Embarassingly Loud Back-Pressure - HELP!

[patterjl]

I've heard that some Backpressure is good, however my Backpressure is just too annoying to deal with and it's embarrassing sometimes.

I have a 99 Mustang GT convertable with the following Modifications:
Borla Exhaust -- Mac Pro Chamber w/o Cats -- Steeda Underdrive Pulleys -- C&L Intake -- 4:10 Racing Gears -- Diablo Sports Predator Tune

The backpressure seems to occur when I'm shifting at Mid to High RPMs (lets say 4500+ sometimes lower) or when I'm just slowing down and the RPMs are decreasing. This pressure sounds embarrassingly bad alot of the time, almost like a backfiring Pop and gourgle (REALLY LOUD). It doesn't seem to have a problem at all when I'm shifting at around 3000 to 3500 RPMs or when the RPMs decrease to that amount. I don't even want to Rev my engine at people most of the time because it sounds that bad. You'd think someone who has spent the money on nice aftermarket exhaust would be very pleased with the sound of his exhaust..... you'd think!

Does anyone have any clues as to why it would be this bad or what I can do to fix it?

My thoughts were, Maybe I have stock headers -- or stock Throttle Body -- and it's not able to pull the air back in fast enough? (I'm no auto techie)

Please help me out here.

 

[BlackenedSVT]

get cats

 

[thomas91169]

i always thought the more free flowing the exhaust was, the less backpressure it creates? your exhaust looks just about as free flowing as it gets.

 

[squares98]

IF you have Borla stingers, that sound is common.

 

[mransr]

back·pres·sure (bkprshr)
n.
Residual pressure opposing the free flow of a gas or liquid, as in a pipe or an exhaust system.

somebody needs to explain to me how "backpressure" is a sound?

patterjl, are you maybe talking about a popping sort of sound after you let off?

if it's that it's just a function of the mid-pipe (X, H, or Pro chamber) and your mufflers; changing things on the intake side will have little or no effect on the sound...

I'd say you'll probably have to change your mid-pipe to something that the Borla cat-back is "happier" with to get ride of the popping/gurgling sound

 

[DropTopPony]

i get it occasionaly when i'm downshifting but its not loud at all...i have borla catback with bassani X with cats....maybe you need a new midpipe.

 

[Mustang5L5]

How can you hear backpressure? It's pressure, not a sound

 

[fastangboi]

i h8 Borla. stupid mario andretti. Give me flows any day

 

[hotmustang331]

Are they the stingers? If so, then thats your main problem...those small straight through mufflers always pop and crap with a O/R mid pipe.
Get the magnaflow catback (not magnapacks) off of www.partshopper.com and use code: magna454 . You wont have that issue anymore....nice and smooth . I LOVE mine!

 

[88CougarMan]

Do you have different size piping? I've heard that the popping sound is caused when the air transfers from one size pipe to another.

 

[hognutz]

you are not hearing backpressure. you either have a leak or you are getting cold air rushing back into the exhaust too fast. I am assuming you are getting popping sounds under deceleration.

I would presonally just change the catback if it is not a leak. I have the normal borla and it sounds good. If it the sound is out both banks then it is proalby the catback. If it is out just one side it is most likely a leak.

 

[exindust]

Personally i like the sound....

I mean how many cars CAN actually do this? I think it just goes with the whole american muscle sound

whens the last time you heard a civic sound like that?


never

 

[BurningRubber]

Personally i like the sound....

I mean how many cars CAN actually do this? I think it just goes with the whole american muscle sound

whens the last time you heard a civic sound like that?


never

x2... My car does it so loud sometimes when its warming up... oh my God... I TRY to find a bridge or overpass so I can just roll the window down, and drop it down a gear and let it coast... It pops like crazy, and it sounds so bad ass, and straight mean. Thats the one thing I will miss if I change my exhaust setup.

 

[Stang|ess]

i h8 Borla. stupid mario andretti. Give me flows any day

I think you mean Magnaflow and Mario .

That popping sound on decel is normal with Borlas
http://youtube.com/watch?v=0pMz_gx5EGg

Does it sound like that?

 

[RoadconeTuning]

you are hearing the air rush back up the exhaust when the throttle plate closes.. you have little to no backpressur and hat happens is you actually create a low pressure in your exhaust which sucks air back up into it... its a fact of life when you have a free flowing exhaust and you NEVER WANT backpressure you want the velocity of the correctly sized pipes... backpressure just happens to be a side effect.

 

[jayssilver4.6]

My opinion is that since you yanked your cats off that is what is causing the louder popping. Mine does it now that I put on my o/r pipes.

Your cats are supposed to burn off excess fuel that gets through the combustion cycle and with out the cats to do that it burns off in your pipes and give that really cool popping noise...I personally like it. I love the look on the faces of the guys in their rice wagons around here...just too much fun.

you guys feel free to correct me if I'm way off base...

 

[DageonYar]

Are they the stingers? If so, then thats your main problem...those small straight through mufflers always pop and crap with a O/R mid pipe.
Get the magnaflow catback (not magnapacks) off of www.partshopper.com and use code: magna454 . You wont have that issue anymore....nice and smooth . I LOVE mine!

That code don't work... and why not packs?

 

[Chili]

I have an offroad prochamber and straight through pipes (SLP LM) and the same thing happens between shifts at certain RPMs. I like the sound, myself. If you do not I would suggest changing either to a catted midpipe (you can buy catted legs for the prochamber) or to a chambered muffler.