Originally Posted by O5C4R

there is definitely more mid range punch, I don't notice it high up as much, no drone, but yeah, loud!

Originally Posted by Jamie@dundonmotorsports

...An engine exhaust isn’t a fan (unless it’s turbo charged and that’s a different discussion) it’s a bunch of well timed gun shots. The pressure waves from the exhaust valve opening bounce around in the primary tube. The length and diameter you make the tube dictates when and how strong that reflected pressure wave (now a “ vacuum” wave) makes it back to the exhaust valve. If you time the reflected wave correctly you get the maximum vacuum wave to occur during intake valve and exhaust valve overlap and you’re able to suck more exhaust out of the cylinder and create a vacuum in the cylinder that sucks more air than atmospheric pressure will push into the cylinder through the intake valve. The 4th tube aids in the strength and timing of the pressure waves. This is how 40whp gains on a “non restrictive” exhaust

So by understanding the pressure waves, doing the math and building a well designed product your able to use the entire volume of the cylinder and actually super charge it a little.

Originally Posted by switchface

Jamie, this is an interesting explanation of your header design strategically built around this timing...by this logic, does this timing only apply to WOT? Meaning, would the timing then be less than ideal at partial throttle inputs?

Originally Posted by Jamie@dundonmotorsports

The timing of the engine firing is the same at part throttle or WOT. Firing order is the same, the cam timing does come into play and you see what altering the cam timing can do with our tune and headers. That said the part throttle power is also improved, the strengths of the waves are less as the cylinder pressure is less at part throttle, but the effect is the same.

Originally Posted by benben01

The 4th tube does act as a heimholz resonator as well since we have little to no drone with the these headers. Added benefits of having more power and no drone. Now waiting on the Jamie and company to finish the 4.5L kit. I know what I want for xmas this year

Originally Posted by Alan C.

Great addition to my GT4. I have over 10,000 miles on my Dundon headers with no CEL or drone..

Originally Posted by Alan C.

I have the Dundon tune. I haven't timed myself on track since I quit Club Racing. What I can say is I don't have trouble keeping up with and sometimes getting slightly ahead of a few GT3s in the Smokies. It's a much improved car. The TPC DSC and links also add into the fun factor. I'm going to have to think long and hard about the next GT4.

Originally Posted by Jamie@dundonmotorsports

And to clarify Alan ran for about 6-9 months (Alan please correct me) without the tune before adding the tune....

He'll be one of the first to trial some of forthcoming super secret squirrel intake parts... (Don't ask, I'm not saying nothing until they're done and ready to ship, but lets just say all the stuff we do with headers is applicable to to the intake manifold as well...)