Questions about Exhaust systems, Catalytic Converters and Headers/Manifolds

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24
votes
3answers
127k 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 ...
22
votes
2answers
2k 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. Why ...
21
votes
9answers
73k 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.. its got a 14mm head and its just plain STUCK. I've tried soaking it overnight ...
19
votes
1answer
578 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 ...
16
votes
1answer
9k 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 ...
15
votes
3answers
13k 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 ...
13
votes
2answers
3k 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, ...
11
votes
2answers
678 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
4answers
475 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 ...
11
votes
2answers
9k 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 ...
10
votes
2answers
442 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
109 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
2answers
469 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 ...
10
votes
1answer
75 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
5k 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 ...
10
votes
1answer
59 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
1answer
98 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 ...
10
votes
2answers
449 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
561 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
3answers
7k views

Catalysator broken? Odd rope coming out of the exhaust pipe

[UPDATE] SOLVED! Hurray! The muffler had corroded inside and it blocked the exhaust system, making bad to motor. I got it fixed and the car energy efficiency improved from 12-15 liters/100km to ...
9
votes
1answer
200 views

How does raw fuel damage the catalytic converter?

I was wondering, if fuel gets in the catalytic converter, how does it damage it?
9
votes
1answer
100 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 ...
8
votes
3answers
75k 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
1answer
74 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 ...
8
votes
1answer
164 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 ...
7
votes
1answer
293 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
3answers
5k 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 ...
7
votes
1answer
75 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
2answers
251 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 ...
7
votes
1answer
37 views

2002 Mercedes E320 - Exhaust getting into the cabin of the vehicle and causing headaches

Experiencing exhaust fumes in the car. It's causing eyes burning and headaches after driving the car for 30 minutes. The Dealer checked and found nothing wrong but every time after driving the car ...
6
votes
3answers
6k views

How effective are exhaust patch kits?

How effective are exhaust patch kits in terms of longevity and limiting noise and leakage? Specifically I'm looking at using the kind that consist of heat-activated tape, an aluminium sheet and two ...
6
votes
1answer
1k views

Clamping two 2" exhaust pipes together

I have a replacement exhaust system that I just bought. Just has a tailpipe, muffler, and a flange that connects to the header. What would be the best way to join these pipes, aside from welding it? ...
6
votes
4answers
76k 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 ...
6
votes
1answer
50 views

08 Silverado 5.3 rough idle and dark cold start exhaust

I recently bought a 2008 Silverado 5.3 with 77k on it. After a couple weeks I noticed that at idle the engine would stumble and my rpms would drop slightly. It eventually set off the check engine ...
6
votes
5answers
4k 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 ...
6
votes
1answer
65 views

2009 Aprilia RSV1000 - Piggy Back ECU, Should I get one?

I have an Aprilia Tuono, 2009. It seems to run lean after putting an Akrapovic exhaust on it. It makes exhaust popping sounds on deceleration. My boyfriend said I need a power commander on it to ...
6
votes
1answer
727 views

Car leaks oil when driving, Oil from exhaust pipe

Car leaks oil when driving not while parked. The bottom of the vehicle is covered with oil and there's white smoke coming from tail pipe when driving. It sat and there no oil puddle in garage but ...
6
votes
1answer
130 views

Volvo S80 II 2.4 D5 DPF (Diesel Particulate Filter) regeneration conditions

What are the conditions required for the DPF (Diesel Particulate Filter) regeneration? Is it only exhaust temperature or speed and RPM also? I'm wondering if DPF can regenerate while car is at ...
5
votes
2answers
7k views

should I replace gaskets when replacing exhaust?

I need to replace a broken section of exhaust. Should I replace the gaskets also? one of the gaskets is directly between the engine and the new part. The other is between the new and an old part of ...
5
votes
3answers
7k 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 ...
5
votes
1answer
331 views

15 ppm of CO levels inside car

I constantly measure 15 ppm of CO inside my car after a long commute (~1 hour of continuous driving, but the overall trip can take from 1.5 to 2 hours depending on my destinations before heading ...
5
votes
2answers
770 views

What is the “dollar bill” test?

One of the questions recently made reference to an exhaust failing the "dollar bill" test. How does one perform it and what does it tell you?
5
votes
2answers
760 views

Will Driving 100 Miles With a Misfire Damage My Car?

Background: I have a 2002 Dodge Dakota Quad Cab slt with 4.7L Magnum V8. My check engine light came on when I was at work. I then drove 20 miles home to my house, pulled out my scan tool and ...
5
votes
1answer
40 views

How does clogging tailpipes result in carbon monoxide in the cabin?

Reports like this of people dying from CO poisoning in idling cars due to "clogged tailpipes" are disturbingly frequent. But how can this happen if the car is outdoors? First of all, how does a ...
5
votes
1answer
5k 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 ...
5
votes
3answers
15k 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 ...
5
votes
3answers
1k views

straight pipes and carb rejetting?

I have a 1984 Honda GL 1200 standard wing and I am going to put straight pipes on it, however some forums say I will need to upjet the carbs, and others say I will not. Has anyone on this site ever ...
5
votes
2answers
4k views

2001 Audi A4 just got really loud

Alright, So I'm driving to work. I'm stopped at the red light to go on the freeway. It turns green so I accelerate. I'm accelerating more than I would on a regular street but I didn't floor it. ...
5
votes
2answers
102 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, ...
5
votes
1answer
215 views

Rust underneath rear of car (Toyota Mk1 MR2)

I have recently acquired an old (1989) Mk1 Toyota MR2 and took a few photos of the underside rear of the vehicle. There seems to be a fair amount of rusting on the rear axle and gear box: gear ...