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 ...


51

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 → ...


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 ...


40

You don't have to have an catalytic converter, they aren't required for the operation of an engine. Catalytic converters use chemical reactions to reduce the pollution in internal combustion engine exhaust, and are emissions control devices which are required by regulation in many countries. So it's technologically possible to build a car without one, it ...


23

The main purpose of putting it right after the manifold is heat. The cat functions best when hot. Placing it as close as possible to the manifold helps the cat heat faster and stay hotter, which produces better results in what it's designed to do: curb exhaust emissions.


22

First of all you're not smelling CO (carbon monoxide) as that is an odorless and colorless gas. What you are likely smelling are combustion byproducts and that is not at all uncommon in the engine oil. The transmission oil is another story and I suspect you are just smelling the oil itself. The thing I'd be concerned about is a sharp "burnt" smell that ...


21

This is a term used to describe the shapes of the pieces of tubing used to create exhaust pieces with very hard turns. Imagine an apple pie. Now cut it in 8 individual pieces (triangles). You can now make complex shapes by arranging the pieces in different ways. In the image below, you can see how each weld marks off each piece of tubing. If you pay ...


21

If there was ever that much water in the muffler such that it was sloshing around, it would be a sign of catastrophic failure in the engine, such as a blown head gasket and the "water" would actually be antifreeze/water mix from the engine. However, my understanding of your question is that you're interested in the normal case of a few drops of water ...


20

Briefly: The exhaust pipes are shaped to suck gasses out of the combustion chamber over a range of RPMs. Somewhat longer: Imagine a 2 stroke engine without an exhaust*1. When the exhaust valve opens, burned gasses leave the cylinder. Leave the valve open for a long enough time and the cylinder will be at ambient air pressure. Now run the engine at a ...


20

There is this nice animation of a 2-stroke engine with an expansion chamber Source It works like this: While moving downwards after ignition, the piston exposes the exhaust opening, and the burned gas streams into the exhaust pipe like a (high pressure) shock wave. Due to the inertia, this gas will create a slight vacuum wave behind it, which helps to ...


16

Yes, at least half of the exhaust is coming straight out of that gap without passing through the muffler. As you've noted, this leads to an increase in noise (or music, depending on your taste). To my eye, that looks like a hassle to fix on your own. There appears to be the rusted remnants of two bolts holding the Y-pipe to the passenger side muffler and ...


15

Cats can stop functioning in a couple of ways: physical deformation due to high temperatures According to this article, the catalyst melts at temperatures above 2100 °F (1200 °C). In the event of a meltdown, the catalyst gets permanently damaged, at which point it doesn't scrub the nastiness out of the exhaust gases and serves as a major exhaust ...


15

That will depend on the market regulations for the target country ie which country that vehicle will be sold in. Cars built to be sold in Europe & US have to meet stringent regulations as regards emissions so they are required to have a catalytic converter. Other countries may not (yet) have that requirement, so a "cat"may not be necessary. The large ...


14

Sounds like a lean condition Here's something to chew on regarding identifying a lean or rich condition on a motorcycle. Symptoms of Lean or Rich carb settings on a motorcycle What I believe you are hearing is backfiring. It isn't loud because the baffling systems on modern motorcycles are so effective. If you have a lean condition that suddenly appears ...


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 ...


13

Even before a cat plugs, you can test your cat using a laser thermometer. You are looking to compare the inlet and outlet temps on your cat. Do the following: Run the engine up to operating temperature (at least ten minutes so the cat should be fully warm) Check and record the inlet temperature. You're looking to measure the temperature right where the pipe ...


13

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 ...


13

IMHO that powder is either: Dust, that got "burned" by the hot exhaust manifold and transformed into some yellow-looking substance. Sulfur, as the color has a striking resemblance to sulfur. The presence of sulfur could indicate a leak and a faulty emission treatment system. There are test strips available to test for sulfur. Should you decide to try a test ...


13

Yes, in theory. The government doesn't care how your engine hits the required emissions numbers. As an engine designer, you get a tabula rasa, and are free to build any system that will do the job. Catalytic converters seem to be a winning choice for most if not all engine builders, because engine building is largely a costing game and cats are the ...


12

Basically you have an exhaust leak, it's dangerous (to you in the form of carbon monoxide) and should not be ignored. An easy way to check for the leak is to pull a vacuum line off the intake and suck a small amount (1 - 2oz) of transmission fluid into the intake via that vacuum line. Make sure the vehicle is outside, because it's going to smoke a lot. The ...


12

Pressure drop is to flow as voltage drop is to current With all else equal, removing the resonator or muffler will reduce the restrictions in the exhaust pipe. This means that the ability of the exhaust headers to flow gases will increase, not decrease. However, this does not necessarily mean that the engine will produce more power, since that is the ...


11

What does it do? (better performance [and how so?]? better mileage? cooler sounds?) It depends. One of the goals of a performance exhaust is usually to create a tuned system: A tuned exhaust system is an exhaust system for an internal combustion engine which improves its efficiency by using precise geometry to reflect the pressure waves from the ...


11

Human Error I have firm belief that the cause of burned valves with short pipes is due completely to human error, lack of understanding and poor judgement. I believe this myth has been perpetuated by actual 'evidence' of having burned valves but the attribution of the cause is incorrect. Guy with burned valves story He has a hot rod he builds. He uses ...


11

I certainly don't claim to have any special inside knowledge as to why Porsche engineers decided to route the exhaust that way, but I think that we can analyze the possibilities and trade-offs from an engineering view and perhaps see how one might come to such a conclusion. The possible options I think we can safely eliminate any front-facing exhaust ...


11

A muffler is a harmonically tuned chamber that is designed to reduce the noise created by the combustion process. Mufflers are usually designed with specific sound frequencies in mind. When a vehicle is being designed, the engineers will measure the sound frequencies emitted by the engine, and using harmonic tuning, create mufflers that specifically cancel ...


11

If your engine was running / exhaust manifold hot; the yellow is then zinc oxide. It would result from a galvanized steel manifold which has naturally oxidized. At room temperature the ZnO is white , I forget the temperature where it turns yellow.


10

I have typically replaced my stock exhaust systems with aftermarket race systems. Many stock exhaust systems have dual-wall designs so you never see the pipe that the exhaust is actually flowing into. All of my exhaust pipes glow orange/red when I ride them hard. It's fine and completely normal. Yamaha dirt bike with exhaust glowing red. Here's a bonus ...


10

Various reasons: It is close to the ground - where you have water, salt, grit etc. It is typically not made of rustproof metals, but is considered a consumable, with portions like the catalytic converter being relatively short lived, so spending lots extra to protect it would be pointless. The exhaust gasses include corrosive gases such as sulphur dioxide, ...


10

Looks like part of the muffler to me. You should have it replaced it could end up obstructing the exhaust.


10

They Exist I was unable to find any manufacturers that have rolled out this technology into production vehicles but there are several manufacturers that have the baseline technology in R&D Formula 1 Formula 1 has always been a playground for engineers and with the new rules implemented in 2012 the current platforms are running this technology and ...


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