When Bunta is driving, there is a close-up of the tachometer where we can also see that the speedometer is not functioning at all. Later in the movie, a close-up of the speedometer shows it working again.
When Bunta is driving the AE86 Trueno the camera closes in on the Tachometer. In the background it is clearly visible that the Speedometer is not functioning at all. Later in the movie a close up of the Speedometer shows it working again.
A few times in the movie before Takumi blows the engine in the AE86 Trueno you get a shot of the dashboard with the new Tachometer, other times it isn't there.
If you look closely in the beginning you can see that Takumi is already driving with a cup of water before his father tells him so.
The actors are Hong Kong Chinese nationality, yet their characters have the original Japanese names.