My Civic VX commuter car build

[jlk16188]

Originally Posted by Jay2TheRescue

I'd recommend replacing the cat converter. Aside from the pollution aspect, there are other issues that can come up from tampering with it.

Care to elaborate? I have no emissions testing here so only visually inspecting that it is in place is all that is needed for inspection purposes here.

The O2 sensor is before the cat and there is no secondary sensor so unless it has some effect on the rest of the exhaust I cant think of anything it would affect other than saving me $200.

[Jay2TheRescue]

The exhaust systems from the factory are designed to provide a certain amount of back pressure. Without it you risk burning or otherwise damaging the engine's valves.

[jlk16188]

its a lean burn engine, its designed to naturally run hot so I doubt taking out a clogged cat will cause damage but thanks for the insight.

i havent changed the diameter of the exhaust and retained a factory muffler so the mass flow and velocity will remain pretty close the tolerances set by the conservative factory tuning of the ECU and material specs of the valves and head. There is a large amount of safety factor engineered into this motor and the entire system to begin with so I am not worried.

Catalytic converters from the factory have a very low impedance on the exhaust to begin with. The VX design has the cat right at the header and when in lean burn it would toast the cat much hotter than a normal car anyway so there would be little to no flow restriction offered by a functional cat on this car.

Back pressure is normally a factor of exhaust diameter size and length as designed by the factory.

[Matt715]

I don't know about in Pennsylvania, but here people pay about $80 for a used cat because of the precious metals the guts are made of. You may want to call a local scrap yard.

[jlk16188]

Originally Posted by Matt715

I don't know about in Pennsylvania, but here people pay about $80 for a used cat because of the precious metals the guts are made of. You may want to call a local scrap yard.

its worth almost nothing here. I threw all of the guts away. came out in very small chunks and powder anyway and I used the shopvac to pick most of it up

[trollbait]

That's where all the platinum was.

With lean burn, the VX will be a smog machine without a cat.

[jlk16188]

Originally Posted by trollbait

That's where all the platinum was.

With lean burn, the VX will be a smog machine without a cat.

In PA we dont have smog regulations so ill run it until absolutely necessary.

[Draigflag]

Surely you have an annual test like we do in the UK to test the car is roadworthy, which includes a very strict emissions test too?

[jlk16188]

Originally Posted by Draigflag

Surely you have an annual test like we do in the UK to test the car is roadworthy, which includes a very strict emissions test too?

annual safety inspection but does not include emissions anywhere past testing the gas cap to ensure a seal and the visual inspection that a catalytic converter and muffler are installed and there are no holes or breaks in the exhaust.

As far as I know California is the only state that requires "strict" emissions annual testing

[Draigflag]

That's crazy, so all the emissions data/tests carried out on new cars are only done once when the car is new basically? I thought the US was strict on emissions and the like?