Bikes dirtier than cars - Mythbusters | Page 2 | GTAMotorcycle.com

Bikes dirtier than cars - Mythbusters

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I don't know how Mythbusters did it, but for the regulatory tests, the emissions are regulated in terms of total grams of each pollutant over the test, which is a fixed distance.

Carbon dioxide, on the other hand, is in direct proportion to the amount of fuel burned. (Yeah yeah, the type of fuel makes a difference, but the number of motorcycles that operate on diesel fuel (more carbon per amount of fuel volume than gasoline) or ethanol (less) are vanishingly insignificant to the extent that they can be neglected.)
 
The post made simultaneously with mine links to an explanatory article. Note that in the table about a third of the way through, the limits are specified in terms of grams per kilometer. The fuel consumption has nothing to do with it except for the CO2 emissions which are in direct proportion (correcting for fuel type for passenger cars, a significant portion of which are diesel-powered in the EU).
 
regder said:
Interesting points, I remember reading something along the lines of it being better for the engine to run on the rich side to get the catalytic convertor up to operating temperature quicker and to maintain it. Running the engine leaner than that, or even at stoich may cause premature catalytic convertor wear, not to mention increased emissions. Same reason why your fuel economy gues into the gutter in the winter if you do a lot of cold starts. Effectively burning more gas, but getting cleaner emissions out of the pipe. I could be wrong on the above, but pretty sure it's something along those lines.
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A 3-way catalyst (oxidizes CO and HC simultaneously with reducing NOx) must operate at stoichiometric - the chemically-correct air/fuel ratio, neither rich nor lean. If it is fed a rich stream, it will be unable to oxidize all of the CO and HC. If it is fed a lean stream, it will be unable to reduce NOx. This requires a closed-loop fuel delivery system (using a lambda sensor to allow the engine controls to achieve this). During certain conditions, e.g. warm-up, the lambda sensor will not be giving a reliable signal. Traditionally engines have had to run rich during warm-up in order to run at all. This results in high emissions during cold starting and warm-up - but those count towards the total, so the manufacturers have been doing various things to address it. One way is to intentionally use late ignition timing (to raise the exhaust temperature) and squirt extra air into the exhaust (so that the catalyst has some oxygen that it can oxidize the CO and HC with) which encourages faster catalyst warm-up. Another way, which is becoming more popular with direct-injection gasoline engines, is to run the engine in stratified-charge mode during warm-up with late ignition timing and an overall lean air/fuel ratio in the chamber, this avoids having to use an air-injection system. NOx is generated by high temperature, which is usually not a big problem during warm-up anyway.

Motorcycle emission control systems are nowhere near this sophisticated yet. Most of them use open-loop EFI set to run somewhat rich, air injection into the exhaust to give the catalyst something to work with, and an oxidizing catalyst which does nothing about NOx. For less stringent emission regulations, it works but results in sub-optimal fuel consumption.

I would expect that upcoming Euro 4 regulations for motorcycles in Europe will finally get the motorcycle engine manufacturers to smarten up. It's not like they don't know how to do it. Lambda sensors are not expensive and that's the only additional sensor required. Extra ECU programming is required, but that's cheap nowadays.

If a lowly CBR125 can have closed-loop EFI with 3-way catalyst and no air injection system (engine runs at stoich) then surely everything else can, also ...
 
Brian P said:
... limits are specified in terms of grams per kilometer.
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This saddens me.
I guess it also explains why bikes really should not be eligable for HOV lane access (with a single rider).

Up till now I had accounted for this by telling myself that even if my emissions per litre of fuel were worse, surely by virtue of burning so much less fuel, I was still generating less emissions overall.

I don't understand why they wouldn't just apply the emissions standards across all vehicle types. Hopefully the government and manufacturers smarten up. This will definately be a consideration with my next bike purchase.
 
jolomatic said:
I don't understand why they wouldn't just apply the emissions standards across all vehicle types. Hopefully the government and manufacturers smarten up. This will definately be a consideration with my next bike purchase.
Click to expand...

I think in the past it made sense because otherwise it would have been too expensive. However these days it's a smaller leap to go from the basic emissions controls they have now to something more up to date. Also, the motorcycle industry is basically self-regulating as far as emissions go, and they had given themselves a LOT of time to stay on Euro 3. Euro 4 is supposed to be the target for 2012, and Euro 5 for 2015 ... still a considerable lag behind autos.
 
Some motorcycles made nowadays should be considerably below the regulatory limits. Some manufacturers use the same equipment on a given model and calibrate it to meet the most stringent standard worldwide, and if the next generation of emission standards is within the expected production lifetime of that bike, it will be designed to meet that standard. The Honda CBR125 and CBR250 are like this, and although I don't know it for sure, I would expect that BMW models are like this.

Others ... use cheap crappy paid-for old technology whenever they can get away with it. Kawasaki, I'm looking at you.

If you're concerned about emissions then the number one thing you can do is make sure your bike is in a good state of tune, and don't circumvent emission controls, particularly by changing out the exhaust system. If there's a catalyst, keep it.
 
Brian P said:
A 3-way catalyst (oxidizes CO and HC simultaneously with reducing NOx) must operate at stoichiometric - the chemically-correct air/fuel ratio, neither rich nor lean. If it is fed a rich stream, it will be unable to oxidize all of the CO and HC. If it is fed a lean stream, it will be unable to reduce NOx. This requires a closed-loop fuel delivery system (using a lambda sensor to allow the engine controls to achieve this). During certain conditions, e.g. warm-up, the lambda sensor will not be giving a reliable signal. Traditionally engines have had to run rich during warm-up in order to run at all. This results in high emissions during cold starting and warm-up - but those count towards the total, so the manufacturers have been doing various things to address it. One way is to intentionally use late ignition timing (to raise the exhaust temperature) and squirt extra air into the exhaust (so that the catalyst has some oxygen that it can oxidize the CO and HC with) which encourages faster catalyst warm-up. Another way, which is becoming more popular with direct-injection gasoline engines, is to run the engine in stratified-charge mode during warm-up with late ignition timing and an overall lean air/fuel ratio in the chamber, this avoids having to use an air-injection system. NOx is generated by high temperature, which is usually not a big problem during warm-up anyway.

Motorcycle emission control systems are nowhere near this sophisticated yet. Most of them use open-loop EFI set to run somewhat rich, air injection into the exhaust to give the catalyst something to work with, and an oxidizing catalyst which does nothing about NOx. For less stringent emission regulations, it works but results in sub-optimal fuel consumption.

I would expect that upcoming Euro 4 regulations for motorcycles in Europe will finally get the motorcycle engine manufacturers to smarten up. It's not like they don't know how to do it. Lambda sensors are not expensive and that's the only additional sensor required. Extra ECU programming is required, but that's cheap nowadays.

If a lowly CBR125 can have closed-loop EFI with 3-way catalyst and no air injection system (engine runs at stoich) then surely everything else can, also ...
Click to expand...

Thanks for the detailed explanation. I find it very strange that in today's sport bikes, that have such a narrow focus on maximizing performance, they don't rely on the readily available tools for monitoring engine operation (wideband o2?) to improve performance, and as a byproduct improve emissions.
 
I just watched this episode. For one, the newer Mythbuster episodes seem entirely too scripted and contrived for my tastes. After having watched several of their early season episodes, I've noticed they had a lot more natural discussions and explanations of the myths they were busting than compared to the newer episodes, such as this one. I suppose it would be alright if they were talking to the camera (at the audience), but they're not, they're talking to each other, having these fake, scripted, conversations and try to sell it as a legit one-person-uninformed normal conversation when you can clearly tell they both know exactly what the other is talking about.

Anyways, that's my little off-topic Mythbusters rant =P. Now, regarding specifically this episode, I was very disappointed in how rushed they presented everything. They rashly picked random bikes and cars from 80s, 90s, 00s, had them drive the same course, then presented the emission figures. The results for the motorcycles were all over the damn place because they used completely different sized bikes to represent each decade. Why they didn't just get an exact model bike/car from each of the same decade, or at least as close as possible, I have no clue.

As for the second part, with the fairing, that was pretty interesting, albeit crude. It was awesome they chose a WR250X to mount it on though. A really interesting result, just from the fairing and aerodynamic perspective was the MPG efficiency. Without the fairing on a closed test course with variable driving conditions, the WR250X got around 53 MPG if I recall. With the fairing on, it got 70, which is quite a damn increase considering the fairing itself must have weighed nearly at least 50lbs (steal cage). It goes to show just how aerodynamically crappy some motorcycles are. Although, granted, with that fairing, you really couldn't do any off-roading either!

As for the emissions part, i'm no expert, but doesn't CO2 still fall unded that category? If so, then EVERY bike they tested had better CO2 emission by virtue of better fuel mileage, no surpise there. CO2 comprises 90% of the emissions. Again i'm pretty naive in this area, but wouldn't a signficant reduction in 90% of a bad thing be considered a much better impact overall than a small reduction in 10% of that same bad thing?

I'm not sure if that last sentence makes any sense, but whatever, I think you get my point. CO2 is BAD for the environment too, lest we not forget!
 
OK, hold on. I never heard of this before.
If you have a car or truck that is 4 wheel drive all the time, emission testing cannot be done because of the other set of tires rotating at the same time, because there is only one set of rollers?????

Man, that's so damn cool.

And I almost bought an X-drive.



mma01 said:
First mod almost every turbo subaru owner does is ditch the pre-turbo cat completely and get a catless downpipe or highflow replacement. There are very few 4 wheel drive drive clean facilities so they only need to pass the idle test - off boost, they are pretty clean even without the 3 original cats. On boost is a different story altogether.
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The dyno testing is being phased out, anyway, within the next couple of years. From then on, they'll just hook up OBD-II on a special scanner, and if it has no codes and readiness is set, it's good to go.

Not having a "check engine" lamp and having "readiness" set are two different things. A lot of aftermarket chip-tunes are not designed with this in mind. If the programming has just bypassed the function checks, then there might not be a MIL and there might not be a code, but there might not be "readiness" either ... I don't think anyone knows publicly yet, how sophisticated their scan is going to be.
 
So what will happen with cars that have no OBDII?
 
Low rider said:
Not computing.
Readiness? What is?
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Roughly speaking, inside the EFI ECU the computer has a series of bits and counters, and a series of programmed tests associated with each bit. Periodically it runs the programmed test on the system in question (e.g. your evaporative system or the EGR valve). If it passes the test then it sets "readiness" for that test. If it fails the test then it clears "readiness" and usually starts a counter, and when the test is repeated again, it either sets "readiness" and clears the counter if it passes or increments the counter. When the counter reaches a certain number of test failures in a row then it sets the trouble code for that failure and you get a MIL "check engine lamp" on the dash.

If the system is working perfectly then "readiness" will be set for all of the emission subsystems. If there is something potentially out of whack then there will be a pending code (your MIL is not necessarily on yet) and "readiness" won't be set. If the computer finds that the subsystem repeatedly fails then you'll have that orange MIL on the dash and "readiness" won't be set.

The reason they do this is to minimize the number of nuisance MIL's for systems that are subject to normal fluctuations. Evap system due to temperature/pressure variations in the fuel tank, misfires because the occasional miss is somewhat normal, plausibility checks for sensor range (e.g. if the throttle is showing the throttle closed then the mass-air shouldn't be indicating an airflow corresponding to full throttle and vice versa), etc.

There are many other systems that are either working or they aren't, the test is "is a signal being received", and if the answer is "yes" then it sets "readiness" and if the answer is "no" then there is an instant MIL. Not receiving an electrical signal from a sensor is one such example. If you forget to plug in your mass air sensor, that's an instant MIL and an instant "readiness not set".

OBD-II is extremely sophisticated ... there is A LOT of programming in that ECU! Every time it runs a test and the test fails, it memorizes all of the relevant conditions so that a technician can see later on the circumstances under which the code is being tripped ...

Regarding chip-tuning, the reason that SOME aftermarket chips or ECU programs could be trouble is that the way they prevent the MIL from coming on is that they simply disable the function test for that code. If it never runs the function test then you'll never get that trouble code and the MIL will stay off ... but it won't set "readiness" either. You, as the user, would never know this unless you scan it yourself with a scanner that is smart enough to look for this!

unL33T said:
So what will happen with cars that have no OBDII?
Click to expand...

Everything (almost) since 1996 has OBDII. I don't know what they're planning for older cars. They'll probably just use the idle test that they've been using up until now. There are not all that many pre-1996 cars on the road any more. Some 1996 and 1997 VW diesels don't have OBDII, in fact, some of them don't have any engine electronics at all! (1997 was the last year for the old mechanical-fuel-injected VW diesel) But those are an automatic pass if they're not belching black smoke at idle ...
 
Everything (almost) since 1996 has OBDII. I don't know what they're planning for older cars. They'll probably just use the idle test that they've been using up until now. There are not all that many pre-1996 cars on the road any more. Some 1996 and 1997 VW diesels don't have OBDII, in fact, some of them don't have any engine electronics at all! (1997 was the last year for the old mechanical-fuel-injected VW diesel) But those are an automatic pass if they're not belching black smoke at idle ...
Click to expand...
I see. I was wondering if they are going to change the drive clean exemption again. It used to be over 20 years but then they changed it to '87 or older. A lot of people don't know it has changed so I've seen a lot of post-87 (but over 20 years old) car ads saying they are exempt when they are actually not. I guess that's kind of off topic though.
 
Brian P said:
OBD-II is extremely sophisticated ... there is A LOT of programming in that ECU! Every time it runs a test and the test fails, it memorizes all of the relevant conditions so that a technician can see later on the circumstances under which the code is being tripped ...

.
Click to expand...
The only problem with that is my $70 OBDII reader also clears all the codes... Pass every time!!!
 
Does it just clear the codes, or does it set readiness? 2 different things.

OBD scanners aren't supposed to set readiness, they're just supposed to clear the codes so that the car itself can re-run all the checks and set readiness by itself.

But then, computers can be programmed to do anything someone programs them to do.
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