NVH Issues

Suspension, including wheel, tire and brake.
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TheHeretic
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NVH Issues

Postby TheHeretic » 13 Dec 2016 22:14

So I finally upgraded my rear suspension from a basically mild setup (slotted crossmember, control arm poly bushings and comp springs) to a Datsport fully adjustable crossmember, whiteline bushings in the control arms, crossmember mounts and mustache bar plus Ground Control coilovers with 250lbs springs. Also a R180 STI diff was installed. Hah! Big changes that have made the handling much better BUT a significant increase in NVH. Can hear some gear whine now. To the point where I am considering what to do to lessen it. So would love some suggestions to go about this. My initial thoughts are:
1. Do some sound deadening and suppression in the interior since right now it's just carpet on metal.
2. Swap out some of the bushings back to stock ones? Maybe crossmember and mustache bar?
3. Would changing the rear coilovers down to 225lbs make that big of a difference or any?
4. Would the CV axle conversion improve some of the vibration?
5. Just suck it up and get used to it!

Any feedback?
Carpe Diem!
Ryan

Three B's Racing
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Re: NVH Issues

Postby Three B's Racing » 14 Dec 2016 05:41

Gear whine from the diff? CV will help with vibration if your 510 is lowered,, alot. Sound deadining is a must but remember it's a 43-47 year old Jap crackerbox car, not a Caddy 8>) Poly bushings in the control arms is a mistake due to binding issues when you go to make rear toe/camber adjustments. OEM rubber bushing for the control arms are still obtainable. Crossmember and mustache poly bushings will transfer some noise but if you can fine OEM for both would make a difference but good luck with that find. I have all of you have except I'm running CV axles and OEM bushings in the control arms and have no rear gear whine and it's damn smooth. Maybe your STI Diff has issues.
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okayfine
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Re: NVH Issues

Postby okayfine » 14 Dec 2016 06:21

Hey Ryan,

1. Sound insulating material will go a long way to improving the NVH, though if there are causes of NVH it would be just as important to address them as well. Lots of different materials out there, depending on your needs and budget. Summit Racing and similar have a large (4'x6' or so) fiber mat with foil on both sides, and it's only $30 or so. This could work well under carpet, but you'd also want to put it under the rear seat and such. I used that same material under the front floor of my white car to reduce trans noise.

2. Swapping out urethane bushings for rubber will also go a LONG way to reducing NVH (again, provided it's not due to an actual problem). However, you bought them so I assume you had a plan to run them? Everything has a compromise, and NVH is always discussed when talking about urethane bushings. Lou brings up an excellent point in that if your rear crossmember a-arm mounts don't swivel, poly a-arm bushings will bind if the car is lowered and aligned. Again, this is also a known and cautioned issue.

3. No, spring rates aren't going to affect NVH.

4. CV half shafts can reduce vibration, but driveline vibration is different than the sorts of no-sound-insulation and poly-bushing-NVH issues. #1 and #2 are choices you make and accept the compromises. #4 is an actual issue that needs to be corrected, if it exists. Measure the angles of your half shafts at ride height. If it's more than 3° then u-joints aren't going to be happy. If it's way more, then that's definitely a cause of vibration, particularly at highway speeds (but less so at in-town speeds). CVs will help to a certain extent, but if your car is dumped in the weeds, CVs themselves won't cure the problem. You'd need to raise either the a-arm mounting locations (such as Penultimate crossmember) or raise the entire rear crossmember (basically impossible).

5. There is a certain amount of this that will be true, given the choices made when you build your car (such as #1 and #2). Vibration can be an issue that should be addressed (see #3), but 510s are generally rattle boxes, especially when suspensions are tightened up.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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JordanTr
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Re: NVH Issues

Postby JordanTr » 14 Dec 2016 07:30

Earplugs!

Seriously though, it is a miserable thing to chase. I REALLY want to get one of our vibe techs from work to do a 2 plane field balance on my drive shaft. I'm quite convinced that Nissan field balanced the driveshaft once everything was all assembled in the car.
Jordan | '72 2 door KA project | '94 240sx RB26DETT | '97 Silvia RB25DET | '90 Audi 90 Quattro 20V (DD)

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bertvorgon
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Re: NVH Issues

Postby bertvorgon » 14 Dec 2016 09:34

Two things..

I made sure my driveshaft angularity was within 1/2 degree..

I had Andy MAKE me a driveshaft, where in the lathe he made sure the yokes were welded in true, and, the tubing used was TRUE.

I have NO driveline vibration......and my driveshaft sees huge rpm
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 14 Dec 2016 14:40

Thanks for the replies so far. Will definitely be using some automotive sludge (http://store.secondskinaudio.com/noise- ... -coatings/) and sound deadening sheets this spring in preparation for an exterior repaint this summer. So that should help a lot!

My crossmember is the V4.1 from Datsport and was built on a jig with the control arms pivots set in a "sweet spot" or middle ground for alignment. Baz suggested the Whiteline bushings and said that any binding would be minimal. But still considering the OEM bushings....no binding at all and maybe a little less NVH. Just don't want to deal with swapping them out AGAIN.

Will check out the driveshaft when I put in the KA24 tranny and the existing driveshaft needs to be shortened anyway.

Will measure the u-joints soon. The rear is 7 inches from the pinch weld to the ground so really not that low. They are original but in good shape with low miles and no play.

Thanks!
Carpe Diem!
Ryan

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bertvorgon
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Re: NVH Issues

Postby bertvorgon » 14 Dec 2016 19:55

While I think of it...NISSAN, with their universal replacement joints, actually supplied them with a shim kit. This was to ensure that the universal was CENTER in the yoke. This gets lost when replacing universals as no one thinks about...is this thing in the center of the yoke.

I have one around somewhere and will take a look next week when I'm back at work, I think there is a P/N there.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

510rob
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Re: NVH Issues

Postby 510rob » 15 Dec 2016 00:12


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okayfine
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Re: NVH Issues

Postby okayfine » 15 Dec 2016 06:20

You could always install a pair of bushings in an a-arm and put it up into the crossmember at ~ride height, then articulate the arm and see if there's binding. I understand what you said about the Datsport piece and "sweet spot," but there's so much variable about what's sweet and what's sour.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

iceD
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Re: NVH Issues

Postby iceD » 15 Dec 2016 08:27

What is NVH

ice D

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bertvorgon
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Re: NVH Issues

Postby bertvorgon » 15 Dec 2016 09:36

Thanks for posting that link up Rob, that is without a doubt the best graphic visual example of what is going on.

I fought driveshaft vibration for years in the early days, then found out about the angularity and phase issue, never looked back after that and ever more so when Andy made me my driveshaft.

Derek, it stands for NOISE, VIBRATION and HARSHNESS...

Basically embodies our 510s as we stiffen things up and get rid of factory sound deadening.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

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Byron510
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Re: NVH Issues

Postby Byron510 » 15 Dec 2016 11:53

510rob wrote:https://www.youtube.com/watch?v=gmV4qwLfOMY


bertvorgon wrote:Thanks for posting that link up Rob, that is without a doubt the best graphic visual example of what is going on.




Agreed - that is an awesome example.

Thanks Rob.

Byron
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because the opposite never works.

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Re: NVH Issues

Postby iceD » 15 Dec 2016 16:22

Thanks for that harsh enough to start with

ice D

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Baz
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Re: NVH Issues

Postby Baz » 15 Dec 2016 23:33

If you have whiteline bushes on the diff brace, they can be reversed which will change the angle of the Xmember. And the angle of the diff.
minor adjustments can be done by adjusting the shims.

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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 18 Dec 2016 08:52

I might be missing it but is there a topic or link to a more in-depth discussion around driveshaft angularity? Don't know if right now is the best time to mess with it but definitely will want to address it when I put in the KA24 transmission. Also what is everyone using to measure the u-joints angle? Was going to just download an app to the phone and use it...
Carpe Diem!
Ryan


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