Great gas mileage gain!

anyone know what size test pipe to get? link?

It's a gen2 with stolen cats.. and the best way to not get stolen again is to not have them.

 

This comes to mind reading this thread:

1. Whether you have emissions tests or not, it's illegal to drive around without a catalytic converter.
2. People who get better fuel mileage from less restrictive exhaust have a heavy foot. Just keeping your foot out of the floored position will do the same thing: reduce exhaust pressure and in turn increase fuel mileage. The only exception are those who pulse and glide.
3. If you're going to remove your cat you might as well as make your engine run lean and block the EGR system. That way you get even better fuel mileage and will largely lower HC and CO emissions. Only your NOx emissions will be through the roof. Or get a #dieselgate VW and call it a day.
4. A happy medium is an aftermarket catalytic converter. While I'll stick with OEM cats since I want to get the best emissions possible in my cars and I'm not convinced that any aftermarket cat will perform near as well as OEM as far as emissions are concerned, some have noted that a change to an aftermarket cat, especially a "High Flow" cat, has made a difference in flow performance for them. And since an aftermarket cat is better than no cat, it could be a happy medium to those who care about both emissions and fuel mileage.

 

One thing people a lot of times don't understand is that bigger isn't always better. And in reality, the "perfect" size pipe all depends on your driving.

The way exhaust and intake work is that things aren't flowing constantly, but in pulses. So flow is largely stop and go. Too small, and yes, you get a restriction. But too big and now you have more mass to get up to speed before the exhaust (or intake) cycle stops and brings it all to a halt, which also acts like a restriction. This is why too big can also hurt flow, and therefore performance and/or even fuel mileage.

The problem with getting the perfect diameter (and length) of exhaust (or intake) tubing is that not only cylinder size, quantity, valve size, valve timing and such all affect how much flow will need to be dealt with, but so does throttle load and engine speed. With performance in mind this is easy to figure out: the tubes need to be the right size be to get maximum flow at top RPM and wide-open-throttle. But when trying to get fuel mileage you're not going for maximum RPM and throttle, but somewhere much lower, therefore necessitating a smaller diameter pipe for best fuel mileage. But how much smaller??

In a perfect world we'd have intake and exhaust tubing that can constrict and expand like blood vessels. That way, with every change in RPM and throttle you could adjust the diameters to fit the circumstances. But when trying to get better fuel mileage you have to go with a happy medium. You can size it for the way you drive. If you're a wide open throttle kind of guy then there are plenty of racing calculators that will get you the right diameters (and lengths in the case of exhaust primaries) of your piping. If you are kind of a lead footed then a slightly smaller diameter would perhaps be better. If you put around town like granny then you may actually benefit from a smaller than stock diameter. Also a lot of people don't realize that cruising even at relatively high speeds is actually lower load and therefore lower exhaust flow than you get with stop-n-go traffic.

If you have the resources, a person could also try variable diameter piping by have two or more different diameter exhaust secondaries (or also primaries if you can) and have valves that can open up the bigger tubing allowing more flow at higher loads and RPM's. But usually you just have to go for a happy medium.

 

Flawed rationalization. The CAT is there to prevent excessive pollution. Put it back on.

 

That's what came to mind when I saw in another thread that someone was cutting a piece out of the intake system of... I think it was 4Gen motor to get it to fit in a 3Gen Prius, or perhaps the other way round. Likewise those aftermarket intakes -- are they the "right" length?

 

Removing the CAT in the Prius is like taking a shower and throwing the bath water in the neighborhood drinking fountain.
Please don't ...

Posted via the PriusChat mobile app.

 

Have you got it figured out? I know they sale angled extentions for the o2 sensors that will put them in needed perimeters without the catalytic. I am wondering if there truly is an MPG gain. The previous owner off my car said he had to have the cat replaced with an aftermarket due to a failure, so may not be as restricted as the OEM once was.

Posted via the PriusChat mobile app.

 

I bet there is a mpg. i have heard there is.

I think the pipe coming out of the flange is 2 Outer diamter" (not sure) and the pipe in front of the resonator is 1 3/4"..OD..

So i'm looking at getting a 2 1/8" ID flex pipe and a 2 to 1 3/4 reducer and clamps.. An elbow 02 extension or defouler is also in my plans.. unless they have a way to turn off the warning lights via techstream or something like that..

 

Not true at all. i'ts more like peeing in the ocean... It's just elements being released back.. A few of us straight piping isn't going to have any noticeable effect compared to all the air polution from china and farting cows in the U.S. You can know it disappears if you can't notice it from 100 feet away.. or if you wait some time and go an occupy that same space and not detect it. I find Diesel trucks far more objectionable than a prius with the cat cut out. also, replacing cats to be stolen again also provides an incentive for theft and immorality. No cats present for a theif, no opportunity for a positive reward of cash to reinforce the criminal behavior.

 

Actually diesel engines without emissions equipment produce fewer emissions than gasoline engine without emissions equipment do, with the exception of particulate matter (which used to not be considered a pollutant and arguably does less damage to the environment). It's just easier to clean up gasoline engine emissions than diesel engine emissions, which is part of what makes modern diesels more expensive.

In other words, cut out the cat of a Prius and you're producing far more HC and CO emissions than even a large diesel would produce without a catalytic converter. Take out the EGR valve and now you're possibly even surpassing the NOx emissions in a diesel.

 

Are you really making a point of morality while you plan to remove your cat and pollute the air for everyone? The rules exist because health is directly linked to air quality. If you and everyone else think they're special and should bypass the rules we'd be going backwards. I just moved 100 or so miles from an area that had smog inspections to a much smaller town that doesn't. I can tell you just from walking around the neighborhood that it absolutely makes a difference to the air quality.
If you don't want your cat stolen, buy a protector or make one. The Prius is so well engineered you're not going to gain any discernible power or efficiency by cutting the cat out. You are not smarter than the hundreds of engineers that designed it.

 

yea i don't care about any of that.. what i can tell you is that my prius without a cat, smells a lot better than diesels. I can deal with gas.. the diesels i can't stand the smell..

I also know the size of mankind is like ants are to us when it comes to the environment. When you go a few miles up into the air you see how insignificant we really are.. and if we could warm the globe that would mean we can pay less in heating bills.. So it's a good thing.
It's easier to keep cool than it is to keep warm.. it's easier to dehydrate in the cold too. Global warming is good. Also note that the weather isn't doing anything it hasnt' done a century ago.. and centuries ago. Eff your scam! The models are full of crap by people who are paid to say what they want them to say.

 

oh and as far as the engineers.. they have to produce the vehicles to meet the laws..
I have no doubt removing the cat will increase MPG. it's been proven.

 

I'm not going to attempt to refute your other statements, but this one in particular is completely wrong. And I should know, I live where it's very cold and been where it's hot.

I have two friends, a man and his wife, who built a geodesic home with a sunroom on the bottom in Silverheels near Fairplay, South Park. I've seen it colder than -50°F there back in those days. Not only that, it's extremely windy there all winter long too. But this couple could leave their home for weeks at a time in the winter WITH THE HEAT OFF and come back and not have any frozen pipes. His only compaint about his house was, "It's sure easier to heat a home than to keep it cool."

And this has been my take on it too. Build a home well enough, and you can keep it warm with nothing more than passible solar sunlight. But it's very hard to make a home that stays cool all summer without electricity and air conditioning.

I used to go to work outside in the dark as cold as -40°F many mornings. I've found that you can always throw on another layer of clothing and be plenty warm. I've even slept outside in the freezing cold before every night all winter long here in Colorado without any heat (and so have my parents, uncles and several other people I know). Again, put on enough clothing and you'll be fine. It's only when you need to change your clothes or take a bath when things become complicated IF you don't have some source of heat.

But when it's hot there's only so much clothing a person can take off. After that, there's not much you can do, unless you have A/C. I've been in other countries where it's well over 104°F (40°) and super humid. So hot and humid that I could take a shower and jump in front of a fan wet and naked and still feel like it was blowing hot air onto me.

Your statement only applies to people who don't know how to dress for the weather. It's far easier to keep warm in a freezing environment than it is to keep cool in a hot one.

P.S. I actually liked the smell of my ol' 1985 VW diesel when I had it. For some reason it smelled like barbecue to me.

 

They also have to meet fuel efficiency laws too.

Also, if you remove all the interior of your car, as well as the seatbelts, airbags, even the seats themselves, and also remove the metal bumpers behind the bumper covers and any other part that's not needed for the engine to run properly and for car to move or that is part of it's exterior shape, then you will also get better fuel mileage, which has also been proven. Why not go and try it?

 

I wasn't talking about keeping a house at a temperature. I was talking about keeping yourself cool. You wet your shirt, and you're cool.. especially if you have a fan blowing you. It's easier to keep cool than it is to keep warm. You burn far less calories. you can cool down almost instantly.. warming up on the other hand.. I know what i'm talking about.

 

as far as MPG I've never needed an airbag.. i've never had any horrible accident.. I drive extra cautious. I could do fine without airbags as i've always had.. i'm not skipping the cat for MPG, i'm just saying it's a by product of eliminating the cat. THe cat is already gone.

We probably should lose some weight in our cars.. and use less gas.. it's better for the environment right?

 

Nope, you don't know what you're talking about. First of all because you didn't read my post and assumed I only talked about warming homes.

Second, because you obviously don't know how to dress for the cold.

And third, because your solution only works if it's not too hot and humid and besides, not everyone has access all day long to a building with running water and electricity and a fan for personal use. I know what I'm talking about because besides working outside in sub-zero temperatures all day long, I've also worked out in fields and on roofs all day long in the middle of summer under the blazing sun in temperatures north of 100°F with no access to running water and electricity. It's much easier to stay warm than cool.

And fourth, I have a feeling you're just trolling here. Your profile says you live in Maryland, which unlike Colorado does have required emissions testing at least once every two years. So how do you pass that without a catalytic converter? And not only do you claim you don't believe in emissions controls, you also claim to have no need for safety equipment either. I'm just saying it doesn't all add up.

 

I'm going to assume you are very young and have not learnt much about how anything within your statements work. Perhaps you should spend more time learning than on forums trying to get a rise out of people with silly claims. Put your own biases aside and look at problems from all perspectives.

 

dressing warm requires people obtain clothing, store more clothiing,..and doing more laundry. (thicker clothing).. keeping cool you just have to find some water which is 87% of the earth. you can find it everywhere.. pour that on your shirt and you've just cooled off for a bit. clearly everyone has access to water or they'd die. most homes have water. we are literally surrounded by water. if you don't go in circles, you'll find water. You don't even have to find a fan.. but water and a fan is a lot easier to find and run and maintain tthan an air conditoner or a heater.and cheaper costing. and who wants to be bundled up all the time? I don't know why you would subject yourself to those harsh conditions.. there are far easier ways to make however much you make doing that.. doesn't sound too swift to me.
I don't even know why people would live in such places.

FYI MD just requires you to plug in an OBD2 reader at a self serve kiosk. it doesn't inspect your pipes. If you trick your computer with a "defouler" you don't get codes and you pass... You can also register in other states.. or register with paper tags . or if your vehicle is over 20 years old you can get historic tags and not need that tax scam either. I prefer the options that are less big brother friendly.. and it aids that you don't get scammed with speed traps, not that I speed, because i generally don't. (who buys a prius if not for mpg?) you probably pay all the scams of the state. haha. I believe in freedom not extortion. meanwhile you probably drive past a stinky go'vt waste facility and don't see the hypocrisy that they can nose pollute but you must spend money to clean up your emissions that would also dissipate but theirs smells way worse..