Exhaust Pipe Size

[Spilner521]

found an interesting article a guy over on j-body.org posted on 2.25" vs. 2.5" piping. shows the 2.5" piping makes more power throughout the whole rpm range than 2.25" on a 2.4 cavalier, which has basically the same exhaust as an alero. could answer a lot of questions people have about piping size on any of our engines...so i figured i'd post.....

http://www.iperformance.biz/dyno/exhaust01.html

[-Alero-]

hmmm interesting. isnt the stock pipe size 1in and 7/8?

[AlbinoMonkeyRat]

^ I thought the stock is 2.25. I haven't done any exhaust work yet, so I don't know for sure.

[Vtolds]

its 1 inch 7/8 I believe or 2 :)

[FormulaNERD]

2.25 makes more power on the VW 1.8t as well.

[Spilner521]

stock pipe size is 2" OD

Originally posted by FormulaNERD@Jul 16 2005, 02:12 PM
2.25 makes more power on the VW 1.8t as well.
Quoted post


usually the bigger the piping the better with a turbo engine. you want to get all the restriction you can off that turbine wheel so it'll spool faster and stay spooled longer.

[-Alero-]

Originally posted by Spilner521+Jul 17 2005, 04:31 AM--><div class='quotetop'>QUOTE(Spilner521 @ Jul 17 2005, 04:31 AM)</div><div class='quotemain'>stock pipe size is 2" OD

<!--QuoteBegin-FormulaNERD@Jul 16 2005, 02:12 PM
2.25 makes more power on the VW 1.8t as well.
Quoted post


usually the bigger the piping the better with a turbo engine. you want to get all the restriction you can off that turbine wheel so it'll spool faster and stay spooled longer.
Quoted post
[/b][/quote]


yeah well he told me he saw the test results between a 2.5 set and this 2.25 set. and this set was proven to be a better upgrade so he boguht it. besides its only a 1.8 its not putting out an astonishign amount of exhaust, and he still has the stock turbo. perhaps when he upgrades his snail he will go bigger.

[Spilner521]

Originally posted by -Alero-@Jul 17 2005, 04:38 AM
yeah well he told me he saw the test results between a 2.5 set and this 2.25 set. and this set was proven to be a better upgrade so he boguht it. besides its only a 1.8 its not putting out an astonishign amount of exhaust, and he still has the stock turbo. perhaps when he upgrades his snail he will go bigger.
Quoted post


i'm just saying usually its better to go with the biggest piping you can fit for a turbo, especially if you plan to upgrade and dont want to redo the exhaust again and again. what works the the vw could be completely different that what works on any other turbo engine.

[FormulaNERD]

exactly, i was just adding in on what you posted.

with any size downpipe the 2.25 magnaflow puts out the most torque out of 10 or so exhaust systems tested, and was #2 in horsepower (by like .6hp or something)

bigger isnt always better.

similar results were had when adding a larger downpipe (3.0"). and tests proved that bigger isnt always better.

[FormulaNERD]

when i originally commented i misread, and thought you said that 2.25 came out on top of 2.5.

my mistake


"The MagnaFlow exhaust proved to be the exception to our rule. We were positive all the 2.25" systems would make less power than the 2.5s, but MagnaFlow proved us wrong. This 2.25" system put down an impressive 171.15hp, placing it second overall for output. It also showed the highest torque number of the day with 182.97 lb-ft. Admittedly, it was only the best by a hair, but remember it's a 2.25".