Mike J

Sounds like a trick question. I think you are only capping one of the two outlets, right?

If so, that leaves one exit. If I assume that the wool does not penetrate into the pipe that feeds the other exit, that means you are restricting the exit area - which can make it louder because the gas velocity is higher (given the volume moving has not changed...).

The wool should not make a difference unless, like I said, it blocks the other outlet.

I am probably totally wrong here - I find exhaust sound design is a black art.

What did you actually find in your science experiment?

Cheers,

Mike

OverBoosted28

My (untrained/non-expert) opinion is it will have little change, in any configuration, other than being slightly louder/sharper.
Maybe try the motorcycle baffles? 4 of them for probably $20-25 usd.

Knight

Interesting, I'd say the capped one is quieter. But like Mike said, it sounds like a trick question for us to think the opposite.

Basal Skull

Using my db meter on the iPhone about 4' behind the car at chest height. At idle, all 4 open was loudest at 97dbish; out side one capped with steel wool 94/95 dbish; outside capped with no wool 92-93 db... Would have thought steel wool would have helped (not obstructing other outlet).
Off idle, not much difference capped with no wool vs all 4 open; but with wool, slightly quieter.
Had been looking at the motorcycle type in tip silencers and was going to make some but decided the air pocket created by those must affect sound so decided to see what capping off one of the two tips ( creating a air pocket ) would do.
Going to keep capped with wool for now. I'm really liking how it sounds although a little loud.
Trying now to think up pins to hold the cap on that is reasonably secure but easier to thread all the way through or something that doesn't have to be thread through..

Basal Skull

Most of the in tip silencers look like they only take a couple to few db off so capping works pretty well (relatively)
When I cap off 3 of the tips, it quiets down quite a bit but don't think I want to do that..

Rick GT3

I will just use a BIG exhaust tips and install inserts.

Mike J

Ryojo and I got together this morning to compare our exhausts - it was raining on and off, so that did not make it that much fun. I could put full throttle withe the AWD, but Ryojo has more power and two wheel drive so it was dicier.

I put together a short video to listen too - nevermine the off-focus parts ,the sounds is fine. The video was shot with using a Rode microphone in exactly the same conditions, cars back to back. As usual, it always sounds better in real life. I think both exhausts sounds pretty good, and about the best you can get sound wise from a Turbo'ed engine.

I have no clue how they are going to make the 991.2's sound as good as the previous models...


Enjoy!

Cheers,

Mike

Basal Skull

Thanx for vid Mike, was good meeting up!
Both cars sounded great, completely different though. I can hear your turbos in the vid but not mine.
For the record I was not even close to full throttle, may be 1/4 to 1/3 blip as the rear stepped out during the very first pass by (and I recalled in my mind you asking if we should go find a part of the road with no median..) I tried to get things 4-5K as I went by. Fun stuff - and good to take our minds off the bad stuff in Paris

Knight

Very noticeably different tones at idle for sure.

I'm guessing Basal's must be quite a bit louder too, given he wasn't even close to full throttle - sounds good on the drive by!

Mike J

Should be louder given no mufflers!

Basal Skull

The audio on the clips sound pretty good with a good pair of earphones connected to the computer.
I can't really use full throttle at all unless I roll on the gas pretty deliberately even with R compounds in the dry. Only do that on the track as I'd get to 'arrest me' speeds pretty quickly.

Mike J

How much HP and torque is that engine putting out?

Basal Skull

You haven't seen my dyno sheet??? on a dynapack at the wheels FWIW...

Mike J

I feel woefully inadequate now ....

Basal Skull

Not many cars that can out pull on the straight at the track, just imagine how much faster it's going to be with the free flowing exhaust and 36lb weight loss!