What is the biggest restriction in the exhaust?

[tips000]

Is it the stock muffler, the stock bends, or the stock pipe size?

 

[agentorange313]

I say all of them to some degree.

The press bent pipes are probably the worst, if your car is still stock, the piping diameter and muffler should be that restrictive. All stock exhaust systems are press bent instead of mandrel. Press bending leaves ridged and undesired turbulence and restriction.

From the factory dsm have a 2.25 inch exhaust piping. Most people consider this to be extremely restrictive on turbo charged vehicles. When upgrading your DSM, your definately want to look into a new o2 housing and downpipe.

The factory o2 housing for 1g is restrictive and often upgrade due to boost problems (boost creep). 2g is a direct upgrade. the evo3 o2 housing is the best stock one, but you will need a special designed downpipe to fir the evo3 outlet. Aftermarket SS housings are by far the best for flow.

Most people replace their stock cat with a high flow and upgrade diameter size.

Most aftermarket mufflers have performance in mind, so you are most lilye getting something less restrictive when you buy an aftermarket exhaust system.

goodluck

 

[bsbllfit7]

If you were just to remove the catalytic convertor as well as the muffler there would definitely be gains seen. With that said the piping is also a limiting factor, turbos like limited backpressure and with the stock system that is all around. I would say in order of restriction, Muffler, catalytic converter, piping. Hope that helps.

 

[GRAVEDIGGER]

All of the above.

The stock muffler isn't a free flowing straight through design like most aftermarket mufflers.
The bends aren't mandrel.
And the stock pipe size of 2.25" doesn't stand a chance compared to 2.5-3.0"

 

[Sphinx]

A: a more strait farward answer; pipe size is the most restrictive on the whole system, although solving that problem leads to all the above replacements and options

 

[HooKnBooK]

They all play a role in restriction, but I would have to say either the stock o2 housing or the cats.

 

[JusMX141]

The stock o2 housing is the same size as the outlet of a T25 or 14B turbo throughout, so the o2 housing is not an issue.

Definitely the catalytic converter and OEM muffler as your largest restrictions. Remove / replace those and I'm sure you'll see gains across the board.


A friend of mine ran a TD05H 20G on his 2G AWD with the full stock exhaust system, and he noted that he wasn't seeing full boost until almost 4500rpms. After running a 12.86 with the full stock exhaust then swapping to a modified system, the turbo reached full boost around 3800.

I should also note that his EGT's were so high as a result of running 25psi on the stock exhaust system that it literally melted the inducer tips clean off the TD05H turbine wheel of his turbo.