

[Syscrush]

OK, OK, I know - nobody does this and it's probably a stupid idea.

I respectfully ask that the thread not be filled with "Why would you wanna do that?" responses. The short story is that I'm a bit of a tree hugger, and unburned hydrocarbons smell like bad karma to me. If fitting a cat will help clean up that cloud/trail of HC without being too big of a pain in my butt, then my preference is to do it.


So, if it can be done without adding too much cost or complexity, I would like to give it a go. I found this catalytic converter insert from Akrapovic:



It is specified for an FZ1, which makes 120+ whp. It should flow plenty for a 100hp CBX. The bike currently has a Gary Wolf 6-2-1 header on it, needs a new midpipe and muffler. I'm planning on adding a 16" Hindle Oval Stealth muffler with dB killer insert, and incorporating this cat insert into that new custom midpipe would not be very difficult.

The main concern I have about doing it is that the cat needs a certain amount of O2 to actually work, and a safe/healthy tune for a CBX is probably too rich to let the cat do its work properly.

If anyone knowledgeable about tuning the carburetion and exhaust can offer some insight or advice, I would appreciate it very much.

Thanks,
Phil.

[EMS]

Phil: Most modern cats work in conjunction with an O2 sensor (and fuel injection) to get them to do what they are supposed to.
Many earlier carbureted applications had exhaust treatments like EGR valves and air pumps
I have no idea how you would facilitate something like this in a CBX. Probably very complex and somewhat dangerous (for the health of the engine).
Anything you do to the carbs goes into your combustion chambers first, regardless what happens in the exhaust.
If you provide more O2 and lean out the mix, you may find yourself with holes in your pistons or a poor running bike at best.

[Syscrush]

Thanks, that's exactly my concern. There's no way I'm gonna fit EGR or an air pump, and leaning out the mix seems like flirting with disaster. For an old carbureted engine like this it's probably a lot better to just tune for rideability and longevity.

Maybe I'll put this idea on the shelf until I get overambitious and decide to do something nuts like fit a MegaSquirt with closed-loop EFI... Or until I hit the lottery, whichever comes first. ;)

[NobleHops]

Thanks, that's exactly my concern. There's no way I'm gonna fit EGR or an air pump, and leaning out the mix seems like flirting with disaster. For an old carbureted engine like this it's probably a lot better to just tune for rideability and longevity.

Maybe I'll put this idea on the shelf until I get overambitious and decide to do something nuts like fit a MegaSquirt with closed-loop EFI... Or until I hit the lottery, whichever comes first. ;)

I don't mean this to sound snarky, but you would do more good by not grilling meat and buying an electric lawnmower and weedwhacker than you would by putting a cat in a CBX that might see a few thousand miles a year. I'm all in favor of your motives and sentiment though, 100%.

N.

[Syscrush]

I don't mean this to sound snarky, but you would do more good by not grilling meat and buying an electric lawnmower and weedwhacker than you would by putting a cat in a CBX that might see a few thousand miles a year. I'm all in favor of your motives and sentiment though, 100%.

And I don't mean this to sound sanctimonious, but I'm vegetarian and I live in a high-density condo, refuse to have a lawn, don't own a car, and my primary transportation is bicycle 3 seasons/yr and public transit in winter.

I'm not trying to get into some holier-than-though BS, just thought it was kinda funny that it seems my lifestyle is already quite a bit farther down the tree-hugger path than you had guessed. ;)

Honestly, it's as much as anything else because I like to give my bike a few mins to warm up before riding - usually do my plugs, helmet, jacket, and gloves wih the bike running, but doing this with a cat-equipped vs. non-cat bike is a night and day difference in our indoor/underground shared parking garage. The cat-equipped bikes (CBR125R and Duke 690) don't stink at all, but with the non-cat bike (Monster 620 with EFI) you can smell the unburned HC like 20-30 feet away after it's been runing for only 2-3 minutes, and I feel like a bad neighbor and a bad ambassador for the sport of motorcycling. Also, when stuck in traffic, the difference is really noticeable. So it's not all about high-minded ideals, there's a personal pragmatic component, too.

Which doesn't much matter because it really looks like doing the retrofit on a carbureted bike is not worth the effort. VERY doubtful that I will ever swap to closed-loop EFI, but if I do, then a cat would be in the cards then.

[NobleHops]

Well Phil, you don't come off one bit sanctimonious to me, just authentic about your beliefs AND actions. Rare enough. Pretty funny how I went 0-fer there .

As I said, respect your motives - all of them.

N.

[Rick Pope]

I'd say you are doing more than your share of being environmentally concious, so the liitle bit of extra stinky stuff you leave behind could be forgiven.

Not a tree hugger, but give one a little pat on the back now and again.........

[Syscrush]

Honestly, it's as much as anything else because I like to give my bike a few mins to warm up before riding - usually do my plugs, helmet, jacket, and gloves wih the bike running, but doing this with a cat-equipped vs. non-cat bike is a night and day difference in our indoor/underground shared parking garage. The cat-equipped bikes (CBR125R and Duke 690) don't stink at all, but with the non-cat bike (Monster 620 with EFI) you can smell the unburned HC like 20-30 feet away after it's been runing for only 2-3 minutes, and I feel like a bad neighbor and a bad ambassador for the sport of motorcycling. Also, when stuck in traffic, the difference is really noticeable. So it's not all about high-minded ideals, there's a personal pragmatic component, too.

And the CBX is really living up to my concerns in this regard. Once the carb tune is dialed in a bit better and the air in the parking garage is a bit warmer this might not be such an issue, but with the way the exhaust smells when warming up on the choke now, there's no way I'd let it sit idling in the parking garage while it warms up. The unburned HC's are bothersome within 10 seconds. I don't like the idea of being "that guy" pissing off all the neighbors - but I guess that's how it's gonna be for a while.

[daves79x]

In the first place, you should not be letting the CBX sit idling on choke - it will soon be screaming at 3-4000 rpm. It will blue your pipes (if you care) instantly. Also not good to be dumping an unnecessarily rich mixture into the engine. Just get your stuff on, fire up the bike and ride away, letting the choke off as soon as you can. If your bike will not let you do this, then the carbs still aren't right. Properly syncing the carbs is what I gather your mechanic will do. This probably won't cure everything, but will let you diagnose further any issues. If your bike indeed has stock jets and settings, with the stock airbox, it should perform quite well with normal emissions for a '79-era bike.

Dave

[Syscrush]

Thanks for the startup/warmup advice, Dave.

As I'm still waiting on the airbox lid screws, the bike is still leaned out a lot, so I don't doubt that it takes more choke right now to keep it running during warmup than it will need once the carbs are dialed in.

[NobleHops]

Phil, as I re-read this thread I'm thinking of my VStrom. Notorious for lean-surging and popping and backfiring when stock, mine, like may, has had it's fueling richened with a PowerCommander open loop spoofer. And now it runs great and the flat spot is reduced a lot and that is swell but it smells like a cloud of unburned fuel, especially when warming up. Wish I could fix that too.

N.

[Syscrush]

I had thought that with such a big motor (in terms of outside dimensions) it might be good for it to have a slow warm-up idling for a few mins before takeoff - my concern with warming up under load was uneven temp distribution through that wide block. But with Dave's assurance that warming up under light load is OK, I'm happy to amend my startup procedure.

Nils, does your V-Strom retain the catalytic?

[NobleHops]

I had thought that with such a big motor (in terms of outside dimensions) it might be good for it to have a slow warm-up idling for a few mins before takeoff - my concern with warming up under load was uneven temp distribution through that wide block. But with Dave's assurance that warming up under light load is OK, I'm happy to amend my startup procedure.

Nils, does your V-Strom retain the catalytic?

Does not have one!