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Old 09-06-2013, 01:22 PM   #103
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Member#: 106116
Join Date: Jan 2006
Chapter/Region: NESIC
Location: Massachusetts
2016 VW Golf R
Limestone Grey


Originally Posted by HyG3nx View Post
How or why did your wtq go down after installing axel back?
I wondered the same thing! The torque loss was what brought me back to the tuner; it was noticeable.

My understanding is that it was a back pressure thing. The back pressure from the more-restrictive STi axle-back that was on the car made more torque, but choked off the flow at high RPM. The Greddy flows better and so produces better HP, but less torque.

I admit, I don't fully understand it myself. See this post:

From that discussion:

"at low rpm the pipes are too big to keep gas flow velocity at it's best if the pipe is sized to keep the flow maxed at high rpm."

"Back pressure loads the engine and produces torque. It's all about compromise. Load early and top end hp suffers as the engine labors."

The loss of that torque was what drove me to a VF39. Once I lost it I really wanted it back. It was a noticeable difference, and I felt more turbo lag. I'm glad I did, because off-boost drivability is much better with the VF39 over the TD04.
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