D-Max noise(s) suppression

[VK4ADC]

It seems like the diesel injector pulses on an early 2012 Isuzu D-Max TwinCab is the major source of noise when the engine is running and I am wondering if anyone has tried to quieten one of these beasts. On 7MHz with a helical at the back of the tub, the pulse noise is around S9+10. I have not yet done much playing around with Noise Blanker, bonding the bonnet to body etc.. but someone may have already achieved results along this route. Radio is an IC-706MK2G with remoted head, in-line LDG autotuner to help the matching off the resonant frequencies of the various whips used.

I also have an S7 broadband noise even with the engine off and I suspect that it is probably the ECU - but I haven't pulled fuses in the engine compartment as yet to see if one will stop that noise. I have pulled all of the passenger compartment fuses without any change.

Vehicle is a 4JJ1 series 3.0L diesel.... & shielding of the injector leads is probably not easily done.

Anybody got any known fixes ??

73 Doug VK4ADC

[VK5PJ]

Hello Doug,
first came across this with a Holden Jackaroo (2000 model) that had the 3 litre Isuzu Diesel in it, never did find and answer ( S9+20 on 7 MHz ) so the way to tell if it is indeed the injectors is to find a slope and then let it cruise down the slope with your foot OFF the acelerator, then the injectors are not being pulsed as fuel will be off (assuming it is a manual transmission car) then the receiver will magicially go very quiet compared to before. Not sure how to do that if its an auto, maybe lock it into a low gear on the shifter?

Once I proved it was my injectors being pulsed, it all got too hard as we were about to take a 3 month trip and I did not want to compromise our reliability by fiddling in the engine bay . . . so it was full throttle on TX and glide along for short RX periods when the need occured, otherwise its was only use the 706 Mk2G when stopped.

I now have a 2016 Holden Colorado spacecab ute with the G.M Duramax 2.8 and it is a whole lot better than what you describe. I did hear of a kit that the holden dealer could fit to improve 'rural AM reception' so I might ask about that for mine, you may want to ask Isuzu if they have some thing similar? I too have other squeaks and squarks from other modules that give me blips across VHF SSB, not looked at them yet.

Regards,
Peter, vk5pj

[VK4ADC]

Hello Doug,
first came across this with a Holden Jackaroo (2000 model) that had the 3 litre Isuzu Diesel in it, never did find and answer ( S9+20 on 7 MHz ) so the way to tell if it is indeed the injectors is to find a slope and then let it cruise down the slope with your foot OFF the acelerator, then the injectors are not being pulsed as fuel will be off (assuming it is a manual transmission car) then the receiver will magicially go very quiet compared to before. Not sure how to do that if its an auto, maybe lock it into a low gear on the shifter?

Once I proved it was my injectors being pulsed, it all got too hard as we were about to take a 3 month trip and I did not want to compromise our reliability by fiddling in the engine bay . . . so it was full throttle on TX and glide along for short RX periods when the need occured, otherwise its was only use the 706 Mk2G when stopped.

Regards,
Peter, vk5pj

Peter et al

I waited until I could try a few things on the D-Max before replying, and that happened today. Yes, there is injector noise but I have turned on the ANR in the DSP unit as well as the NB and it looks like it should be workable. I won't really know for sure until I get a highway drive in place.

The continuous S9 buzz (similar sound to normal video buzz) as soon as the accessories position was activated was located as due to the rear view camera. I tried a few things to reduce the buzz - like a braid strap to chassis of the metal mounting flag at the camera itself etc - but minimal improvement - rubbish was only down to S8. While I couldn't solve the actual noise, I did do a workaround. The power to the rear view camera now passes through a dashboard mounted rocker switch so I can power down the camera when not actually required, and certainly not while I want to work HF mobile.

My impression is that the lead from the camera itself is not actually shielded cable hence radiates rubbish noises really well ( ), particularly into the HF whip only a metre and a bit away at the rear of the tub. I was half tempted to cut away insulation immediately behind the camera proper to see if I could set a up braid to earth to the vehicle chassis, but for a change I resisted temptation as I would then probably end up with water ingress issues given its exposed position and downward orientation. I also tried winding the camera's power & video leads through a iron powder toroid a few times but no real change was obvious.

At least I now have the possibility of operating HF while "on the move", impossible before.

Doug VK4ADC

PS It is a "automagic" so the off/on throttle effect won't work well for me