The turn down pipes will only reduce the high frequenzy sound the engine makes as the concrete absorbs those, and even than concrete bounces back 99% of the sound waves.

http://itsolution.lindab.com/LindabW...theory-ads.pdf

Thanks F1 that was a good read. The curved pipes then, would seem to be the biggest factor in sound absorption. Last sound check was at Calabogie and that was on asphalt.
It would still be useful to know decibel levels with turn downs on both concrete and asphalt

Homer997,

The system was designed with the goal of passing Mt. Tremblant. We took some decibel readings without the turn down tips and measured 89-91 db at 50' / 3500-4000 RPM's.

The car was noticably/dramatically quieter with the turn down tips installed. I was very surprised at the difference. I think the car is going to pass Mt. Tremblant with the TD tips, but I'm not certain. The owner is going to compare his car to other cars that are known to pass at Mt Tremblant with a decibel meter, while at Watkins Glen tomorrow.

We all thought it was like a completely different car with the turn down tips installed - much quieter to the bystander. They made a huge difference and I think we are certainly in the running for a good outcome at Mt. Tremblant...

I am waiting with anticipation of this comparison. Your system appears to address well many aspects of exhaust design that is appealing, especially the modular aspects. I really hope this meets the DB limits!!

We do too!

John,

any updates?

Vince

Hi Vince,

Yes, the car was compared to a 997 GT3 that has passed the sound test at Mt. Tremblant and it was slightly louder (without the turn down tips installed). We feel that with the turn down tips it will pass, but we will not know for sure until it's there...

99%? Really? Is this an actual figure and what was it based on?

Mike, As I am sure you know, there is quite a difference in sound level with turn down tips from behind or beside the car. It's actually sounds like a different car - it's that dramatic.

John, you know I do. Just poking our friend with a stick!

Mike

Do you have a db reading from 50'?

Sorry, i didnt read all the posts first

John,
Have you or will you be dyno testing your system? I think the majority of your audience knows the real benefit of exhaust on these cars is weight and sound, however we still need to know we aren't putting something on the car that could potentially cost power.

There were custom build mid pipes independently built and tested recently on another board and shockingly one of the designs lost power and torque vs stock. Personally I dont think it matters if your system makes no power I think people like myself need to see that it doesn't cost power as a final selling point. The sound is awesome, the weight savings great, push me over the edge with dyno testing and make me a customer!

Audion19's,

The car that we designed the system with is not ours and will not be dynoed by customer request. That said, we have used the exact same "X" design system on 996TT and 997TT cars and realized substantial gains over the stock system in both cases. It is a straight thru muffler design with no restrictions, baffles,etc. and also has high flow cats, in place of the OEM cats. Based on our experience of building and testing exhausts, there is no way this system will lose power over an OEM system. Just the weight savings is like adding HP, although I am not referring to that aspect, that's just an additional freebe.

If you read the scientific article you will see why ;)


Or I can break it down to you. If you need me to tell you how the math works :)




John,

Yes it sounds completely different because the tarmac absorbs certain frequency waves. Cmon guy's it is basic college science. hilarious Physics 101b. The graphs and the math tells it all.