Exhaust System thoughts

I've got a 2013 LFX V6 in my 1966 Chevelle. It's 3.6L, 217 ci, 4 valves per cyl, direct injected and naturally aspirated. These engines have internal exhaust manifolds so just one exhaust port in each head. There are down pipes with 4 catalytic converters (2 per bank). I'm running the stock down pipes but only the primary cats. The secondary cats located after the second O2 sensors have been removed. The down pipes are 2.5" diameter.

From the end of the down pipes I've installed a Pypes 2.5", 16 gauge stainless steel, mandrel bent exhaust system all the way to the rear bumper. It includes an X pipe and is supported by factory hangers at the rear of the mufflers and the rear of the tail pipes.

I originally installed Flowmaster 50 Series Delta Flow mufflers. They were pretty quiet but I wasn't happy with the drone so I have since installed Walker QuietFlow lll mufflers. The QF lll's are 2.5" in/out but do neck down to 2.25" internally.

So while the drone is gone the system is much more raspy. I mean it sounds like crap. It sounds like an old truck or even a tractor. In thinking that maybe the system at 2.5" was too large for the 217 ci displacement, I blocked one half of the system at the tail pipe outlet. It sounded WAY better but still raspy. 

So here are my questions:

1. When I blocked one half of the system at the end of a tailpipe I basically turned everything past the one leg of the X into a huge Helmholtz chamber, muffler and all. What affect could this have had and should I have blocked it at the X instead?

2. Should I be considering a single exhaust for this tiny engine? Would mixing and keeping the exhaust flow together for the entire length disguise the V6 cadence any? Maybe smooth it out some? And if so, is a single 2.5" muffler/tailpipe adequate for 217 ci? 

3. The Flowmasters had a MUCH lower tone so I'm thinking I probably should have kept them and added resonators in the tailpipes to kill the drone. Anyone have experience with resonators after Flowmasters?

4. Chevelles locate the mufflers just before the rear axle. This as far back as you can locate a muffler in these cars. Would there be any benefit to moving the mufflers forward a little? I read somewhere that you should always have a minimum of 6" of straight pipe after a muffler before any elbows.

5. Would dropping the tail pipes down to 2.25" or even 2" affect the sound any? I'm quite sure with 2- 2" tail pipes I have plenty of pipe for my engines displacement? 

6. I do not have a flex section in the system. Would adding SS flex sections after the cats and before the X help any with resonance? 

7. Should I update the hangers to something more current to further isolate the system from the body/frame?

8. I swear I've seen muffler wraps before but can't seem to find any now. If I'm remembering correctly they were preformed of that multi layer dimpled material you would normally see in later cars as heat shielding and were held on with stainless zip ties.

Any other suggestions, ideas, feedback would be appreciated. I'm looking for the quietest, lowest tone I can get given I'm challenged in the displacement department. 

I'm just spitballing and have no real understanding of how to make an exhaust sound better or worse so grain of salt all of this.  I wonder what it would sound like with under-car turn-downs instead of the over-axle pipes.  It seems like cars with a lot of pipe after the last muffler can have odd outcomes that are not welcome.  I doubt moving the mufflers a bit forward or not will change things.  

I think I'd go on Youtube and go looking for folks posting videos of their exhaust setups with that engine and see what you like and then emulate as best you can.  This is one engine that I do not have a concept in my head as to what it sounds like.  As far as low tones with an engine of that general size and type, it's definitely possible, as I have heard some pretty low toned exhaust sounds from Alfas.  This car won't sound like a 454 but it shouldn't sound like a Buick 3800 with glass packs, either.

I've been to YouTube to try and get sound clips but this engine is only offered in late model GM cars and I've only seen swaps into Miatas. The mufflers, resonators, pipes etc and the packaging of the components in those vehicles would be impossible for me to reproduce. Plus most of the clips posted are by guys who think loud is cool.

For example I saw a late model Impala with the same V6 in a parking lot and it rumbled pretty nicely. I asked the guy and he told/showed me that he had stock cats and then Flowmasters located right at the rear bumper. From the cats to beyond the rear axle it was just one pipe. I can't locate mufflers at my rear bumper and I can't merge my exhaust together as quickly as the Impala did because of my transmission, crossmember, floorboards, etc.

For me dumping the exhaust at the axle doesn't work. I'm looking for QUIET  and the noise reflecting off the ground under the car would be too much.

A lot of drone is the exhaust resonating front to back under the middle of the car.  Putting mufflers as close to the engine as possible, even just a simple glasspack type muffler (perf core only, no louvers!) in each pipe ahead of the X, will do you good.

The exhaust cools and shrinks on its way out.  If you have 2.5" pipe at the front, you don't need 2.5" at the tips, you can drop down to 2" behind the axle.

I picked up the exhaust system off a Camaro SS of some nature, so that's at least a 5.3, maybe a 6.0, and a performance car. The pipes are 2.5", so that suggests yours could be somewhat oversized. The Camaro had two large mufflers, right at the rear bumper and twin bullet resonators just after the crossover pipe. The gas velocity likely matters. Other than that, I know nothing about tuning exhausts for sound.

Edit: The lower spec Camaro came with a 3.6 V6 too, so what size pipes would it have? Does a V6 Camaro sound right ot your ear?

I'm still tripping over a lfx powered Chevelle!

where you been man? You fit in well here. 

My engine is from a Camaro and the stock down tubes are 2.5". That's why I went with the 2.5" Pypes system. In retrospect, I'm not sure what the balance of the Camaro V6 exhaust was. I never saw it. It could have necked down somewhere.

The YouTube videos I was able to find for this engine were Camaros and they all sounded like crap. Raspy, loud, terrible cadence. There were all different types and brands of mufflers, resonator deletes, cat deletes, etc. All terrible.

When I redo this I want to make sure that I've got the best layout and the best mounting system.

67LS1 said:

I've got a 2013 LFX V6 in my 1966 Chevelle. It's 3.6L, 217 ci, 4 valves per cyl, direct injected and naturally aspirated. These engines have internal exhaust manifolds so just one exhaust port in each head. There are down pipes with 4 catalytic converters (2 per bank). I'm running the stock down pipes but only the primary cats. The secondary cats located after the second O2 sensors have been removed. The down pipes are 2.5" diameter.

From the end of the down pipes I've installed a Pypes 2.5", 16 gauge stainless steel, mandrel bent exhaust system all the way to the rear bumper. It includes an X pipe and is supported by factory hangers at the rear of the mufflers and the rear of the tail pipes.

I originally installed Flowmaster 50 Series Delta Flow mufflers. They were pretty quiet but I wasn't happy with the drone so I have since installed Walker QuietFlow lll mufflers. The QF lll's are 2.5" in/out but do neck down to 2.25" internally.

So while the drone is gone the system is much more raspy. I mean it sounds like crap. It sounds like an old truck or even a tractor. In thinking that maybe the system at 2.5" was too large for the 217 ci displacement, I blocked one half of the system at the tail pipe outlet. It sounded WAY better but still raspy. 

So here are my questions:

1. When I blocked one half of the system at the end of a tailpipe I basically turned everything past the one leg of the X into a huge Helmholtz chamber, muffler and all. What affect could this have had and should I have blocked it at the X instead?

no idea, ive never had to try this.

2. Should I be considering a single exhaust for this tiny engine? Would mixing and keeping the exhaust flow together for the entire length disguise the V6 cadence any? Maybe smooth it out some? And if so, is a single 2.5" muffler/tailpipe adequate for 217 ci? 

Single 2.5" would actually be on the small side for the HP.  Factory V6 camaro has 2.25" duals.

3. The Flowmasters had a MUCH lower tone so I'm thinking I probably should have kept them and added resonators in the tailpipes to kill the drone. Anyone have experience with resonators after Flowmasters?

You do not have sufficient room back there for the large cans required to tune out most drones.  Strange you even had drone with them as the 50series features a built in Helmholtz chamber to combat typical drone frequencies.

4. Chevelles locate the mufflers just before the rear axle. This as far back as you can locate a muffler in these cars. Would there be any benefit to moving the mufflers forward a little? I read somewhere that you should always have a minimum of 6" of straight pipe after a muffler before any elbows.

With chambered mufflers, its ideal to have at least a foot of tubing before it terminates to restablish laminar flow exiting the muffler.  I have never heard this 6" minimum before bends suggestion.  I see no harm with it, but I do not see it as a requirement.

5. Would dropping the tail pipes down to 2.25" or even 2" affect the sound any? I'm quite sure with 2- 2" tail pipes I have plenty of pipe for my engines displacement? 

I like doing size shifts after mufflers as there is typically a large tempurate drop across most mufflers, usually enough to lower the need for the same size pipe to exit the muffler.  It often helps boost scavenging velocity.  With your X and chambered mufflers, 2" should work very well.  It will quieten it up but also raise the tone a little.

6. I do not have a flex section in the system. Would adding SS flex sections after the cats and before the X help any with resonance? 

Not much at all.  Flex is primarily for thermal expansion and FWD-based drivelines.  However it does help a little if using hard rubber mounting methods.

7. Should I update the hangers to something more current to further isolate the system from the body/frame?

Definetely could not hurt.  I am a fan of retro fitting late model VW/Audi and Mopar hanger brackets especially on older muscle. 

8. I swear I've seen muffler wraps before but can't seem to find any now. If I'm remembering correctly they were preformed of that multi layer dimpled material you would normally see in later cars as heat shielding and were held on with stainless zip ties.

I believe DEI had something like that, wont make a lick of difference with drones and sound.  Its primarily for heat isolation.

Any other suggestions, ideas, feedback would be appreciated. I'm looking for the quietest, lowest tone I can get given I'm challenged in the displacement department. 

I would looking into Dynomax SuperTurbo hemi mufflers, the fiberglass packing will help with the higher tones, and the smoothed out internals keep flow up while toning everything down.  Combine this with a smaller tailpipe and you should be good to go.  If you would of brought me the car as a customer this is exactly what I would have suggested from the get go. 

I gave my inputs directly in the quote

In reply to malibuguy :

I found a clip of a LFX V6 with the Dynomax Super Turbo mufflers (not sure about the Hemi reference) and the tone is OK but there still louder than I would like. Would resonators before or after them help any?

67LS1 said:

So while the drone is gone the system is much more raspy. I mean it sounds like crap. It sounds like an old truck or even a tractor. I

Any other suggestions, ideas, feedback would be appreciated. I'm looking for the quietest, lowest tone I can get given I'm challenged in the displacement department. 

“If you focus solely on noise cancellation or reflection, your going to end up with a real ‘tinny’ sound and not really a desirable tone. If you rely purely on absorption, you don’t cancel frequencies at the right areas and you get drone,” says B&B Exhaust’s Billy Boat. “So, what we have learned in the last 20 years of muffler design, through trial and error and practical application, is that a combination of both is what we found to be the best.”

Basically, if you added resonators (which are absorptive type mufflers that cancel out the high frequency tinny sound) with the Walkers (reflective type mufflers that cancel out the low frequency drone), you should get a decent sound out of it.  Adding resonators to the Flowmasters probably won't be as effective because it sounds like the flowmaster design already cancels out the same frequencies as a resonator.

TL;DR walkers + resonators = good

67LS1 said:

In reply to malibuguy :

I found a clip of a LFX V6 with the Dynomax Super Turbo mufflers (not sure about the Hemi reference) and the tone is OK but there still louder than I would like. Would resonators before or after them help any?

The hemi mufflers is really just a referral to the large case (20"~) mufflers.  Which are a bit quieter then the standard 14" ones.  You can definitely put some glasspack "resonators" after them however due to their size most glasspacks work at higher frequencies.  

The combination should be really quiet.  I put a set of hemi super turbos on my friends 383 stroker gbody Bonneville...3" off the headers into an Xpipe, then 2.5 from the X thru the mufflers and tails.  The Holley fuel pump was considerably louder.

In reply to malibuguy : Is there a big difference between the Dynomax Super Turbo muffler and the Walker QuietFlow lll ? The QF is 1" shorter at 19" and the same width and height. I really don't want to change mufflers (again) and have the same issue. 

 

Wonder if there's space for resonators or "bullet" mufflers right before the tips aft of the rear axle.  Something to knock down the sound a bit more could be helpful.

I went and listened to some different exhaust videos of Camaros with that 3.6 and none of them sound all that great.  The setup from a high level seems to be pretty similar to what was described in the first post.  Maybe changing out the X-pipe for a Y-pipe and running a single pipe from the middle of the system onward would sound better?

Any recommendations for the best resonator? I'm going to measure today to see how much space I have in the rear for them.

67LS1 said:

Any recommendations for the best resonator? I'm going to measure today to see how much space I have in the rear for them.

The ST has fiberglass packing which helps remove higher, harsher tones.  the QF3 has none (unless something has changed).  Plus the ST outflows the QF.

Resonators, hard to beat the Flowmaster HP2 for the given size, which will fit on your Chevelle no problem depending on how tight your tailpipes are to the frame.  With Flowmasters new owners shipping out production to China, I cannot comment if they are still as good as they were, as I have not handled any in a couple years.

Next up would be the Vibrant Ultra Quiet resonator.  The shear size and immensely dense packing of the Vibrant unit gives it a wider control.  Often I use them solely as a muffler.  A top notch product.

Vibrants "bottle" resonators are very nice, just much slimmer so their affect in the system is not as strong as the UQ units.  The more packing, the greater the affect.

But again these primarily focus on the higher end frequency spectrum, so as an add on to your existing system either of these might just fit the bill for you.

Yikes! Those Flowmaster HP2s are more than their mufflers, which are expensive. Between the Super Turbos and the resonators I'd be spending almost $500. 
I'd sure like to hear the combo on an LFX before spending that amount.

Single muffler, dual outlet for appearance.   

V6 cylinder engines never sound good with split manifolds and dual exhaust.

Streetwiseguy said:

Single muffler, dual outlet for appearance.   

V6 cylinder engines never sound good with split manifolds and dual exhaust.

I like to argue its really up to the engine, and in the end use the owner.  Generally, I like to keep 6cyls with a single pipe because it gives a richer, more intense note to work with.

But I have done many dual exhausts that sounded absolutely glorious, especially when I am given artistic control.

I have also done many per customers request that sound heinous.  And often they come back for me to rework.   However there have been some where they liked what they got, even tho Id say the vast majority of people would not like that sound.  A good point is v6 mustangs with chambered mufflers.  Sound ok at like idle, everywhere else...eeek its bad.

In reply to malibuguy : You sound like your in the exhaust business. Do you know of any manufacture that offers mandrel bent, 2" tail pipes for a 1966 Chevelle? Everything I can find is 2.5" which is what I have now. I'm leaning towards the Super Turbos and down sizing the tailpipes. Then if this doesn't cut it adding resonators just forward of the rear bumper.

67LS1 said:

In reply to malibuguy : You sound like your in the exhaust business. Do you know of any manufacture that offers mandrel bent, 2" tail pipes for a 1966 Chevelle? Everything I can find is 2.5" which is what I have now. I'm leaning towards the Super Turbos and down sizing the tailpipes. Then if this doesn't cut it adding resonators just forward of the rear bumper.

 

I am.  I do not know of anyone offhand that will have a 2" mandrel file.   However MBS Exhaust should be able to bend you up 2.25" pipes.  The radius is close enough to set the bender up with the 2.5" set points but use 2.25 tooling.  I know this because Ive done it on/for a chevelle, there with their machines.

If I was still there Id could probably bend you up a 2" file with some extra lengths with a 2piece method to give you some flexibility.

However I only do bespoke from scratch stuff now in my own shop.  So I cannot say make a set for you with out the car here to be a jig.  Since I have no computer mandrel bender.

When you call MBS tell Tim that Greg sent you and if they question the task tell them to call me lol.

Heartthrob Exhaust offers 2 1/4" mandrel bent tail pipes for your application, but for your power level, I think "regular" 2 1/4" tail pipes would be fine.  Either Waldrons or Classic Exhaust (I forget which) will sell you pipes bent to stock specs in 1/4" over stock diameter.  They'll fit right and tuck up nice and tight.  You may need to call as it appears they are no longer advertising the oversize option (or I didn't dig around their web sites long enough).  

I'm going to buy the Super Turbo mufflers and I have a question about sizing.

they only offer the 20" case, offset-offset in 2.5". They offer the 2.25" offset-offset but only in a 14" case. What's more important for sound reduction, case length or pipe size?

Note that I would have to cone down from 2.5" to make the 2.25" inlet work and would also change to 2.25" tail pipes.

If I buy the larger case 2.5", I would install them in place of the QF and try them. Tailpipe size reduction would be in the future only if needed.

I'm pretty sure the answer will be the larger case...

If the tailpipes don't do the trick, I wonder if just before the x on either side running a reducer to 2.25 then back up to 2.5 would have an effect, by interrupting resonant frequencies.

In reply to 67LS1 :

The case ultimately has the most influence.

67LS1 said:

I'm going to buy the Super Turbo mufflers and I have a question about sizing.

they only offer the 20" case, offset-offset in 2.5". They offer the 2.25" offset-offset but only in a 14" case. What's more important for sound reduction, case length or pipe size?

Note that I would have to cone down from 2.5" to make the 2.25" inlet work and would also change to 2.25" tail pipes.

If I buy the larger case 2.5", I would install them in place of the QF and try them. Tailpipe size reduction would be in the future only if needed.

I'm pretty sure the answer will be the larger case...

The tubing stub on a 2.25" muffler is sized to fit over a 2.25" tube, so the ID of the tubing stub on the muffler is 2.25". If the tubing has a wall thickness of .065", which is common, the OD of the muffler tubing end will be 2.38", which is .010" over the ID of the 2.50 OD exhaust tubing, if it has .065 wall thickness. With a pipe expander and a little grinder action, you can use 2.5" intermediate pipes, 2.25" in/out mufflers, and 2.25" tailpipes with no adapters. With thinner wall tubing, it'll fit easier.