Questions tagged [exhaust]

Questions about Exhaust systems, Catalytic Converters and Headers/Manifolds

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38 votes
3 answers
375k views

What does a water-like drip coming out of the exhaust of the car signify?

Sometimes while driving in the traffic, I come across a car or two which would be dripping water-like drops from its exhaust steadily in 4-5 second intervals. I tried to ask a couple of people at the ...
Sandman's user avatar
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32 votes
7 answers
12k views

What is the point of the exhaust?

I was thinking today, what is the actual point of an exhaust? Why can't we just have a pipe going out the front of a car instead of taking all the gases to the back of the car? I can only see ...
George's user avatar
  • 6,545
31 votes
2 answers
30k views

Why do two-stroke engine exhaust pipes look so strange?

Two stroke gasoline engine exhaust pipes are shaped strange. They expand into a wide diameter and then shrink down to a very small diameter where the exhaust gasses emerge into the environment. - ...
DucatiKiller's user avatar
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26 votes
12 answers
257k views

What is the best way to remove a stuck/rusted exhaust bolt?

I'm trying to disassemble the exhaust system on a 2000-2003 Nissan Maxima and I'm having trouble removing one last bolt. It's got a 14mm head and its just plain STUCK. I've tried soaking it overnight ...
NoCarrier's user avatar
  • 2,902
21 votes
1 answer
3k views

What does pie cut exhaust mean?

As the title says, when looking at building a custom exhaust system I've heard the reference called pie cut exhaust but I was unable to find any definition or terminology so I was curious to know what ...
Hᴇʀʙɪᴇ's user avatar
19 votes
1 answer
26k views

Is this what is making my car sound like a racecar?

Recently, my car (2000 Mercury Grand Marquis) started sounding like a racecar: the engine became very loud. There's clearly something going wrong with the exhaust system. I'm trying to understand ...
cheeken's user avatar
  • 293
16 votes
3 answers
15k views

How can I tell if I have bad cats?

No, not that cat! Catalytic converters - or "cats" - have a nasty habit of failing with age. What are the symptoms associated with a cat that's gone bad? Are there any tests that could definitively ...
Zaid's user avatar
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16 votes
5 answers
76k views

When car is standing still, I smell Diesel exhaust. Why?

In my 2003 Opel Vectra, the cabin air smells of Diesel exhaust while stopped at e.g. a red light. The exhaust smell goes away when driving, and it also doesn't come back if I turn the ventilation off ...
Torben Gundtofte-Bruun's user avatar
16 votes
2 answers
11k views

Should motorcyle exhaust headers ever glow red hot

I've got a '99 Pegaso 650 which hasn't been running for about 7 years. It's was in a quite a deteriorated state when I got it, i.e. seized carbs, tank full of water, sump full of an ugly fuel/oil mix, ...
Ian Oakes's user avatar
  • 668
13 votes
7 answers
6k views

Why have I had to replace so many exhaust pipes?

My largest car maintenance cost is exhaust pipes, mostly catalytic converters. I do not think this is the case for most people. What am I doing wrong? I tend to buy cheap cars (<£500), change the ...
User65535's user avatar
  • 385
13 votes
4 answers
7k views

What is this yellow powder on my exhaust manifold?

I took off the heat shield from the exhaust manifold on my 2003 Nissan Primera while looking for an exhaust leak, and I noticed this yellowish poweder / dust on it: Any ideas what it is? EDIT ...
Robert S. Barnes's user avatar
13 votes
2 answers
11k views

How does condensed water get sent out of an exhaust system?

We've all seen water dribbling out a car exhaust when we're following someone accelerating out of a stoplight. I know that the water is an inevitable product of combustion, but I find myself wondering ...
Daniel Griscom's user avatar
13 votes
1 answer
5k views

What are the pro's and con's of compression braking vs. exhaust braking?

My truck supports 2 types of engine brakes: Compression release brake Exhaust brake Both can be selectively deactivated using switches. What are the pro's and con's of each type of engine braking ...
niko's user avatar
  • 343
12 votes
4 answers
6k views

Is it possible for a vehicle to be manufactured without a catalytic converter?

Can a new vehicle from a plant be produced without a catalytic converter? Is it possible? I am a lecturer at a college in Zimbabwe, and my students recently asked this question, so I am researching.
Charly K Mwamber's user avatar
12 votes
1 answer
7k views

What are the tell tale signs of a catalytic converter that might be going bad?

I've owned two vehicles whose catalytic converters were recalled due two a couple of reasons: one being the quality of the CC and the other being a reduction in power due to a material building up and ...
Cᴏʀʏ's user avatar
  • 1,190
12 votes
2 answers
4k views

Can (possible) exhaust system damage cause random misfires?

2001 Honda Prelude SH. About three weeks ago while travelling 10-15 mph I pulled off the side of a dirt road to park and it turns out there was a row of a few railroad ties laying in the grass there....
Jason C's user avatar
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11 votes
3 answers
9k views

What's the purpose of having the cat right after the exhaust manifold

In a lot of the cheap cars I have looked at their exhaust components, I always find the catalytic converter right after the exhaust manifold instead of being after the down/front pipe in a "typical" ...
method's user avatar
  • 2,760
11 votes
2 answers
14k views

Do naturally aspirated engines need back pressure in the exhaust pipes?

I was thinking about removing the resonator from my exhaust but I watched a video saying that it will negatively impact the car as naturally aspirated cars need back pressure as it helps get rid of ...
method's user avatar
  • 2,760
11 votes
3 answers
30k views

Is the catalytic converter broken? An odd rope is coming out of the exhaust pipe

Old Volvo GL 440 and this is coming out of the exhaust pipe. No noise, all working fine but this cosmetic thing: does it mean that the exhaust gases are now not well filtered out? Does this mean that ...
hhh's user avatar
  • 451
11 votes
2 answers
1k views

Performance Exhaust -- what, how, why?

I've seen performance exhaust pipes on sale for cars and motorcycles, and my questions are these: What does it do? (better performance [and how so?]? better mileage? cooler sounds?) Is/how is it ...
Ben Mosher's user avatar
11 votes
2 answers
4k views

How does raw fuel damage the catalytic converter?

I was wondering, if fuel gets in the catalytic converter, how does it damage it?
George's user avatar
  • 6,545
11 votes
2 answers
22k views

Muffler off car. Safe to drive with exhaust open underneath?

So leaving work yesterday I heard a clang! - the muffler simply fell off. Further inspection revealed a lot of rust in one particular area on the pipe. Thankfully the forward muffler is still intact ...
MeltingDog's user avatar
  • 3,726
11 votes
1 answer
1k views

What Can I Learn From Exhaust Manifold Temps?

I was wondering what I can learn from the temperatures on the individual exhaust pipes coming out of each cylinder. The question is general, and my specific example is on my 98 Mazda 626 GF 2L. Last ...
Robert S. Barnes's user avatar
10 votes
8 answers
3k views

How should I remove this corroded nut without rounding it?

I have a 1982 Porsche 911 and need to remove the heat exchanger on one side. It's held on with three 13mm nuts and 3 barrel nuts. The barrel nuts were no problem, but two of the 13mm nuts are so ...
Edward's user avatar
  • 2,857
10 votes
5 answers
2k views

Is an exhaust pipe broken at engine connection fixable by a DIYer?

I took my 1999 GMC Sierra 1500 w/5.3l to a transmission shop to have it replaced. The process requires disconnecting the exhaust pipes going into the engine to get access to the transmission. When the ...
Stay-at-home-dad's user avatar
10 votes
2 answers
2k views

Motorcycle exhaust rattling / clunking / popping / burbling on deceleration

Lately I noticed a change in the sound my exhaust is making when decelerating from ~4000+ revs while in gear with the clutch not squeezed (that would be engine breaking probably). I'm unsure how to ...
Alin P.'s user avatar
  • 1,334
10 votes
3 answers
10k views

Do straight/short pipes burn out valves?

I have heard that straight/short/custom pipes can burn out valves on an engine. However, with a 4-cylinder Ford Model A engine, I have been told this is not the case because it has such low ...
Jonathan Musso's user avatar
10 votes
3 answers
71k views

Mass Air Flow Expected Values

I have a 2002 Audi A4 Quattro 3.0. I have a Vagcom USB cable and I am trying to diagnose the MAF sensor. I had a friend get some readings from an OBD2 scanner, which indicated that both precat O2 ...
SSH This's user avatar
  • 237
10 votes
1 answer
824 views

Porsche 918 - benefits of top mounted exhaust

Is the Porsche 918 the first production car with a top mount/exiting exhaust system? This article points out that by routing the exhaust up, Porsche was able to equip a completely flat underbelly and ...
MooseLucifer's user avatar
  • 6,007
10 votes
1 answer
744 views

semi loud growling noise at all speeds

I have a 1998 GMC Sonoma SLS with a 4.3 l V6 Vortec. It used to purr, now it growls, sounds like a small diesel engine. Vibration can be felt (mostly in the dead pedal) and also vibrates/growls in ...
Thor's user avatar
  • 101
10 votes
2 answers
760 views

Ferrari 3.0L V8 - muffler positioning, and x-flow for specific sound

I am re-designing a Ferrari exhaust system with 2 objectives: 1: enhance the specific high pitch raspy sound that you expect from a small Ferrari V8. 2: achieve a good free-flow design. There is ...
Digital Lightcraft's user avatar
9 votes
5 answers
2k views

Making a custom exhaust

I drive a 1990's Citroen BX TGE16 with no o2 sensors or anyhing fancy on the exhaust as far as I can tell. My exhaust is all rattly most surely from rust and age so I'm planning on changing soon. ...
EChan42's user avatar
  • 1,005
9 votes
4 answers
31k views

What does it take for a modern muscle car to sound like a classic muscle car?

To preface, I would grade my exhaust knowledge with a "B-". I know what the major components are and what they do, but I don't know if and when certain exhaust parts became mandated or introduced ...
Trevor D's user avatar
  • 1,193
9 votes
1 answer
1k views

My feet turn black

I left the pedicure salon, started my car and drove less than 3 miles to pick up something from the store, when I stepped out of my car my feet were black... and I don't meant just from dirt, It ...
Morgan 's user avatar
9 votes
4 answers
52k views

Effects of leaky exhaust valves

While rebuilding my valves, I noticed that 4 out of 6 exhaust valves on one side of the V6 engine were leaking after lapping and I had to relap them. I determined that by doing a water test. I am ...
amphibient's user avatar
  • 6,653
9 votes
2 answers
420 views

What type of welder would I need in order to weld titanium?

Want to weld up some titanium tubing for an older motorcycle exhaust header. I would like the material to be titanium. I'm considering doing this myself in order to learn. I understand that getting ...
DucatiKiller's user avatar
  • 32.9k
9 votes
1 answer
757 views

What effect will replacing manifolds with headers have on oil temperature?

I drive a big heavy car (2011 Mercedes E63, somewhere around 4200lbs) that I take to the track. It has the NA 6.3L engine (M156) with no modifications. I struggle with oil temperature issues on hot ...
RJStanford's user avatar
9 votes
1 answer
410 views

Aftermarket Exhaust

I have a Volvo c30 D5(2007) and my exhaust has started to rot through from the inside, I obtained several quotes from various part providers and they all said an after market exhaust would be allot ...
scriptss's user avatar
9 votes
1 answer
28k views

My car's diesel exhaust smells really bad

First of all let me say I apparently have no exhaust leak. For a long time I've been asking myself how was it possible that the exhaust of my car smells so bad. It does it when in the morning, I ...
Noldor130884's user avatar
8 votes
3 answers
204k views

Why am I smelling exhaust inside the cabin of my car?

When I drive my car the first few miles, I smell exhaust inside the car with the windows rolled up. It happens when I have either the AC or the heat/air on... What's going on?
studiohack's user avatar
8 votes
5 answers
46k views

Why is my exhaust pipe so rusty?

I think all cars exhaust pipes get very rusty after not very long. Why is that? I know that the pipe gets extremely hot, but how come that makes it rust more than any other part of the car?
Sponge Bob's user avatar
  • 1,557
8 votes
5 answers
15k views

How to fix broken exhaust pipe?

I was driving down the highway and I heard a bang, a beep, and then constant scraping. I pulled to the side of a road under a bridge and looked under my car, to see this: From what I can understand, ...
Forest Kunecke's user avatar
8 votes
1 answer
599 views

What is the muffler? How does it work?

After my previous question, lots of people said that having pipes coming through the bonnet/under the car etc would bypass the muffler. What is the muffler though? How does it work? People said ...
George's user avatar
  • 6,545
8 votes
1 answer
28k views

Does it make the most sense to replace an old car's entire exhaust system all at once?

Back story: The Check Engine light came on in my 2005 Chevrolet Malibu LS Sedan (V6 3.5L). I took the car to a mechanic #1 (M1), an independent shop. They replaced the EGR valve. A day later, the ...
Chris W. Rea's user avatar
8 votes
1 answer
792 views

Is it possible to extend the length of the shaft on an existing turbocharger, further distancing the compressor from the turbine?

I'm toying with turbojet engine ideas, and over the course of my research it occurred to me that the combustion chamber could be more power-efficient and space-efficient if it was aligned in the ...
Giffyguy's user avatar
  • 215
8 votes
2 answers
3k views

How to inexpensively replace missing baffles on a classic bike

Dilemma I have a 1980 Suzuki GS550L. Not only did one of the previous owners completely remove the baffles from the exhaust pipes, but they welded fender washers on the end of the pipes, so the OEM ...
Oran D. Lord's user avatar
7 votes
1 answer
4k views

Why no exhaust gas turbine generator in hybrid vehicles?

I found something interesting on Wikipedia today: a hybrid turbocharger. This is a device that charges a battery with an exhaust gas turbine, and at the same time operates an air compressor using the ...
juhist's user avatar
  • 14.5k
7 votes
1 answer
1k views

Locating the O2 sensors and the cat along the exhaust

I gather that the upstream O2 sensor is the one right in the center of this picture. I also gather that the catalytic converter (the "cat") is the bulbous part of the exhaust right behind this sensor. ...
Calaf's user avatar
  • 1,555
7 votes
4 answers
200k views

Sputtering while driving & idling

[My car: 2004 Mazda 3] So, my wife came home from running some errands and told me the check-engine light was on and that the car was sputtering and felt like it was going to stall while stopped at ...
Trev's user avatar
  • 255
7 votes
2 answers
3k views

Exhaust Backpressure and Its Impact on LTFT Values

This is a follow-up from my initial question which can be found here : LTFT and STFT values are off and don't make sense. Car : BMW 2015 F10 M5 Modifications : Eisenmann Race Catback Exhaust, ...
DerStig's user avatar
  • 421

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