# EXHAUST AFTERFIRE



## armyadarkness (Dec 7, 2020)

After a 2 year battle with my exhaust, I finally have it sounding right, but now I have afterfire (usually misdescribed as backfire) when I shift.

I always believed this to represent a lean condition, but that's not what the internet is saying!

So, my car didnt have it before, and now that I opened up the exhaust, I do have it. Any ideas for tuning it out? Anyone else with the issue?


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## 67ventwindow (Mar 3, 2020)

I have been driving with the teen in the Gray ubiquitous blob getting passed by many a car on the two lane country roads. I was surprised how many cars do that when they let off after passing. The teen calls them car farts. Cars you cant hear the exhaust but you hear the popping. Its been an embarrassing two weeks and she is legal now. Time to buy her a 4x4 truck.


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## AV68 (Aug 18, 2021)

I think I may have fought with a similar issue on an old Bronco, I would get crackle pops bordering on backfire volumes out the exhaust on decel or off throttle conditions, I changed from Flowmaster mufflers to Dynomax turbo mufflers and that helped some (a little more restrictive exhaust flow) but the most improvement came when I changed fuel injection to the Edlebrock set up that allowed me to richen up the fuel mixture on decel conditions, so long story short carbureted richen the idle circuit, fuel injected the same or add fuel to decel ?


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## GTO Yeah (Dec 6, 2021)

Does it happen more when you're really getting on it? Or does it happen when you're cruising as well?

If it's happening when you're shifting hard through the gears, my understanding of it is you create a momentary rich fuel mixture when you left off the gas abruptly--which burns incompletely then makes it's way to your exhaust where it ignites. It's exacerbated by shorter or higher flowing exhaust.

It's not apples to apples, but I get the same thing on my R1 with my Coffman shorty exhaust. A tune helped it a bit, but there's no getting around it completely in my experience.

But I think that's just one possible reason. This video helped me wrap my head around the other factors:


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## michaelfind (Dec 14, 2018)

I have no idea, but I'm curious because I often hear that with the local bikers as they let off throttle to shift.


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## GTO Yeah (Dec 6, 2021)

michaelfind said:


> I have no idea, but I'm curious because I often hear that with the local bikers as they let off throttle to shift.


I don't know how common it is with classic cars. I did a google search, but no videos of afterfire come up with classic muscle.

It's all Ferraris and newer Corvettes/Mustangs.


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## armyadarkness (Dec 7, 2020)

GTO Yeah said:


> Does it happen more when you're really getting on it? Or does it happen when you're cruising as well?
> 
> If it's happening when you're shifting hard through the gears, my understanding of it is you create a momentary rich fuel mixture when you left off the gas abruptly--which burns incompletely then makes it's way to your exhaust where it ignites. It's exacerbated by shorter or higher flowing exhaust.
> 
> ...


All of my R1's and FZR's do it... Cycles are much more prone.

It only does is when cruising, and only when pushing in the clutch. If I shift fast it does not do it.


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## armyadarkness (Dec 7, 2020)

michaelfind said:


> I have no idea, but I'm curious because I often hear that with the local bikers as they let off throttle to shift.


For sure motorcycles always do it... My theory was that it was because when you let off the throttle, in gear, the engine kept turning, therefore continuing to draw in air, but no fuel... however, that was just a guess.

Now my GTO has a very aggressive exhaust, and thats what started it.


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## Baaad65 (Aug 29, 2019)

Probably happening now that the exhaust is shortened up, what's your AFR meter showing for the carb mixture? How's the timing? Like young Sheldon covered in the video


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## armyadarkness (Dec 7, 2020)

Actually, with motorcycles; you can turn off the ignition but leave the key on while driving... and it's a load of fun to zip down the road, flip the ignition off, but stay on the throttle. Then when you flip it back on, it sounds like a mortar round. It's a sure fire way to cause a pedestrian to drop a deuce.

So I guess that it it unburnt fuel igniting, but why would a free flowing exhaust bring it on... unless it's the improved scavenging?


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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> Probably happening now that the exhaust is shortened up, what's your AFR meter showing for the carb mixture? How's the timing? Like young Sheldon covered in the video


Afr's in the 13's. I richened up for the new trans and open exhaust


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## michaelfind (Dec 14, 2018)

armyadarkness said:


> For sure motorcycles always do it... My theory was that it was because when you let off the throttle, in gear, the engine kept turning, therefore continuing to draw in air, but no fuel... however, that was just a guess.
> 
> Now my GTO has a very aggressive exhaust, and thats what started it.


What exactly did you do to make your exhaust sound more aggressive?


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## armyadarkness (Dec 7, 2020)

And... why only when the clutch is depressed, slowly?


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## armyadarkness (Dec 7, 2020)

After two full exhausts, two different x pipes, open pipes, and three sets of mufflers in a year... I finally bought the loudest exhaust made for the car... and since I was skeptical that it was going to be loud enough, I got a kit with cutouts built into it.

Sure enough, it wasnt nearly aggressive enough... and unfortunately, with the cutouts open, it was too LOUD and sounded like crap!!!!

So... I made my own baffles/ mufflers out of straight pipe, and bolted them to the cut outs. NOW ITS PERFECT!!!!!!!!!! No more being embarrassed by the Chevelles and Mustangs.


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## armyadarkness (Dec 7, 2020)

Only down side is wicked afterfire, when I push in the clutch and shift slow.


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## AV68 (Aug 18, 2021)

Are you carbureted or EFI and are you letting off the throttle between shifts?


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## GTO Yeah (Dec 6, 2021)

armyadarkness said:


> All of my R1's and FZR's do it... Cycles are much more prone.
> 
> It only does is when cruising, and only when pushing in the clutch. If I shift fast it does not do it.


I think that means you've just gotta go balls out everywhere you drive! Problem solved.


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## Lemans guy (Oct 14, 2014)

I think you are a bit lean lean Army. Yes rich can do it also. But lean is more common. At cruise with a light pedal you are getting a lot of timing which you need to burn the lean cruise mixture. But yours may be a tad too lean for your setup.

when you slowly push the clutch down you also slowly “Decrease the load” on the engine by letting your foot off the gas pedal. Youkinda work those feet at the same speed. When you clutch easy your foot comes up easy andwhen you shift hard your foot comes up fast.

So depending on the speed where this happens an enrichment of that carb circuit may be called for.

say at 3000 Rpm you are at 60 mph light throttle. That will be on your main jets and idle circuit. ( because idle circuit never really stops, it is just overdone by th email jets.

then I would increase the main jets two sizes and see if the after fire changes.…then see what the AFR is if it is gone.


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## AV68 (Aug 18, 2021)

If you have an AFR gauge in there keep an eye on it while shifting and see if its changing momentarily from the cruise readings and in which direction

Sounds a lot like my Bronco, it did it worse on solid to aggressive acceleration and with the truck tranny, shifts were never real fast and it would let out some pretty solid backfires (for lack of a better word) if I didn't feather the gas between shifts


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## armyadarkness (Dec 7, 2020)

AV68 said:


> Are you carbureted or EFI and are you letting off the throttle between shifts?


Carb and yep, lazy/ slow shifts. Racing doesnt do it.


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## armyadarkness (Dec 7, 2020)

Lemans guy said:


> I think you are a bit lean lean Army. Yes rich can do it also. But lean is more common. At cruise with a light pedal you are getting a lot of timing which you need to burn the lean cruise mixture. But yours may be a tad too lean for your setup.
> 
> when you slowly push the clutch down you also slowly “Decrease the load” on the engine by letting your foot off the gas pedal. Youkinda work those feet at the same speed. When you clutch easy your foot comes up easy andwhen you shift hard your foot comes up fast.
> 
> ...


Ive always (for decades) kept my AFR's on the lean side (as you may or may not recall). But the manual trans exploited it, so I did bump up two stages richer, earlier in the week, but then the new exhause went on, so I'll pay close attention to the AFR's.

It's definitely in the 13's, but it has four mufflers now. I also am battling a s slight header gasket leak, at the head... so lean would make sense.


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## armyadarkness (Dec 7, 2020)

I still havent revisited my timing, after the new cam and 5 speed, either... so that's up on deck as well.


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## AV68 (Aug 18, 2021)

I'm with LeMans Guy, I would start with richening the idle circuit and see if you can notice a change


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## AV68 (Aug 18, 2021)

that exhaust leak could be the culprit


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## O52 (Jan 27, 2019)

armyadarkness said:


> I still havent revisited my timing, after the new cam and 5 speed, either... so that's up on deck as well.


Was the exhaust "quiet" before the cam change?


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## geeteeohguy (Feb 2, 2008)

It's happening because you changed to a stick and are now closing the throttle between shifts. Which means higher intake vacuum and richer mixture, temporarily. You may have a slight exhaust leak, and the combination of combustible fuel in the pipes and added O2 from the exhaust leak= BOOM. I remember a lot of stick cars I worked on in the early 80's had de-cel valves on the carbs which delayed the throttle closure on let-off just to keep emissions from getting too rich. Annoying to drive, as the rpm 'hangs' for a bit on the shifts. 
In your case, I would verify exhaust leaks. My old stick GTO's and Corvette don't backfire between shifts. Yours shouldn't either.


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## armyadarkness (Dec 7, 2020)

O52 said:


> Was the exhaust "quiet" before the cam change?


There was noticable difference in the heartbeat, between the two cams, but no, the exhaust has always been far too quiet for me, before and after.

My new exhaust still maintains a humble idle, but now you know that its angry. Before it just sounded tame.

Videos will be up soon.


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## armyadarkness (Dec 7, 2020)

geeteeohguy said:


> It's happening because you changed to a stick and are now closing the throttle between shifts. Which means higher intake vacuum and richer mixture, temporarily. You may have a slight exhaust leak, and the combination of combustible fuel in the pipes and added O2 from the exhaust leak= BOOM. I remember a lot of stick cars I worked on in the early 80's had de-cel valves on the carbs which delayed the throttle closure on let-off just to keep emissions from getting too rich. Annoying to drive, as the rpm 'hangs' for a bit on the shifts.
> In your case, I would verify exhaust leaks. My old stick GTO's and Corvette don't backfire between shifts. Yours shouldn't either.


Here's my only data:

I put 2000 miles on the manual, with no afterfire. My 70 Vette had none either.

I put 50 miles on the car, the night before I did the exhaust, and it was missing the front two driver side header bolts the entire time... it didnt afterfire at all. Ive since replaced the bolts, but not the gasket...

Which leads me to believe (but not sure) that it's being caused by my new exhaust mods.

I opened the cutouts and then added a 17" long piece of 2.5" pipe, with homemade baffles inside them, and then resonators on the end. They're just prototypes at this point, but they did what I wanted them to do.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> Here's my only data:
> 
> I put 2000 miles on the manual, with no afterfire. My 70 Vette had none either.
> 
> ...


I've never had after fire on my 4spd even with the cutouts open that are right before the muffler. Probably due to the vacuum leak and that the exhaust exit is so close to the motor maybe.


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## armyadarkness (Dec 7, 2020)

Well it's interesting that I did put beefier springs on the needles, the day before.

On the Eddy carbs, you can externally swap needle springs, to cater your transition to your engine vacuum. I put the heaviest spring in there, which means at low vacuum, my mains are wide open... I should look at my vac gauge when it's firing and see if that might be it.

But I assume Im at high vacuum when shifting at cruise, so that wouldnt be it. Tonight I can test!


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## AZTempest (Jun 11, 2019)

Hey Army, drowned out the sound. Crank up some Cowsills ..........lol.

"Give me down to there hair, shoulder length or longer
Here, baby, there, momma, everywhere, daddy, daddy..........."

I know, I'm no help.


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## armyadarkness (Dec 7, 2020)




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## geeteeohguy (Feb 2, 2008)

I'll bet the neighbors with the Prius just LOVE you.......LOL...


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## PontiacJim (Dec 29, 2012)

armyadarkness said:


>


Are you going to post another video for us with the cut-outs open?


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## armyadarkness (Dec 7, 2020)

PontiacJim said:


> Are you going to post another video for us with the cut-outs open?


I was going to email you a clip so you could use it as your doorbell. It's incredible how quiet it is inside the car. The baffles that I put inside the cutout almost work too well


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## PontiacJim (Dec 29, 2012)

armyadarkness said:


> I was going to email you a clip so you could use it as your doorbell. It's incredible how quiet it is inside the car. The baffles that I put inside the cutout almost work too well


Keep in mind that the cut-outs are not a diverter valve sending all the exhaust out the cut-out pipes. Some exhaust/sound still flows out the mufflers and tail pipes. Maybe you should just go with uncapped headers...............ah, never mind, you'll just insist that they aren't loud enough.

Got an idea, however. I am willing to post a "Go-Fund-Me" page for you so we can buy you a set of hearing aids and then you can hear how loud the exhaust really is. Whatta ya say????


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## 67ventwindow (Mar 3, 2020)

Is this your lawn mower?


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## armyadarkness (Dec 7, 2020)

PontiacJim said:


> Keep in mind that the cut-outs are not a diverter valve sending all the exhaust out the cut-out pipes. Some exhaust/sound still flows out the mufflers and tail pipes. Maybe you should just go with uncapped headers...............ah, never mind, you'll just insist that they aren't loud enough.
> 
> Got an idea, however. I am willing to post a "Go-Fund-Me" page for you so we can buy you a set of hearing aids and then you can hear how loud the exhaust really is. Whatta ya say????


Yes as the video points out, there's a substantial and equal volume of exhaust coming out the tail pipes! And as I showed, my cutouts are not just open pipe... they are essentially additional mufflers.

Do you guys really think it's loud? Yes I know that riding a Harley and being a performing bass player for 35 years, has taken it's toll on me, but every Chevelle and Mustang I hear is sooooo much louder.

In the world of muscle cars, people use sound to determine what is the baddest, and Im tired of silently creeping through these car shows, where everyone stares to see the cool GTO, and then struggles to hear it over the Mustang.


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## armyadarkness (Dec 7, 2020)

67ventwindow said:


> View attachment 153562
> 
> 
> Is this your lawn mower?


You know damn well that my mower has a K&N and headers... And so does my hair dryer and toaster.


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## PontiacJim (Dec 29, 2012)

armyadarkness said:


> Yes as the video points out, there's a substantial and equal volume of exhaust coming out the tail pipes! And as I showed, my cutouts are not just open pipe... they are essentially additional mufflers.
> 
> Do you guys really think it's loud? Yes I know that riding a Harley and being a performing bass player for 35 years, has taken it's toll on me, but every Chevelle and Mustang I hear is sooooo much louder.
> 
> In the world of muscle cars, people use sound to determine what is the baddest, and Im tired of silently creeping through these car shows, where everyone stares to see the cool GTO, and then struggles to hear it over the Mustang.


You are running 3" pipes, right? 

Compression ratio, cam specs, and overall HP will make a louder sound. The position of the muffler will change sound. Place your mufflers right at the end of the headers or thereabouts and see what happens. Did that on a stock '54 Buick and then had turn downs. Was enough to get pulled over for loud exhaust. My 409 had factory cast exhaust manifolds that were very streamlined for 1965, then ran 3" pipe, turbo mufflers, and then a 4" pipe just past the rear axle put to the bumper. You could here the car coming 1/2 mile away, and so could the cops. They would challenge me and I'd tell them it is legal - mufflers & tail pipes. They would always suggest a resonator.

Think about the "big rigs" with their 4", 6", and 8" stacks how loud they are with no mufflers compared to the guy who simply removes the muffler and runs a connector pipe in place of the muffler - no comparison in sound as the larger pipe guys drown him out.

Pontiac's are not "other" makes. Each manufacturer engine has its own sound and sound level. Hmmm, how can I get my Honda motorcycle to sound like that Harley with straight pipes. I know, I'll install a Kerker Header and pipes and it'll sound better than a Harley - NOT.

Have you not ever heard a Harley that was a street bike as opposed to one with an S&S built engine - apples & oranges in sound.

You are chasing after the Holy Grail and not going to find it. You are putting a lot of effort & time into your system and coming up empty. Pull that Pontiac engine and drop in an old school Big Block Chevy LS7 and I think you will have the sound you are looking for. 

In the meantime, check out this video:






AND, if all else fails, you can install these to the tail pipes:


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## armyadarkness (Dec 7, 2020)

The sound Im after is the sound that my old 66 and 67 had... so a Chevy engine wouldnt do it. I just want the same "attitude" that the Mustangs have, with their baby engines. 

I only have 2.5" Pypes continually talked me out of the 3", which now I fully regret...

My compression ratio is 10.10 and my cam is healthy. I have Dougs headers.

Yes, I do know that header mufflers are the loudest. I read that long ago and I experienced it first hand... That being said, my low performance vette with stock manny's and mufflers at the back bumper, sounded like a dragster compared to my GTO.


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## armyadarkness (Dec 7, 2020)

All this being said, I shouldve followed my instincts and got the 3". The car is simply quiet, and all joking aside, it's not my hearing. If it was, then Mustangs and Chevelles wouldnt sound loud either.


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## Jared (Apr 19, 2013)

PontiacJim said:


> Keep in mind that the cut-outs are not a diverter valve sending all the exhaust out the cut-out pipes. Some exhaust/sound still flows out the mufflers and tail pipes. Maybe you should just go with uncapped headers...............ah, never mind, you'll just insist that they aren't loud enough.
> 
> Got an idea, however. I am willing to post a "Go-Fund-Me" page for you so we can buy you a set of hearing aids and then you can hear how loud the exhaust really is. Whatta ya say????


I've been asking him about getting his hearing checked for months.


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## Baaad65 (Aug 29, 2019)

Jared said:


> I've been asking him about getting his hearing checked for months.


What?


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## Jared (Apr 19, 2013)

armyadarkness said:


> Yes as the video points out, there's a substantial and equal volume of exhaust coming out the tail pipes! And as I showed, my cutouts are not just open pipe... they are essentially additional mufflers.
> 
> Do you guys really think it's loud? Yes I know that riding a Harley and being a performing bass player for 35 years, has taken it's toll on me, but every Chevelle and Mustang I hear is sooooo much louder.
> 
> In the world of muscle cars, people use sound to determine what is the baddest, and Im tired of silently creeping through these car shows, where everyone stares to see the cool GTO, and then struggles to hear it over the Mustang.


Your added baffles and piping may actually be causing it to be quieter inside the car. They may be acting as resonance tubes which can be used to eliminate exhaust drone.


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## Jared (Apr 19, 2013)

armyadarkness said:


> The sound Im after is the sound that my old 66 and 67 had... so a Chevy engine wouldnt do it. I just want the same "attitude" that the Mustangs have, with their baby engines.
> 
> I only have 2.5" Pypes continually talked me out of the 3", which now I fully regret...
> 
> ...


Do I need to send you another clip of my SN95 Mustang?


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## ylwgto (Oct 27, 2009)

I think it sounds badass, army!

I often think my set up is too loud. I have janky, booger welded 3" pipes off full length Hedman headers, a DIY H pipe, 40 series flowmasters (those are the 2 chamber ones, right?) and turndowns in front of the axle. Loud as F. Maybe try that next?

In high school I was cruising on El Camino and hit an epic road construction hole I didn't see. bashed both pipes off at the collector...don't know how my oil pan survived. My dad always said carry a coat hanger or bailing wire in the car and man was he right. I rigged the pipes up and drove the car home and it has NEVER sounded better since!!! 

Your car is already tall so just run straight side exit pipes off your collectors. That outta cure your afterfire issues too. Cobras do it, so why not a '67?


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## O52 (Jan 27, 2019)

You know that the newer Mustangs are adding exhaust noise over the audio system. Make you think you have a great exhaust sound but its coming over your speakers rather than the pipes. 


_Ford has admitted that its Active Noise Control system, as found in the Ford Mustang, pumps fake engine sounds through the in-car speaker system to replicate the growl of the older models.

Thanks to the EcoBoost engine, the old roar of the four-cylinder engines of the past has been muted somewhat, but to compensate, Ford has revealed that it uses digital audio technology to give drivers a similar aural experience.

"With the EcoBoost engine we have both active noise cancellation and we also amplify the existing engine sound order," said Mustang chief engineer Dave Perciak.

However, he claims that instead of pushing completely fabricated sound through the stereo speakers, the car manufacturer simply amplifies the sound that is already there. "We don't create an artificial sound; we don't pluck one off the shelf; we bring in the real sound, process it, and play it through the car's speakers," he added.

"Today's V6 sounds fantastic, and although the EcoBoost won't sound like a V8, it won't sound like it doesn't belong in a Mustang, either."

How owners of new Mustangs feel about that is unknown, but it has shocked car magazines and websites. Road & Track discovered that if you disable the car stereo system, for example, the Mustang sadly loses its "voice"._


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## Jared (Apr 19, 2013)

O52 said:


> You know that the newer Mustangs are adding exhaust noise over the audio system. Make you think you have a great exhaust sound but its coming over your speakers rather than the pipes.
> 
> 
> _Ford has admitted that its Active Noise Control system, as found in the Ford Mustang, pumps fake engine sounds through the in-car speaker system to replicate the growl of the older models.
> ...


My kid had a Fiesta ST (hit a Grand Cherokee head on so the key word is had). That car had the piped in sound too but it wasn't done through the stereo. They had a tube that ran from the intake to the firewall. Basically, a stethoscope to the passenger compartment. Car actually sounded pretty good.

I actually get what Amy is talking about here. Figure the fox body Mustangs from the 80s had a little over 200 horse but the engines sounded massive and way more powerful with hotter than stock mufflers. I'm still thinking he will never get that kind of sound from a Pontiac because of head design. SBF and SBC both have the headers sticking out the side of the head where Pontiac has them bolted beneath.


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## armyadarkness (Dec 7, 2020)

ylwgto said:


> 0 series flowmasters (those are the 2 chamber ones, right?) and turndowns in front of the axle. Loud as F. Maybe try that next?


Thanks for the compliment. I actually love the way it sounds now, and it's super quiet in the car. 

Yeah, I will say that all of the loud Chevelles I keep mentioning, have turn downs at the rear axle on flow masters, so obviously the tailpipes make a HUGE difference. 

At idle, the Violators sound mean, but they just need a little more OOomph! However, with everything Ive tried, the Race Pro's, Cherry Bombs, and Flowmasters, when you get on it, it sounds like the Hammers of Hell. The Violators just make it x10.

My issue with dumping at the axle is that I like the way tailpipes look on classic muscle cars, and I didnt just want dummies there.

Although, now I have the added aesthetic of side dumps, so until I get to see the car outside, in full view, I cant say whether Ill like them.


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## armyadarkness (Dec 7, 2020)

Jared said:


> My kid had a Fiesta ST (hit a Grand Cherokee head on so the key word is had). That car had the piped in sound too but it wasn't done through the stereo. They had a tube that ran from the intake to the firewall. Basically, a stethoscope to the passenger compartment. Car actually sounded pretty good.
> 
> I actually get what Amy is talking about here. Figure the fox body Mustangs from the 80s had a little over 200 horse but the engines sounded massive and way more powerful with hotter than stock mufflers. I'm still thinking he will never get that kind of sound from a Pontiac because of head design. SBF and SBC both have the headers sticking out the side of the head where Pontiac has them bolted beneath.


Weather is breaking soon, so I'll know this week.


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## armyadarkness (Dec 7, 2020)

Still too soon to tell if I like the aesthetic, but I love the sound and performance increase of the open flow!!! I rewelded the collector dumps yesterday, and the afterfire was dramatically reduced, so I obviously had a leak there.

Also, I have a leak at the header on the driverside, but the number four bolt is so hard to remove, that new gaskets will have to wait a bit.


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## IceBolt (Jul 28, 2020)

Smart kid!


GTO Yeah said:


> Does it happen more when you're really getting on it? Or does it happen when you're cruising as well?
> 
> If it's happening when you're shifting hard through the gears, my understanding of it is you create a momentary rich fuel mixture when you left off the gas abruptly--which burns incompletely then makes it's way to your exhaust where it ignites. It's exacerbated by shorter or higher flowing exhaust.
> 
> ...


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## 67ramair4 (Mar 2, 2016)

Put a rag at the rear of the tailpipe, if it sucks it in, you have a burnt exhaust valve!


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## Montreux (Mar 8, 2009)

armyadarkness said:


> For sure motorcycles always do it... My theory was that it was because when you let off the throttle, in gear, the engine kept turning, therefore continuing to draw in air, but no fuel... however, that was just a guess.
> 
> Now my GTO has a very aggressive exhaust, and thats what started it.


You’re close! When the throttle slams shut, it cuts off the air; high manifold vacuum then draws more fuel—it’s too rich.
Many carburetors have a dashpot fitted—a vacuum canister that holds the throttle open slightly during very high vacuum. If the diaphragm is ruptured or the dashpot is removed, you’ll get backfires on overrun, like during a shift, or coasting down a mountain.


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## Eric Animal (Oct 28, 2007)

armyadarkness said:


> After a 2 year battle with my exhaust, I finally have it sounding right, but now I have afterfire (usually misdescribed as backfire) when I shift.
> 
> I always believed this to represent a lean condition, but that's not what the internet is saying!
> 
> So, my car didnt have it before, and now that I opened up the exhaust, I do have it. Any ideas for tuning it out? Anyone else with the issue?


Usually cause by LACK of backpressure and/or a timing issue.......


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## PopsRedCar (9 mo ago)

armyadarkness said:


> My issue with dumping at the axle is that I like the way tailpipes look on classic muscle cars, and I didnt just want dummies there.


You could dump after the axle right behind the rear wheel similar to the Nova II. Not quite tailpipes, not quite axle dumps.

I may catch some hate but 'm part of the axle dump generation. I loved the way it sounded. Fox bodies with Flows and an X/H pipe or F bodies with single chambers straight pipes. Music to my ears.


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## armyadarkness (Dec 7, 2020)

PopsRedCar said:


> You could dump after the axle right behind the rear wheel similar to the Nova II. Not quite tailpipes, not quite axle dumps.
> 
> I may catch some hate but 'm part of the axle dump generation. I loved the way it sounded. Fox bodies with Flows and an X/H pipe or F bodies with single chambers straight pipes. Music to my ears.


Yes, I agree that it's music to my ears, as well!!

However, ever since I saw my first hot rod at 10 years old, I have used fat tires, air shocks, and dual exhaust to define one. Obviously it was an industry standard, since to this day, many single muffler cars, have two tail pipes at the back bumper. In fact, with the old Trans Ams, they had two tail pipes on a single muffler, despite the fact that the car made better power with a single.

All that being said, axle dumps are VERY popular hear, so you'll get no hate!!!

As for me, I solved my problem. I have functioning tail pipes and side dumps


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## armyadarkness (Dec 7, 2020)

Deleted


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## geeteeohguy (Feb 2, 2008)

Montreux said:


> You’re close! When the throttle slams shut, it cuts off the air; high manifold vacuum then draws more fuel—it’s too rich.
> Many carburetors have a dashpot fitted—a vacuum canister that holds the throttle open slightly during very high vacuum. If the diaphragm is ruptured or the dashpot is removed, you’ll get backfires on overrun, like during a shift, or coasting down a mountain.


This is what I stated about 30 posts ago. But thank you for your support.


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