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240 +T... 2.5 or 3inch Exhaust?

edited August 27 in General

Just wanted to hear some peoples experience with upgrading the stock NA exhaust on a 240+T.

At the moment I'm running a 12b on an 80's manifold - 3" downpipe to stock na two muffler system (2.25 inch?) and have noticed it's quite a restriction. It's also generating huge amounts of heat. So much so that the manifold can be seen glowing red if it spends a prolonged time boosting upwards of 7psi.

I plan to upgrade my 12b to a 16T and have already sourced a 90+ manifold. My question is whether a 3" cat-back would be overkill? Plus there seem to be some affordable bolt-on 2.5" options, and a custom 3" job would be costly. Would I notice much of a difference?


EDIT: Should mention the car is an auto and I don't plan to run much more than 12psi. Not after crazy performance

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Comments

  • SpacSpac (@Spac) Canberra-ish.

    2.5” is easier to keep quiet, particularly avoiding drone on the highway.

    2.5” with decent mufflers should be fine unless you are looking for big power.

    buddyglitch
  • Yes for your usage, 2.5" is enough.

    If planning more speed, 3" which with decent mufflers won't be any louder than 2.5" if you're smart about muffler selection

    buddyglitch
  • I vote for 2.5 inch. My dad has a custom 3-inch on his 240 turbo conversion and the clearances are too tight and it just looks cartoonishly large when you look under the car...I think it’s probably overkill to be honest.

    buddyglitch
  • 3inch as the price difference should be near zero

  • Yeah if you can get it routed without hitting the floorpan, axle, tank etc. :)

  • I'd at least do a 3" downpipe, that made a huge difference in power and response on my 740T. After that, you could get away with 2.5, however there should be plenty of space under a 240 for a 3".

    buddyglitch
  • GhettobirdJulian (@Ghettobird) Melbourne - SE Suburbs

    2.5 inch system with a nice 3 inch DP will do just fine, any bigger for the rest of the system than 2.5 and you'll be chasing rubbing and clearance issues forever

    carnut222buddyglitch
  • I really don't think there'd be any clearance issues with a 3" exhaust, unless for some reason you were going over axle with it.

  • The 2.5 inch under-axle OE Volvo pipe has a dent in it for clearance, so if you go under axle with a 3-inch pipe it will be even worse clearance or larger dent than OE 2.5 inch pipe, unless you want to sacrifice ground clearance. FWIW...here’s a pic of the dent on the OE turbo 2.5 inch under-axle pipe


  • DauntlessDauntless (@Dauntless) Central West NSW
    edited August 28

    My 2.5" will touch the axle tube when jacked up, apart from that no clearance issues ever and no dent in the pipe. These pics are before the rear was lowered, so there's at least 1" more clearance to the axle tube now. Ground clearance is fine, I've never scraped the exhaust on anything.




  • 3" over axle is entirely possible with no clearance issues, it just takes a bit more time and hence $ if you can't do it yourself. I built one for my 242. By built I mean I took a 3" exhaust off a car I had and ended up pretty much redoing the whole thing because it hung to low and at full suspension compression interfered with the torque rod bracket on the axle.

    Back to the question at hand, 3" future proofs your build. Your not going to save much $ by only going a 2.5" which might not meet your future needs.

    DauntlessbuddyglitchGingerNinja
  • @Dauntless that looks good and looks like plenty of clearance. I assume the reason Volvo put the dent in the top of the pipe was to allow a bit of extra ground clearance on a stock ride height car without having the axle hit the pipe too often when the suspension goes into hang. Car manufacturers can’t get away with as much stuff as we do on our own cars as we’re willing to put up with a few drawbacks to achieve an end result. On my car, 2.5 inch should be sufficient since I don’t plan to run more than standard boost. As @VolvoHordz said if you have the capability to build it yourself, then you can do it properly. I just don’t like the idea of paying an exhaust shop $1000 for some f**ked-up mess...that’s why I bought the OE Volvo 2.5 inch system. There’s also a Simons sport Turbo exhaust system available that could be a good option for somebody looking for a bolt-on system, however the shipping on that system is pretty expensive.

    buddyglitchDauntless
  • Thanks guys, these are all good points! Hmmmmmm.. what would future me do?!?


    carnut222nugget_940
  • With a 3" downpipe and 2.5" back from there with straight through mufflers, you should see minimal restriction running 15psi on a small turbo like a 15G. I think that's worth considering, as a stock turbo on wastegate pressure makes for a pretty dull/slow car.


    It's important to find an exhaust shop that will do what you want, though.

    buddyglitch
  • Does anyone have any experience with JT Tuning? They do a nice looking bolt on 3" catback for 250 euros.. I guess after shipping it would come to $500-$600.. Not crazy considering some custom quotes I've heard.

    Ex850R
  • Seems pretty good price if you can get it delivered for that. You can be the guinea pig and let us know! :)

    buddyglitch
  • gavinhGav (@gavinh) Parmelia, Perth

    Ipd do a 2.5" system off the shelf

  • carnut222Greg S (@carnut222) Daylesford VIC
    edited August 29

    But postage and exchange rate...YIKES! IIRC the Volvo GCP 240 Turbo system is cheaper and genuine Volvo...I’ve heard some of the ipd systems may not be great...but that’s anecdotal. They do have some nice-looking SS systems...most of theirs say non-turbo though, not sure why??

  • SpacSpac (@Spac) Canberra-ish.

    Exhausts vary wildly in prices depending on the shop and how much they want the job. If $600 for a cat-back system seems like good value, then keep talking to more shops.

    Even in over priced Canberra, I can get a custom system for less than that.


  • Have it open at like 5psi with a boost tee, straight after the 3" cat. Retain stock exhaust. it's what I'd do if I had my time again - no drone, no clearance issues, only noisy when it actually needs to be.

    Ex850Rbuddyglitch
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