straight pipe?

i have a 95 tsi i just got a 2.5 downpipe no cat, i want to run straight pipe the rest of the way back. my question is what are the other 2 resignators and an 02 sensor for? are they needed? and there will be no muffler just 2.5 inch pipe all the way back will this be to loud?
thanks

Without any kind of muffler, yes, it will be very loud. The purpose of resonators and mufflers is to dampen sound and allow the exhaust to collect in larger areas so it isn't flowing so quickly through a small opening. It will be very loud with no sort of muffler.

As far as necessity, there is no major function other than to dampen sound. The absence of the rear o2 will trip a CEL though (but won't cause performance loss or problems), so if that is a huge problem for you, don't do it.

I would encourage you to do straight pipe back to a cheap ebay N1 or dual tip muffler. If you wish to avoid police pulling you over for your exhaust being too loud, this is the route to take.

i might sound stupid but what is trip a cell mean?

If you disconnect the rear o2 sensor, the ECU will turn on your Check Engine Light. CEL.

Sorry...damn forum abbrevitations have me brainwashed. Thanks Joe.

lol oh thanks

can i just put it in the new pipe?

i have mine on a bung in my 3'' exhaust with no CEL. it is there so that the ECU will know when your cat converter is bad. oh i got no cat, i got a cat-eliminator DP :)

I just pulled my o2 and wrapped it in tin-foil then ziptied it up out of the way under the car. never threw a CEL.

Keep in mind if you run a straight pipe you have eliminated all emission law (vary from state to state) components and may get you car impounded if a cop looks underneath. I live in Toronto and a friend with a '99 mustang gt ran straight pipes, got pulled over for noise pollution, the cop looked underneath his car to notice its a straight pipe, now his car is impounded 2 years. Dont know much bout emision laws in the states, but in canada this is a big no no unless your vehichle is a 1979 or previous

i love not having emissions here in Minnesota!

Canada must suck for moddin cars, dont they give you tickets even if the car is lowered an inch, and BS like that.
No emissions here in MI either :D

i hate emissions here in cali. u cant do nothing, and we have low octane gas. :(

i have to echeck in ky.. but its only once each two years i believe and i just echecked in august.. so if i put a test pipe on id just have to save my cat so i can throw it back in b 4 next echeck

but yeah i think if i get pulled over and they find no cat its a fine here.. not sure imma hafta look into it

no you cant get a ticket for lowering your car in Canada, at least not in Ontario

you can do whatever you want to your car as long as all emmisions realted components are still there. What i have done is gut my cat, so it looks like its there, but noting inside

dude u know u will lose HP cause u have no back pressure!!!

LOL, i have a cold air (ram air) installed meaning i get more air into the engine, meaning i have to get it out quicker to get more air in. It's all about free flow. Somebody tell him please

BTW my car is a 4g63NT so it makes even more sence

Sorry for posting 3 in a row, but most people will install just and intake, or just an exhaust thinking they are gaining significant HP. You will not gain significant HP unless u do your intake, headers, and exhaust, due to free flow of air, the quicker it gets out, the quicker it can get more, meaning more compression = more HP.

well macder man was i even talkin to u about losin back pressure no i was talkin to riff he has no mods like u so y dont u just stfu!!!!

ok first of all... macder use the edit button if your goin to post 3 times in a row! and second of all... your wrong! your not goin to get a significant about of hp out of intake and full exhaust! and yes you need back pressure on a n/t. thats why its hard to find 3" exhaust for a n/t eclipse! and it does not make more compression by making the motor breathe easier. the only way your goin to get a significant amount of hp is if you have a forced induction (turbo/supercharger). oh and its header not headers! ;)

91 tsi talon... take it easy, no need to start fights!

91 talon, please adjust your attitude, and speak proper english (see rules).

On a turbo car you need no additional backpressure from the ehxuast. On any car, backpressure is bad. Let me see if I can use the search button to find an old post of mine...

False. Backpressure is never good. ashah000 got it right. You want velocity, to exploit the scavenging effect and pull more aif/fuel in during valve overlap. Smaller pipes increase velocity, thats physics. Increased backpressure is a sideeffect of smaller pipes. So unfortunately poeple confuse the two. Its also possible to increase velocity efficiently, meaning less increase in backpressure pre increase in velocity. Thats the whole trick... Ehxuast backpressure has no effect on comrpession ratio.



http://www.automotiveforums.com/vbulletin/showthread.php?t=202335&highlight=backpressure

well in that case you need back pressure... cause there is no way to get velocity without it! am i right?

(damn, you guys both posted in the time it took me to write that reply)

Nope. Its easy to confuse the two, but they are seperate. Block off the tailpipe. TONS of backpressure, no velocity ;) The size of the pipe (given some gas flow level) has a large effect on velocity and a small effect on backpressure. Cats and other restrictions have a large affect on backpressure and velocity, making both worse. Just going from a 3" straight pipe down to a 2" straight pipe (no mufflers/cats/etc) will have a very small impact on backpressure, but the velocity will go up significantly. Thats the best way I can think of to describe it.

yes you are!!

sry man i just got mad cause i know what im talkin about i went to school for this stuff.


Being "educated" and "knowing what you are talking about" have nothing to do with being right ;) Automotive schools are another big perpetuator of common automotive myths...

true i think they basically made me think to much of myself. LOL

Not your fault they gave you bunk information ;) Just dont be afraid to listen to other explainations of a particular subject and possibly reform your opinions about it. :)

i know you dont want back pressure but you have to have atleast some... thats why when you have 3" exhaust = no back pressure and a low velocity, and when you go to a 2.5 the back pressure gets greater! there is no way to get rid of it without hurting the hp of the motor!

Reducing backpressure ALWAYS increases HP. The highest HP DSMs dont use any exhaust. A local guy dropped his catback and went from ~132 to ~135 mph in the quarter (thats nearly 30 whp).

Now, loss of lowend torque is another story, and not an issue on turbo cars as the originator of this thread has.

Edit> Look at exhaust scavenging from headers. If timed properly, the exhaust pulse from one cylinder can put a negative pressure at the valve of the next cylinder to open the exhaust valve. That will make more power than just running open heads. Now, those headers will provide more backpressure than an open head would have. But its not the backpressure than made the power increase, its the increase in velocity at the scavenged port to the the low pressure area behind the scavenging exhaust pulse. 7000 HP dragsters run a 1 or 2 foot pipe off the heads. With forced induction scavenging is far less effective. Thats the lowest they could ever dream off getting backpressure (they have to run thos short pipes so the exhaust doesnt set the car on fire, they simply divert the exhaust away). You wont find any measurable backpressure on those 7000 hp motors...

well i wasnt talking about a turboed car... i was talking about a n/t, of course you dont want a small exhaust on a turbo... all that will do is slow down the turbine and reduce the flow.

EDIT: oh most definatly not... i have also heard that they have to run those pipes so when they shut the motor down, cool air wont enter the exhaust ports and crack the valves since the motor gets so hot then the air would enter and cool the valves so quickly... dont quote me on it, its just what i have heard from different racers

wow i learned alot by reading that post

Even on a NT car, no exhaust will still make more power. You will lose low end torque, but gain it on the hgih end, increasing peak HP. Now, wether that change is the right thing to do depends on the application. Many times the low end torque is not worth losing, and thats what I'm assuming you're refering to.

yes thats what i was talking about.

same here... plus with a n/t eclipse that only has an intake and exhaust, i dont think your worried about gaining too much high end hp! if you want high end hp... get a turbo :D

so i have a TSI, what u guys are sayin is that no back pressure is better for a turbo car? correct? oh and im in OHIO i dont think there is any emmisons here.

yes... your best bet would be to get a 3" turbo back exhaust if you plan to do bigger and better mods to the motor. if you dont plan to go that big get 2.5" just cause its cheaper and will work for what you are planning to do. but if you are planning to make your car run fast, motor work, bigger turbo setup, stuff like that, i would get 3" right away just so you dont waste money and have to upgrade twice

same here... plus with a n/t eclipse that only has an intake and exhaust, i dont think your worried about gaining too much high end hp! if you want high end hp... get a turbo :D

so jake, are you saying that my n/t is not fast :screwy: ?

YES!!!

sad to say they are slow cars!

Off topic: oh and what style MSR rims do you have? i have 190's on my GST and so far really like them, black rim with a machined polished face! :thumbsup:

lol, i know they are slow. When i drive the gs-t, i feel like the gs is a joke. Anyways i have MSR rims, i think they are style 103. I like them, they are kinda offset i wish they were more :biggrin: . Here is a link for a pic of it.

http://www.discountedwheelwarehouse.com/Store_Detail.cfm?ID=112216&InfoID=3015&ShowLarge=True

thanks

Another note... Just because your area doesnt have emissions doesnt mean that cats arent required. Having a cat is a Federal law, not state or local. So that covers all of the US. The thing is there are no federal agents driving around looking for people without cats, and the states that dont have emissions are unlikely or unable to enforce the federal law, so you typically get away with it. But it certainly is still illegal.

yeah no emissions is a plus. mn rocks, lol

hey im looking to get more power from my engine is striat pipe or pipe with backpressure going to give me more power?

Did you read the 6 year old thread you replied to? Try that first.

Holy crap 2004! Still, lots of good info. Also search. This has been answered numerous times in countless threads.