Downpipe Turbo Subaru FAQ

Downpipe Turbo Subaru FAQ

Are there any downsides to downpipes? There have not been significant amounts of problems with downpipes. There have been some reports of wastegate issues with split bellmouth and divorced or twin dump downpipes. These type of downpipes have a “splitter piece” that juts into the turbo to separate the exhaust from the wastegate. Sometimes this piece is too long and requires some slight cutting or grinding for a perfect fit. The telltale sign of this occurance is less than full boost or irratic boost upon installation. As with any aftermarket part, even “perfect” ones, sometimes you run into a rogue issue. From research, this is not a widespread issue at all, only an advisory if this situation should occur.

Where do I buy a downpipe?

Invidia HS08SW1DPN Divorced Wastegate Down Pipe for Subaru WRX STI/Legacy

GrimmSpeed 3″ Catless Bellmouth Downpipe – 02-07 WRX / STi – 04-08 FXT

Invidia HS08SW1DOC Twin O2 Bung Down Pipe for Subaru WRX STI/Legacy

What is some good background information about exhaust pipe fitment?
Generally speaking, there are two types of catbacks:
Type 1: It has a sliding flange designed to bolt up to the stock downpipe.
Type 2: It has a flat flange designed to bolt up to 3″ downpipes.

Generally speaking, there are two types of downpipes:
Type 1: It is designed to bolt up to the stock catback and other type 1 catbacks.
Type 2: It is designed to bolt up to only type 2 catbacks.

Type 1 catbacks do not bolt up well to type 2 downpipes, and type 2 catbacks do not bolt up well to type 1 downpipes.
Type 1 catbacks and downpipes taper to 2.5″ where they meet.
Type 2 catbacks and downpipes are full 3″.
Type 2 downpipes are usually less expensive than type 1 downpipes.
Type 1 and 2 catbacks are relatively similar in price.

All 2.5″ catbacks are type 1.
Some 3″ catbacks are type 1, and some are type 2.

What questions should I ask of the retailer or manufacturer before purchasing?
1. Will this unit mate up to the rest of my exhaust? Some downpipes will fit the stock exhaust, or must be fitted to a larger exhaust.
2. Will this unit throw a CEL? Some do, some don’t, so find out beforehand.
3. Does it come with new gaskets? It is always a good idea to replace exhaust gaskets.
4. Does it come with a CEL fix if needed and is it the right one? In the case of the electrical fix, there are two unique fixes, one for the 02/03 and one for the 04. The 05+ does not currently have an electrical fix.

How hard is it to install a downpipe? Allow around one-two hours for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished by even the greenest shade tree mechanic.