stock straight pipe vs. 2.5 straight pipe SOUND

October of 2012 i straight piped my 02 golf and i fell in love with the sound.

i had an emissions test in august 2013 and i was required to put my cat back in. since i no longer have a welder, i had to pay someone to re-install the cat. i don't want to cut the exhaust again so i have decided to upgrade to 2.5 or 3 inch turbo back straight pipe from Kerma or Buzzken.

I was excited to order my new exhaust until i came across a post on this site that said the "woosh" sound between shifts was eliminated with a larger diameter exhaust. i went on youtube and started watching video after video of alh's with modified exhausts and i am unable to come to a conclusion on this.

i love the woosh sound of the stock exhaust, will i lose that sound with a larger exhaust?

If so, i will buy a second oem downpipe and experiment with that.

input from people with first hand experience would be greatly appreciated.

What do you mean by "woosh"? Do you mean a turbo spool down sound kinda like a blowoff? I have a full 2.5 straight pipe and it sounds great. I got a streettoys 2.5DP from kerma a few years ago and had a local shop do the rest. DP came with a flanged diesel hiflow cat and a flanged straight section so i can swap the cat in or out at my leisure.

yes, i mean the blow off sound. a 2.5 will still have this? i know you said it "sounds great," just trying to clarify.


the flanged straight section will not work in my case, only the OEM cat will pass smog in california... makes no sense to me.

Mine had a really LOUD woosh sound after the staight pipe.

Someone at a Get Together commented on it, that it was more than one would expect. Turned out my turbo actuator was out of adjustment and that is why it was extra loud.

Adjusted it with a mitivac to lift at the proper vac and it quieted it down.

The GOOD of that, is with out out of ajustment, it was also overboosting, so it was a good catch overall.

anyone have experience with a 2.5 or larger?

I LOVE the way my car sounds. I bought kermas 3" turbo back kit. I had it dumped under cab with a turbdown for a while, sounded good. Then installed the rest of the exhaust, but decided to install a 4" tailpipe section, and a 5" tip. Now It sounds even better. I did however lose the b.o.v. sound with the 3" exhaust, which I thought was strange. It had the noise when I got the car and it had stock exhaust straight piped...

I have a 3" cat back system and it sounds great! It does have a big rear muffler but it sounds like a big ass diesel truck. I just love the sound of it firing up, a very deep diesel rumble.

It's galv piping, has been on for 10 yrs and is still going strong.


http://[url=http://pics.tdiclub.com/showphoto.php?photo=79510&title=rear19&cat=504][/URL]

ghohouston said:

I LOVE the way my car sounds. I bought kermas 3" turbo back kit. I had it dumped under cab with a turbdown for a while, sounded good. Then installed the rest of the exhaust, but decided to install a 4" tailpipe section, and a 5" tip. Now It sounds even better. I did however lose the b.o.v. sound with the 3" exhaust, which I thought was strange. It had the noise when I got the car and it had stock exhaust straight piped...

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This is the information I'm looking for.
This rules out the 3 inch exhaust for me. Anyone know what causes the b.o.v. To disappear?... Lack of back pressure?

How about the 2.5?

Trying to get definitive answers before I make my final decision. Thank you all for the help so far.

Ill also add, I noticed an honest to god seat of the pants power increase going from stock to 3", and im not a person who is easily bought off or suffers from the placebo effect.

i doubt there will be any noticeable performance gains from a larger exhaust in my case. i have come to the realization that my tdi will never be fast, thats what my sti is for, i just want it to sound appealing... to myself at least.

ghohouston said:

Ill also add, I noticed an honest to god seat of the pants power increase going from stock to 3", and im not a person who is easily bought off or suffers from the placebo effect.

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What did the dyno show? You'd probably be disappointed

LNXGUY said:

What did the dyno show? You'd probably be disappointed

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My butt dyno showed a slightly bigger grin when I floor my car/going through the power band . I NEVER claimed to have actually gained any power, although im sure it probably did have a very minute increase. And of course sounds exponentially better now.

It's worth it for the sound alone

I have stock down pipe cut in front of old cat. Then 2.5" pipe back. I have sound you are looking for. Stock downpipe provides it. Get rid of it, sound goes with it. If your current downpipe needs replaced, get another stock one for maximum blow off valve-like sound.

I am considering putting a Moroso Spiral Flow muffled on mine to cut down on drone at 65+ mph. Getting tired of it.

LNXGUY said:

It's worth it for the sound alone

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Completely agreed. I just got my car back together and drove it for the first time since cleaning the vanes. One, I cant believe how much it shifted my power bamd around and just all out boosted my performance. And two, it made my car A LOT louder than it already was, exhaust noise wise, not just turbo whistle.

LNXGUY said:

What did the dyno show? You'd probably be disappointed

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Yeah I agree with you. Stealth TDI here gained 9WHP from a straight 2.5" piping IIRC. Here it is http://stealthtdi.com/Performance.html

BTW LNXGUY I your comments and the way you stick out for yourself sir! (hope you remember the ones about the hot swap)

I guess I will find another stock downpipe then. A little disappointed I cant get a new larger polished stainless steel down pipe and keep the blow off sound.

Thank you all for your input and help. I love this site.

Does anyone have a downpipe for sale?

TDI_ said:

Yeah I agree with you. Stealth TDI here gained 9WHP from a straight 2.5" piping IIRC. Here it is http://stealthtdi.com/Performance.html
BTW LNXGUY I

your comments and the way you stick out for yourself sir! (hope you remember the ones about the hot swap)

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9whp is totally believable if you've got an upgraded turbo or other serious mods.. 9whp on a car with upgraded nozzles and a tune is a stretch

bump.

looking for a stock downpipe, anyone have one for sale?

I just removed mine about 4 weeks ago.
And I already removed the stock cat for you.
Unfortunately, I'm using the cat if that matters.
The DP looks to be in perfect shape. Yours for $50.