3" exhaust

[jhale101]

Am seriously considering 3 inch exhaust system.
Do the new systems usually include a new catalitic converter or do they usually connect after existing cat.

[littleriver]

Am seriously considering 3 inch exhaust system.
Do the new systems usually include a new catalitic converter or do they usually connect after existing cat.

You can get either ... but better to go with the 200 cell

https://www.factorydirect4x4exhausts.com.au/mitsubishi/

Give them a call for more info ...

...

[fourocker]

Diesel I'm guessing, go 2.75 inch (3 inch can contribute to over boost ) right off the back of the turbo, the first metre or so is the most beneficial to replace and if you include a cat don't install it in that first metre.
3 inch is totally unnecessary and of no benefit as is any replacement of the exhaust after the rear diff, just no gain there.
You may be able to save some money by having a custom setup done how you ask for it versus an entire off the shelf setup unless you plan to fit the off the shelf stuff yourself......then it may be better to get a quote.

[nj swb]

Diesel I'm guessing, go 2.75 inch (3 inch can contribute to over boost ) right off the back of the turbo, the first metre or so is the most beneficial to replace and if you include a cat don't install it in that first metre.
3 inch is totally unnecessary and of no benefit as is any replacement of the exhaust after the rear diff, just no gain there.

How does a larger exhaust contribute to over boost?

[rotare]

3 inch is totally unnecessary and of no benefit as is any replacement of the exhaust after the rear diff, just no gain there.

Not this old chestnut again....

[rykiel575]

From my reading beaudesert do a 2.75" to differentiate themselves from the others but there was a poster on here who argued that 3" is better which i am more inclined to believe.

[Chooseboost]

From my previous performance car experience with turbos bigger exhaust is always better. Overboosting could be a problem but am unsure.

[erad]

Even the standard 2.75 inch exhaust can suffer from over boost. Boost is controlled by the ECU, regulating the vanes on the turbo. If the sensor or the ECU fail, you can get over boost. A 3" exhaust will have less back pressure so the turbo will spool up quicker that the standard 2.75 inch (a good idea) and thus there is a possibility of over boost if the ECU does not control it quickly enough, but this should be only for a short time and then the ECU should pull the boost back to design conditions. My NW (2.75 inch standard exhaust) boost occasionally gets to 22.5 psi, but then the ECU pulls it back to around 17.5 PSI. A 3" exhaust will get you max boost earlier int he rev range than the standard 2.75 inch, ubt the difference will be marginal.

[fourocker]

How does a larger exhaust contribute to over boost?

I have read this occurs because it's not a simple waste gated turbo (which is more reliable), it is an ecu controlled turbo and if the extra exhaust flow has the turbine spinning faster than expected it can take the ecu a little time to regain control.
If you believe it or not that's up to you but I thought the op should be aware of the possibility.

[nj swb]

I have read this occurs because it's not a simple waste gated turbo (which is more reliable), it is an ecu controlled turbo and if the extra exhaust flow has the turbine spinning faster than expected it can take the ecu a little time to regain control.
If you believe it or not that's up to you but I thought the op should be aware of the possibility.

So it's a short term thing? A few seconds? If so, that's nothing to worry about,because it won't have enough time to raise any temperatures to the point they will do damage. Sustained overboost is the problem.

[Uncle Fester]

From my reading beaudesert do a 2.75" to differentiate themselves from the others but there was a poster on here who argued that 3" is better which i am more inclined to believe.

Ive had both on my 2010 NT Auto and I couldn't notice any difference between the 2.75 BD and the 3.00 Scotts Rods one I have on now.

[rotare]

I have read this occurs because it's not a simple waste gated turbo (which is more reliable), it is an ecu controlled turbo and if the extra exhaust flow has the turbine spinning faster than expected it can take the ecu a little time to regain control.
If you believe it or not that's up to you but I thought the op should be aware of the possibility.

This has been discussed before. Plenty of people are running 3 inch exhausts on their Pajero's, including myself, and have never experienced any over-boost - ever. In previous threads on this topic some people have pointed out various other makes and models of vehicles have known issues with over-boost when larger exhausts are fitted - so blanket statements are made and conclusions are drawn that it will be an issue on the Pajero as well, but it appears not to be for most.

In regards to your comments that a 3 inch is totally unnecessary. A turbo charger works best when the pressure differential across the turbine is maximised. The best and easiest way to achieve this for most people is to have zero restriction / back pressure on the outlet side of the turbine (ie, the exhaust). Hence why the largest and least restrictive exhaust will give you the best outright performance and responsiveness. In theory the 3.2 engines may only need a 2.75 inch exhaust to achieve this, however factor in weld protrusion inside the pipes, mismatch of pipes when welded together, mismatch of flanges and gaskets, friction losses from bends, back pressure created by mufflers etc etc, and what you end up with is a systems that flows much less than 2.75 inches....

Hence why it makes sense to fit the largest practical exhaust which helps negate and offsets these common issues when exhausts are constructed. The other consideration is that 3 inch pipe, mufflers and components are way more common to source than 2.75 inch. Every exhaust shop carries the stuff. So if you ever need to have repairs done to a 3 inch exhaust you'll find it will be much easier and cheaper, and you'll have more choices of mufflers, than 2.75 inch.

Unless you have space limitations under your car that requires you to fit a 2.75 inch exhaust, a 3 inch exhaust will work just fine, likely perform better and probably be cheaper to purchase than the 2.75 inch exhaust anyways

[Scouter1]

Another member of the 3" gang here - no overboost issues since installation over 4 years ago.

[thorno]

The standard system is definately not 2.75". Lol. Some sections are 2.25". You will benefit from a 3”. I have a Beaudesert 2.75" and am super happy with it.

[Poita]

As rotare already mentioned, turbos work on differential pressure. Go as big as you can practically fit in other words.

And there is zero point only replacing some of it. If you do it, you need to do the lot of you are wasting your money. The pressure seen will be from the smallest diameter point in the whole system.