I'm planning on getting a DanMoto exhaust for my California f4i. As such, I've been doing a bit of research regarding the O2 sensor. I'm an SAE master technician and I've been working on cars and bikes since I was 14.

Now, many people on this forum seem to believe that replacing the O2 sensor with a 330 ohm resistor or a "specially designed module" is a simple and harmless modification. After all, the O2 sensor is just there to make the bike look "green" for all the tree-huggers in the California Air Resources Board, right? Or, maybe it only operates in a VERY narrow window of infrequent riding scenarios, as suggested on the DanMoto website. Well if you believe that, you should read this; it comes straight from wikipedia:

"Tampering with or modifying the signal that the oxygen sensor sends to the engine computer can be detrimental to emissions control and can even damage the vehicle. When the engine is under low-load conditions (such as when accelerating very gently, or maintaining a constant speed), it is operating in "closed-loop mode". This refers to a feedback loop between the ECU and the oxygen sensor(s) in which the ECU adjusts the quantity of fuel and expects to see a resulting change in the response of the oxygen sensor. This loop forces the engine to operate both slightly lean and slightly rich on successive loops, as it attempts to maintain a mostly stoichiometric ratio on average. If modifications cause the engine to run moderately lean, there will be a slight increase in fuel economy, sometimes at the expense of increased NOx emissions, much higher exhaust gas temperatures, and sometimes a slight increase in power that can quickly turn into misfires and a drastic loss of power, as well as potential engine damage, at ultra-lean air-to-fuel ratios. If modifications cause the engine to run rich, then there will be a slight increase in power to a point (after which the engine starts flooding from too much unburned fuel), but at the cost of decreased fuel economy, and an increase in unburned hydrocarbons in the exhaust which causes overheating of the catalytic converter. Prolonged operation at rich mixtures can cause catastrophic failure of the catalytic converter (see backfire). The ECU also controls the spark engine timing along with the fuel injector pulse width, so modifications which alter the engine to operate either too lean or too rich may result in inefficient fuel consumption whenever fuel is ignited too soon or too late in the combustion cycle."

So, not only is an O2 sensor delete, bad for your fuel economy, it's also likely to cause poor engine performance in the long run, and can potentially cause serious engine damage. Now, you may be saying to yourself, "That's all well and good, but this is a high performance sports bike, not a toyota camry!" All I can say to that is go to an online parts supplier and look at the part numbers for a california bike's ECU and a non-california bike's ECU. They're completely different computers. Now, there's a very slim chance that the only difference between those two computers is that one flashes a little light on the dash when there's no O2 sensor hooked up to it, but remember, this is a fairly modern Honda we're talking about, not a hyosung or kymco. So the odds are that the california ECU is specifically tailored to work WITH the 02 sensor to calculate the A:F ratio especially when doing something like cruising on the freeway. Think freeway miles are the most stress-free for your engine? Not if you have the 02 sensor disconnected!

When you think about it, you spend quite a bit of money on good oil, valve adjustments, maybe even premium fuel to enhance you're bike's longevity, so are you willing to take the chance that sending your bike's computer false data is harmless? I'm not. That's why my plan is to order the exhaust and take it to a shop to have a bung welded in (maybe $40 at the most) because it's cheaper than replacing fouled spark plugs, cheaper than losing 6 mpg, and definitely cheaper than a new engine. If you REALLY hate all that emissions stuff and you want to eliminate it without risking damage to your bike, go online and order a non-california ECU.

 

"SAE" master tech.
LOL

 

surely someone sells a california model slip on. i wonder if you could just dangle the o2 sensor in the canister, and when you want more power you just pull it out.

 

What's funny about that? Do you feel it's an invalid credential? Or did you simply mistake my presentation of credentials as an attempt to boast?

Also, 74demon, since you're a moderator, how come my account still has such limited privileges? I can't even view pictures in other posts. I actually have more access if I DON'T log in.

 

As a new member, your account privileges are limited. After you make a handful of posts, an administrator will set you free. If you are still in moderation when you reach 15-20 posts, find me and I will follow up with the admins about it.

Now, your post was funny because I've been an ASE certified master tech for over 20 years and have never heard of an "SAE" certification.

California ECMs are different because they have EVAP controls as well as the o2 sensor. The stock map is a little different for emissions reasons, so most of us use power commanders to get around it. The article you quoted is true for cars, but not for our bikes. If the sensor did work like that, wouldn't bikes outside California need them?

 

Oh thanks for all the information. Looks like my dyslexia got the better of me. I'm sure you're right that certain measures can be taken to mitigate the affects of removing the o2 sensor but it's my opinion that the o2 sensor is there not only for emissions but also for fuel economy and engine longevity, meaning, it's an UPGRADE. Kinda seems like removing it would be something you'd do if you thought carbs were and upgrade from fuel injection.

 

Only cali models and all 06 models used the 02 sensor, and its purely an emissions and milage device. The bike runs on pre-determined fuel maps. It runs the map and then makes small adjustments based on the 02 sensor feedback. With the resister in place, it thinks its always running perfectly. It won't be, it will be running rich because the oem's will always default to that as its safer. Richer is fine and normally when one does these mods they tend to do a power commander and dyno tune which would elminate the 02 sensor variable completely, not to mention its required for said dyno tuning.

That being said, if your a master tech you should have already known and understood such basic principles as this. Basing all your knowlage on wikipedia isen't going to end well either.

 

I don't base all my knowledge off of wikipedia. I'm am co-owner of a race shop and I base most of my knowledge off of the 20+ years I've spent working on cars and bikes. That being said, I'm sure you're absolutely right. With a dyno tune and aftermarket piggy-back ECU, removing the o2 sensor is a perfectly reasonable option. However, it seems that many members are under the impression that simply slapping on an aftermarket exhaust and replacing the o2 sensor with a resistor w/o any other modifications is a great idea. My argument is simply that these people might want to think twice about the complex engineering and computerized control that goes into making a 600cc engine produce 100hp reliably and efficiently.

 

Well, I can't argue you on that one. I kept the 02 sensor on my bike.

 

I spent $12 on a bung on ebay and welded it in myself. Cheaper thn buying a proper delete, better for everything anyways. Win-win in my book. I have a 2006.