Noise levels for a 2.0 L FI set up - interior vs exterior padding Options

[Tdskip]

Good morning, hope everybody’s having a good week so far. I know that from the factory there was padding in the engine compartment as well as having an interior back pad. My question is if I put additional sound deadening on the inside and then the back pad is that roughly equivalent to the sound pad that was in the engine bay originally?

I’m sure not having the pad in the engine compartment does lead to increased noise, but not sure how dramatic of an increase that would be with a fuel injected car.

I know this is a subjective topic, but looking for experiences and thoughts if you don’t mind sharing them. I’d like the car to be civilized and usable for fall day driving without feeling overly fatigued ( which I am comfortable doing another vintage cars and don’t feel the need to have a modern vehicle to do ).

Thanks!

[914Sixer]

I am guessing that there is/was benefits to adding engine compartment insulation because 70,71, some 72 cars had none. Porsche engineers must have though it a plus. The negative side of if was the poor choice of material that held water and caused massive back wall rust. Wondering if some insulation on the engine lid might also help noise level in cockpit since the back window is also an entry port. Choice of exhaust is the big culprit in a lot of cases.

[DRPHIL914]

Good morning, hope everybody’s having a good week so far. I know that from the factory there was padding in the engine compartment as well as having an interior back pad. My question is if I put additional sound deadening on the inside and then the back pad is that roughly equivalent to the sound pad that was in the engine bay originally?

I’m sure not having the pad in the engine compartment does lead to increased noise, but not sure how dramatic of an increase that would be with a fuel injected car.

I know this is a subjective topic, but looking for experiences and thoughts if you don’t mind sharing them. I’d like the car to be civilized and usable for fall day driving without feeling overly fatigued ( which I am comfortable doing another vintage cars and don’t feel the need to have a modern vehicle to do ).

Thanks!

I think it helps, that's my subjective opinion, I drove it some after putting motor back in but before the new outer pad and inner pad went back in. I have the 914rubber.com new pad in engine bay and the stock rubber pad on inner firewall and then of course the back pad which is a recovered but original back and foam.
fyi my car also is a 2.0L, d-jet with back dated SS he and Triad muffler dual out exhaust. has a nice sound with acceleration but is pretty quiet cruising on the highway. at one time I had achart with decibel levels I took with and without top on and with and without the pads, etc but don't remember the numbers. I can tell you the Monza muffler that had the quad tips on it was horribly loud and more raspy, like those ricers and suby cars with their bad loud raspy mufflers. anyway, I don't tire of the sound of my system it does not get on my nerves.

Phil

[Chris914n6]

Cheap and easy is sound pad under the seats. Sounds bounce off the street.

I went kinda extreme with Jute carpet padding on the floorboards, firewall, and door panels with cloth instead of vinyl upholstery.
I still need to put a sound absorbent under the engine lid.
And I need to do a mod to the firewall before I can stick things to it.

[Superhawk996]

I know this is a subjective topic . . ..

Thanks!

(IMG:style_emoticons/default/lol-2.gif)

@TdSkip . Don't take this the wrong way. It is not subjective.

There is a whole field of automotive engineering dedicated to Noise Vibration & Harshness. I've spent a small portion of my career doing this sort of work.

Forget whether you have FI or not. Aircooled engines suck for NVH. They make a lot of valve clattering, rattling, knocking, piston slapping type sounds when they are running perfectly.

Air cooled is not in any way comparable to a water cooled engine that has waterjackets surrounding the cylinders. That is why I absolutely LOVE aircooled. They are different and unique.

So know that whatever you do, you're starting at a HUGE disadvantage from a NVH perspective.

Bottom line, if you want anyting even resembling quiet(ish) you need an exterior engine pad AND a constrained layer damping material (Dynamat) on the interior and I'd still probably put the heavy factory inner pad over the top of that + some thin shoddy on the back of the back pad if I could fit it.

I think there was a whole seperate list in a different thread so I won't rehash that here.

The only thing subjective about it is what one person prefers vs. another but I assure you there is engineering science to use if you want to make it as quiet as it can be.

[Tdskip]

I know this is a subjective topic . . ..

Thanks!

(IMG:style_emoticons/default/lol-2.gif)

@TdSkip . Don't take this the wrong way. It is not subjective.

There is a whole field of automotive engineering dedicated to Noise Vibration & Harshness. I've spent a small portion of my career doing this sort of work.

Forget whether you have FI or not. Aircooled engines suck for NVH. They make a lot of valve clattering, rattling, knocking, piston slapping type sounds when they are running perfectly.

Air cooled is not in any way comparable to a water cooled engine that has waterjackets surrounding the cylinders. That is why I absolutely LOVE aircooled. They are different and unique.

So know that whatever you do, you're starting at a HUGE disadvantage from a NVH perspective.

Bottom line, if you want anyting even resembling quiet(ish) you need an exterior engine pad AND a constrained layer damping material (Dynamat) on the interior and I'd still probably put the heavy factory inner pad over the top of that + some thin shoddy on the back of the back pad if I could fit it.

I think there was a whole seperate list in a different thread so I won't rehash that here.

The only thing subjective about it is what one person prefers vs. another but I assure you there is engineering science to use if you want to make it as quiet as it can be.

Absolutely taken the right way @superhawk996 , you’ve posted some great links about the science of this before. The subjective part is how loud is too loud since people have different tolerance levels.

[Superhawk996]

The subjective part is how loud is too loud since people have different tolerance levels.

Yeah, good luck with that. (IMG:style_emoticons/default/laugh.gif) I've spent countless hours looking at data from one OEM vs. another benchmarking and determining what the target ought to be.

About 20 years ago Buick had some of the highest customer satisfaction numbers but also pretty poor objective noise measurements using the best NVH equipment costing well over $100K for the microphones, accelerometers, etc.

Turns out there average owner age was about early 70's. Could it be that they can't hear due to age realted hearing loss? Could it be they were comparing to some previous low end car and the Buick was a real step up for them? Could it be that they were comparing to the 1934 Packard they learned to drive in?

Other times the data is highly correlated.

Sometimes there is no answer, only more questions. Just one person's opinion on a particular day the survey arrived. (IMG:style_emoticons/default/dry.gif)

(IMG:style_emoticons/default/popcorn[1].gif)

I like to watch these theads though!

[Mark Henry]

I am guessing that there is/was benefits to adding engine compartment insulation because 70,71, some 72 cars had none. Porsche engineers must have though it a plus. The negative side of if was the poor choice of material that held water and caused massive back wall rust. Wondering if some insulation on the engine lid might also help noise level in cockpit since the back window is also an entry port. Choice of exhaust is the big culprit in a lot of cases.

It depends, granted my car has always had a sheltered life, but when I removed the back pad I didn't find a speck of rust. I cut a BFH in my firewall for access to the /6 but when it was done I cut to fit the stock back pad back in place. I installed it a half inch high at the bottom just to be sure water can't be trapped there. I also cut and replaced the inner rubberized tar mat.
I have a weber /6 with a stock 911 banana, my interior noise levels are good, you can carry on a normal conversation with a passenger. I'm keeping the pad.

BTW the "BFH" in this case = Big Fuching Hole

(IMG:http://www.914world.com/bbs2/uploads/post-26-1497236248.jpg)
(IMG:http://www.914world.com/bbs2/uploads/post-26-1497236287.jpg)

[dr914@autoatlanta.com]

maybe check what you have. In stock dress 73-76 914s out of the box were very quiet. Maybe something is going on with yours like a loose back window an exhaust leak an aftermarket muffler, no floor pan tar, no insulator pad UNDER the back pad, no engine insulator pad, carburation!!! or stainless steel heat exchangers

Good morning, hope everybody’s having a good week so far. I know that from the factory there was padding in the engine compartment as well as having an interior back pad. My question is if I put additional sound deadening on the inside and then the back pad is that roughly equivalent to the sound pad that was in the engine bay originally?

I’m sure not having the pad in the engine compartment does lead to increased noise, but not sure how dramatic of an increase that would be with a fuel injected car.

I know this is a subjective topic, but looking for experiences and thoughts if you don’t mind sharing them. I’d like the car to be civilized and usable for fall day driving without feeling overly fatigued ( which I am comfortable doing another vintage cars and don’t feel the need to have a modern vehicle to do ).

Thanks!

[PCH]

Rode in a friend's 914 that was really quiet.

He's trick was to put sound insulation on the underside of the rain tray. It really worked well to keep the noise level down.

[Tdskip]

@mmichalik - my memory needs some help, does the black/black car have a sound pad in the engine compartment?

For everyone else, that was a 2.0L car with carbs that was plenty fine as to noise level over an extended trip.

[mmichalik]

@mmichalik - my memory needs some help, does the black/black car have a sound pad in the engine compartment?

For everyone else, that was a 2.0L car with carbs that was plenty fine as to noise level over an extended trip.

I'll check today and let you know.

[Tdskip]

@mmichalik - my memory needs some help, does the black/black car have a sound pad in the engine compartment?

For everyone else, that was a 2.0L car with carbs that was plenty fine as to noise level over an extended trip.

I'll check today and let you know.

Thanks!

[VaccaRabite]

I can tell you first hand that the engine side pad makes a TON of difference!

I have my floor pans and cabin side of my firewall lined with FatMat, but was running no engine side insulation and a GT engine lid. The car was LOUD.

I drove a friends (Bob's) 2056 and his was a ton quieter.

After installing a 914Rubber engine side pad, and putting back in my stock engine lid and rain tray, I can now hear all the annoying cabin groans and squeaks that I was never able to hear before over the sounds of the engine. You can also have a conversation without yelling at the passenger.

I still need to add something to the targa top (no headliner, just bare FG right now) but my 914 is like a whole different car in the cabin.

Zach

[mmichalik]

@mmichalik - my memory needs some help, does the black/black car have a sound pad in the engine compartment?

For everyone else, that was a 2.0L car with carbs that was plenty fine as to noise level over an extended trip.

It has a very thin (maybe a 1/3 of an inch) thick pad in there. Obviously not stock though.

[bbrock]

Bottom line, if you want anyting even resembling quiet(ish) you need an exterior engine pad AND a constrained layer damping material (Dynamat) on the interior and I'd still probably put the heavy factory inner pad over the top of that + some thin shoddy on the back of the back pad if I could fit it.

^^^ This! (IMG:style_emoticons/default/agree.gif)

The sound deadening material needs to be matched to the type of sound being attenuated. The tar on the floor of our cars and foil-faced butyl mats (a.k.a. constrained layer) is good at attenuating booming noise generated by vibrating metal panels. Attenuating airborne sounds often use a fiber or foam pad. The engine bay back pad looks to me to be something of a hybrid. It is a fiber pad encased in heavy rubber. Don't forget that it is matched on the inside with a rubber mat.

I doubt that replacing the engine pad with only something like Dynamat is going to match the sound deadening of the factory pad but the best way to find out is with data. (IMG:style_emoticons/default/beerchug.gif)

[Tdskip]

@mmichalik - my memory needs some help, does the black/black car have a sound pad in the engine compartment?

For everyone else, that was a 2.0L car with carbs that was plenty fine as to noise level over an extended trip.

It has a very thin (maybe a 1/3 of an inch) thick pad in there. Obviously not stock though.

Thanks @mmichalik , know you are busy, appreciate the extra effort.

Just checked and the ‘73 1.7 FI car does not have an engine side pad but does have the interior backpad and presumably any other factory material on the inside. Non-stock muffler but quite livable so intake and exhaust seem to be VERY significant contributors...(not shocking).

Thanks!

[eric9144]

My super stock (2nd owner) 2.0 is actually pretty dang quiet if I'm off the pedal and just cruising, wouldn't hesitate to take it on super long drives. It has the factory engine bay deadening and whatever is behind the stock back pad (had never been removed until I resealed the back window 5-6 yrs ago). I'd be happy to let you check out the sound levels if we're anywhere near each other in SoCal...

[Tdskip]

My super stock (2nd owner) 2.0 is actually pretty dang quiet if I'm off the pedal and just cruising, wouldn't hesitate to take it on super long drives. It has the factory engine bay deadening and whatever is behind the stock back pad (had never been removed until I resealed the back window 5-6 yrs ago). I'd be happy to let you check out the sound levels if we're anywhere near each other in SoCal...

Thanks @Eric9144 , appreciate the offer.

[Tdskip]

Just to follow this up with the experience I shared yesterday of driving a couple cars back to back - while the '73 1.7 with FI is definitely quieter the '74 2.0 with EMPI dual carbs isn't overly loud. Neither car has an engine side pad so, but both do have a driver side pad.

So to my ears anyway you can "get" away with running just the interior sound deadening. Now on a 914/6....I suspect it will get pretty loud with just the interior pad.