I recently redid my exhaust setup, and went with a 4'' SS downpipe matched to an aluminum straight thru catback. No muffler or resonator in between and currently looking to modify it in an attempt to make it quieter (at idle...etc).

I purchased a 4'' QTP cut-out and looking to place multiple 1/2'' holes thru the butterfly plate, and install the valve inline with the exhaust.

The question I have; would the overall noise reduction be higher if the valve is placed at the down-pipe or near the end of the exhaust (aluminum side)? I am hoping to hear from those that have tried such a setup and share their experience.

Pic below is from a similar valve that MAP sells to give you an idea of what i am looking to do.

Thanks in advance!




here is a pic of the current setup

 

I think dampening the pulses closer to the discharge will be better. my thoughts are based on decreasing the amount of exhaust available to resonate by restricting it upstream.

BTW do you have an idle video ?

 

When you say earlier in the discharge meaning closer to the hot side of the turbo? … I tend to agree with this approach, I too think the energy of the pulses will be diminished by the time it exists the exhaust tip… more surface area to bounce off.
However, I will be operating the QTP valve in the “hotter” zone, and not sure what their limits are…. Nor would I like to find out but luckily they are replaceable for ~$60.

I will capture an idle video and share it with you guys soon!
Thx

 

What kind of horsepower do you currently have? Why such an oversized exhaust? There are plenty of proven exhaust setups running 3" making north of 900whp plus. Just curious why such a large exhaust?

 

no matter what it's always good to lower delta P. and other shops have proven in this forum gains from larger exhaust. Sometimes it's a lot sometimes it's a little. but I've seen the results and I belive it was e r that did the testing.

here's a super Street article. less than 900 hp with gains