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Trackerrrr 12-01-2010 02:19 AM

Putting catalytic converter on older car?
 
Hi all,

I've been kicking around the idea of picking up an old car like a '64 Chevy Impala with a 6 cyl engine with a 1 bbl carb to see what kind of mileage I can squeeze out of it. Yeah, I know they aren't the most efficient cars ever made but I like to try just to shut the naysayers up. Anyway, the one thing I hate about older cars is the STINK out the tailpipe. I'd like to put cats on to eliminate most of the pollution, but can you put a three way cat on a carbed engine? Is this a good idea? Another thought I had was to adapt a two bbl fuel injection unit from an S-10 which might work better.

SentraSE-R 12-01-2010 02:45 AM

Just a guess, but a '64 Impala is such a gross polluter, my guess is it would clog a cat in 100 miles of driving. Do yourself and all the air-breathing organisms in the world a favor, and let that dinosaur rot in the junkyard. A carbureted '64 isn't capable of burning close to stoichiometric. It lacks the oxygen and temperature sensors and feedback systems needed to control its emissions, and to prevent the cat from being destroyed.

cfg83 12-01-2010 02:53 AM

Trackerrrr -

Welcome to EM! While I'm no expert, I am *guessing* that a 1964-tech Chevy would poison a catalytic converter because it wouldn't have the right "mix" of emissions for the cat to function properly.

But I don't know, so I asked Wiki :

Catalytic converter - Wikipedia, the free encyclopedia
Quote:

History
The catalytic converter was invented by Eugene Houdry, a French mechanical engineer and expert in catalytic oil refining who lived in the United States. Around 1950, when the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of automobile exhaust in air pollution and founded a special company, Oxy-Catalyst, to develop catalytic converters for gasoline engines - an idea ahead of its time for which he was awarded a patent (US2742437). Widespread adoption had to wait until the extremely effective anti-knock agent tetra-ethyl lead was eliminated from most gasoline over environmental concerns, as the agent would "foul" the converter by forming a coating on the catalyst's surface, effectively disabling it.
The catalytic converter was further developed by John J. Mooney and Carl D. Keith at the Engelhard Corporation, creating the first production catalytic converter in 1973.
...
Three-way
Since 1981, three-way catalytic converters have been used in vehicle emission control systems in North America and many other countries on roadgoing vehicles. A three-way catalytic converter has three simultaneous tasks:
Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O
These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This point is between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline. The ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels. Generally, engines fitted with 3-way catalytic converters are equipped with a computerized closed-loop feedback fuel injection system using one or more oxygen sensors, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used. While a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Within a narrow fuel/air ratio band surrounding stoichiometry, conversion of all three pollutants is nearly complete. However, outside that band, conversion efficiency falls very rapidly. When there is more oxygen than required, the system is said to be running lean(as all the fuel got burnt,the emission of CO and hydrocarbons are minimized)and thereby, the reduction of NOx is favoured, at the expense of CO and hydrocarbons. When there is excessive fuel, the engine is running rich; the reduction of CO and hydrocarbons is favoured, at the expense of NOx.

CarloSW2

Trackerrrr 12-01-2010 02:55 AM

I suspected the carb would be the sticking point for a cat. Too many variables and inability to control the air/fuel ratio closely enough.

BrianAbington 12-01-2010 04:53 AM

In alot of newer cars they put a cat under the hood as part of the exhaust manifold.
If you had a shorty header and attached the cat right to it this may help get the temp up in the cat getting to the light off temp easier.

If the header is thermal coated and wrapped...this will help to keep more heat in the manifold it self.

Then do some research to find a cat that starts working at a lower temp.

I'd maybe go for a smaller car like a nova, or fairlane.

They are alot lighter, had a straight 6 available, and I have read plenty about people changing the rear gears and averaging upper 20's to lower 30's for hwy MPG's

I think you could get one of these cars even with a carb to pass modern emissions testing.

Frank Lee 12-01-2010 08:44 AM

My '84 Tempos came with carbs and cats.

mcrews 12-01-2010 10:20 AM

In 1979, I had a 1966 mustang coupe with a 1bbl 200ci straight six, automatic 3spd and a 2.87 rearend ratio.
I installed clifford headers that were 3 cyl on each header then did a "y" pipe into a 2 1/4 pipe w/ a single muffler, then 'y' piped uot to the two GT exhaust tips.
I was running E-70 radial series tires on the 14inch rims.
I had purchased a trip computer from jcwhitney and got it all calibrated. (yeah I was into ecomodding in 1979!!!)
I consistantly got 28+ mpg on the road.
I had to put a rebuilt long block in and went to have it smogged (in California). the results were less than 10% of the allowable level. It barely registered on the machine.
What really surprised me was that with the rebuilt engine I could actually 'chirp' the tires on take-off.

Ryland 12-01-2010 10:35 AM

The carburetors that are going to allow you to do this are going to be complex, the early 80's Honda civic pulled this off with a carburetor but it was with a mess of vacuum lines that very few could figure out.
The nice thing about the type of car that you are talking about is that the engine block for it most likely stayed the same for the next 30-40 years, other then getting a few more holes for sensors and a refinement in quality control, so you might be able to put an updated engine in that would bolt right in.
In my mind fuel injection is going to be the way to go, not just because it burns cleaner but because it lets you use less fuel by giving better control and that is what you want.

UFO 12-01-2010 12:54 PM

If you convert the engine to fuel injection, you could fit the exhaust with a converter. Fuel injection has been developed to the point where anyone can do it now, and cheaply too. Megasquirt comes to mind.

DonR 12-01-2010 01:07 PM

I have an awful Carter BBD computer controlled carb on my Jeep. The vaccum diagram is just as complicated as the electrical diagram. Alot of guys end up putting on a Ford Motorcraft 2100 or MC-2150 stand alone carb & still pass emmissions tests. Husquavarna also put some catalytic converters on 2 stroke chain saws. So running a cat with a fairly simple carb is certainly doable.

I would look into some emmissions systems of some very early cat equiped vehicles & see what all was required. Most cats are killed by running rich, the unburned fuel burns at the cat causing the substrate to melt, plugging them up. This robs power & makes the car hiss everytime you hit the gas.

Someone else had mentioned some Clifford Performance products. They specialize in straight 6 parts. They sell cams for torque

A 4.3l v-6 is only slightly larger than the 230 cid 6 that chevy used & may bolt into where the small block v-8 would go. All the modern bits to help with emissions & fuel economy.

Good luck

Don


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