Question about header outlet size and system diameter

[Shinare]

OK, I'm a complete novice about these things but since catching the yaris upgrade "bug" several months ago after finding this site, i've been looking to do things I can afford to my yaris to make it more my own and a little more "peppy". (by afford I mean from the standpoint of a 37 year old father of 2 living paycheck to paycheck, hehe)

I've been looking at ways to "cheaply" upgrade the breathing and exhaust. I want to do a full exhaust system. Looking around I see lots of things that advertise exhaust diameter as "the bigger the better". BUT... it seems that every exhaust header I've seen on ebay that advertises the outlet diameter all say 2". Do all headers have an outlet of 2"?

If so, if the header restricts your exhaust flow to 2", why would you need any other part of the exhaust to be bigger diameter?

[cali yaris]

A 2" exhaust works great on the yaris, and is larger than stock. I've done 2.25" before boosting the car, and that worked pretty well too.

"bigger is better" isn't exactly true. If you lose your back pressure, you're going to lose some power too.

bigger is also usually louder, so most aftermarket companies are probably taking that into consideration as well.

[Shinare]

Thanks CY. Is the stock header 2" outlet as well? Is there benefit of a new exhaust header over stock or should I just concentrate on cutting at the end of the cat where the diameter narrows down and going custom from there back?

[haschel]

stock header 1.904" outlet

[Shinare]

OK, thanks. Anything wrong with using something like this cheap header from ebay?

[cali yaris]

^ Besides that it's a Megan knockoff, you'll have no recourse when something goes wrong, and they claim 10-15hp increase (which is false advertising)?

Other than that, it will probably work just fine. Even if it breaks, you could buy 3 or 4 of those and still come out ahead.

[Shinare]

By "something goes wrong" do you mean as in something goes wrong with my engine and it screws up my engine I have no recourse, or do you mean if something goes wrong with the header? If I'm out $60 because the header busts a year or two down the road I'm OK with that, but if there's cause to be alarmed that this may damage my lump in some manor then I think I had better take another look at it.

[cali yaris]

"something goes wrong" meaning it cracks or breaks. If that happens and you hear the exhaust leak that's fine, if you don't, further damage could result. It's not going to blow up your motor, if that's what you're asking.

As a customer, I buy proven high quality backed by good customer service. I don't want to have to deal with problems later, so I spend more up front. But that's me.

[Bluevitz-rs]

I've got a Improve Motoring Header for my '05 Echo for $135 shipped to canada. I considered it a "cheap" header at the time and I've never had a problem with it. It's going on 7 years old now, and the company doesn't even exist anymore. I've had it off the car once too to install a turbo system and the only thing wrong was that the stainless steel was kinda rusty. It's now back on the car.

[Shinare]

Originally Posted by cali yaris

...As a customer, I buy proven high quality backed by good customer service. I don't want to have to deal with problems later, so I spend more up front. But that's me.

Unfortunately I have to work with what I can afford or do nothing at all. So sometimes it means throwing some money off to China and dealing with problems if they occur. hehe

[sickpuppy1]

Garm is right about a little back pressure is a good thing. Exhaust goes out in small pulses as each cylinder fires. With a properly sized exhaust you will get a light "scavenging effect". In other words, one pulses moving out the exhaust tends to pull out exhaust as another pulses is moving out so it pulls and pushes it way out, in harmony so to speak, hence the name "tuned" exhaust. With a system that's over sized it will actually stop in the pipe, so it has to push only on its way out...no scavenging effect so the cylinder is no totally purged,hence less power. A system that's too small has to literally push it out and has to use power just to get rid of exhaust!!
On V8's, many higher end full exhaust systems will put a crossover pipe in between the two side to help increase the scavenging effect. This is only one of the reasons why the higher cost of a name brand systems cost more...They actually domputer design and then dyno the headers to know what length pipe,diameter will do best and collector legnth etc. So copycat systems will emulate what megan or whom ever have designed. Are there differences? Yes! Materials used, weld type and quality etc add up. Now is there enough of a difference for joe daily driver to notice? probably not. Garms car will, thats for sure, but he's a cutting edge kinda guy with more HP than 99.8% of us will ever get to. Lucky stiff......