Questions tagged [exhaust]

Questions about Exhaust systems, Catalytic Converters and Headers/Manifolds

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38
votes
3answers
369k views

What does a water like drop 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 drop from it's exhaust steadily in a break of 4-5 seconds. I tried to ask a couple of people at ...
32
votes
7answers
11k 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 ...
29
votes
2answers
25k 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. - ...
25
votes
12answers
222k 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 ...
21
votes
1answer
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 ...
19
votes
1answer
24k 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 ...
16
votes
3answers
13k 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 ...
16
votes
5answers
56k 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 ...
14
votes
2answers
10k 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, ...
13
votes
2answers
10k 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 ...
13
votes
1answer
4k 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 ...
12
votes
4answers
5k 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.
12
votes
2answers
5k 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 ...
12
votes
1answer
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 ...
12
votes
2answers
3k 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....
11
votes
3answers
7k 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" ...
11
votes
2answers
12k 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 ...
11
votes
3answers
23k 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 ...
11
votes
2answers
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 ...
11
votes
2answers
3k views

How does raw fuel damage the catalytic converter?

I was wondering, if fuel gets in the catalytic converter, how does it damage it?
11
votes
2answers
18k 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 ...
11
votes
1answer
503 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 ...
10
votes
8answers
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 ...
10
votes
2answers
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 ...
10
votes
2answers
7k 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 ...
10
votes
3answers
65k 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 ...
10
votes
1answer
725 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 ...
10
votes
1answer
727 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 ...
10
votes
2answers
727 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 ...
9
votes
5answers
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. ...
9
votes
1answer
524 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 ...
9
votes
4answers
44k 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 ...
9
votes
2answers
242 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 ...
9
votes
1answer
637 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 ...
9
votes
1answer
401 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 ...
9
votes
1answer
22k 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 ...
8
votes
3answers
192k 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?
8
votes
5answers
42k 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?
8
votes
5answers
12k 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, ...
8
votes
4answers
29k 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 ...
8
votes
1answer
443 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 ...
8
votes
1answer
24k 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 ...
8
votes
1answer
553 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 ...
7
votes
3answers
4k views

What does exhaust smell on oil and transmission dipstick mean?

I was inspecting a used car and the oil and the transmission dipstick smelled of exhaust (carbon monoxide?). What does this mean? Does it mean that the engine's gone bad and I should stay away from ...
7
votes
1answer
3k 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 ...
7
votes
1answer
925 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. ...
7
votes
4answers
197k 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 ...
7
votes
2answers
2k 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, ...
7
votes
3answers
3k views

Options for replacing rusted exhaust mounting bolts

The car is a 2005 Mini Cooper. The bolts that hold the exhaust mounts in place have rusted and snapped on both sides: I've taken up the floor of the boot and have located their heads on either side: ...
7
votes
7answers
19k views

Remove rounded manifold bolt

I'm trying to take off the manifold bolts on an old Chevy 350 (the ones that connect the manifold to the header). I got 4 out of the 6 bolts out, but 2 are extremely struck and rounded due to all the ...

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