I understand when you close a valved exhaust, it will quiet down, but I’m wondering how restricted the flow is in the closed position. Are there any HP gains with a valved system even in the closed position or is closed the same or even worse than stock? Last, what exactly to the valves control? Divert the flow through the only muffler or an extra muffler?

 

I don't think there is any noticeable difference in mine. I guess technically with the valves closed, it gets a bit more restriction as it goes through the muffler but I don't think it does much change. I have the Bazooka Valvetronic exhaust from RR- Racing and basically the valve is right by the muffler so when it is closed, the exhaust is forced to go through the muffler only and when opened, it just goes straight out before it even gets to the muffler basically bypassing the muffler.

 

it will be a little bit restricted when closed and might loose ~5 hp from the gains you get with the exhaust according to exhaust experts I asked. if the exhaust makes 15-25 hp when opened, when closed you will loose ~5hp, therefore you will still gain 10-20 hp when closed.

 

Here is a super quick diagram to show you. With the valve closed in normal driving conditions, the exhaust will follow the red path through the mufflers. When you open the valve (arrow pointing to it) then the exhaust will be forced out of the straight pipe instead and bypass the muffler for full flow. Hope this helps.

-Justin
RR Racing

 

Thanks… Makes sense