Is smog equipment really junk?

I think proper working cats are good but all the other stuff was pretty much junk but I am not an expert on this stuff. I would like the exhaust to be within legal limits.

Helmut

 

It does keep the air significantly cleaned. Old cats are pretty restrictive so a modern free flowing cat would be a good move. EFI makes more hp and less pollution. Boost adds lots or hp without really adding any pollution. Lots of options.

 

Yes, it works.

Before modern computer engine management and computer designed combustion chambers, etc, things like air pumps and cats and ignition retard did eliminate well over half (est ~70-80%) the nitric oxides and hydrocarbons compared to pre emission autos, even though they did increase fuel consumption somewhat to accomplish this.

That said, if you took off the Webers and put on a sequential EFI system with electronic programmable ignition, you could program these old motors to run cleaner than any of the original smog stuff made them, using no cats and air pumps.

Doug

 

Brian,

With regards to catalysts, you may find that for the most part you can have your cake and eat it, too, with modern high-flow catalysts.

- TK

 

Anyone have flow statistics for a good set or OEM cats versus those sold as Hi-Flow? The originals have a pretty healthy cross section area for the 1.5 liters each had to handle.
As a aside, airpumps make a big difference on CO output, and I believe the problem with these older carb cars is that if the pump fails to do it's job, the cats are fed so much unburned fuel they self-destruct.
TomB

 

If somebody is suggesting that air pumps help keep the air clean, then they clearly do not understand how an air pump functions.

In case it's not clear, the air pump is simply adding supplemental air to the exhaust flow in order to "water down" the level of pollutants on a percentage basis. There's exactly the same amount of total HC/CO coming out the exhaust pipe, it's just less concentrated with an air pump installed, and thus will more easily pass the typical state sniff test. In fact, air pumps tend to cool the exhaust temp going into the cat, which can reduce the efficiency of the cat.

Catalytic converts, on the other hand, certainly do lower the HC/CO coming out the tail pipe, on both an absolute and a percentage basis.

 

No, that is not what the air pump does.

In order for the cat to combust the unburned fuel in the exhaust air is required and the air pump supplies it on early designs. In later designs they realized the high velocity exhaust creates a low pressure and all that is require to introduce the air is a check valve. So, if you have neither air tubes and a valve or an air pump then the cat is doing nothing.

 

Yup.

You can't make CO2 and H20 out of unburned HC in a cat unless you add O2.


Simple chemistry lesson. H=hydrogen, C=carbon, O=oxygen.

these are intransmutable,and in order to have something with O's come out, you have to have O's going in..

CO2 is carbon burned to its limit, it can't burn or combine with oxygen any more.

H2O is hydrogen burned to its limit, you can't burn combine the hydrogen with oxygen anymore.

HC or CO passing thru a cat, will not turn into CO2 or H2O unless you add supplemental oxygen from somewhere, like from an air pump.

At least these cars didn't EGR valve to pump exhaust gas into the intake stream to lower teh combustion temps to keep NO formation down.

Doug

 

Wow, the times are a changin'.

I remember a few years back when everyone was saying you'd be stupid NOT to remove all your emissions stuff. I'm glad we've all become more responsible and environmentally aware (including me).

There are multiple parts and systems to an emission system. Not sure if I can remember them all...

The one we all are familiar with is the tailpipe emissions. The tailpipe testing measures, HC (hydrocarbons), NOx (oxides of Nitrogen), and CO (carbon monoxide). HC and NOx are elements (along with sunlight) that create smog. CO is a poisonous gas. These are controlled by the catalytic converter and air injection (from the air pump) in our cars. Fuel mixture, timing, and ignition also play a big part in these emissions. Newer cars can get away without air pumps because of the more complex engine management systems they have. Cats now adays are much freeer flowing than the first generation (pellet) type. Cats are also kind of a miracle worker because they can clean up a whole lot even when the engine is not running properly.

There is also the evaporative system. This has to do with evaporation of gasoline. The gas fumes are present in all the gas tanks and in the fuel systems (especially) carburetors. The ones in the gas tank are controlled by the sealing gas cap, the "accordian" hose on the fuel nozzle, and charcoal canister. These parts when operating properly will control emissions w/o affecting engine output.

There are also the EGR & PCV on some cars. For the most part I say if they are working properly, let them do their job. I love HP just as much as the next guy, but I don't want to have to hold my breath, just so that I can drive fast.

Henry

 

Actually, you can (if the engine is running near the stoichiometric point) as a byproduct of the NOX reduction in a three-way catalytic converter is O2:

http://en.wikipedia.org/wiki/Catalytic_converter

On all of the Lambda-based F made since 1984, the air injection system only runs when the engine is cold (because the engine is running with a rich A/F ratio when cold).

 

Oh, I dunno. If it don't make HP, I don't see any reason to keep it there. I also subscribe to the idea that I need to use as much gasoline as I can now, before it is gone.

If I can get clean exhaust thru modern technology while increasing fuel economy and HP, that is a side benefit, but not a goal in its own.

The PCV system actually helps your motor by scavenging water vapor and HC fumes and keeps them from condensing in the crank case. The fact that it helps keep the air cleaner is a side benefit.

My air pump, and cats and evap carbon system are long gone, as they add weight, rob HP and are in the way regarding maintenance. And the minuscule amount of added pollutants that my car adds, based on it low mileage usage, isn't adding to the pollution equation.

Doug

 

I think that's why the smog pump went away when the three-way catalytic converter was introduced.

From what I've seen, smog pumps are only used on cars that came with 2 way cats. I know that's what Porsche did, not sure about Ferrari.

 

I wondered about that,as the EGR went away in the late 1980's or early 1990's sometime.

Dunno if it is from better cats or just better stoich control or both. New cats are infinity better than old ones, as they add no back pressure to the system, and are not heavy lumps impeding exhaust flow anymore.

Doug

 

Platinum cats convert harmful carbon monoxide into beneficial carbon dioxide. Sulfur compounds in the fuel are also removed by adding trace chemicals to the platimum and ensuring the temperature of this little chemical factory stays within limits to work properly as well as ensuring all fuel is fully burned before getting to the muffler.

Robs bhp? All test I've seen conclude by measurement that the reduction is miniscule, under 1-2%, mostly psychological. The air is cleaner...no longer can you commit suicide by locking yourself in the garage with motor running. That said, my car cam with test pipes and no pump belt, so the po believed as you. And with the very real fear of busting camshafts by leaving the pump belt is place and the pump seizing...there are probably very few 308s with a fully working system..

What cat removal does is allow tampering with engine parameters to allow real increases in hp.

 

My 84 had no air pump or any way I saw of controling the air system...just tubing with a check valve on the end. I'm not sure what newer cars did.

 

A car with an oxygen sensor in the exhaust, controling a circuit to modulate the air/fuel mixture - typically by regulating the pressure on the CPR. The first F-use was called "K-Jetronic with lambda" in some camps. Others called it "K-lambda".

My gray-market '83 Mondial QV has a straight K-Jetronic. When federalized, the shop added the sensor, feedback electronics and electric valve in a bypass line from the CPR to the fuel distributor. It of course, failed and has now been removed. The oxygen sensor sits in the pipe, probably a little lonely.

 

The '84-'85 US 308QV don't have a belt-driven, rotary vane air pump, but they still have an air injection system controlled by an on/off air valve (called the "cut-off valve" in the OM that is controlled by an electrovalve that is controlled by the coolant thermoswitch). When the cut-off valve is open (engine cold = coolant thermoswitch closed = electrovalve energized = cut-off valve open = air injection system "on") air from the airbox is drawn into the exhaust stream by the "pulses" of exhaust gas (hence, it's called a "pulse" air injection system); When the engine is warm = coolant thermoswitch open = electrovalve unenergized = cut-off valve closed = air injection system "off".

 

It is certainly true that the earliest versions of pollution equipment did everything bad re power that folks say. But by the 80's that wasn't true any more. Cats from that period on do not restrict power and the biggest loss of power was never directly due to the emissions add-ons but to the fact that compression and camshafts were changed to help emissions. THAT was the loss in power, not the cats/airpumps, etc per se.

Removing correctly operating emissions equipment will make no difference in HP at all. Removing it to eliminate weight will also make no practical difference - the weight of all the equipment cannot be more that 50 lbs at the most - probably more like 1/2 that. 50 lbs of weight reduction in a 3200 lb car could, in theory, improve the 1/4 mile acceleration by .1 (one tenth) seconds. This is totally imperceivable and not worth the slightest bit of consideration UNLESS you are racing the car in actual competition events.

 

There were many pre-cat cars that had air pumps. I can speak from experience that their removal had a large impact on CO readings. It was explained to me that the added O2 had an afterburn effect, not simply diluting the exhaust. Any thoughts guys?
TomB

 

Absolutely - the volume of air delivered by the air pump is small compared to the volume of exhaust gases so the dilution is a minor factor. Much bigger bang from driving the oxidation reactions (even with no cat) especially on non-Lambda cars that typically run rather rich by today's standards:

1. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
2. Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: CxH2x+2 + 2xO2 → xCO2 + 2xH2O (a combustion reaction)

 

Ypu are correct.

I spent about 6 years with a "test" pipe. I finally moved to a Hyperflow back in 05. I cannot feel any difference.

 

So then- does running a carb car without an air pump make cooking the the cats likely? When I got my car it had a new air pump and very melted cats.
And does anyone have comparative flow rates for the later style high flow cats versus what they came with? The high flow cats get a lot of positive press, I would be interested in numbers if they exist. Again, the cats that came on a carb car looked pretty large for only 1.5 liters of engine per cat.
Tom B