Background:
This post compares vendor-supplied dyno data for the Golf R’s IS38 tune stages. This is similar to a prior post comparing the IS20 turbo’s stock, Stage 1, and Stage 2 tunes using vendor dyno charts.
The same four tune vendors from the prior post — APR, EQT, Revo, and IE — are referenced for the summary charts shown in this post. As before, all four were tested on 93 octane fuel and reported results measured at the wheels.
Comparison:
The charts accompanying this post show the average gain for each upgrade, with a shaded band indicating ±1 standard deviation across all four vendors.
A dashed line marks the just-noticeable difference (JND) threshold — the minimum gain a driver can actually perceive.
WHP Gains:
WTQ Gains:
Conclusions:
As with the IS20 turbocharger, if you’re on Stage 1 and wondering whether Stage 2 is worth stepping up to, the data says you will notice the difference. Stage 2 isn’t as large a change as stock to Stage 1, but it is a perceptible increase in power and torque.
Note: This comparison should be treated as a broad pattern and not relied on for precise values at specific RPM points