I purchased an m50 swapped e30 coupe as a rolling project/family cruiser, and am slowly making it a better all-rounder.
It had many of the right parts, but wasn't quite sorted. It was setup with solid bushings all around, and was simply too rough/noisy for my use.
Going to solid rubber front and soft urethane subframe bushings made a huge difference. I suspect swapping Bilstein for Konis may help some more.
Now I'm looking for next steps to further reduce road noise. Dynamat? MLV? Any tips would be appreciated. It started as a low spec 316i, so likely had less insulation/deadening than the higher spec cars.
Cheers!
Not sure you will see any souls difference with a shock change. Ride quality maybe but sound/noise? Not sure on that.
The only thing shocks would help is that the transfer of bump noise will be "spread out" with less peak pressure being applied to the bushings at one time... but as an actual noise help, you'll never notice a difference.
I tried this on an E30 and had very little success, but mine was a cabrio so I was chasing a fool's goal. They were built as a driving machine.
With that small interior, cloth seats would go a long way to help. Any appreciable sound help from Dynamat comes with serious weight. Dynamat focuses on low frequency noise cancellation by the addition of viscous weight to the panels. Low frequencies easily pass through body panels because they simply transfer their SPL waves to the panel which makes the panel vibrate and pass the sound straight through. Having a heavier, more viscous panel reduces that, but the smooth skin of it still lets higher frequencies just bounce around. Consider lizard skin or something a bit lighter for low frequency attenuation.
For high frequency, you want soft, light stuff; fiberglass insulation, fuzzy fabrics, foam, etc. High frequencies enter and two things happen. The light fibers are more easily moved by the wimpy SPL of the higher frequencies and transfer their energy as kinetic and heat to the fibers. They also bounce around inside and get lost. Think of it like a runaway truck ramp. The energy of the truck in the spinning tires encounters billions of small stones and transfers miniscule amounts of energy to each one. It's just that there are billions of tiny transfers and it stops the truck fast.
Think of the physics. Low frequencies are long like a spear. You want something beefy to stop it by preventing the spear from moving it. High frequencies are short and squiggly and don't have much forward oomph. You want something fuzzy and soft to "snare" it. Think about your microwave door. Ever notice the perforated grid behind the glass? That's the only thing preventing you from getting cooked when you look in the microwave. The microwaves are super short and squiggly, so they encounter that perforated grid and get absorbed.
I am wondering what the PO removed from the car to make it so loud. An E30 should be relatively vault like, even compared to more modern cars.
I'm guessing the factory sound deadening has been removed for weight savings. There should be thick pads under the dash on the firewall and layers of it around the HVAC parts and in the console. The floor pads are built into the carpet and would be near impossible to remove without it looking really loose but it is possible. The trunk floor has like 30lbs of a sprayed on deadening that can be dug out.
Trent (Generally supportive dude) said:
I am wondering what the PO removed from the car to make it so loud. An E30 should be relatively vault like, even compared to more modern cars.
Depends on what Nathan is used to. Old cars are...old. My bone stock E36 M3 is louder than my 2006 Tundra. It's difficult to carry on a cell phone conversation in a stock 2nd Gen MR2 at Interstate speeds. Nostalgia often glosses over what old cars were really like.
The #1 thing that kills the driving experience in BMWs is poly / solid bushings. You've addressed that. The #2 thing is aftermarket strut mounts. If the car has camber/caster plates, ditch those things for stock strut and shock mounts and it will be a lot nicer place. I has Bilstein PSS9s on the M3 and spent almost $400 in OE M3 mount parts just to get away from the Vorshlag camber/caster plates and it made a world of difference. The stock M3 strut top has plenty of static caster, and it's not like I was going to play with caster settings frequently. Unless it's a dedicated track car, not worth it.
Also, look for anything obvious from the engine swap. Performance engine mounts? Custom exhaust bracketry or anything that is contacting the body can introduce a lot of noise. Solid shifter bushings and transmission bushings transmit a lot of noise, too.
If you can find a clean, stock E30 (lol,) see if you can score a ride to see how it compares, so you know what your're likely to be able to achieve? Great looking car, BTW. I'm sure it's fun with an M50.
I've had a few e30s over the years, and keep coming back to them. I'm not sure if this is louder than the rest, or if I'm getting old. Probably both.
The Bilstein replacement isn't so much about noise, but about ride quality: it feels overdamped on small bumps.
I fairly certain the previous owners took weight reduction fairly seriously, or the car had minimal sound proofing from the factory. (Originally a no radio/no sunroof/manual lock/no option 1.6L car). The car had a bunch of 14.2 sec 1/4 miles slips in the glove box. :)
There is definitely no insulation behind the dash or in the centre console.
The car is a blast to drive, but I'm ok adding a few pounds to make it more enjoyable with the family. It's livable now, with the new bushings, but a bit quieter would be nice. Current daily drivers are a Prius V and late model Hilux, which are both very quiet, and an unfair comparison. :)
Can you find a parts E30 nearby and grab all of its interior sound deadening?
Interesting....I have a fully guttted e30 rally car with no interior at all, M50 swap, UHMV bushings in a lot of places, and a straight-through exhaust with a magnaflow muffler and I don't consider it all that loud (and I daily drive a new GTI, which is silent as the grave). You must have a low sound tolerance. :)
One thing that the 316 probably doesn't have is the thick tar soundproofing under the rear seat - that was REALLY thick and is probably a major soundproofing area since it's all the noise from the rear driveline and rear suspension. You can't "take" it from another e30 though, it's not removable, so you'd just have to duplicate it on yours. Trunk firewall behind the back seat too.
Other than that, I guess dynamat the doors (inside the outer skin), transmission tunnel, etc. These cars are boxes, so wind noise is something you're not gonna be able to do much about - make sure all your door seals are in good shape, etc.
Alternately, a good stereo system :)
by the way, the car looks great.
Depending on what the PO removed but as the others have said, every e30 I've owned had heavy tar like sound deadening on the floor pan and a heavy foam mat under the carpet. Since yours was a 316 originally it might not have had all that so it's something to check. All my e30's were very quiet as far as road noise and such even compared to my old mk6 GTI.
Which Bilstein and which koni?
The Bilstein sports ride rather rough. So do the konis. The aggressive damping also often causes more squeaks and rattles.
The Bilstein HD ride a bit softer as do whatever non sport konis.
What type of noise issues are you having? Can you pinpoint if it's tire noise, wind, exhaust or something else?
Thanks for the input (and compliments) guys. I've never really chased noise issues before. I absolutely love driving the car solo, but become more aware of the noise when out with the family.
Bilstein Sports currently. My only Koni (yellow) experience was with the 964, on which the ride quality/damping was exceptional once I dialled in the rebound damping.
Engine note is nice, and not too loud.
Wind noise doesn't stand out, but the road noise does. I helped my nephew swap his auto e30 to manual, and drove it yesterday: it's much quieter inside. Original everything (but gearbox)
I dug into the car a bit, and all the tar(?) based sound deadening has been removed....
Also running Advan AD08r's. Not prepared to give them up at the moment. :)
Pic of nephews (1st) project:
