Hot answers tagged

52

Safety, comfort, noise and space are the things that come to mind. Safety Exhaust gasses are hot as hell. Hot enough that we put heat shields all over the exhaust line. In engines, we are actively trying to remove heat. Adding more from the exhaust goes completely against that and would increase overheating. Also, would you want a hot exhaust pipe near ...


46

Well, we can have a pipe going out the front of a car as in this design here: or its heavier predecessor: Arguably, the aerodynamic properties are not optimal in both, but here is a similar approach where aerodynamics have been considered for sure: other designs (like trucks) do account for aerodynamics by putting the exhaust tubing behind the relevant ...


37

It signifies that the car is running absolutely correct. Here is the reason why: A gasoline (petrol) molecule is made up as such: C8H18 (or 8 Carbon atoms and 18 Hydrogen atoms) Energy is obtained from the combustion of it by the conversion of a hydrocarbon to carbon dioxide and water. The combustion of octane follows this reaction: 2 C8H18 + 25 O2 → ...


14

Several things; Exhaust coming out the front is dangerous. If the fumes are ingested into the cab the driver may be harmed. Normally a car is driven forward. If the exhaust is coming out the back this gives the least chance of the fumes making it inside the cab. Mufflers are large components. Often there is not enough room inside the engine compartment to ...


12

The recall is not to remove the cheating logic; it is to actually make the engines meet emissions requirements so they do not violate the law any more. From Autoblog's initial article on the scandal: Volkswagen intentionally installed software in nearly a half-million diesel vehicles that helped the cars evade substandard results on emissions tests, the ...


12

A catalyst is a chemical that contributes in a chemical reaction but remains unchanged after the whole reaction is complete. In a catalytic converter platinum is the catalyst that converts unburned hydrocarbons into H2O and CO2. If there is too much unburned hydrocarbons going into the catalytic converter, it greatly increases the temperature inside the ...


11

They aren't better for the environment But efficiency is often confused with emissions. The average person would think that because diesel engines are more efficient and burn less fuel, they must be less harmful to the environment. I think few can be more authoritative than the folks at Bosch on why diesel engines are so prevalent (emphasis my own)¹: ...


9

Gasoline is a pretty toxic liquid. And it evaporates pretty easily. The Carbon Cannister is a system to help keep toxic fumes from gasoline out of the environment. So here's how it works. You fill your car up with gasoline at the gas station. You add a gas cap to seal off the tank. Cool, no evil fumes can evaporate from your gas tank and contaminate ...


9

The exhaust also creates a pressure differential, which can help scavenge exhaust gases from the chamber. So a properly tuned exhaust will therefore increase the fuel efficiency of the engine. Whilst an engine without an exhaust would make more power, it would also consume more fuel.


8

For a pre OBD-II vehicle such as this one, the best thing to do is get it running as smoothly as possible, using normal maintenance and repair procedures. This means no misfiring, smooth idle, smooth acceleration, not overheating, etc. The same stuff you'd expect to work well in every day driving. There should also be no check engine light. This vehicle will ...


8

Gasoline is made in large batches. Each batch has a number of attributes that should be met; Octane, specific chemistry, volatility, contaminates, ethanol content, and others. The output is dependent on the crude that went into the refinery and the processes the refiner has at hand to process it. Refineries vary in there capabilities. There are over 60 ...


7

Looking at the description of the California O2 sensor for your car, the only thing different on it (besides the internals) is the electrical plug. The wrench which you tighten it down with is 7/8", which means the sensor bung should be the same size as well. I don't think there is any real external difference between the California and non-California sensor....


7

tl dr: By adding a throttle plate, it creates the vacuum needed to draw in gasses from an EGR valve. Since diesel engines are designed to run lean, they don't need throttle plates to run. They utilize the amount of diesel fuel needed to keep the engine running and to provide the work needed to do the job required of them. One of the inherent issues with ...


7

The voltage being a little low (13.75 is not low enough to be considered a problem in any case) is not going to affect their RPM reading - as it's the frequency of voltage variations that is measured to get your RPMs. I'd be tempted to say your tach is out slightly. You could ask them about that. There is a smartphone app that you can use to gauge RPMs - ...


7

Adding to the excellent answers already given. An important point to note is that we need to have a catalytic converter somewhere in the exhaust a short exhaust will not have room to fit it. Then there are a host of other things car manufacturers determine while designing an exhaust system. For an engine to have optimum efficiency, the intake , ...


6

since installing new 02 sensor engine light has not reappeared after clearing w/obd2 device and torque free app. TOTAL COST= ~$27 7 31 13 ordered Koolertron F-12 ELM 327 OBDII PC Car Diagnostic Scanner Electronics EggDeal via amazon $9.50 to use w/android smartphone torque free app to read & clear obd codes 8 10 12 friend sprayed hoses he knew to be ...


6

Every gallon of fuel your vehicle burns produces a gallon of water out of the exhaust. If the weather is cold you will see it as steam. If the rear of the exhaust system is still cold even in warm weather it will be for a short time after start-up, you will see the drips. On a hot engine/exhaust you will not see any drips from the tail-pipe. If there are ...


6

The federal test procedures for vehicle emission certification(FTP) is run on a dynamometer. It starts with the vehicle at an exact temperature and barometric pressure and humidity. It is run in a lab that has carefully controlled exact air conditions that are maintained throughout the test. The vehicle is kept is stored at the test temperature for hours ...


6

Combustion Chemistry from Princeton This isn't much of an answer but here is some data from a Princeton class related to Combustion Chemistry. You will see that the table you are looking for is plotted. Here is the link to the PDF. Manufacturers of Emission Controls Association Here is a study from Manufacturers of Emission Controls Association. ...


5

Just to add to the other answer as I ran into this same issue, what kind of emissions do I have on my mitsubishi galant? I had this code: P0421 and I had to replace my O2 Sensor & the catalytic converter but I wasn't sure if I needed the CARB (California Air Resource Board) compliant ones or not. There is a label that identifies what type you have. I ...


5

There are two ways to tell. Your local ford dealer can tell by decoding the VIN (the vehicle indentification number). It is usually located on the dashboard at the base of the windshield on the drivers side. If you look under the hood there is usually a sticker on the frame near the radiator that will say complies with California or 49 state emissions. The ...


5

Open up the hood and look at the emissions control system label. That will indicate whether it meets California emissions standards or not. See this page from the California DMV for what to look for. Also, at least for California (Not sure about other California-standards states), you can register a 49-state vehicle in California after you move there if ...


5

Locally worse, globally better Diesel exhaust versus gasoline: about 15-20 % less CO2 about 4-100 times the NOx (highly temperature dependent, mitigated by proper use of diesel exhaust fluid, ref the VW scandal) and a fair amount of soot (esp. before common rail, mitigated by a particle filter). What this means for the local environment: Local CO2 is ...


4

As a vehicle technician for BMW I can assure that it is good for your engine to get rid of EGR. EGR systems are there to improve the exhaust gas quality and slightly win a few miles on a tank (in theory). What really happens is quite different. Your oil will become polluted quicker, your manifold / intake will get clogged by excessive amounts of soot and ...


4

Disadvantage is that tampering with emissions systems makes a vehicle no longer street legal. Other than that, it probably won't hurt anything at all. I don't see how removing EGR will increase power though. EGR closes at high power settings anyways. The gain would be entirely from some other feature of the racepipe (perhaps it's bigger). The fact that ...


4

The diagnostic trouble code is not to be looked at as a root cause of the system failure. (example. Replacing a blown fuse is NOT a solution) In all cases there are multiple components that can cause the same code to trigger. For instance, a possible vacuum leak, or EGR problems, and even a PCV issue, could all show o2 sensor readings with tendencies towards ...


4

With the check engine light on, the car is going to be running a fixed set of parameters from the Engine Control Module. For instance Fuel Pressure will be held at max pressure and timing and spark adjustments (if done electronically) will not retard or advance. One of the reasons this happens is because the Engine Control Module is not recieving all of ...


4

Yes, it will probably be necessary to fix the problem in order to pass emissions requirements. The secondary air injection pump on the Beetle is apparently used to accelerate the transition from cold start to hot catalytic converter operation. Without this system, it will take longer for the catalytic converter to reach operating temperature. The ...


4

The way I understand the issue, VW wanted to increase performance and fuel mileage. The easiest route was to allow the car to pollute more. This was not possible while meeting the stringent emission standards So they developed software that would allow the vehicle to pass the emission requirements only while in test mode. Then essentially alter the emission ...


4

I think you miss-understand how OBD tells that your car is passing emissions. All the car does is make sure that the emissions control systems are functioning and then it hopes that what is coming out of the tail pipe is OK. The car verifies that the fuel mixture is within tolerance, that the EGR is functioning, that the evaporative emissions system has no ...



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