Exhaust noise

[BennyMac]

Don't want to wast peoples time but i think something is just not right with my car.
Got a full DF 4>1, 2.5 twin zorst with hiflow cats in December and all was well. Last Sunday week took the car for a workout, was coming to a set of lights and changed down from 4th to 3rd then 2nd (as you do) when all of a sudden BANG! Massive backfire. Since installing the exhaust it had some popping and crackling but now has a much louder and very noticeable backfire on deceleration, especially when the car is cold.
Fuel consumption is up a little bit.
I have taken it back to APS where they took it for a quick spin but the noise did not happen nearly as loud as before. They explained that it was unburnt fuel burning in the exhaust and this was normal but they would still go over it if i still was not happy. With that said off i went. Well now im not 100% happy and hope APS can find the fault (if any).

Also there is, what only be described as, a very loud rattle noise when changing up gears and under deceleration. WOT sounds nice but decelerating under high rpm and when gear change it sound as if there is something rattling around in the pipes/cats. I have read a little about how the 4 pipes in the collector could be hitting each other and tack-welding all 4 pipes together might solve this.

Has anyone else had the same or similar problems as me? Or am i just wasting peoples time?

Benjamin

[emg]

i have the same problem, looking forward to a response from the exhaust gurus

[brentonsav]

sounds to me like it may well be your o2 sensors from the rattle and the fuel consumtion diagnosis. it happened to me and has since bene all good...

[Panelman]

Hi mate. I had the same problem. Although my system is Di Filippo 1 7/8" 4>1 and 3" stainless hi flows, into 2 1/2" stainless Remus Racing (straight through pipes- no centre mufflers).

After intalling the big extractors and hi flows, man, the crackle and pop was heaps worse than before, and i was very suprised.

Anyway, apparently the engineering that has gone into the DiFi's design and construction, allows for so much to pass through the system, that you do hear everything that is going on. This I understand because like you, under decelleration, at higher revs, there is a high-spinning ticking sound which resembles a rattle! It shits me! having said that, it's only under heavier decelleration compression at say 4-4800 rpm.

The crackle & pop I have reduced, by installing 2 x 16" hotdogs as centre mufflers just after the cats. It has deepened the sound, and minimises the backfire a lot. Haven't checked the O2 sensors, but workshop reckons they'd be fine with only 50,000 k's on the clock.

This will not happen when i get my Sureflow 3½" Single catback!

Talk to the guys in here, search (heaps on this stuff) and wait for a lot of responses. Di Filippo is a very good system as many will agree. It's very free flowing and I'll assume you've had the engine edited with the install to match the new system. What figures are you getting? Does it feel good?

I've got 240 rwkw just with my system plus a 2 hole mod / edit tune. You should have the around 228 - 240?

Anyway, let us know
Cheers
Panelman.

[TUFFIE]

Hi mate. I had the same problem. Although my system is Di Filippo 1 7/8" 4>1 and 3" stainless hi flows, into 2 1/2" stainless Remus Racing (straight through pipes- no centre mufflers).

After intalling the big extractors and hi flows, man, the crackle and pop was heaps worse than before, and i was very suprised.

Anyway, apparently the engineering that has gone into the DiFi's design and construction, allows for so much to pass through the system, that you do hear everything that is going on. This I understand because like you, under decelleration, at higher revs, there is a high-spinning ticking sound which resembles a rattle! It shits me! having said that, it's only under heavier decelleration compression at say 4-4800 rpm.

The crackle & pop I have reduced, by installing 2 x 16" hotdogs as centre mufflers just after the cats. It has deepened the sound, and minimises the backfire a lot. Haven't checked the O2 sensors, but workshop reckons they'd be fine with only 50,000 k's on the clock.

This will not happen when i get my Sureflow 3½" Single catback!

Talk to the guys in here, search (heaps on this stuff) and wait for a lot of responses. Di Filippo is a very good system as many will agree. It's very free flowing and I'll assume you've had the engine edited with the install to match the new system. What figures are you getting? Does it feel good?

I've got 240 rwkw just with my system plus a 2 hole mod / edit tune. You should have the around 228 - 240?

Anyway, let us know
Cheers
Panelman.

Good to see that you are still aimning for that Sureflow 3.5:serenade:

[MADR08]

I've also got a DF 4 into 1 2.5 system. Mine's untuned at the moment, but yes I also get a lot of crackle and pop and as you describe the occaisonal backfire, usually when gearing down from 3rd to 2nd. The ticking sound is also very apparent when backing off the accelerator from high rev's. I asked my mechanic about this on my last service and he said it is quite normal for the DF systems to make this noise.

[vyssbeast]

what cats are you running?? sounds like the inside of the cat could be rattling about?? causing this sound perhaps?

[Toddler78]

I aggree the cat centres sound like they have fallen out that is why you are hearing the rattle.

Fuel comsumption up case the car sounds good so you drive it harder?????? (that would be the case with me)

under deceleration you will always get the crackle and pop with exhausts, if you listen closly enough you will also get it with standard exhaust but because they are designed to be restrictive and be quieter those sounds are muffeled. the crackling and poping has got to do with back presure and the headers no being of tuned length. In an ideal world you will have exectly the same compression in every cycinder and tuned length headers designed percifically for that engine, that will minimise it almost to nothing.

Personally I think the crackly and pop sounds tough and like it. different fuels will also aid/reduce the amount of crackle. in my old commodore I would use BP ultimate and the car would crackle very crisp but on the few occasions I used mobil synigy the car would sound more farty when decererating.

so all in al normal, and not much you can do apart from either muffling the exhaust or contracting an engineer to make percific headers for that engine.:thumbsup:

[vt350phantom]

[QUOTE=Panelman;838195]
This will not happen when i get my Sureflow 3½" Single catback!

Yes it will mate, my 3.5 inch single crackles pops and farts when decelerating on ocassions, but it sounds good IMHO

As for your noise, I agree with the posts above, cats could be rattling. Mine rattle at similar times too

[Oztrack Tuning]

The crackle and pop on back off and throttle entry is the car transitioning in and out of DFCO Decel Fuel Cut Off. Its tuneable based on afrs and timing change rates.

[evlss1]

i have seen quite a few 4>1 (pacemaker mainly) headers being tack welded together to solve the rattling issue, sounds to me like it is more than likely a cat has let go and is starting to disintegrate inside the casing. mine did this only last week and it sounded like crap!

as or the pop and crackle, that is one sweet noise!

[ASSASIN]

Haven't checked the O2 sensors, but workshop reckons they'd be fine with only 50,000 k's on the clock.


Anyway, let us know
Cheers
Panelman.[/QUOTE]

My o2 sensors were rooted at only 50000 km apparently when you put headers/extractors on they can get clogged from possible dirt entry during instalation. Any way very easy to check just plug it in and make sure they are switching on and off replaced both mine fuel consumption is heaps better and i dont get anywhere near as much pop and crakling

[RED R8]

The crackle and pop on back off and throttle entry is the car transitioning in and out of DFCO Decel Fuel Cut Off. Its tuneable based on afrs and timing change rates.


Yeh I agree oztrack:confused:

[Capt.LS2]

I have the same symptoms with my DF system and I think it is just one of their traits. You really can hear just about everything with them and have noticed it since day 1 of owning them especially on downshift.

It was even more pronounced when I had the cam put in but it still sounds awesome! Love the crackle and pop! My Clubbie has 30,000kms now and the DF system has been on since 5,000kms.

I recently drove from Canberra to Mt Isa via Brissy return and she averaged an honest 10.5l/100 km so the O2 sensors were working fine. :)

I love my DF system...subtle when you want/need it to be and a sweet sweet sound when you open her up!

Cheers.

Alex

[BennyMac]

When i had the system put on it had the usual crackle and pop. Ever since Sunday week its been backfiring, more so when cold. I just cant work out how everything was fine until the first initial loud backfire. Could be a number of things so booked her in for next Friday (23/2/07). APS are going to go over her and check everything.

Here's a link to what i have had done with some figures
http://www.ls1.com.au/forum/showthread.php?t=68194

Thanks all

Benjamin

[hollaz]

Sounds like one of your cats its gone for sure... can you remember hitting and bumps / speed humps that woul dhave damaged your undercarrage in any way?

When its next up on the hoist, wack both the cats with your fist, if either rattles, the cat needs to be replaced

[BennyMac]

Sorry for the delayed response. Dropped the car off Thursday night so APS could have her all day Friday. Let me just say i would rather spend a little bit of money on a fault now before it becomes a major problem down the track. Having said that, nothing is wrong with my car. Oztrack was right. The back firing is from the Decel Fuel Cut Off and also having a full DF system with 239rwkw. APS went over the car and assured me everything is fine. About the rattling, i asked if the 4 pipes in the collectors could be tack-welded together. I was advised that this could be done BUT the 4 pipes need a little bit of give to allow the metal to expand and detract when hot/cold. All in all, thanks to everyone for the comments and advice here, also to APS for peace of mind.

Benjamin