Radio interference

Post Reply
Message
Author
Marlowboy
New member
Posts: 14
Joined: Sat Feb 29, 2020 9:14 pm

Radio interference

#1 Post by Marlowboy » Mon Sep 28, 2020 11:33 am

Hi all, BMW X5 radio is great on Petrol, changes to LPG and on MW (I know, I’m old but like the Sport) Interference is dire. Increases with engine speed.high pitched whine......any suggestions please? Thank you in advance.

LPGC
Installer
Posts: 4069
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: Radio interference

#2 Post by LPGC » Mon Sep 28, 2020 11:59 am

You could have a look to see if/how the installer has routed an rpm detection wire to one of the ignition coils / general routing of wires to injectors etc.

Is the interference a ticking noise (if so is the ticking happening around 5 times per second at idle rpm or more often) or a whine? *Edit - noticed you did say a whine (as opposed to a tick).

Out of interest, what LPG system do you have fitted (ECU and injectors)?

A lot of systems lower current to injectors during the hold stage by using PWM, for every 1 millisecond of injector hold open time current may be switched on/off to injectors around 50 times giving a PWM frequency of 20 microseconds or 50kHz and 8 of those (for 8 injectors) might be able to produce 400kHz with plenty potential for interfering with LW and MW.


But this is probably more Gilbert's field... what do you reckon Gilbert?
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

Gilbertd
Advanced Member
Posts: 8543
Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Radio interference

#3 Post by Gilbertd » Mon Sep 28, 2020 12:35 pm

Dunno without hearing and seeing it, but could the installer have taken the switched supply from the radio? In which case it will need either a choke or a cap to deck.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

LPGC
Installer
Posts: 4069
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: Radio interference

#4 Post by LPGC » Mon Sep 28, 2020 12:47 pm

Gilbertd wrote:
Mon Sep 28, 2020 12:35 pm
Dunno without hearing and seeing it, but could the installer have taken the switched supply from the radio? In which case it will need either a choke or a cap to deck.
On X5's some installers do take the switched live from radio / cig lighter socket, especially if it's a Valvetronic and especially if they've connected the LPG ECU to OBD.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

Gilbertd
Advanced Member
Posts: 8543
Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Radio interference

#5 Post by Gilbertd » Mon Sep 28, 2020 1:12 pm

Isn't the radio on an auxiliary supply so power is cut during cranking? I wouldn't have thought that to be a good idea, surely taking power from the injector feed would be better?
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

LPGC
Installer
Posts: 4069
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: Radio interference

#6 Post by LPGC » Mon Sep 28, 2020 7:46 pm

Gilbertd wrote:
Mon Sep 28, 2020 1:12 pm
Isn't the radio on an auxiliary supply so power is cut during cranking? I wouldn't have thought that to be a good idea, surely taking power from the injector feed would be better?
I've never actually seen it connected to the radio but certainly have seen it connected to the cig lighter socket, I believe Tubbs used to do this.
Could take the view that it doesn't much matter if power is cut to the LPG system ign on wire during cranking unless it's going to be set up to start on gas (start on gas when the engine is warm enough). A lot of installers set quite a high minimum changeover time on Valvetronics anyway.
On some BMW's petrol injectors and other engine electronics have positive feed for a while after the engine has been turned off... This means the LPG ECU is kept awake, if the LPG ECU is connected to OBD (canbus) it keeps talking to the petrol ECU which apparently then keeps the petrol ECU awake, which continues to keep the injectors supplied with 12v, latched on situation for both the petrol ECU and LPG ECU. I don't connect LPG ECU's to OBD/canbus so I've never had to wire to anything except injector positive but this does mean the LPG ECU can stay awake (drawing hardly any power) for a few minutes after turning the engine off.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

Fox vehicles
New member
Posts: 39
Joined: Tue Feb 04, 2020 9:41 pm
Contact:

Re: Radio interference

#7 Post by Fox vehicles » Fri Oct 02, 2020 9:23 pm

Just a thought, but as the battery is not located in the engine bay on a X5 I would check where the installer connected the earth wire for the gas ecu, also the live feed. The load on the gas ecu is pretty minimal whilst running on petrol but once switched to gas the load increases and a bad earth could, maybe, cause some strange interference? Can't say I have ever experienced this with any lpg systems but have had radio noise due to bad earths on cars for sure.
LPG Installer & Vehicle repairs
Technical Support for Tinley Tech Customers

Post Reply