2 into 1 Exhaust Muffler choices -Done, now I have serious DRONE!

[xcntrk]

Here's what the Magnaflow in the BCB kit sounds like:


[youtube]n88uaGgv9aw[/youtube]
https://www.youtube.com/watch?v=n88uaGgv9aw

 

[AZ73]

Nice video. You using an antisway bar? Which one?

 

[xcntrk]

Nice video. You using an antisway bar? Which one?

Yes. Hellwig front bar for EB. Works very well.

 

[casadejohnson]

BC headers and pipes are now installed with a "Y" into a simple Dynomax Super turbo muffler. I have not done a tail pipe yet so I just have a turn down on it. The photos show how it is set up (Photos are from mock up before I installed the hanger and clamps). In general, it sounds very good but the Drone is still bad starting around 2200-2500 RPM. It might even be worse than the flow masters were. If I'm sitting in the driveway and I run the RPM's up it does not seem to drone, it only does it on the road. I am attempting to reserve judgment because I do not have a tailpipe yet. For those of you who have gone from the turn down to a tail pipe, did it have any effect on drone or did it just lower the sound level over all? Maybe I'm getting ahead of myself but I have read some very encouraging results have been achieved using branch resonators like the one described in this link. Anyone tried this on a Bronco?

 

[xcntrk]

I wonder if you're jamming too much flow into that muffler. It appears to have the same diameter inlet outlet. So you're taking x2 2.5" pipes, jamming that flow down to a single 2.5" pipe (with the Y), then through the muffler with a single 2.5" out? Is that muffler designed for 2-into-1 applications?

 

[casadejohnson]

I wonder if you're jamming too much flow into that muffler. It appears to have the same diameter inlet outlet. So you're taking x2 2.5" pipes, jamming that flow down to a single 2.5" pipe (with the Y), then through the muffler with a single 2.5" out? Is that muffler designed for 2-into-1 applications?

No, it's not all 2.5", the muffler is 3" and 3" out. The "Y" is 2 x 2.5" in and 3" out. The Muffler is supposed to flow 700CFM according to the folks at Dynomax. Everything I read says a turn down under the vehicle will tend to drone bad so I hope thats the problem.

 

[WorkerBee]

Cascade,

A complete tail pipe should help a lot. Turndowns typically drone really bad no matter what muffler you have. In addition, I would shorten the distance between your Y and your muffler as much as possible. I have the same Y piece on mine and found that the smaller the amount of 3" pipe you have between the muffler, the more defined the exhaust pulses=less drone.

Keep in mind, that the muffler may flow 700cfm, but the velocity through the pipe is high.

I have a 50 series delta flow dual outlet and it sounds perfect. No really nasty drone. It sounds pretty rowdy on the gas but quiets down a lot when you let off. I have a video on youtube but it's before I did my explorer motor EFI swap. still sounds similar but even more defined now. I'll try to post a new video soon. Good luck!

 

[01Dudley]

http://wiki.answers.com/Q/What_is_the_difference_of_scfm_and_cfm

There is a big number difference between CFM and SCFM, so be sure you are comparing apples to apples. A CHERRYBOMB TURBO(which is identical to a Dynomax/Thrush turbo) has a CFM of 290 @ 20.3" of water. This is test was done on a SF-1200 flow bench and this is the most common way to test the flow of a muffler in the exhaust industry.

That seems like a lot of exhaust for a small very stricted seamed turbo muffler even if it is 3" diameter. Yes it will be the quietest option, but it is also very strictive so you will be getting more heat in the engine. If you used a better flowing muffler you could reduce the amount of heat that is being forced to stay in the engine. I bet that when you add the tail pipe you will find that your Bronco feels a little more torquey at running temp than it did w/the Flowmasters. This will be because of the amount of pack pressure you now have, caused my a more restrictive muffler which is causing more heat in the engine which ignites at a different rate in the cylinder than a cooler running engine.

Yes adding a tailpipe will eliminate the drone. I have heard bad things about the Dynomax VT muffler. I have heard the butterfly valve will rust shut if the vehicle sits w/moister in it. Just FYI. A Flowmaster 40 series has a CFM of 470(Just like a CHERRYBOMB PRO and other chambered mufflers) and the CHERRYBOMB VORTEX has a 598 CFM rating. Again make sure you compare CFM to CFM and not SCFM.

 

[casadejohnson]

Your correct its SCFM not CFM, typo on my part. I'll be putting together a tail pipe tonight so we will see about the drone. This is just a simple Turbo muffler not the VT from dynomax. I read about that one but didn't like the idea of moving parts in the muffler.

 

[broncoitis]

I also originally had dumps on my truck under the middle and it DRONED like crazy. Something had to give so I changed it out with a different muffler and ran it out the side and a HUGE difference. Also helped with the fuel smell. Good Luck and let us know what happens.

 

[casadejohnson]

I went out and pulled the muffler off last night, Now I'm debating going to the 3" version of the Walker Quiet Flow before putting together the tail pipe. It was -9 degrees last night so my comfort level in the garage was pretty low. Maybe it will warm up and I can get some work done tonight.

 

[casadejohnson]

From what I have read, the walker quiet flow is basically a larger turbo muffler. The website indicates that it also flows pretty well (as compared to a stock muffler I suppose).. The problem I see Is that the muffler is freaking huge! On the upside I Think I figured out my tailpipe routing.

 

[nvrstuk]

VT's and moving parts...

I agree, but with an unlimited lifetime warranty and using SS band clamps before and after the muffler makes it beyond easy to replace if I ever needed to...

 

[casadejohnson]

Well, I made some changes and we have major improvement! I went to my Exhaust guy today because my plan to build my own tailpipe looked like it was going to be more trouble than it was worth. I decided to stay with the Dynomax turbo muffler because I tried the walker muffler at the shop and the sound difference was not huge (at idle in the shop) and the extra length was going to be a major hurdle when it came to doing the tailpipe the way I wanted it. Using a 3" tailpipe made it much more difficult to snake it through than it was with the 2 1/4" that I had with the old duals. As an added effort to combat drone, we added a weight in front of the muffler. We used a weight from a diesel exhaust setup that someone had just had removed earlier in the day. All in all, I'm happy now. It is substantially quieter in the vehicle and I'm guessing that the drone is at least 90% improved. I can now hold a conversation inside without yelling at 65MPH. We had to make the tailpipe two pieces to get the bends close enough together to make the needed turns but there is the added Benefit of being able to remove the last foot and a half of pipe if I ever smash my tailpipe closed while wheeling. The only problem now is that when I got home from the test drive, it was idling higher than normal. I'll pull codes tomorrow after another test drive and see what I find. Is it possible that the idle was effected by the O2 sensors being much closer to the engine than they were with my old long tube headers? Here is what it looks like now.

 

[xcntrk]

Looks great! Do you think the weight makes that much difference or was the tailpipe what primarily solved the problem?

 

[casadejohnson]

I'm sure it's mostly the tailpipe but we figured the weight couldn't hurt so he cut it off the old system it was on and welded it on to mine for good measure.

 

[red hot71]

I ran into the same problem years ago, large single into a 3" muffler 3" out. Drone is a under statement.

Removed that muffler from the bronco and used it on a pick-up that I had. All can say is same basic system but with longer pipes made it so much quieter, no drone.

My muffler friend say if you think you have problem in your bronco try a CJ5.

 

[DEEPWOODS]

I am going with BC broncos headers and pipes.I am going to try a magnaflow 12468 it is 2 in and 2 out with internal X crossing 18" long according to the mustang crowd on corral it has no drone because the tru x muffler intersects in the center to pull gasses,rather than push them. I am about 3 or 4 months before getting to this I will let you know if it works and is truly Quiet.

 

[casadejohnson]

I'm interested in seeing how that X muffler works out. I wish I had a Go Pro camera setup so i could get inside and outside video clips. I'm going to go do a little driving it here in a bit and see if my High idle issue persists.

 

[01Dudley]

I'm telling you guys you should try the Cherrybomb Vortex muffler.