How to retro-fit the rear subframe harmonic damper from the Audi A3 Saloon (2013->)

[golfdave]

I just ordered one of these - excited to try it out based on this thread. Any thoughts on if it should be torqued down with a load on the suspension (ramps) or without (jackstands)? Or does it not matter either way?

You are bolting the item to the rear subframe...there is no movement laden or unladen.....

You are over thinking this....weighted/unweighted only makes a difference when tightening bolts that pass through bushes with a lot of movement/travel arch, especially on suspension links/arm/dampers etc..

 

[EEeegolf]

I just mounted the damper today. Took 3 minutes including some photos.
Next I went to my std measuring straight. Pretty smooth asphalt and cc at 82 km/h.

Clear difference in the resonance at 120 Hz.
Then I selected a rough road as well. Also asphalt but quite rough. 41 km/h

Again a reduction in the resonance. A bit lower frequency as speed was lower too.

I must admit I was surprised as the effect was bigger than expected. Made the investment totally acceptable. This was on a 2020 e-Golf with additional sound deadening added.

 

[golfdave]

I just mounted the damper today. Took 3 minutes including some photos.
Next I went to my std measuring straight. Pretty smooth asphalt and cc at 82 km/h.
View attachment 283292

Clear difference in the resonance at 120 Hz.
Then I selected a rough road as well. Also asphalt but quite rough. 41 km/h
View attachment 283293Again a reduction in the resonance. A bit lower frequency as speed was lower too.

I must admit I was surprised as the effect was bigger than expected. Made the investment totally acceptable. This was on a 2020 e-Golf with additional sound deadening added.

Blue is before & red is after???

 

[EEeegolf]

Sorry. Forgot the legend on these graphs. Indeed. Blue without damper and red with.

 

[mrmatto]

Very nice data collection!

 

[golfdave]

I just mounted the damper today. Took 3 minutes including some photos.
Next I went to my std measuring straight. Pretty smooth asphalt and cc at 82 km/h.
View attachment 283292

Clear difference in the resonance at 120 Hz.
Then I selected a rough road as well. Also asphalt but quite rough. 41 km/h
View attachment 283293Again a reduction in the resonance. A bit lower frequency as speed was lower too.

I must admit I was surprised as the effect was bigger than expected. Made the investment totally acceptable. This was on a 2020 e-Golf with additional sound deadening added.

For reference, your MK7.5 e-Golf weighs circa 1615Kg

My MK7 GT 1.4lt manual estate weighs circa 1354Kg

& the average 5dr GTI-PP with DSG weighs 1402Kg


That just shows, that even with a heavier car, with the additional weight in the floor pan, that the rear multi-link sub frame is what causes the ringing, & that the bodyshell amplifies it. In your case not as much as a lighter car but a measurable difference nonetheless!


That rear-sub frame was designed way back for the MK5 Golf & has had those two holes for the harmonic damper in it since it was first mass-produced...& yet VAG ditched the item & only brought it "back" when the MQB Audi A3 saloon car bodyshell was resonating a bit too much!...

 

[EEeegolf]

Not only is the e-Golf substantially heavier but the rear axle weight is close to double to a normal 1.5 Golf.

Being under the car and seeing the subframe I cannot understand why it isn't attached to the body with bushings. At least it looked like bolted solid. I'm very tempted to try some tricks there....

 

[golfdave]

Not only is the e-Golf substantially heavier but the rear axle weight is close to double to a normal 1.5 Golf.

Being under the car and seeing the subframe I cannot understand why it isn't attached to the body with bushings. At least it looked like bolted solid. I'm very tempted to try some tricks there....

Because its not the "mid-luxury" sector...the Passat uses the same base components in the rear-subframe, but has bushes along with all other VAG cars based on the Passat MLB platform, which include the Audi A8...!!.....More "refinement"...which costs more £££...or $$$....or...€€€.....

 

[EEeegolf]

I googled the Passat subframe. Indeed, that's the way it should be made. It wouldn't actually be too difficult modifying the stock to Passat style bushings.

There are many makers for rear subframes, but all for racing. Would be nice if some would make an option to make it comfortable.

Googled some more. The Golf 8 has bushings:
https://dalys.lt/en/car-parts/product/154720

Any idea if the attachments are identical?

 

[zwalk]

So wish there was a AWD equivalent lol

 

[EEeegolf]

The AWD has the subframe attached with bushings. Much more effective for NVH than a simple damper.

 

[zwalk]

The AWD has the subframe attached with bushings. Much more effective for NVH than a simple damper.

Yeah I suppose I just still get a good bit of nvh

 

[golfdave]

So wish there was a AWD equivalent lol

Of the harmonic damper?....I get asked that repeatedly over the years....

I think because the subframe is mounted to the body via bushes VAG hope the NHV in the rear subframe would not transmit through to the bodyshell....I reckon they also thought the added mass of the Haldex & bevel box would also dampen it out!.....

 

[EEeegolf]

I think because the subframe is mounted to the body via bushes VAG hope the NHV in the rear subframe would not transmit through to the bodyshell....I reckon they also thought the added mass of the Haldex & bevel box would also dampen it out!.....

I agree. And it also makes sense.

Looking at more pics, it really looks like the AWD subframe could be an easy swap to the FWD cars. The attachment points are definitely the same. It also seems the control arms are the same. Anyone having better knowledge about this?

 

[golfdave]

I agree. And it also makes sense.

Looking at more pics, it really looks like the AWD subframe could be an easy swap to the FWD cars. The attachment points are definitely the same. It also seems the control arms are the same. Anyone having better knowledge about this?

It won't fit..due to the spare wheel well...the rear most part of the FWD subframe is the hollow tube which is bent down towards the road to clear the spare wheel well...The AWD subframe is straight across to allow for the Haldex unit...this is why the AWD hatch has a shallower spare wheel well than the FWD hatch

On the estate the spare wheel well is not in the way as its 1ft further back due to the extra length after the rear axle in the estate... FWD & AWD use the same body shell in the estate....so it could be done on the FWD estate...

Only other way would be to cut the bush arms off a AWD & remove those same sections off the FWD subframe, & weld on the AWD bush arms......or cut the straight section off the AWD & weld on the bent hollow tube from the FWD....