After receiving a fresh set of Cat Cams 3658 Billet Camshafts, we were able to do some dyno testing and determine the viability of utilizing the factory 1.8T VVT cam tensioner to improve the powerband of our Time Attack B5 Audi A4.
We verified clearance for up to 30 degrees of advance on the intake camshaft (the VVT tensioner itself only provides about 22 degrees of advance) on our 2.2L stroker motor with the 3658s, plugged in the VVT tensioner to our 034EFI Stage IIc Standalone ECU, and got to work.
Turning on the VVT tensioner resulted in about ~400 RPM quicker spool, and solid power gains up to ~6200 RPM. We netted gains of over 60 foot-pounds of torque at the wheels at ~4000 RPM.
Take a look at the dyno chart below, which compares one pull with the VVT tensioner turned off for the entire pull, and one pull with the VVT tensioner turned on for the entire pull.
By calibrating our ECU to switch the VVT tensioner on at low RPM, and off at ~6200RPM, we were able to combine the best of both worlds. This results in a much broader powerband, with a substantial pickup in low-end torque without sacrificing the impressive top-end power that the 3658s allow.
We strongly recommend checking clearances on your 1.8T build before attempting to utilize the VVT tensioner. Depending on the specifics of your motor, there may not be enough clearance to turn the VVT tensioner on without piston to valve contact.
Obviously, the potential gains and optimal switchover point will vary from build to build depending on the cams you’re using. For example, on stock AEB cams, there was only a ~5WHP gain at extremely low RPM.