Tonight on my way home from work I saw a friend of mine in his WRX. He's got a ton of mods and always wants to race so we did. We did a pull from 40-140, then another pull from 30-155 (this was on private property. After the second pull I noticed sparks shooting out of my exhaust. It wasn't just for a couple seconds, it was the entire time I was decelerating. My mods are K&N filter, Greddy Profec-b set at 20psi, cat delete, 3" CB exhaust, and an S-afc II leaned out 6% from 4600rpm up. We pulled over afterwards and the car was running fine. This has me really worried. I'm not sure what I should check first. I'll probably do a compression check to make sure it wasn't part of a piston ring or something. Any feedback would be greatly appreciated.

 

Thats normal. Just unburnt fuel since you you dont have a cat which would normally burn it up.

 

Yeah, but unburnt fuel still coming out 15-20 sec after letting off the gas?

 

Can't help you there.

 

ur running really rich still.

 

mine sparks but only for about 2 seconds after i let off the gas

 

are you VTA?

 

The majority of cheaper made exhausts use a loosely packed mat of fibreglass or fiberglass cubes in their muffler and resonators. Since you deleted your cat and running leaner with higher boost, your muffler sees higher heat.

The combination heat and friction of the fiberglass against the surface of the piping in the muffler (kind of looks like a cheese grater) breaks off pieces of the fiberglass and flies out the back bright red. Eventually this will hollow out your muffler eventually and you'll probably notice the car getting louder. This is probably happening to your car every time you drive it, and get on it.

Mechanically, it's nothing to worry about.

Unburnt fuel won't create sparks out of the tail pipe since that part is much cooler. If unburnt fuel had enough heat ignite inside the pipe it would cause combustion/backfire/fart/flame

ya dig?

 

are you talking about actual sparks or little flames? When you run really rich and have alot of backfires/afterfires the packing material instide your resonator or muffler starts to deteriorate.. This happened to me with an exhaust I had on my gti.. Straight pipes to a muffler, built motor, gt3071r etc... after a while, i'd be on it and people behind me would tell me little spakrs were flying out of the exhaust.. it turned out to be the packing inside the mufffler, burning up, and falling out... just an idea.. good luck

 

I'm not VTA, and my cat-back is the borla w/ the XR-1 muffler. I can see how it might be deteriorating. People have told me before that they would see a big flame from the exhaust when i let off. Now it's not really doing that, it's just a bunch of sparks. Lets just say it looks like someone threw a handful of burning cigarrette butts behind the car. Hopefully it's the muffler, but I'm still going to look over the motor to be safe.

Edit: I also think I'm going to put the cat back on the car for a while just to see if it makes a difference.

 

I've seen a lot of videos of STis spitting flames, but that's because they're running really rich. You're car is probably also running really rich.

It may look cool to have a car that spits flames, but it won't be too cool if your gas tank catches one of those flames.

I wouldn't want flames spitting out anywhere near the vacinity of my gas tank, even if it is the exhaust....

 

I just went out to investigate and I think is probably the exhaust. I checked the plugs and they look perfect. The turbo had no play in the shaft. I looked in the muffler and saw some small piece of steel-wool looking stuff sticking through the perforation in there. This stuff is probably breaking loose and coming out.
Here's a pic so you can see what I'm talking about:

 

yep there it is... you can see the packing coming out.

 

My car sometimes has little sparks, too.



Seriously, though, it's probably just burning bits of the rockwool stuff used in the muffler. If you have no cat, though, unburned fuel can cause actual flames, especially if you have an atmospheric BOV.

--Dan
Mach V
MachEVO.com

 

blown out muffler...hmmm my buddy with a S/C rsx blew his muffler out from running too rich