EXHAUST: does going from 2.5in to dual 2.25 in piping cause drone?

[ellerth23]

Looking to build a custom exhaust and I was looking at a magnaflow muffler to replace the mid muffler and it is a 2.5inch in and dual 2.25in Outlet. This is perfect because the mufflers i want for the dual exhaust are both 2.25 in and dual 3.5inch tips.

My question is... ive heard changing piping diameter can cause drone. Let me know what you guys think..

Here is the muffler to replace the mid muffler
http://www.summitracing.com/parts/mpe-12580/overview/

here is the mufflers ill be running for the quad tip.
http://www.summitracing.com/parts/mpe-14805/overview/

Thanks!

[dbv2]

It should increase back pressure, I may be wrong don't quote me.. Larger piping = louder system.

Purchase the correct inlet sized muffler.

[ellerth23]

yeah ill have the right inlet but im worried that if the outlet is smaller if it will cause problems. Considering its sold as a whole muffler id assume it shouldn't cause any issues because the transition will be done by the muffler dual 2.25 inch outlet has more room for the pressure to get out as apposed to one 2.5in pipe outlet

[Shimmy]

you should be fine. you may want to double check the dimensions of the new muffler and the exhaust tip lengths to ensure they will fit without clearance issues. there's lots of room but just in case

[A4 Centaur]

The Avant exhuast by Billy Boat is necked down after the second resonator for that exact purpose. The muffler shop where I had the 3rd resonator added said the same thing or confirmed what I had read previously.

[MagnaFlow]

Hey ellerth, a smaller diameter will not increase drone, in fact it is usually the larger piping that tends to drone more. Our Y mufflers, such as the one mentioned above, step down when they split since the exhaust flow is now being divided among 2 pipes, and maintaining the larger diameter is not necessary. The smaller diameter also helps maintain velocity so the exhaust does not slow and cool down as much. We do offer smaller 5x8" versions of that resonator which maintain 2.5" on the outlets, too if you would prefer those instead.

[ellerth23]

Hey ellerth, a smaller diameter will not increase drone, in fact it is usually the larger piping that tends to drone more. Our Y mufflers, such as the one mentioned above, step down when they split since the exhaust flow is now being divided among 2 pipes, and maintaining the larger diameter is not necessary. The smaller diameter also helps maintain velocity so the exhaust does not slow and cool down as much. We do offer smaller 5x8" versions of that resonator which maintain 2.5" on the outlets, too if you would prefer those instead.

You e been extremely helpful! Thank you so much

[MagnaFlow]

You e been extremely helpful! Thank you so much

No problem! If you have any other questions, wed be happy to help.

[adamazing]

There's also a seldom discussed factor of thermal-dynamics of gasses. It's usually an overkill topic for street cars, but too-large of piping can also cause an increase in pack-pressure - there's an optimum desired diameter. Too small and you create restriction. Too large and it will allow exhaust gasses to slightly cool, slowing it's velocity and, essentially, also creating back-pressure. There's a sweet spot in the middle of those two limits that free exhaust flow while also keeping the gasses hot enough to maintain velocity.

This is more beneficial knowledge for GT and LeMans type cars so it's massively overkill for street driven cars, but the same principals apply.

[A4 Centaur]

Magnaflow do you offer a center muffler that I can replace either the BB end mufflers or the center section if they become degraded over time?

Looking at a Magnaflow rear resonator which has a 3" inlet and exit shown in the pic below:

[MagnaFlow]

There's also a seldom discussed factor of thermal-dynamics of gasses. It's usually an overkill topic for street cars, but too-large of piping can also cause an increase in pack-pressure - there's an optimum desired diameter. Too small and you create restriction. Too large and it will allow exhaust gasses to slightly cool, slowing it's velocity and, essentially, also creating back-pressure. There's a sweet spot in the middle of those two limits that free exhaust flow while also keeping the gasses hot enough to maintain velocity.

This is more beneficial knowledge for GT and LeMans type cars so it's massively overkill for street driven cars, but the same principals apply.

You are spot on. We take factors like that into consideration when developing our systems, which is why you'll see 99% of our exhausts use 2.5" piping.

Magnaflow do you offer a center muffler that I can replace either the BB end mufflers or the center section if they become degraded over time?

Looking at a Magnaflow rear resonator which has a 3" inlet and exit shown in the pic below:

We sure do! We offer a bunch of mufflers in various sizing with 3" inlet/outlet. What you may want to do is measure the dimensions of your current mufflers, so you can match them as close as possible. Its hard to tell from just looking at the picture, but the center resonator looks to be around a 5x8x14", and the rears maybe 5x11x14". If those sizes are accurate, then you could check out our muffler # 12219 (satin)/14219 (polished) for starters. Our website makes it easy to filter mufflers by inlet/outlet size, so you can see all of your options!