Exhaust diameter question

[chuck1022]

Let's say I have a plan to do a stock-ish Explorer swap. Stock exhaust manifolds.....to catalytic converters to muffler to single exhaust exit out the passenger side.

Should it be 2in pipe from exhaust manifolds to two catalytic converters

2 inch exhaust pipes to single muffler

3 inch pipe from muffler to exit.?

 

[DirtDonk]

Might also depend on what type of muffler you’re going to use. But maybe not much given the stock manifolds and cam.
Generally speaking, I would do at least 2 1/4 from the manifolds to the convergence. Then 2 1/2 the rest of the way, using either a straight through or other performance type (but quiet-ish) muffler. If you’re going for quiet, then there’s really not much difference and the same recommendation would work.
No real reason to go 3 inch out for a stock explorer engine unless you’re trying to give it more rumble, maybe more drone, and perhaps gain a tiny bit at full throttle at 5000 RPM?
If you’re hoping to be able to rev it up to the maximum then a straight through muffler and 3 inch pipe going out the back might help.
I say “might“ because your stock exhaust manifolds will be the primary restriction.
If you want to maximize flow throughout, then yes, 2 1/2 from the exhaust manifolds to the merge and then 3” the rest of the way are pretty much guaranteed to give you more flow than your engine would ever ever need.
Maybe too much at the expense of some off idle performance, depending upon the computer tune.

Either some Dynomax, super turbos, or ultra flows, should give you good performance with relatively quiet sound. The flow master will have that nice tone and depending on which one you get, could be quiet or noisy. A straight through Magnaflow’s type or similar. Will give you plenty of breathing, but Again, depending on which model could be too noisy.

So what is it you’re looking for performance wise?

 

[chuck1022]

Performance wise I am looking for quiet!!!!

I am not a high hp high rpm kinda person.

 

[Slowleak]

I have a Dynomax Superturbo on a otherwise stock exhaust system. I don’t have a drone at any speed and it has a nice pleasant tone at idle. Flow seems much better than the stock exhaust.

 

[Broncobowsher]

I don't think 2" was ever used even on the lowest HP 302. I would go 2¼ off the manifolds.
3" is too big for a quiet exhaust. You don't have the HP for 3". 3" will be very prone to drone. Go 2½". Still has lots of flow potential (I know 300+HP engines going through a single 2½" exhaust.

For quiet, forget any aftermarket performance branded muffler. They will all be loud. Find a generic stock replacment muffler that fits. The bigger the better. The more volumetric displacment the muffler is, the better it will flow and be quiet (in general). I've had good luck with Walker quietflow mufflers.

Be sure to run full length exhaust. Distance is your friend. Go to the stock location. Out the side, behind the rear tire. Under the floor will be loud (as well as exhaust fumes) Out the side in front of the rear tire is slightly better. But that tube length does help is converting pulses into a steady flow.

Exhaust isn't an exact science, it is a bit of a black art. There are some rules of thumb that are generally true, but not always. The number of variables are nearly endless as well. Even the sound that does get out has variables in it. Not just loud to quiet, but the noises that make up the sound. Burble, crackle, tinny, boomy, and don't forget the drone. Get quiet enough and there may even be some hiss and jet noises. Add in the options to put secondary noise treatment on the exhaust (resonators and quarter wave resonators for example). Sometimes some stuff will make zero difference, but a different application and adding a simple bend to the pipe will have a major change to the exhaust.

 

[chuck1022]

Exhaust is a black art to me. It would be interesting to talk to a fluid dynamics engineer or whomever specializes in that.

Maybe my plan should be to mimic the Explorer exhaust

 

[Slowleak]

I guess quiet is a relative term but the Dynomax Superturbo 17742 I have is comparable in noise level to the stock exhaust. It’s advertised as a “performance muffler” with a high flow rate. Round stock looking muffler, just shorter, with a 2” inlet and outlet. I’m not any kind of muffler guru. I only know what I’m hearing.

 

[DirtDonk]

Are you going to make it all yourself, or have a local exhaust shop do it?

 

[DirtDonk]

The good news is that the super turbo won the turbo muffler shoot out on engine masters. Beating out even some of the cheaper straight through type in performance.
Quite a feat!

 

[spap]

If you are going to have catalytic converters on it that will quiet it down too.

 

[Speedrdr]

If I understand correctly, engine exhaust noise is comparable to “gun” exhaust in that when you quieten a rifle round, the suppressor is giving an expansion chamber of sorts and helps cool down the burning gasses. Cooler ‘air’ out the end is quieter and that’s the way I see engine exhaust; having a large and long exhaust system means quieter. At least my mind tells me that.

Randy

 

[chuck1022]

Are you going to make it all yourself, or have a local exhaust shop do it?

Probably have a shop do it

 

[DirtDonk]

Around here most of them don't even have 2" tubing anymore, at least that I remember. You'd think they'd keep it for the old 4 and 6-cylinder equipped vehicles, but it's probably just not that popular anymore. They had 2.25" coming out of their ears however, and even 3" but in some cases they didn't stock 2.5" and had to order it.
It's been awhile, and as far as I can tell 2.5" tubing has gained quite a following in recent years. Both for single and dual exhaust systems, so maybe that's changed.
But at least around here that was the case a few years ago.

Paul

 

[76YETI]

just watched engine masters and they have done several episodes on exhaust...very interesting findings: https://www.motortrend.com/news/eng...-the-backpressure-myth-3-vs-2-5-inch-exhaust/

 

[pcf_mark]

18" after a properly sized header nothing really matters about the exhaust unless it is too small. Stock manifolds you already left it all the power and torque on the table just use whatever is cheapest..

 

[SavageBurro]

Once upon a time I was able to modify/make the exhaust from a 98ish explorer work in bronco, with explorer 5.0. Even used the explorer manifolds. Few minor tweaks here and there and the entire system fit nicely as a two into one. I'm sure it was restrictive as heck but it ran great and was whisper quiet! People on the trail would often comment that they couldn't even hear it running. Still had a nice quiet rumble when on the throttle. Don't recall size of everything. If you still have the exhaust from donor rig - you might see if you can make it work?

 

[chuck1022]

Once upon a time I was able to modify/make the exhaust from a 98ish explorer work in bronco, with explorer 5.0. Even used the explorer manifolds. Few minor tweaks here and there and the entire system fit nicely as a two into one. I'm sure it was restrictive as heck but it ran great and was whisper quiet! People on the trail would often comment that they couldn't even hear it running. Still had a nice quiet rumble when on the throttle. Don't recall size of everything. If you still have the exhaust from donor rig - you might see if you can make it work?

That is a good idea....