Flowing between 2 Audio Curves - car engine

Hi there,
I’m trying to make a car engine operate by using audio curves to increase the pitch of an engine loop. The system works by following two curves: acceleration and deceleration, and changing the pitch based on these 2 curves depending on the speed of the car.
The problem I’m having is that when the car changes from accel to decel or vice versa, it jumps between the two numbers, and no matter what I try, I cant get it to switch between the 2 curves smoothly.

Essentiallly what I want it to do is keep track of the 2 numbers, interpolate between them and switch to the new curve, and I’m not quite sure how to do this

Any help would be appreciated, pics below of the current system, as well as the 2 curves.