What size exhaust should I go with?

Guybo

Torque Junkie
Points
52
From
Tampa, FL, USA
Car
13 GenCoupe 2.0T
2.0L Turbo, the turbo squeezes up to 18psi (124.1 kpa), I have an Injen intake.

I read a lot about 3" exhaust being better, but here at TorqueCars there's an article saying anything below about 2.4L should have 2.5" exhaust (which my car has- but the stock exhaust is terrible with bends and constrictions). My turbo has a twin scroll, does that make any difference? It spools up pretty fast with minimal lag right now as it is.

I'd like to go with a straight pipe to a high flow single exit light weight axleback. Yes, loud :) The 2nd cat will be either gutted or replaced when I get the extended "for offroad use only" mid pipe. The stock O2 housing and primary cat are going to remain unchanged (warranty purposes) but I'll go for a 3" down pipe if that's best. the stock 2.5" downpipe is well made and straight so if 2.5" is adequate, I'll stick with it otherwise I'll upgrade to a 3" downpipe. the mid pipe and the axleback will be replaced either way. I could go 3" downpipe to 2.5" catback too.

I don't race or anything. If given a choice, I'd go for low end power over top end for stop-light shredding acceleration. Although weaving through traffic at 90 is fun too :p
 

Guybo

Torque Junkie
Points
52
From
Tampa, FL, USA
Car
13 GenCoupe 2.0T
Published is 274 HP/ 275 lb-ft torque

I haven't dyno'd it so I'm going with those figures. I have no tune- stock ECM
 

Guybo

Torque Junkie
Points
52
From
Tampa, FL, USA
Car
13 GenCoupe 2.0T
Thanks, here at this forum I always find the information much more practical. Other places just like to spend gobs of my money!

Will I benefit from a 3" downpipe or is that fine too? I'm going to go 2.5" catback and delete the cat. There's a straight pipe system for my car that's not too expensive. I can't afford one of those titanium setups though
 

HDi fun

TC ModFather
Points
637
From
Buckinghamshire UK
Car
Passat 2.0 TDi
I think I'd go with a well designed 2.5" downpipe. Turbocharged engines don't rely upon scavenging in the way that free breathers do - the turbo compressor itself is an exhaust gas restrictor but the faster that the exhaust funnels into the turbo then the less likely you are to encounter excess lag and turbo latency. So a 2.5" might actually perform better than a 3" in this application.
 

Guybo

Torque Junkie
Points
52
From
Tampa, FL, USA
Car
13 GenCoupe 2.0T
The more I read the more I'm thinking the same thing because too wide of a pipe will result in less pressure but less velocity too. Exhaust gas velocity is a good thing.

So OEM O2 housing & downpipe (it's a single), secondary cat delete (replacing with a resonator), 2.5" straight midpipe to a 4.5" resonated axleback- the one I'm looking at is 3" up to 4.5" and has no muffler (thus the extra resonator). This setup is lighter than a dual exhaust (which the OEM is- single mid pipe to axleback with 2 tips) and will have better flow through.

It'll be loud, but my wife will actually like it so that won't be an issue. Happy wife, happy life!
 

old-git

Moderator
Points
617
From
Essex
Car
Elan & Robin Hood
A loud exhaust can be very tiring on long journeys so, if you plan any, I suggest having a 2.5" rear pipe and box hanging up in the garage :)
 
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