I've been tinkering with my 2011 Outlander Sport which shares the same 2.0L 4B11 Engine as many of the Lancer models.

What is the typical tubing size that the upgraded intake kits are using?

I just recently upgraded my throttlebody from the 55mm stock to an Evo X 60mm and was able to barely fit the stock snorkel back on with a bit of stretching using a bench vise to spread it open. There was a casting tab that interfered with swapping the throttlebody electronics directly but after grinding that away it assembled perfectly.

There are gains along with the coolant bypass mod but I feel the MAF is now a restriction since it's only 57mm ID (2.2") where the sensor is mounted, plus the actual sensor blocks a fair chunk of airflow through the center of the tubing.

The stock tubing is basically a giant flex piece of rubber with ribs in it so it doesn't collapse but a smooth mandrel bent 2.5", 2.75" or 3.0" replacement should help. Going too large means a drop in velocity so 3" might be overkill.

I have a feeling that 2.75" (68mm ID) would work really well which is about 10% larger than stock tubing (good for maintaining velocity) and 20% larger than the MAF sensor tubing. I have access to the MAF compensation tables on my Outlander Sport so re-calibrating the tables isn't a huge deal.

Also has anyone seen the EGR return tubing that enters the plastic intake manifold? Seems like it blocks a good 15-20% of the airflow right after the throttlebody which can't really help matters. I plan on grinding it down after sealing off the area but wanted to see if anyone else noticed it and took action.

 

MAF sensor is not big restriction, it's designed aerodynamically. It's shape is like airplane wing, so I wouldn't worry about it. Larger tubing would help, but I would advise to not go bigger than 2.75". Some intakes uses larger tubing, but their MAF section is with stock diameter, so you maintain correct readings and won't have to scale your MAF.

 

Yeah I figured the wing shape does help flow around it so it's probably not that bad. It is interesting that on the stock setups the MAF section is always a bit smaller diameter than the hose diameter leading to the throttlebody. That would make tubing after the MAF slow down in velocity which isn't really what you want so making it 2.75" mandrel from airbox to TB should help smooth out flow. If anything making the MAF larger to account for it's slight flow restriction at 3.0" and the tubing 2.75" would probably be ideal, just a matter of calibrating it all to keep the AFR's the same.

 

I'm not sure exactly what the ID is of the aftermarket exhausts. I'd love to know though. I have read that the 2.0 and 2.4 have identical intakes, but I haven't verified this, so it's speculation.

I've attached the measurements taken from my 4b12, most of the values are air-path related inside diameters. The MAF housing increases in diameter by 5mm to accommodate the turbulence created by the MAF. That rubber elbow is a good candidate for replacement, similar to crush bent vs mandrel bent, the diameter can be reduced. I think 66-68mm would be a good range. Replacing the rubber elbow with a hard pipe would probably work better with the 60mm throttle body rather than stock.

The EGR tube in the IM I assume extends into the highest velocity part of the airstream to help it cool, or mix better. If it were near the wall, it would accumulate, and may not divide evenly between the 4 runners. I really am torn between decreasing the turbulence it creates, and keeping the mixing properties of having it as the core of the airstream. There is likely a better shape for that inlet port though. Of course, if you're talking about removing the extra EGR entirely, then it's a moot point.