I own a 04 sedan with 83k miles. I recently developed what seems to be a plugged muffler. Only one of the two tips on the muffler seems to be blowing out exhaust. I don't however, have any check engine lights showing, so I assume it's not too serious. I have ordered a new Megan Y-pipe and cat-back, which of course is currently back ordered. I also have purchased a ztube and K&N filter, which is on its way. If my arm is twisted, I might just get some Unorthodox pulleys for the car, but I'm really not trying to get too involved in modding my G. At this point, I'm looking for sound and some balance in my mods, and I figured opening up the exhaust beckoned opening the intake as well.

Now the dilemma. Should I go ahead and buy some HFCs to go along with the new system? From what I understand, Ultimate Racing HFCs are among the best on the market, and are my front runners.

Pros: 1. Seeing as the car already has 83k, odds are good that the cats are past their prime, or won't last too much longer in any case. 2. It'd be a shame to let any gains from the new exhaust be wasted.

Cons: 1. This is a daily, and I have another project car to bleed money over. 2. Maybe the cats are fine, and will be for a while. 3. Since it is a daily, noise and general raspy unpleasantry would be a bummer.

So, what's the general ideas out there? Stick around with old cats, or bite the bullet and get some HFCs already? Will I see any bang for the buck?

 

if you want to open the car up cats are the most restrictive point. it would only be logical that you get hfc or tps. and yes you will feel a difference. they are the 2nd best bang for the buck mod after md plenum spacer.

and i would get Fast Intentions HFC or Berks HFC.

 

there is one pipe that goes into the muffler on the sedan. Inside the muffler it is split into two. I just put on hfcs on yesterday. I now have better throttle response, better gas mileage (i put 80 miles on them already), and the exhaust note is soooo nice. I have kinetix version 2 HFC

 

Flow out of one of the stock muffler tips is a normal function. It is a variable muffler that opens up the second side when it reaches a certain rpm. If there is no flow at rpms say above 3.5k then something could be wrong such as the flap shut close. Rev it up after the motor has warmed up and see if flow comes out of the other tip.

 

Definitely get HFC, you won't regret it. I would go with F.I. or Berks. I have F.I. and it doesn't sound raspy.

 

I would go with Berk HFC only bc the CEL count is 200cel versus FI cell which is 300cel. A lil more restricted =\

 

HFC are a great mod

IMO, HFC are HFC. You will get good gains with all versions out there.

 

Well, there is another symptom of plugging. After the car gets warmed up, and i'm sitting idling in traffic, there is a smell of hot rubber or plastic coming through my vents. The smell is originating in the engine bay. I assume the exhaust is hotter than normal, and is overheating something. While doing an oil change yesterday, I pulled off all the underbody shields, but couldn't find any evidence. I'd like to think its just a plastic bag somewhere stuuck to the exhaust, but it's been going on since November.

 

HFC's will solve your issues, once the OE cats get really plugged your car won't start. It also helps once you get the HFC's installed try buying quality gas, that doesn't mean Costco or Granny's station on the corner....LMAO
Gary

 

BP only since I've owned the car. Pretty sure it sat on the dealer lot for some time though, and god knows what they put in it.

 

If the cats are "plugged" that means one of two things have happened. Either the car is running too rich and is fouling the cats with excess fuel or the air/fuel ratio is lean making the cats too hot, therefore melting them. Basically, if the cats are clogged, then you've got other issues with the car that need to be addressed first. The only other failures I've seen with late model OEM cats is in those rare cases the cat "brick" gets loosened in the case and rattles annoyingly.

As for the burning rubber/plastic smell, that's not the cats. There's no plastic or rubber in close proximity of the cats, even if they were getting overly hot. If you suspect an issue with the cats, a simple test is to get the cats up to running temp and hit the cats with a temp gun.

 

I went ahead and ordered some kinetix hfcs and their velocity plus plenum. I figure it will go well with the megan exhaust and ztube plus k&n filter that just arrived. At that time, i'll pull and check the plugs to see how they read out, and act accordingly.

 

Just an update:
I've replaced the plugs. They were worn, but not showing much else. I also found a not-insignificant amount of oil in cylinder 6. I cleaned that up and my idle stink cleared up immediately. I've installed the z tube, k&n filter and kinetix v+ plenum. When I did that, I also cleaned the MAF and throttle body with their respective cleaning solutions, and a microfiber rag on the throttle body. I did all the ECU reset procedures. The car is a lot louder and more aggressive in tone, and will actually break the Blizzaks loose in 50 degree weather, where before it wouldn't. (Making me think perhaps there was nothing wrong with the exhaust in the first place, but hell, since I have the parts already on order/on hand...)

Still waiting on my Megan cat-back to arrive, it's hung up in customs out west, apparently. The y-pipe and Kinetix hi-flows are in my garage, and waiting for installation. After my experience with the intake installations, I can't wait

Not related to the thread, but also awaiting installation are some Hawk HPS pads and Power Slot Power Alloy rotors, as well as a set of 19" PIAA Super Rozzas. Now just to track down a solid solution to drop her about an inch and finish the tint job that only covered the rear windows when I bought it, and I'll be done with the car for now... I love my G!