Backfire when downshifting

[slayer]

Ok, so a few months ago my Cat converter cracked between the 2 cats, i got a repalcement that was extremly nice looking, but turned out to be poor quality, and even worse customer service after the fact

ok, long story short, my cat clogged about 2 weeks after i installed it, and i lost all power, was afraid i wasnt even going to make it home after work

i had no choice but to hollow the cat out for now until the nice weather came and i can afford to cut out the old cat shells and have a better quality one put on

my question is since i have done this i get some pops and backfires when down shifting
1: is this normal for anyone running either a hollow cat, or testpipe?
2: will this cause any damage? either to the muffler behind it, or the turbo?

this is my first turbo car, and dont want to damage anything

here's some pics, cause well who doesnt like looking at pics

Here's what it looked like new

Here's what it looked like 2 weeks after i installed it (they claimed it was my car causing the issue, and they "dont use cheap cats") like manufacture defects dont EVER happen!

FYI that ball is the entire honeycomb melted together, and shoved it down the pipe

hollowed out the second one as well cause i wasnt crawling up there again in a couple weeks in the snow again

so, recap, is the backfire normal? does it hurt anything?

 

[tweety2300]

If its more of a crackle like straight pipes Harley's and trucks yes it's normal. My Honda did it pretty loudly and going through down town would scare the s*** out of people

 

[slayer]

its not a crackle, its more of a pop

it only does it when im cruising at a constand speed and RPM for a while, when when i down shift i get a bit of a pop, if i give it some gas its pop louder and scare pedestrians,

im not too worried about the sound, kinda growing on me, but i dont want to damage anything

im guessing its more distinct because im not "straight" pipe on the cat, its got a couple open chambers for exhaust gases to collect in due to the cats just being hollow for now

 

[protege3690]

happens to me all the time. i have a 2.5in corksport exhaust with a hollowed out cat. i pop all the time, not too loud but its there. when i was running open downpipe pretty much due to my stock midpipe cracking by the cat as well i would pop really loud haha. but no damage ever done. its just really the exhaust gasses from excess fuel which the cat is designed to break down and keep from happening.

 

[slayer]

that was my suspision, i just wanted to verify, thanks for the help. Thats exactly why my cat needed to be replaced, i cracked after the first cat, i loved the sound personally, but the wife wouldnt like it too much lol

however when the jerk drivers on the highway dont want to get out of my blind spot cause they know im trying to get over, dropping a gear and taking off made them back waaaay off

 

[StealthWyvern]

yes its normal.. mine makes a loud pop when i down shift but it doesnt do it all the time.

 

[thecrash91]

i have an 80mm exhaust (3.1 inches or something like that i believe) and when i downshift and RPM goes below 2k i get pops, i love it, sounds awesome. also if i cruise a 2.1k RPM and blip the throttle real quick i can usually get a mean sounding backfire, sometimes loud enough to be mistaken for gun shots, lol whoops. definitely fun to do in tunnels to scare the s*** out of other cars/pedestrians.

 

[Alamo1]

I was straight pipe 3" but now have a straight through muffler added into the mix. My car pops all the time whenever I'm on or off the gas going down a hill or just cruising slowly. It's from all the extra unburned fuel in the pipes igniting due to the excess heat.

Does it do it when cold?

 

[slayer]

It's defiantly more once it's warmed up. By the sounds in the last couple posts it sounds like the same thing. I kinda like the sound now and again. Just wanted to make sure I wasn't going to break something prematurely


Thanks everyone

 

[StealthWyvern]

It's defiantly more once it's warmed up. By the sounds in the last couple posts it sounds like the same thing. I kinda like the sound now and again. Just wanted to make sure I wasn't going to break something prematurely


Thanks everyone

Its from the overly rich stock tune, perfectly normal.