Hot answers tagged

19

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 ...


18

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 ...


13

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 ...


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

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 ...


11

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 ...


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 ...


10

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 ...


10

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 ...


9

Cabin filters on modern cars use something called activated carbon (or at least some of them do) which is basically two paper / cotton sheets either side of a fine layer of carbon particles. It looks to me as though your cabin filter has a hole in it and therefore is blowing carbon all over the inside of the cabin. I'd take it back to wherever installed ...


8

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 ...


8

Possibilities Yes! Absolutely you can have this done. The quality of work may vary depending on the level of experience of the shop you commission to do the work but you could end up with something like this, if you want. I would not remove the entire exhaust and take it to a shop. How are they going to know where the exhaust should run without ...


7

Under normal use (non-performance type use), the valves, both intake and exhaust, should last the life of the engine. If and when they do leak, it will not take long for the valve to become a burnt valve. In your case, I doubt they were leaking prior to pulling everything apart. If the exhaust valves had leaked, they would have been fried. If valves do not ...


7

This NIH (National Institutes of Health) Study monitoring CO inside the cabin of a vehicle during commutes over an extended period has some pretty interesting data. From the study the mean CO concentration was 9.8 ppm, with a standard deviation of 5.8 ppm Here is another study Here is another study that reflects older data ('80's and '90's) sampled ...


7

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 ...


7

I would not advise running with open headers or decatted exhausts. NOx and CO emissions are not a nice thing to breathe in. Plus the stench will make for an uncomfortable driving experience.


6

The bottom line is yes, if you drag your exhaust over the speed bumps, it will cause damage to your car. It will be mainly localized to the exhaust on the vehicle. Besides flattening out the exhaust pipes, you also put stress on the joints and the hangers for the different mounting points. If you hit the exhaust hard enough, you can cause further damage to ...


6

If you don't want to weld, you can use a joint like this: NOTE: The above image is for demonstration purposes only. I couldn't readily find one which was 2" on each side. The only difference is, the inside diameter on both ends would be 2". Your outside diameter 2" pipes would fit inside. Use two muffler clamps to attach. You'll need to match the outside ...


6

The dollar bill test is quite simply using a dollar bill (any denomination ... doesn't have to be American currency, even) and placing it against the exhaust tip while the vehicle is idling. You are looking/listening to what the bill does while against the exhaust tip. If it just flutters there without making much noise, you have healthy exhaust valves. If ...


6

Generally when an engine runs, if it is running lean, it will run hotter. If an engine is running rich, it will run cooler. Each individual cylinder is no different. After an engine is completely warmed up, if one measures each cylinder at the same basic place on the exhaust manifold, you can get an idea of which cylinder is running lean and which is running ...


6

While zaid's answer is correct for the OP's 4 stroke engine, the exhaust design for a 2 stroke engine can be more complicated. Rather than benefitting from a free flowing exhaust, exhausts for 2 strokes are often tuned to create wave fronts that suck exhaust fumes from the cylinder and at the same time stop unburnt fuel being sucked out. Small 2 stroke ...


5

You shouldn't need to use sealant on the gaskets. Most exhaust manifold gaskets either come with their own sealant (like Fel-Pro's do with the silver looking stuff), or they are metal and don't require it either. I believe sealants (such as high temp Permatex Copper) will just burn off anyway, because the heat at the head/header interface is far beyond what ...


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

A few things to consider if you end up doing this: A longer shaft will reduce the speed that you can safely spin the turbos up to It's got to do with something engineers call rotordynamics, although I highly doubt you would need to spin something up to 125,000 RPM for a turbojet application :) You may also find that the existing journal bearings are not ...


5

One way I could explain it from that photo, is that there will not have been any snow under the car, so the exhaust fumes will have easily been able to exit from the tail pipe and spread under the car. The fumes will then have gone into the engine compartment and from there could have been sucked in by the fan. Alternatively the exhaust could have had a ...


5

Popping I too have a Tiger 800xc (2013) and have noticed it popping when downshifting and revs are too high for that gear. I did notice a significant difference in this behavior after 12,000 mile service, and using 91 RON fuel (not all brands and outlets are same... for me ARCO has worked best). At this point, I consider some of it as normal behavior. ...


4

Q1: Is that a reason to worry or replace them, provided that they don't actually malfunction? The only reason you'd want to replace stock manifolds is if they are cracked (or broken) or if you want to do a performance upgrade. Q2: Do exhaust manifolds have a propensity to rust faster than other parts and why? Yes. The reason is because of the ...


4

A little water is normal especially in colder weather. It is not likely that it is coolant coming out of the exhust, if it was you'd have a lot of other symptoms. If you vehicle is leaving a noticeable black dusty or dark damp patch behind then this may indicate an issue. Along with that if your mileage has taken a slight dip as well as your vehicles power ...


4

There is nothing wrong, water is a byproduct of gasoline combustion. 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O where C8H18 is the gasoline reacting with oxygen (O2) and giving Carbon-dioxide (CO2) and water (H2O) as the byproduct. So, this simply is: 2 * Gas molecules + 25 * Oxygen Molecules → 16 * Carbon Dioxide Molecules + 18 * Water Molecules So ...


4

According to this website from the University of Washington: Manifolds and/or exhaust pipes on some vehicles can reach 1200 degrees F. It is rare to find temperatures this high in normal operation. If your laser thermometer can read up to at least that high, you should not have any issues. EDIT: As pointed out by @Zaid below: ... if a cylinder ...



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