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Many car enthusiasts remove the catalytic converter for a combination of additional power and/or better sound. It has a massive impact on emissions and what you

by Braxton1980 9mo ago

Many car enthusiasts remove the catalytic converter for a combination of additional power and/or better sound. It has a massive impact on emissions and what you might be smelling is hydrogen sulfide which is normally converted to sulfur dioxide which is orderless. I should note the power increase may not have a major impact on newer cars where the cat has been optimized to reduce it's negative power impact. Infact a popular tuner company, APR, that provides flashes tested the recent Volkswagen GTI and R generation with their most common tune and determined that with their tune removing the cat had a nominal impact. *Basically they can bring the cars power as high as the OEM internals can handle reliably while keeping the cat. There are cars where it still has some impact and of course, different from power ,"straight piping" a car can offer a subjective sound change.

mr_toad 9mo ago
For every car enthusiast there are probably a hundred poorly maintained vehicles on the road. Black smoke is likely soot, and white smoke is almost certainly an oil leak.
- drzaiusx11 9mo ago
  Oil in the exhaust in quantities high enough to produce acrid white smoke is extremely common on a number of ICE engines, like blown head gaskets on E25s (found in most Subarus before their Toyota involvement in 2010) for example
  - cucumber3732842 9mo ago
    Subarus with bad head gaskets leak combustion gas into the cooling system displacing the coolant. If you run a flat engine low on coolant it will score the upper cylinder walls and the you will have oil consumption. This is fundamental to all flat engines. Oil in the exhaust is blue smoke. Coolant is white.
    - drzaiusx11 9mo ago
      I never got the "blue" and "white" thing. Both look "white" to me, but you're right about subarus also leaking coolant in the exhaust which is easily identified by a "sweet" smell. Blown gaskets on ICE engines like E25s leak both oil AND coolant, no? I might be mixing up blown heads with cracked manifolds which often go hand in hand since temp extremes in engines fissure cast parts like the manifold. Either way the end result is the same: noxious fumes in the exhaust.
      - cucumber3732842 9mo ago
        You've never see an old vehicle blow a substantially "bluer than normal" cloud. That's what I'm talking about. > Blown gaskets on ICE engines like E25s leak both oil AND coolant, no? This is way, way too broad of a statement. The Subaru EJ25 tends to leak oil externally from the valve covers. When they have head gasket problems it tends to be combustion gas into coolant which blows the coolant out the expansion tank until equilibrium is reached. Typical head gasket failures cause some degree of that but coolant mixing with oil is more typical. Many V engines have intake gaskets that can leak coolant into the intake or oil or both. Regardless, if you can taste coolant in the exhaust the car is basically at the point of "fix it now" > I might be mixing up blown heads with cracked manifolds which often go hand in hand since temp extremes in engines fissure cast parts like the manifold. A sizable minority of cars don't even use cast manifolds anymore. While it's possible for cast manifolds to crack in a way that makes them leak that's rare and it's more common for them to crack their mounting tabs off. Steel exhaust tubing can and does sometimes break after many years of vibration, say nothing of rust. While cylinder heads can crack it usually takes the kind of overheating that requires major work to fix in order to make it happen so just about nobody is driving around with a cracked head.
        Braxton1980 9mo ago
        So I was going to reply to mention that all VWs sold in the US at least for the last 10 years use an iron block. I wanted to know if the EA888 (VWs go to 4 cylinder engine) was cast so I asked chatgpt. "No — the VW EA888 Gen 3 engine block is not cast iron in the latest versions. engines.... use an aluminum alloy block, not traditional cast iron." So I know for sure it's iron so I said "Are you sure it's an aluminum block on the gen 3" "No — the VW/Audi EA888 Gen 3 engine does not have an aluminum block"
lostlogin 9mo ago
> Infact a popular tuner company, APR, that provides flashes tested the recent Volkswagen GTI and R generation with their most common tune and determined that with their tune removing the cat had a nominal impact. Do you mean minimal impact?
- spockz 9mo ago
  Probably. I read it as “had an impact but kept the performance stayed nominal.”
- Braxton1980 9mo ago
  Yes. I made a mistake in how I worded that. They are able to tune to other bottlenecks in the car while keeping the cat.
deleted 9mo ago
[deleted]
ehaliewicz2 9mo ago
As someone into performance cars and motorcycles, removing a cat is pretty uncommon, and you're generally seen as a dick if you do it.
- xnx 9mo ago
  There are a lot of "street mechanics" who will remove your cat for free without even needing to ask.

mr_toad 9mo ago

For every car enthusiast there are probably a hundred poorly maintained vehicles on the road. Black smoke is likely soot, and white smoke is almost certainly an oil leak.

drzaiusx11 9mo ago
Oil in the exhaust in quantities high enough to produce acrid white smoke is extremely common on a number of ICE engines, like blown head gaskets on E25s (found in most Subarus before their Toyota involvement in 2010) for example
- cucumber3732842 9mo ago
  Subarus with bad head gaskets leak combustion gas into the cooling system displacing the coolant. If you run a flat engine low on coolant it will score the upper cylinder walls and the you will have oil consumption. This is fundamental to all flat engines. Oil in the exhaust is blue smoke. Coolant is white.
  - drzaiusx11 9mo ago
    I never got the "blue" and "white" thing. Both look "white" to me, but you're right about subarus also leaking coolant in the exhaust which is easily identified by a "sweet" smell. Blown gaskets on ICE engines like E25s leak both oil AND coolant, no? I might be mixing up blown heads with cracked manifolds which often go hand in hand since temp extremes in engines fissure cast parts like the manifold. Either way the end result is the same: noxious fumes in the exhaust.
    - cucumber3732842 9mo ago
      You've never see an old vehicle blow a substantially "bluer than normal" cloud. That's what I'm talking about. > Blown gaskets on ICE engines like E25s leak both oil AND coolant, no? This is way, way too broad of a statement. The Subaru EJ25 tends to leak oil externally from the valve covers. When they have head gasket problems it tends to be combustion gas into coolant which blows the coolant out the expansion tank until equilibrium is reached. Typical head gasket failures cause some degree of that but coolant mixing with oil is more typical. Many V engines have intake gaskets that can leak coolant into the intake or oil or both. Regardless, if you can taste coolant in the exhaust the car is basically at the point of "fix it now" > I might be mixing up blown heads with cracked manifolds which often go hand in hand since temp extremes in engines fissure cast parts like the manifold. A sizable minority of cars don't even use cast manifolds anymore. While it's possible for cast manifolds to crack in a way that makes them leak that's rare and it's more common for them to crack their mounting tabs off. Steel exhaust tubing can and does sometimes break after many years of vibration, say nothing of rust. While cylinder heads can crack it usually takes the kind of overheating that requires major work to fix in order to make it happen so just about nobody is driving around with a cracked head.
      - Braxton1980 9mo ago
        So I was going to reply to mention that all VWs sold in the US at least for the last 10 years use an iron block. I wanted to know if the EA888 (VWs go to 4 cylinder engine) was cast so I asked chatgpt. "No — the VW EA888 Gen 3 engine block is not cast iron in the latest versions. engines.... use an aluminum alloy block, not traditional cast iron." So I know for sure it's iron so I said "Are you sure it's an aluminum block on the gen 3" "No — the VW/Audi EA888 Gen 3 engine does not have an aluminum block"

lostlogin 9mo ago

> Infact a popular tuner company, APR, that provides flashes tested the recent Volkswagen GTI and R generation with their most common tune and determined that with their tune removing the cat had a nominal impact. Do you mean minimal impact?

spockz 9mo ago
Probably. I read it as “had an impact but kept the performance stayed nominal.”
Braxton1980 9mo ago
Yes. I made a mistake in how I worded that. They are able to tune to other bottlenecks in the car while keeping the cat.

deleted 9mo ago

[deleted]

ehaliewicz2 9mo ago

As someone into performance cars and motorcycles, removing a cat is pretty uncommon, and you're generally seen as a dick if you do it.

xnx 9mo ago
There are a lot of "street mechanics" who will remove your cat for free without even needing to ask.