Backpressure Issues

[SilverBolt]

There is no way fuel is trickeling down the inside of your exhaust. If that were happening your truck likely would not run. Do you have a long length of straight pipe before the Flowmasters? I have never been a fan of Flowmaster mufflers. The are finicky about where there are placed withing the system. The sound will vary depending on their placement. Tried them on my Lightning and lost 14hp (same dyno same day).

 

[pirate air]

If you're talking about the rhythmic popping noise I hear in your video, its normal. Mine made the same sound when I pulled my muffler off for a few hours. Sometimes you get popping noises from rich conditions. After the combustion processes, there may be some unburned fuel left over. When it exits the exhaust port its in a gaseous state, not liquid. The fuel is still hot enough that when oxygen in the exhaust pipe is introduced it ignites giving you a popping noise. But I don't think the problem is that, the engine management is way too precise to let unburned fuel exit the exhaust at 5000+ rpm every time; even with different back pressures present. The problem is I think you've gone beyond what the single chamber is capable of muffling. I bet with the stock exhaust, the engine makes the same rhythmic popping (from sound frequency not fuel), you just don't hear it because the stock muffler is canceling it all out.

 

[Hockster]

You do have unburnt fuel in the system. That is why there is a catalyst system on vehicles to burn off the unburnt gases. The cats are made of ceramic and precious metals that allow the exhaust gases to burn again. ultimately reducing the emissions so it will pass state and federal allowed amounts.
By adding another exhaust pipe to your system you have increased the oxygen levels in the system and there is a little bit more burning going on and you are hearing it because you reduced the noise suppression abilities of the exhaust by going to this muffler you have.

 

[SoSmoked]

Thank you gentlemen

Appreciate the valuable info

 

[SOCOMech]

The fellas have already given you the best info.......so I'll add that Flowmaster's have typically had this characteristic, especially if you're not running an h or x-pipe to help with pressures and flow. I have long tubes with high flow cats, a single 3" all the way out and a Magnapack (which could be compared the Flow's you're running, just a strtaight through design) so I'm sure my back pressure has been reduced from stock. With that said, the popping and crackling that I had when letting off the gas doesn't happen anymore and that's due to the loss of back pressure, no more pressure waves to cause the popping. I also have a tune to make it all work correctly though too. You're set up, especially being on stock cats, shouldn't cause you any worries, it's pretty much normal and expected.

 

[WarSurfer]

If you are still running cats, you have no significant loss in back-pressure. The cats are the choke point in the exhaust, NOT the muffler - as proven by the near zero hp gain with cat-back kits.

Yes it flows 'better' with headers, larger pipe, etc... but until you eliminate the cats you do not have to worry about loss of scavenging and back-pressure issues.

The popping is caused by cold, fresh air mixing with hot unburned mix coming down the pipe. It won't hurt anything other than sounding bad. The only way to totally eliminate it is to remove all the band clamps and have the entire system welded up.

Not everyone will have popping, that doesn't mean you built the perfect setup, It just means you don't have cold air being pulled into the system.

 

[SoSmoked]

Just picked up an X pipe online will get back to ya guys when it's installed and see if it makes a difference

Thanks again for the help gentlemen

 

[SilverBolt]

Just picked up an X pipe online will get back to ya guys when it's installed and see if it makes a difference

Thanks again for the help gentlemen

Just a heads up that there is some science in the placement of the X-pipe in your system. Ideally you would want to exit the cats into the X, short pipe into your mufflers and the to your exit.

 

[whtrapta]

have you tried a different muffler? Maybe its what normally goes on in the cats and with only having 10's you can hear it better?

 

[SoSmoked]

Trying the xpipe then will go from there

Thanks silver appreciate the info

However how am i supposed to run it directly after the cats they are spread apart so far for about three feet of pipe

I was thinking of doing it as close a I possibly can tho