FormulaJoe

You guys know what Im talking about. You know, you rev the engine up to 4 or 5 grand and when you let off, it sounds like a gunfight from an old John Wayne movie.

What is it that makes this noise? Is it the single exhaust? Is it because there is so much pipe between the headers and the muffler?(compared to other cars) This is annoying. I dont think ive ever heard a dual exhaust car sound like this.

Anything you can do to get rid of it? I like that smooth "ripping" sound of 5liter Mustangs and old hotrods with dual exhaust and flowmasters.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

MikeS

I thought that was the standard Flowmaster response to letting off the throttle...crackle, gurgle, pop pop.

FastElectrics

I don't have that problem on mine, it sounds pretty good when you let off on the gas. Perhaps it is a Flowmaster thing..


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89 RS Camaro, LO3 305 TBI
L69 Duel Snorkel Intake
Dynomax Ultra Flo Cat Back

84TransAm

My Flowmaster doesn't do that. However, my friends 87 Fiero makes the pop sound, it's really mellow, so it has a nice feel to it.

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--Steve S--
1984 Trans Am 305 LG4, 5 speed Daily Driver, Flowmaster 80 Series
Holley 600 cfm & vacuum advance Soon: Edlebrock Intake & TES

karstenkurtz

I know exactly what you are talking about my buddies 88 Mustang LX does that he has a flowmaster exhaust with really tiny tips (I think they are 2 1/4 or so). He likes it but to be honest with you I hate it it sounds like a POS making this popping noise all the time.

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Karsten
86 IROC-ZZ4... too much to list.

Joey1986Z

Mine pops alot more now with duals, more so than with the stock 2.25" intermediate.

NTChrist

When I have the cut-out plate taken off, the popping is brutal. It sounds like a scca trans-am car downshifting. It's quieter through the flowmasters, but still noticable.
I think it has more to do with regular internal combustion engines, rather than f-body versus mustangs.

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No guts, no glory.

Jason86Z28

as much as i hate flows, my hookers do the same thing every so often. I was thinking it was b/c i'm going from stock 2.25" to the cat, and 3" cat back, so all that extra space. But since you've got full exaust I guess thats not it, unless it's happening for 2 different reason (a. being flows blow, b. being all i have is catback right now)

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1986 Z28 LG4 M5
Alpine 6x9's 2 10" MTX Thunder 4000's MTX Thunder 102 Amp Hooker Aero-Chamber Cat-Back

JPrevost

I'm going to take a stab at this one. I don't think the popping sound has anything to do with a muffler or pipe size. When I first fired up my new engine I didn't have a muffler on. The car was running WAY rich when it was popping the worst. When I got that fixed the popping was a lot less. When it was running rich I was even getting backfires from the cat getting so hot. I have a feeling it has something to do with fuel and the fast stopping of air/fuel more so than the type of muffler. Keep in mind the design of the flowmasters, they have now actual sound deadening material, just sound cancelation baffles (known for the tinny snappy sound).
"During engine deceleration (when the throttle valves are closed), air flow is shut off to the engine while the fuel flow continues. This causes a rich mixture in the cylinders. Because of the lack of air this mixture will not burn in the cylinders. However, when this hot, rich mixture hits the exhaust port it meets clean, oxygenated air and POW! - a backfire."~www.gordon-glasgow.org
So it could be because of the 3 way cat converter or any "clean air" entering the exhaust system.

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, Jon (350 TBI! getting 23mpg highway)
91 Red RS w/grey int, sq stereo (Alpine v12, kicker solo, MB quart premium etc)AIM: JPrevost

• Holley 670 TB unit w/ 1/2" spacer/adapter
• Edelbrock RPM vortec intake
• 350ho 330hp vortec crate motor
• 8" harm. balancer
• Stewart stage 2 water pump w/160 thermo
• SLP tri-y headers to full 3"
• Rebuilt trans w/ SLP shift kit
• Centerline 16x8's all around
• 36/24 mm sway bars
• Full poly bushings, even motor mounts
• SLP LCA and panhard
• Alston SFCs
• Edelbrock 3 point STB
• Global west steering brace aka wonderbar
• Eibach pro kit springs
• Bilstien high perf. struts and shocks
• All this and I still have AC

My websiteAny questions?

[This message has been edited by JPrevost (edited April 15, 2001).]

Eric 91RS

You need to check your timing and see if you are running rich. I am new to fuel injection/emission controled vehicles, but popping usually occurs when unburnt fuel enters the hot exhaust pipe. That is why it happens when you let off. The 55 Chevy was popping a little just above idle, so we advanced the timing and it got better.

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91 RS 700R4. Open Element and Ultra Flow Muffler. ET 15.86

55 Chevy on 76 4x4 frame

vortecfcar

for these reasons I always notice the popping is a lost worse on non-cat F-bodies

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 224/230 duration and .477/.480 lift. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, 3000 stallconverter. Edelbrock TES, 3inch cat, flowmaster with single 2.5 inch exit.
Best time yet to come
12's?? :crossthumbs:

This is a Pic of my car in race trim www.tbns.net/billyjay/camero.jpg

Yes I know how to spell camaro- so dont ask. I didnt make the link

1989camarorsrs

iTrader: (-1)

yea since i took my cat out it pops a lot now where before it didnt

RoadRocket L98

Can this 'popping' ( around here we call it cackling ) be eliminated by decreasing fuel pressure? Because I just put on full exhaust and mine cackles real bad. I know its not too restrictive because my backpressure has to be next to nothing. Any ways to get rid of it besides timing?

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'83 Firebird 2.8
'89 Firebird Formula 350
red/grey, t-tops, and a 3.27:1 rear
K&N, TB bypass, No MAF screens, CAI, full Accel ignition, no cats, Hooker Supercomp shorties, Hooker catback

FormulaJoe

I have asked a lot of people about this and the general concensus is that this popping is caused by the YPipe being so close to the headers.

Many people have also said it is caused by the muffler being so far away from the headers.

The rest just say it is just something that comes with single exhaust.

Is there any way to make a single exhaust sound like a dual exhaust car.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

TheWraith

i can't believe no one knows this one!

lack of backpressure causes backfiring. If you put some crazy exhaust setup on a car that doesn't need it, you're not gonna have enough backpressure, and you're gonna backfire sometimes.

You want to hear some serious backfiring? take off your muffler and drive around

Spyder

Okay, I know this is not technical at all, on my 92 Rs when I started to mod it, the first thing I did was put on a flowmaster system. Sounded real nice, no problems. Then I gutted the cat and removed the muffler the same day. It was cracking and making lots of, intresting, noises. This was with the single snorkel intake. When I switched to an open element some of that went away, when I put in a K&N filter and put in a good breather it went away. I know this has no technical meaning but that is how I got it to go away.

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--Spyder--

1992 Camaro RS
LO3, T-56,centerforce clutch, ported and polished heads, Edelbrock Performer Intake, 14X3 Open Element w/ K&N, hiflow cats with two pipes going back, AC delete, SMOG delete, alu drive shaft, 3.73 posi, 170 stat w/ fan switch, STB, Subframe connectors, KYB AGX, Eagle GSC, and poly bushings.

1982 Z-28
327ci CSB, Turbo 350

Ragin'87

Wraith,
SWEET JESUS.. I was gonna have a heart attack if I didn't see your post! Not to put anyone down, it's rarely a problem anymore, with more restrictive factory systems... and the smog-**** regulations.

However, if the same question was asked 20 years ago(of couse the internet would have had to have been as widespread as it is now, but you know what I mean), the answer would have surfaced immediately. Granted I wasn't even thought of 20 years ago, much less born. At any rate, Wraith is right. The "popping" is caused by a rich mixture being in the exhaust pipes(caused by the letting off), and pressure inside the pipes dropping off enough to draw fresh air into the pipes where it hits gas hot enough to ignite with the oxygen in the air.. and POP there you go! Keeping back pressure at an acceptable/ideal level for your engine reduces this, but under hard racing you can get damn near ANYTHING to pop(got my nissan to do it once.. several high RPM on/off/on/off throttle changes.) So there's the answer.

Anthony

P.S If you watch a SCCA or Speedvision World Challenge race.. and get to see a slow-motion take of a pass made in a turn, you can almost always see this actually happen, if the climate is moist, you'll see a swirl of outside air get sucked into the sidepipe, and BOOM.. out pops some fire.. it's really cool.

johnyIROC

I don't think my car sounding like an SCCA car is a problem... I love afterfire! I took my cat-back off on purpous just to get more afterfire.

JPrevost

Hey now, I wasn't that far off. I did say it was when unburnt fuel hits the "clean air" it backfires so HA. Reread what I posted. Deceleration causes a rich mixture in the cylinders and when it hits the exhuast port (aka exhaust "tip") it meets clean, oxygenated air and POW!
Give me some credit TheWraith and Ragin'87!

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, Jon (350 TBI! it's trenuous and efficacious while getting 23mpg highway with off the shelf eprom)
91 Red RS w/grey int, sq stereo (Alpine v12, kicker solo, MB quart premium etc)AIM: JPrevost

• Holley 670 TB unit w/ 1/2" spacer/adapter
• Edelbrock RPM vortec intake
• 350ho 330hp vortec crate motor
• 8" harm. balancer
• Stewart stage 2 water pump w/160 thermo
• SLP tri-y headers to full 3"
• Rebuilt trans w/ SLP shift kit
• Centerline 16x8's all around
• 36/24 mm sway bars
• Full poly bushings, even motor mounts
• SLP LCA and panhard
• Alston SFCs
• Edelbrock 3 point STB
• Global west steering brace aka wonderbar
• Eibach pro kit springs
• Bilstien high perf. struts and shocks
• All this and I still have AC

My websiteAny questions?

purpleworm

I still have manifolds and mine pops and gurgles but I love it. I love cruising though toen in 3rd and backing out of the peddle and hearing the motor slow the car a bit and crackle a bit. I think mine has one of the best rumbles to it. That is why I put a Flowmaster on in the first place!!! they all ping and pop and I love it!!

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit
One sweet sounding system

Ragin'87

Jon,
my bad man.. u did indeed mention the rich condition.

Anthony

defpony

the popping sound is just unburnt fuel isnt it?

Like when the v8-supercars release the accelerator the flames come out the exhaust.

Mines not too bad and i kinda like the sound.

RS Chris

defpony, you should change your name to Romero.

defpony

why

Abird4u2nv1

iTrader: (-1)

I don't really get a backfire on mine, Its an LO5 TPI, see sig. Only thing I don't like and when I go down the road and get the rpms up and let off, its very raspy, but thats a flowmaster thing, and probably something to do with the 5 speed, I don't tend to hear automatic cars do that b/c it revs down when you let off the gas.

defpony

i only hear it when i rev it in high in idle and then take my foot off. Never when im driving.

crazy3rdgen

iTrader: (1)

now srt-4's , they crackle/pop like a ****

irocbirdbuilder

I have no muffler a catco cat and 3" exhaust stock y pipe and manifolds and i like the sound its not a backfire just like a rumble on mine especially when your doing like 70 in drive and let off, scares teh hell outta people