Exhaust Question

[Tampa G35 Sedan 6MT]

Ok so I got the headers installed, Testpipes, 350z Y pipe and I went back to using the stock muffler and Coupe Mid pipe.

What is it that makes the Test Pipes Rattle so bad.

It sounded like a freaking honda!

I just had the cats put back on today...

It sounded like this But this guy has HFC's I had test pipes? http://www.youtube.com/watch?v=jQvBVYZRQQ4

Is their a way to solve this?

DJ

[SteveTheTech]

That noise is the sound of power... well not low end power.

The noise you are talking about most likely has something to do with the unique pulses of the 3 cylinders per side. The 05+ coupe and sedan 6 speed use variable exhaust timing and intake valve overlap to draw back a portion of the combustion gasses. Since there is no EGR on modern cars they need to reduce emissions somehow and valve overlap is much more effective at controlling tailpipe emissions. The area between the exhaust valves and catalyst material was designed originally to maximize the effects of this while decreased harmonic disturbances like what you are describing.

Although maybe this is something I have seen on the two Gs that were still running with HFCs on them.

Top Gear FTMFW

[Tampa G35 Sedan 6MT]

So what do you guys do that have test pipes... What is the solution for this?

[pfarmer]

That noise is the sound of power... well not low end power.

The noise you are talking about most likely has something to do with the unique pulses of the 3 cylinders per side. The 05+ coupe and sedan 6 speed use variable exhaust timing and intake valve overlap to draw back a portion of the combustion gasses. Since there is no EGR on modern cars they need to reduce emissions somehow and valve overlap is much more effective at controlling tailpipe emissions. The area between the exhaust valves and catalyst material was designed originally to maximize the effects of this while decreased harmonic disturbances like what you are describing.

Although maybe this is something I have seen on the two Gs that were still running with HFCs on them.

Top Gear FTMFW

How about the ones that are no longer running?

Perry

[SteveTheTech]

Those usually end up like http://forums.g35club.org/zerothread/433767

Yet another reason I do not like HFCs. Other mods I'm fine with but that stuff is not worth the risk IMHO.

[tollboothwilley]

Are you using resonated test pipes?

If not, you should be.

Also, you need to check for a loose bolt or two. Retorque every bolt down. I had some rattle issues when I had installed my y-pipe and it sounded really loud too...and raspy. I felt like a retarded honda driver and i couldn't hear anything. I got back under my car and found that one of the nuts had wiggled itself loose and it was causing a slight leak.

Test pipes will have a lot more rasp than what you will get with HFC.

Headers + TP = much more exhaust noise.

[Tampa G35 Sedan 6MT]

Yes they were resonated! Everything was tight... It was the test pipes... I put the cats back on and its gone!

I would really like to know what everyone does!

[tollboothwilley]

what brand are the test pipes?

[pfarmer]

Those usually end up like http://forums.g35club.org/zerothread/433767

Yet another reason I do not like HFCs. Other mods I'm fine with but that stuff is not worth the risk IMHO.

At first I didn't fully understand what was being said in the other post about the HFCs until I got a grasp about the emissions factor in regard to overlap. It makes a lot of sense that this could contribute or even initiate a failure of this type. I figure spark advance is another area of concern since I had a timing gear fail due to this problem on a Mustang. This was actually a known issue with a fix that could end up backfiring into a similar problem with a crank. Combine all of this on the same car and a lot can be explained.

Perry

[Tampa G35 Sedan 6MT]

The test pipes are just from ebay... I didn't think that you could screw up a hollow pipe lol... are the more expensive ones the same?

Perry, I don't understand either... Steve are you saying that it is best for the dependability of my motor to keep the Cats on?

DJ

[SteveTheTech]

I have seen several coupes with HFC that were on long enough to rust (I really don't know how long) (People tend to get awful quite when you mention HFCs).

The ones that have made their way into my bay through severe driveability or persistent check engine lights and are usually beyond repair. The life span of these parts is not nearly as long as OE and people often overlook the early warning signs. The signs seem to be rattling niose when under load. Very similar to that video. This is the material separating from the housing. If you are lucky the material breaks in a large chunk and your engine will only ingest catalyst dust.

However if you have something like a brief ignition missfire the cats can detonate in seconds. Raw fuel and heat will cause the cat to break up into much smaller pieces. This is where the real bad stuff happens. I had one that sucked in a small piece of honeycomb shrapnel into the #5 cylinder and destroyed the plugs and made a complete mess out of the cylinder.

You would really be better off with test pipes. Although I am not a huge fan of the violating federal emissions rules bla bla bla, mostly I dislike the noise, smell, and poor fuel economy that usually accompanies this type of modification. The G is not a car for this, Honda maybe.

I don't have the pictures anymore of the engine that I have seen, although the next one I get I will be sure to give you all some more pictures.