Great gas mileage gain!

Full marks for that!
I respect an "I'm not sure." much better than a "I just know it must be this way."

I've googled about a bit and haven't found much on this yet.

What I did find was this:
"Under the federal Clean Air Act, no one is allowed to tamper with a vehicle’s emission controls. If you have discovered that your car is missing its catalytic converter, you should have another one installed immediately."
in Minnesota Pollution Control Agency - Catalytic Converters.

 

Here's an interesting tidbit I got from Lawn Mower Savvy:

Emissions

It has been widely reported in recent years that typical lawn mowers are relatively more polluting than a modern car. Mowing a lawn for half an hour with a gasoline engine makes as much smog as driving a new car 170 miles. Gasoline-powered garden equipment accounts for 5 percent of all U.S. air pollution. California introduced tough new emission standards last year, and by 1999 is requiring another 55 percent cutback in emissions. The cleanest power mowers are the solar/electric. Battery and 110-volt electric mowers are next. Gasoline engines with overhead valves are less polluting than those with side valves. Mowers powered by two-stroke engines, for which gasoline and oil are mixed prior to ignition, are dirtiest.

For the record, all the gas lawn mowers I've used are 4-stroke. The chainsaw I've used is 2-stroke.

 

Well, it's illegal, but i'm just interested in the mpg gain, not in it being legal or not. It seems like a good mod if it will actually help a lot.

 

I know many of us didn't buy the prius simply because it is better of the environment. I myself bought it for one reason. I drove a jeep, drove 30k miles a year and wanted to spend less on gas.

However, just because we bought it for one reason, doesn't mean we should overlook everything else it has to offer. I've become much more aware of the environmental affects and benefits the Prius offers.

So, is more pollution worth 4-5mpg? I for one don't think so. And I would bet, that even without burning that extra gallon or so you might be saving, that the fuel you are burning is far more polluting than a stock Prius that gets worse mileage.

 

Still Googling but I haven't found anything yet to support or discredit this.

I also haven't found (and strongly suspect I won't be able to find) anything that would give emission numbers for a Prius w/o a CC for comparison with SUVs, etc.

I have a mechanical engineering degree and I suspect that removing the CC from a system designed to have one would produce more emissions than would a vehicle designed without a CC.

 

Priushappy,

Maybe you are getting the mileage increase you stated in your original post. But how did you get the converter off the car? Isn't welded (I would assume it is) in the exhaust system? Even if it weren’t I still imagine it would be a royal PIA to get off. So you would have to use a cutting torch and then you have to reweld the straight pipe back in the exhaust? And doesn't CA still have mandatory emission tests annually? So that means it you would have to go through the same procedure twice each year.

If you need warranty service on anything dealing with the ICE, well I would believe all bets are off.

If the above is correct, sure seems like a lot of trouble for the mileage increase.

Let's say you drove 20,000 miles a year at 50 mpg and increased your mileage to 57 you save 49 gallons a year; maybe $125 or so...

The whole idea of removing the cat just doesn't make sense...

And I still find it hard to believe a cat converter with today’s technology is responsible for a 15% drop in mileage.

Rick

 

Still, no one can provide actual evidence that removing a catalytic converter raises mileage. It is proven removing the cat raises emissions, and is illeagal to boot, though you probalby wouldn't face a penalty unless you forget to replace it before your smog check.

One person's experience is just anecdotal evidence, and coudl be explained by many things. Even the replacement O2 sensor could make an impact. I can get a 4-7MPG change just by switchig drivers.

 

According to California Bureau of Automotive Repair:

Most areas of the state require vehicles to have a Smog Check performed every two years, when being sold (except when the sale is between family members), and when being initially registered in California.

The Prius is exempt until January 1, 2010.

My worry would be if the Prius had to go for repairs when there would be no time to switch back. Examples would be if the car shut down (this is a 2004 remember) or an accident. Once they got it up on a lift, the discovery would be made.

 

Plus... if you are using the HOV stickers you are violating DMV since the vehicle is no longer SULEV and if you took a tax deduction from the IRS and they found out they'd probably try to take your house and then the feds would subpoena your search records and charge you with ecoterrorism... vacation in Guantanamo anyone?

 

On the subject of lawn equipment, I use a Black and Decker battery-powered lawn mower, a battery-powered edger/weed-eater, and a battery-powered leaf-blower. They work great for my front and back yards.

BTW my vote is to keep the catalytic converter installed on your car. I wish the govt would mandate converters on all internal combustion engines regardless of application.

 

anyone try a high flow cat?

 

Priushappy

I know where you can stick yer catalytic converter! :lol:

http://www.latimes.com/news/local/la-me-co...-home-headlines

 

I think that everyone in this thread that is making a big fuzz about how much more pollution is being formed, needs to remember that it is only a matter of 20 to 30 years until we have full force Hydrogen powered electric vehicles dominating the automotive industry; which of course means "no more pollution due to automobiles". So I feel that we should leave PriusHappy alone and let him drive around with no exaust if he wants. 30 more years of smog forming emmisions is no match for human curiosity in the search for better gas milage.

The first thing I will do when I get my prius next month is to chop off my catalytic converter, weld on a test pipe, and embrace the joy better gas milage.
All things said, Mr. Bush is not going to come knocking on your door to fine you for not having a catalytic converter on your car.

And for all those worried about pollution; not to worry! I will be putting my unused catalytic converter to good use on the cows in California's San Joaquin Valley.

I will post my findings for both the prius and the cows ASAP.
See you all soon!

 

I agree.. Better fuel economy is more important than smog output to me too. SOME of us didnt buy our prius because we care about the envornment to tell you the truth. I only bought mine because I think it's a cool high tech car and it get great fuel economy.

 

Hey, it's HIS catalytic converter. And, it's his Prius. Unless you live on his street or maybe in his town, arguing about his emissions is misguided, controlling bull. If you want to condemn the guy's choices, get a ministerial license. It's not like he's suffocating the Brazilian rain forest.

 

This take the prize as the most irresponsible suggestion I've seen on PC. Chopping off the cat is unlikely to be the source of the "milage gain". More likely the faked-out O2 sensor is running the engine too lean. I hope your pistons fry and you wind up needing $4000 in repairs a year down the road.

Just MHO of course. Here: let's exit on a happier note.

 

We forget that even a ZEV is not pollution-free. Particulate matter (soil dust, tire dust) is thrown into the air as a vehicle moves along. Hence PM 2.5 µm is still a concern, even with a bicycle or hydrogen-powered vehicle. The rule still holds - TANSTAFL (there ain't no such thing as a free lunch).

 

The secondary o2 sensor only verifys to the OBD2 computer that the cat is actually working. The primary o2 is BEFORE the cat and that's the actual one that that corrects the a/f ratio for the car. So i'm sorry. It won't fry his pistons. It won't do anything.

 

I know this is a terribly old thread, but I wanted to revisit and ask: besides the 02 sensor sim, what other mods did you need to make this work? Also: how did your car sound?

 

No lawn mower I've owned in the past 20 years has had a two-stroke/two-cycle engine, and I don't recall seeing that any of the ones I considered buying were two-stroke either.