Popcorn Mufflers with S/C

poneypower89 · May 11, 2005

Hey guys, here the scenario.

My entire mod list is in my sig. Im running the base sc-trim vortech kit with the fmu and stock injectors.

Before I put the SC-Trim on my car, the mufflers would seen to crackle and pop every now and then. Now that the SC is on there, its almost a completly constant "popcorn" sound coming from my flowmasters. This only happens when coasting in gear (usually after getting on the throttle a bit). For the first time a couple days ago the car backfired pretty hard while I was just coasting around 30mph.

If it matters, I put my car up on the car lift the other day to take a glance of the underside and noticed my tailpipes are pretty badly rusted through about an inch after the flowmasters. If that matters at all for this problem.

Anyways, I know everyone is going to give me "you need a tune" speech but you can go ahead and by-pass that because I already have that on the backburner I just want to go and get my maf/injectors/tb before I take it to the dyno.

With all that said, does anyone know what would be causing this to happen? Im thinking the FMU is making the car run just pig rich and excess fuel is just kinda burning off in my exhaust, but im not sure if that is totally possible. I know that is what a backfire is, but what is making this popping noise? Anyone opinons, suggestions, or insights would be greatly appreciated! Thank You!

-Adam

70lightning · May 11, 2005

The muffelers getting old?

poneypower89 · May 11, 2005

70lightning said:
The muffelers getting old?

Who knows They were on there when I bought the car. The tailpipes have rusted through some bit right after the mufflers so one could probably guess they have some age on them. But either way, would old mufflers pop normally? And would the SC increase this?

ninety15.0 · May 11, 2005

we just bolted a Kenne Bell onto my buddies 94 gt and he has an O/R H pipie and three chamber flows. before the KB it crackled a little bit, but after the supercharger it does it so much worse. I would say thats prolly normal, but i do suspect that those small rust through spots on the tails would have a lot to do with it also. when your Done with the tb, inj, and maf you should just get a nice catback with straight through because dlown cars like less packpressure and the flows create more than others. good luck man

Stang8URMPRT · May 11, 2005

That sound is unburn fuel popping in the exhaust... Common for it to happen more when you add a blower, cause... duh.. You're adding more fuel... And usually with an FMU, you're adding too much just to be safe.

JJPA · May 11, 2005

yep im a newb with mustangs but not forced induction. Its def. unburnt fuel in the exhaust, depending on how rich you are running you could probably also throw some flames out the back if you were to get rid of your mufflers/cats

BlackFox5.0 · May 11, 2005

If you have holes in your exhuast, then that would cause popping. It's caused by hot and cold air colliding, I think of it as mini thunder, since thats essentially what thunder is.

poneypower89 · May 11, 2005

Wow, I get some techinical answers, and then some scientific ones

Good Work guys, yeah I will look into some new muffs.tailpipes and see if that fixes the problem. Heck, maybe even after the maf/injectors and a more lean tune the popping would stop too. So This will be solved one way or another. Just wanted to extend some thanks to you guys

85mcLaren · May 12, 2005

I would go with a muffler that is not a chambered design when you are running boost. Dynomax as well as magnaflow are decent choices. They are more of a straight thru design which your car should like.

Daggar · May 12, 2005

I hate to be the one to burst everybody's bubble but....

That popping you're hearing is the result of your Air/Fuel ratio being lean as hell under decelleration. You're not running too rich and for god sake don't lean out your mixture unless you've got a way to measure your AFR. Adding a blower of course, would make it worse. Even decellerating, you're motor is taking in more air while the blower spins down, even with a bypass valve. Old or bad mufflers just make the effect sound worse. Remember that there's still a compression stroke even during decelleration. Shut off (actually, turn way down) the injectors, the light off the mixture and you get tiny lean explosions. Mine does the same thing... I like it though. Sounds mean as hell when you let off the gas and doesn't do the motor any harm. Of course the WB02 is off-scale lean when it happens. You can tune the injector duty cycles to get rid of the noise. Basically all you do is upen up the injectors a bit more during decelleration to provide a bit more gas while the RPMs are falling. I doubt that you'll be concerned enough about it to worry once you get a new cat-back.

Popcorn Mufflers with S/C

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