[Heresy] How To Make 911 Quieter

jyl · jyl's Garage

So, my wife has now taken a number of 2+ hour trips in the Porsche (89 3.2) with the two kids in the back. Her main complaint is that the car is "noisy".

I figuratively stepped back and listened, and while I have no problem with the exhaust note and mechanical sounds, I do agree with her on one score, which is road noise. On California freeways I do get enough rummmble, thrumm, drumming, and thumpa-thumpa to actually drown out the pleasant "power" sounds.

Has anyone experimented with undercarpet sound pads, Dynamat, or similar to reduce road noise? I don't really care about ten or twenty extra pounds of weight. After all, I expect to lose 20 pounds by year-end (right), so adding 20 lbs to the floor area would just lower the CG. And in California we use oxygenated gasoline, which is lighter than regular gasoline.

It's not a big deal. Unlike my better half, I'm not inclined to sell the Porsche and get a 740iL because of the road noise. But it would be nice to reduce the whining. I mean the car.

911pcars · 09-03-2002, 05:13 PM

An '89 is too noisy? She should ride in an early 911 for about 5 minutes. A return trip to the Carrera will sound like being in a Cadillac (or Chevy .... same thing).

Road noise is sometimes exaggerated by the brand of tire you use. Some tires are more noisy than others. See if you can borrow someone's wheels/tires and see if it makes any difference. Note: You must not "lose" this one. I don't want to see a Caprice in your driveway :-)

BTW, does the noise subside after the kids get out of the car? Just for data, what kind of tires are on the '89?

Sherwood Lee
http://members.rennlist.org/911pcars

dean · 09-03-2002, 05:17 PM

I have Dunlop SP8000s on my SC and it does the same thing. I say get her another car. That might quiet her up.

gchappel · 09-03-2002, 05:18 PM

I did have the same problems and concerns. I took an extra set of floor mats- my PO had about 4 sets of them- and I mounted Dynamat to the undersurface. It probably added 10lbs. It definately helped cut down on the road noise- enough that friends commented they could hear me on my cell phone. It is still noisy in the car- but better. Of coarse the floor mats come out for the track.
gary

jyl · jyl's Garage

I have Dunlop Sport 8000 tires too, as a matter of fact. I will probably replace them this year. Tire Rack has Yokohama AVS Intermediate's for $60/each, but I sort of have my heart set on Bridgestone SO-3s - unless someone tells me they are noisy.

So, Dynamat under the floor mats helps. That's the sort of thing I had in mind. Thanks!

I wonder if Dynamat will help more than subtracting the kids? Actually the kids are pretty quiet most of the time, they curl up in the cozy little buckets and snooze. The sun beating down on their little heads through the rear window and the minimal ventilation in the rear both help.

No, I won't "lose" this one. But "winning" means we get to take the Porsche on trips to Monterey, Napa, etc rather than the kid-mobile.

billwagnon · 09-03-2002, 05:35 PM

wrap the tykes in sound-absorbing foam

Doug Zielke · 09-03-2002, 06:06 PM

Wrap the wife in sound-absorbing foam.

Rennline · 09-03-2002, 06:10 PM

Put a louder exhaust onit and the road noise will be history.

nostatic · nostatic's Garage

invest in a better stereo and apply liberally to affected area

island911 · 09-03-2002, 06:21 PM

Quote:

Originally posted by nostatic
invest in a better stereo and apply liberally to affected area

That's what Porsche did when they choose the Becker as the standard deck. It actually turns-up the volume with increased speed. (Reads off the speedo pulse)

Ove · 09-04-2002, 03:40 AM

John,
I used asphalt mats on my M@zda, and it helped a lot. I removed the interior and put mats on every metal surface, including the roof and inside the doors. Not sure how much extra weight it was, but I think asphalt mats in 4mm thickness are 7,5kg (around 15 pounds) per sq. meter. It quickly adds up to a lot of unwanted weight!
Because of this I will be using liquid Noise Killer on my Porsche later this year. This product sprays on easily and is light, but very good at reducing vibration.
Quote:
"Since it's waterbased, anyone can safely use it, plus mistakes are easily fixed with a wet rag. Better yet, it dries to a waterproof seal which means you won't every have to worry about it again."

I've bee told that you need around 10 liters to do the entire car. For high resonnance areas like the floorboards, you could even add a mat on top of the liquid material.

http://www.noisekiller.com/Products.htm

You should be able to get this or a similar product at a car stereo shop.

RoninLB · 09-04-2002, 04:21 AM

I did Dynamat aplenty..it does help with the high frequency tin can sound from road and tranny noise.the sound deadner works mostly on higher Hz..But the engine will now sound cleaner..the engine lower Hz exhaust is not disturbed anymore by higher Hz..to my understanding the ear becomes some what acustomed to volume, so the exhaust will be her next complaint.. and you may be disturbed that you don't have a Danske sport or Monty muffler.....I believe there are noise canceling electronic devices on the market that transmit a opposite curve of your car noise...I don't know who sells that stuff..supposed to work great..we have 2 audio experts on this BB that I know of..bell in Akron and Steve in LA ...............Ron

09-04-2002, 04:35 AM

When the road noise is under control a new problem will occur: Wind noise

Seriously, I have experienced an increase in road noise after I fitted Bilstein Sports and 17 inch cup wheels. Especially rough bumps/holes in the road surface will send a powerful *KAKLUNK* up through the cabin.

With Boge and 15 inch balloon tires I didn't have those problems.