[taibanl]

Technic, VP, anyone smart on noise...\

In the interest on minimizing any noise on the system (this is preventative), I am not trying to rectify any issues...

What is the optimal way of running grounds?

My plan is to use the left trunk well grounding point as the main ground...but additionally (since its already in the wire bundle from the battery well) run a small bonding strap back to the battery ground point. Good plan?

[superjay]

run an 18g wire from the source unit to the ground on the amplifier. This will prevent 90% of all noise by bringing ground potential to the same point. Engine noise happens in only a few instances...radiated noise or ground loop. Ground loop comes from different ground potential (different resistance to ground, since nothing is 100% efficient). Radiated noise is a different animal altogether.

I always, without exception, run a ground wire between the source unit and the amplifier.

When you ground the amplifier, run the ground directly to the battery. The is the most effective way to ground, and keeps you from having to drill another hole in your car.

[taibanl]

Originally Posted by superjay

run an 18g wire from the source unit to the ground on the amplifier. This will prevent 90% of all noise by bringing ground potential to the same point.

I think my bonding strap as described above meets this criteria. Please confirm.

Thus, 4ga will run from amps, to local (left well) ground point. Bonding strap (14 or 16ga) will run to the battery ground point (not the negative terminal directly).

[Thumperx]

Originally Posted by Superjay

run an 18g wire from the source unit to the ground on the amplifier. This will prevent 90% of all noise by bringing ground potential to the same point. Engine noise happens in only a few instances...radiated noise or ground loop. Ground loop comes from different ground potential (different resistance to ground, since nothing is 100% efficient). Radiated noise is a different animal altogether.

I always, without exception, run a ground wire between the source unit and the amplifier.

When you ground the amplifier, run the ground directly to the battery. The is the most effective way to ground, and keeps you from having to drill another hole in your car.

X2, this is one of best additions to your install which may prevent additional noise. The head unit's source ground point and amp grounding point (more than likely) has different "ground potential" values due to: distance, layers of metal, spot welds, and material resistance. The idea is to have the closest amount of ground potential value as possible to one another. Go 14-12 AWG just for added coverage.

Originally Posted by taibanl

I think my bonding strap as described above meets this criteria. Please confirm.

Thus, 4ga will run from amps, to local (left well) ground point. Bonding strap (14 or 16ga) will run to the battery ground point (not the negative terminal directly).

Bonding straps are good, but not in this proposed application. You want to run a separate wire from the head unit's grounding point to the amp's grounding point. So you can equalize the ground potential.

[afsar]

Very good suggestion indeed, so this will mean running a cable from the HU body all the way to the boot? Is taking ground on HU (CCC/CIC/MASK) body a good practice, or shall we tap the HU input directly?

What is best practice to keep engine whine away? This seems to be the radiated one.

[taibanl]

Originally Posted by Thumperx

X2, this is one of best additions to your install which may prevent additional noise. The head unit's source ground point and amp grounding point (more than likely) has different "ground potential" values due to: distance, layers of metal, spot welds, and material resistance. The idea is to have the closest amount of ground potential value as possible to one another. Go 14-12 AWG just for added coverage.

Bonding straps are good, but not in this proposed application. You want to run a separate wire from the head unit's grounding point to the amp's grounding point. So you can equalize the ground potential.

Ok. Guess i was confusing power source with audio source.

I presume the hu ground is somewere in the vicinity of the fusebox? On the electrical system pdf, there are no ground points depected in the center dash area.

Shame...i just pulled out an extra center apeaker wire that would have worked for this!

Edit...and as to bonding straps, perhaps the terminology is different between audio and acft mx where i learned it, but that would be its application...equalizing the charge/potential between two otherwise grounded items.

[superjay]

you'll need to ground the amplifier directly to the source unit in the dash IN ADDITION to the main ground of 4g, or whatever you're using. IT's the only way to be sure you ahve the amplifier and source at the same potential.

[Thumperx]

Originally Posted by taibanl

I presume the hu ground is somewere in the vicinity of the fusebox? On the electrical system pdf, there are no ground points depected in the center dash area.

You may need to locate and run the ground wire from head unit to grounding point. Not sure which PDF you're looking at, but I'm sure the BMW TIS CD may indicate it somewhere. Most BMW's PDF are not 100% updated and accurate.

Originally Posted by taibanl

and as to bonding straps, perhaps the terminology is different between audio and acft mx where i learned it, but that would be its application...equalizing the charge/potential between two otherwise grounded items.

Yeah, but a bonding strap is a bonding strap. But in spirit, it can be loosely called this. In this case, size and material is the major difference and the idea is the same.

[Buddstar93]

Is it ok to use the OE grounding point in the boot or is it better to use the battery ground point by the back light?

[bmw325i]

Either the battery or the battery grounding point is best if your ground is not long enough use one of the factory grounding points.

[Technic]

Originally Posted by taibanl

Technic, VP, anyone smart on noise...\

In the interest on minimizing any noise on the system (this is preventative), I am not trying to rectify any issues...

What is the optimal way of running grounds?

My plan is to use the left trunk well grounding point as the main ground...but additionally (since its already in the wire bundle from the battery well) run a small bonding strap back to the battery ground point. Good plan?

I only use the left fender top ground point... no noise in any of my installs. No need to run a ground wire from the OEM HU/iDrive, as in never.

[taibanl]

So apparently the OEM HU IS grounded to the left fender well...just the forward side! Just under the tip of my index finger it says "AUDIO"

[afsar]

hi taibanl, slightly off-topic, the white plastic clip in the above picture (top middle) is that holding the seat bloster?

I am retrofitting thru loading heated rear seats and I believe same connector is used to hold the side bloster however on ETK no part number has been mentioned. Can you please give me the part number for the clip.

[bmw325i]

That is the clip that holds the bolster. Unfortunately you can't buy it separately from the bolster.

[afsar]

Originally Posted by bmw325i

That is the clip that holds the bolster. Unfortunately you can't buy it separately from the bolster.

I won't believe this. Are you saying if I break that I need to buy the whole bloster?

How about this part # 52 20 7 258 156

[bmw325i]

That part numbers not for an e90 but it looks the same. I bought rear folding seats off a member here last year I believe. Anyways they arrived without one of the bolster clips and tischer said it isn't sold separately and real oem didn't show it separately either. The seller was cool about it though and had a new bolster sent to me.

[afsar]

Guess what I bought that part number I mentioned above and they are precisely the same. It clicked in the chassis happily and there is no reason why it won't click in to the seat blosters but I have no plan to put them on now as they may be hard to take out, so waiting for all the wiring to finish first then I will install them.

Though they they are solid and fair strong bit of plastic, but still plastic hence will break a day. No way BMW will tell you to replace the seat bloster at £200 each for broken bit of plastic worth £2.

[mweisdorfer]

Originally Posted by taibanl

So apparently the OEM HU IS grounded to the left fender well...just the forward side! Just under the tip of my index finger it says "AUDIO"Attachment 694666

I really like your idea of using what's already there and working. It looks like you can put two more grounds in that harness. What type of connectors are used bullet or female?

[david in germany]

Originally Posted by superjay

When you ground the amplifier, run the ground directly to the battery. The is the most effective way to ground, and keeps you from having to drill another hole in your car.

I know this is an old thread but this is a REAL bad idea. Connecting anything up to the neg lead on our cars it a quick trip to dead IBS city on the fast train. On any car without IBS it is perfectly fine though.

[mweisdorfer]

Originally Posted by david in germany

I know this is an old thread but this is a REAL bad idea. Connecting anything up to the neg lead on our cars it a quick trip to dead IBS city on the fast train. On any car without IBS it is perfectly fine though.

Gotcha ya.

[ctuna]

I have had my amp connected up to my battery terminals
with eyelet connectors for years. And this was recommended
and supplied by MusicarNW a major west coast high end shop.
One thing you should do is check your ground with an ohmeter
and be sure you have no voltage drop between the battery and
your equipment.

[dmatre]

Originally Posted by ctuna

I have had my amp connected up to my battery terminals
with eyelet connectors for years. And this was recommended
and supplied by MusicarNW a major west coast high end shop.
One thing you should do is check your ground with an ohmeter
and be sure you have no voltage drop between the battery and
your equipment.

One additional thing:

I have a MusicarNW upgrade to the HiFi system on the E90.

When I first installed it, it was fantastic.

Over the past years at some point, a noticeable whine had entered the system.

It was barely audible at highway speeds, but stopped at a light it was annoying.

I had found another poster here had a similar problem, and he said he fixed the problem by re-seating the connector at the back of the radio.

Well, today I'd had enough, so I Googled radio removal on the E90 (incredibly easy - only need a plastic pry tool and a Phillips screwdriver), and I gave it a shot.

Low and behold, it WORKED! I only removed the radio from the dash, disconnected the connector at the left side of the radio (power/ground/signals for each channel) and re-seated it.

Now, the system is back like it was, silent other than the intended audio output.

Unfortunately, I can't find the original post, so I don't know who to thank. Hopefully, anyone searching for the answer to their noise problem sees this and it helps them (as I was helped).

While not technically about the topic of this thread (amplifier grounding), it's similar enough that this experience may apply.

Thanks to everyone who contributes to make this the place to come for answers to BMW questions!!!