Engine sounds coming from speakers
Many Electric cars play petrol engine sounds through their cabin speakers. This apparently makes for a more engaging drive. Obviously a 5L sports car has no need for such things, or does it? Well in line with taming the more wayward characteristics of the early cars, the new models can be so quiet that Jaguar has fitted them with Next Generation Power Train Sound Quality (NGPTSQ) system.
I stumbled on this while using the claws out mod. I have fixed the exhaust valves in their closed position then pressed the active exhaust button. Instantly the cabin was filled with a low and slightly strange rumble.
Example sound file
You can hear it in the sound file below. The valves in the exhaust are physically shut throughout by removing fuse 15. To start the active exhaust button is pressed to ‘on’ and the car revs raised from idle to 2000rpm while stationary in park. The active exhaust button is then pressed to off and the same increase in revs performed. The final time the test is repeated with the active exhaust ‘on’.
As you should be able to hear the car is making a weird phasing rumble type sound. I believe this is the NGPTSQ. Its active all the time but at a much higher level when the active exhaust button is pressed.
Characterising the sound
Fishing around the sound is mainly coming from the larger door speakers and the speakers behind the seats. A quick FFT shows the frequencies involved.
The orange line is with the exhaust button lit (but valves closed) while the blue is unlit. Reading around a bit I expect much of these sounds are being generated at a low frequency where they are more felt than heard. So looking at lower frequencies.
Scan of lower frequencies, left hand active exhaust off and right hand on. 17dB is a significant increase!
Removing the sound
Once you hear this sound its difficult to unhear it 🙂 I didn’t buy an Ftype to listen to warbly sounds coming through speakers! Again Jag Bass on the Jaguar Forums.com comes to my rescue by reporting this sound is transmitted to the amp through a grey wire.
Finding and cutting the wire should remove the sound. Turns out to be slightly challenging getting to the wire as the amp is well sandwiched between a bracket and the outer panel of the car and not removable with out a lot of disassembly.
However buy removing some trim in the coupe boot you can just about see the wire in question.
Here I have used a couple of blue crimp T connectors to provide tails to this wire should I want to reconnect it. Then the wire is cut.
It you are tempted to do the same the picture below might help. Its a shot of the connector the grey wire goes into at the amp. I cant see this listed on wiring diagrams but I suspect its the inner core of a coax cable with the shield cut back to where it leave the wiring loom.
The car without NGPTSQ
The effect is a much quieter cabin if the car is driven in normal/comfort mode. Below is the same 3 runs from idle to 2000rpm without the NGPTSQ,
I have tried to keep all the sound levels consistent with the recording further up this page. You may need to turn the volume up for this one! But no weird phasing and chugging is heard and all the engine sounds are real!
The corresponding FFT of audio and low frequencies are below.
As a slight negative I do now have a persistent DTC B1D9F(13). Though no engine check light, the fault is described as
open circuit or high resistance in the Engine Speed Input circuit for the Audio Amplifier module, often signalling a communication problem with the Infotainment system
Given I have cut the wire I guess this is bang on 🙂
I do feel the car is more relaxing to drive on motorways or around town, and when flicked into dynamic mode it good to know its all real petrol noises getting into the cabin.