i would i would say a 2.75 to 3" DP is great, but i would just stick to the standard cat backs. the benefit of the high flow cats are these. 1 it will keep you from throwing the oh so popular CEl of the second 02 limit surpassed, and most importantly it will keep you from getting those funky exhasut smells. like i have right now. It stinks, and worst of all it does get in the car. right now i have a 2.5" DP straight through no cat. it works and clears but it was homemade lat time i had the car appart, and although it is a decent fit it is not perfect. thats why i'm making another one. I can have the guy make them from 2.5" as well if you guys want them that size. but still get a 3" cat.

 

pricing is coming next week. there will be a 3" or 2.5" with and without cat. pieces will be picked up by me or i can ship them from their location. i would probably charge less, but its up to you. there wont be any other runs on this pipes. as they are custom made and i'm only taking my car to a shop 1 time. i hate paying people to do stuff for me.

 

I'm interested as well. I'm in AZ so I could drive there if need be.
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Stupid question...but cant you use a pipe from a VW 1.8?

 

not sure what you meant FXRocket....

 

here is the final pricing. he will not budge on this so dont even try. i tried to lowball him already and he said its not worth the time it will take, considering the parts he has to get. flex pipe, flange, o2 bungs and cat and stainless piping

2.5" DP no cat 300
3"DP no cat 310
2.5"DP with high flow cat 410
3" DP with high flow cat 450

hope you all decide to get one. the pricing is preety good. as most pipes for the tt225 start at about 450 or so without the high flow cat. later on you can do the ATP eliminator kit which will bolt right up to stock and allow you to go back to a k03 without too much work. (if smog happens, or fix it ticket) The DEADLINE is the first of next month (5/1/07)and they will be made on 5/7/07, andshipped out by the weekend 5/11/07
PM me if you want one, and i will reply with instructions for what to do and a phonenumber so we can get in touch and set it all up. talk to you all soon.
Andrei

 

I have read that with a small turbo, a 3 inch full exhuast can cause the turbo to over spin which I guess could cause problems later on, is this right?


The article said that with too big an exhaust there is not any pressure on the turbo so it just keeps spinning, so Im guessing that the turbo does need some pressure to keep it from spinning too fast.

 

I was under the impression that the turbo created it's own pressure and that a downpipe restricted it.

Wouldn't that cause more pressure/build up with a restricted downpipe?

I just down see how having a larger downpipe would cause a turbo to "just keep spinning".
Now if there was too much boost/air going into the turbo I can see that being a problem.
Where did you read this article? Any links?

 

Well I can see a turbo keep spinning if there is nothing to slow it down and I think that is what the back pressure does but you dont want too much back pressure, but this is what I have seen in an article about small turbos. Now bigger turbos they say you can use a 3 inch exhaust. If I understand this right the turbos spinning is created by the exhaust airflow which is why you want it free to a degree, but if there is nothing to restrict the flow then the turbo just keeps spinning and this would cause damage to the turbo. Now again this is what I have read but I am curious as to wheather this is right or not as I will be doing a new exhaust on my new TT when I get it. Now I have heard that a 3 in downpipe into a 2.5 exhaust is good too.

This is from an article I read about it:

A warning should be made about extremely big bore systems. A turbo charger works at its best efficiency with no back pressure at all to stop it spinning up. Some manufacturers warn of over spin but in all intensive purposes you would only ever achieve this scenario in running with no exhaust! A problem arises though with exhausts that are too big. Off boost, at low rpm, cruising etc the engine is basically a normally aspirated engine. Acceleration from low rpm will be severely affected as the engine running in NA mode can not achieve the power fast enough to spin up the turbo. By gradually increasing the back pressure by causing a restriction in the exhaust will improve things. Of course there will be the situation that you end up with too much and it then throttles the turbo! A compromise between the two is required.

 

the turbo over spinnig wont happen since you have pressure on the other side fighting against it. but yes at low rpms when you are not boosting, you mignt loose a little bit of torque, but even that is doubtful. want to know why. well its because the small turbos we have,(k03) have a tiny little opening for the turbine wheel and thats the main restrictor. there wouldnt be a point to going too big, but since atp made the eliminator, you could later upgrade to a gt2871 and not have to buy a new DP for anyone who wont go much bigger than stock, get a 2.5" DP its going to be more than enough. i'm going 3" as i'm also keeping a cat on there, and soon am also going gt2871r...........