Anyone measure exhaust noise level?

[J.Jensen]

Reading up on our national regulations (Norway) for approval and registration of amateur built vehicles, and the maximum exhaust sound level is 84db.

Has any of you ever measured yours?

An iPhone apparently has a pretty decent mic, so I would really appreciate it if someone would test.

The test procedure describes:
Mic at exhaust level, or 200mm from the ground - whichever is highest.
Mic placed at a 45 degree angle from the exhaust outlet, in the direction giving the most distance from the car

The measurement is to be performed at 3/4 of the maximum power rpm. If this rpm is not available, the test can be performed at 2/3 of the engines maximum rpm.

Does bigger displacement equate to more sound? I´m planning a FIA build with a small block.

[DanEC]

If 84 dB is your limit I think it would take some serious mufflers to get under that. An FIA can be equipped with an undercar muffler system and front-of-rear wheel outlets, but you would need a really good reverse flow muffler to get under 84 dB I think. Your description doesn't say what the distance the mic has to be from the car - just height and angle from the outlet. What is that specification?

[Tommy]

First thing I'd suggest is that you get an RPM limiting ignition and set it for 4,000 RPM maximum. Second, consider dumping the exhaust out under the car and toward the ground between the wheels. Last, consider what exhaust that can pass the test is easiest to swap out for track events. 84db is well below what a typical American Cobra makes, IMHO.

[patrickt]

95 decibels, at idle, from a few feet away from the pipes. And I have the "quiet type" pipes. To my ears, the sound is perfect -- I wouldn't want it any louder, and I certainly wouldn't want it any quieter. I've seen a few small block 427 type cars that did not make the nice FE rumble and, to me, it just wasn't right.

[Dwight]

yes a larger engine makes more noise

air in
air out

I quieted mine down by installing a Classic Cobra Pack muffler that was 4" longer. I kept the overall length from the bents to the exhaust tip the same.

[mln385]

Originally Posted by patrickt

95 decibels, at idle, from a few feet away from the pipes. And I have the "quiet type" pipes. To my ears, the sound is perfect -- I wouldn't want it any louder, and I certainly wouldn't want it any quieter. I've seen a few small block 427 type cars that did not make the nice FE rumble and, to me, it just wasn't right.

Same here with Roush 427 stroker.

[strictlypersonl]

The good part is the FIA Comp exhaust is much quieter than the 427's. The bad news is that it is probably still much louder than 84dB. The "stock" street under-car system is a little better, but I suspect is still too much. There's a little room at the far-back end to add an additional muffler, but you might have to modify a panel.

[Tommy]

Originally Posted by patrickt

95 decibels, at idle, from a few feet away from the pipes. And I have the "quiet type" pipes. To my ears, the sound is perfect -- I wouldn't want it any louder, and I certainly wouldn't want it any quieter. I've seen a few small block 427 type cars that did not make the nice FE rumble and, to me, it just wasn't right.

J.Jensen,
Keep in mind that due to the way decibels are measured, 95db is more than twice as loud as 84db.

[SunDude]

Measured mine once: 105 decibels at 4,000 rpm. Which is why I wear earplugs.

[Bernica]

These are handy. I bought it to comply with OSHA rules and whatnot on construction projects, but it has many uses..

[J.Jensen]

Is having V-band clamp connections aft of the headers and two sets of pipes a viable option - or is simply side pipes not an option with that noise level?

It would need to pass the initial inspection, and a reinspection after 2 yrs. I wouldn't mind having a quiet and a "proper" set

[Tommy]

Originally Posted by J.Jensen

Is having V-band clamp connections aft of the headers and two sets of pipes a viable option - or is simply side pipes not an option with that noise level?

It would need to pass the initial inspection, and a reinspection after 2 yrs. I wouldn't mind having a quiet and a "proper" set

I see no reason why not. I have two sets of side pipes that can attach to the headers at a square, 8-bolt flange. One set is lightly muffled and the other is fully open for track days. I only used the open set once or twice because even race tracks often have noise limits, and it was almost painful backing it out of my enclosed trailer. ... If you're willing to spend the money for custom built, highly muffled pipes for testing, I suspect there is enough room to build a system that will pass your 84db limit.

[Tom Wells]

J. Jensen,

You can use V-band clamps. I have had some 3" ID clamps connecting the collectors to the exhaust pipes on one of my cars for more than 10,000 miles. They still look and function as new, and are pretty easy to remove and replace.

Here's the URL for the ones I use: Vibrant Performance ::.

I had the flanges welded to the collectors and pipes by a really good local exhaust shop.

BTW, the engine in that car is a 557 stroker, so it does give them a workout. I ran the Daytona track last week with them using the 24-Hour Rolex course, and also take the same car to the lumber store.

Two interchangeable sets of exhaust parts could be practical...

Tom

[J.Jensen]

Thanks

[vector1]

Use a vacuum advance on the dizzy, makes a big difference at all rpm, full throttle loses the vacuum advance and you still get the sound. Engine runs cooler and your exhaust valves will thank you, I have heard.

[J.Jensen]

I think what ignition the engine gets will be chosen by the engine builder - not me.

[BAsque1]

https://youtu.be/icvDoDWSDG0

How dare you call this engine noise??? This is mechanical music man!!!!

[lippy]

I measured mine and got these results:
- Loud enough to piss off the neighbors
- Loud enough to set off the alarms of lowered Hondas parked on the street
- Loud enough so I need earplugs when I drive.