I'd like to add sound deadening material to my car. How adversely will it affect MPG?

[user removed]

On a recent highway trip we picked up two passengers, total weight about 300 pounds. Mileage was unchanged.

regards
mech

[GearHead]

Thank you for the advice! So far, I've added about 50 lbs with the current sound deadening material. To finish the car I'll need about another 18 lbs. I was hesitant to order the last bit, but I checked this forum again to re-read the information everyone has posted here. Looks like I'll be ordering it after all.

I should have a total of about 85 lbs including my audio equipment.

I hope that being my car is a VX, it doesn't struggle more from the lack of HP it has. I'm already getting roughly 30 MPG and I can't figure out why it's not better than that.

I'm beginning to have doubts... Some people are saying 80 lbs is a lot for a car that only has 95 HP. Can anyone shed some light on this?

[MobilOne]

Let's go back to the rattle of the hatch. In general, if something rattles, it is loose somewhere. If the back hatch is loose, road noise will enter; lots of it. So, why not fix the hatch so it doesn't rattle. Low cost. Then, do the rubber hose noise listening thing to see where the noise is really coming from. Low cost. Then you will KNOW where to put your attention.

[Piwoslaw]

Originally Posted by MobilOne

Let's go back to the rattle of the hatch. In general, if something rattles, it is loose somewhere.

And if it is rattling because it is loose, then something is wearing away. And this means it will fail sooner than it should.

[digital rules]

If sound, abundant power & fuel economy are important to you, you may want to consider a quieter car if in your budget. The older Hondas & Acuras I have owned were not nearly as quiet on the road as my 11 year old Corolla. It easily averages mid 40's with a big sub box in the back & only mild hypermiling. No EOC & rarely P&G.

Steely Dan never sounded better!!

[GearHead]

I don't have rattles in my Honda. I wanted to eliminate road noise while maintaining as much MPG as possible.

I picked the VX because it was on the Governments website for one of the best fuel efficient economy cars. I haven't been able to achieve anywhere over 40 MPG. So, I'm taking the steps to replace components that may have an impact on the MPG.

I'd say it's a little too late to switch out cars. I've already invested a lot into it and I really have no way to get my money back to switch cars. It would be a huge waste at this point.

[HiFlite]

Hondas, until perhaps recently, I've always found insufferably noisy, especially so in the lower end of the frequency range. Low frequencies, once created, basically can only be killed off by adding mass, though panels trying to resonate in sympathy can be dampened. I think Honda's big fail must lie with their design of suspension bushings which play a big role in transmission of road noise into body structures. My 1999 Toyota Solara was tomb quiet compared to the same year Accord and I doubt if the difference was due to "sound proofing".

Others are much better at isolation; I noticed fairly recently that my Chevy Volt even uses composite, rather than steel, sway bar end links for that purpose.

So far I've found Second Skin Damplifier covered with Dynamat's Dynaliner foam to be both effective and easy to work with. (The tar-based stuff is messy, smelly, and heavy.)

I've also found, especially for stereo purposes, doing the inside of the front door skins is the single most effective location, followed by underside of the roof, rear doors, trunk rear surface, trunk upper surface, trunk floor, then lastly, passenger compartment floor.

Seldom-mentioned, I also consider damping material on door beams and cross braces between the rear seat and trunk to be a good idea - they will ring like tuning forks without much provocation.

Also, stay away from tires restricted to rolling only in one direction. Rolling in a single direction often causes the individual blocks of rubber on the tread to cup, creating a racket that increases with age.

[GearHead]

Can anyone comment on the MPG a 95 HP motor will suffer from the extra weight I've added?

[HiFlite]

The EPA states a 1% reduction in mpg per 100 lb increase in weight for a ~3200 lb car.

Based on this study: http://www.drivealuminum.org/researc...ardo-Study.pdf

Which is an awesome read btw. See page 24 for your answers.

[GearHead]

That's a very good read! Thanks for the link.