3 inch exhaust question

For the people with 3 inch exhaust...does it affect the acceleration of the car a lot? On my old civic, it was the worst idea ever...please help!

Imho it helped a little when I put my 3in downpipe with hi-flo cat.. Seemed like it smoothed it out abit.


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Carsonmkvi said:

For the people with 3 inch exhaust...does it affect the acceleration of the car a lot? On my old civic, it was the worst idea ever...please help!

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It's all about keeping the flow of exhaust gas velocity up, the closer to the engine the change the more noticeable the drop off. I had the same issue on my Integra, its always best if you make a reducer with a gradual taper.

i believe you want some back pressure on a N/A car, and free flowing on a turbo car. So on a NA 2.5, 3" cat back is probably too big. Most of the performance exhausts on the market are either 2.25 or 2.5, and the manufacturer dyno results are all from stockish car, definitely NA. That gives you an idea on what makes power on a NA 2.5.

Is there any reason for you to go 3"? And I didn't know the US have a 2.slow (gas 2.0 na) mk6 golf. The only mk6 with a 2.slow that i know of is the base trim Jetta. What exactly do you drive?


Peter

I have a GTI but if I remember correctly, I did not notice much of a difference, if there was any at all, between the stock 2.5" exhaust and my 3" turboback exhaust with a Stage 1 tune. The idea behind going to a larger pipe is to reduce the amount of loss generated from a smaller diameter pipe to get the turbo spooled up at a lower RPM.

For a naturally aspirated car, going to a 3" pipe would serve no benefit, and would actually decrease the performance of the car, although slightly, from the decrease in back pressure generated from the larger diameter piping. The turbo provides back pressure for the GTI, but for a golf it's important to keep back pressure in your exhaust.

tl;dr no. Bigger pipes don't do shit in a n/a car

gugu1981 said:

Is there any reason for you to go 3"?

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There's a guy on here with a GTI eurojet exhaust, but on his 2.5 NA, which is what I have. And it sounds really good, and my car is already slow, so I might as well embrace it and make it sound cool. Just wanted some input for our cars specifically.

I have 3in from the cat-back. Its only for sound on a 2.5, you wont be able to tell a difference in power/throttle with it.

I only wanted to know if people with a 3 inch exhaust on the 2.5 engine experienced a big drop in back pressure. I don't want my car to feel slower than it already is and I understand that larger pipe diameter affects back pressure, or at least in my civic it did.

Carsonmkvi said:

I only wanted to know if people with a 3 inch exhaust on the 2.5 engine experienced a big drop in back pressure. I don't want my car to feel slower than it already is and I understand that larger pipe diameter affects back pressure, or at least in my civic it did.

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For what I've read researching the SRI manifold the NA motor needs pack pressure, without it power is affected. I intend to install a SRI manifold at some point so I installed a GTI muffler I got for $40 but only the rear suitcase, I ditched the centre resonator/muffler and kept all the original 2.5 plumbing except the rear suitcase.
http://www.golfmk6.com/forums/showpost.php?p=2460855&postcount=36798