Chim exhaust modification
Discussion
Hi all,
I know there have been past discussions regarding the wonderful aural merits of having the rear exhaust box cut modified i.e. [box cut open, packing removed ,perforated tube replaced with a straight through tube and box welded back together] but I have a further queries that I would appreciate some feedback on :-
1)I was just wondering does the modification cause any uncomfortable droning within the cars cabin whilst driving at speed?
2)Does the cutting open and re-welding of the rear box compromise the strength and integrity of the box or exhaust system in general with regards to introducing any weak points for blowing or the possible on-set of corrosion etc?
3)Is the aforementioned modification effectively the only difference between a standard Chim exhaust system and commercially available "Sports exhaust"?
4)Does the exhaust mod have any effect on engine performance?
5)Any other down sides to this mod other than possible annoying the neighbours?
6)Best place to get this done in East Anglia area?
Cheers,
Keith
I know there have been past discussions regarding the wonderful aural merits of having the rear exhaust box cut modified i.e. [box cut open, packing removed ,perforated tube replaced with a straight through tube and box welded back together] but I have a further queries that I would appreciate some feedback on :-
1)I was just wondering does the modification cause any uncomfortable droning within the cars cabin whilst driving at speed?
2)Does the cutting open and re-welding of the rear box compromise the strength and integrity of the box or exhaust system in general with regards to introducing any weak points for blowing or the possible on-set of corrosion etc?
3)Is the aforementioned modification effectively the only difference between a standard Chim exhaust system and commercially available "Sports exhaust"?
4)Does the exhaust mod have any effect on engine performance?
5)Any other down sides to this mod other than possible annoying the neighbours?
6)Best place to get this done in East Anglia area?
Cheers,
Keith
chimster said:
Hi all,
I know there have been past discussions regarding the wonderful aural merits of having the rear exhaust box cut modified i.e. [box cut open, packing removed ,perforated tube replaced with a straight through tube and box welded back together] but I have a further queries that I would appreciate some feedback on :-
4)Does the exhaust mod have any effect on engine performance?
5)Any other down sides to this mod other than possible annoying the neighbours?
6)Best place to get this done in East Anglia area?
Cheers,
Keith
Hi Keith,
I can't comment on many aspects as mine is yet to be done (next month).
AFAIK it doesn't have any performance benefit, it does however, make the engine sound like a V8 should.
Offords, in Offord Darcy do the conversion using a couple of cherry bombs rather than straight through pipes which can sometimes sound a little tinny.
This conversion sounds awesome, I've heard Gills (Rooster - she has had this done to hers by Offords) chim next to mine which is standard and it sounds great.
chimster said:
1)I was just wondering does the modification cause any uncomfortable droning within the cars cabin whilst driving at speed?
Not really. IMHO it sounds good all the way through the rev range, and even at constant speeds. Others have complained about a slightly 'hollow' sound at around 60mph in 5th. However, this is easily cured with a little right foot flex!
chimster said:
2)Does the cutting open and re-welding of the rear box compromise the strength and integrity of the box or exhaust system in general with regards to introducing any weak points for blowing or the possible on-set of corrosion etc?
Not that I'm aware, most metal components in a car will be welded somewhere along the line. Provided this is done properly (a mate of mine in the welding game assures me
), the join can actually be stronger than the original piece of metal. Lots of people have had the mod done, and I'm not aware of any problems like you describe... chimster said:
3)Is the aforementioned modification effectively the only difference between a standard Chim exhaust system and commercially available "Sports exhaust"?
What we're talking about is commonly referred to as the 'sports exhaust mod', which is a bit of a misnomer as there's no performance benefit. There are proper sports exhausts available (e.g. the JP exhaust available from ACT), which do more than just sound nice. chimster said:
4)Does the exhaust mod have any effect on engine performance?
No, there are some that claim that a modified car may lose a tiny amount of BHP due to the loss of back pressure. However, I am not aware of anyone who has had the mod done (and I know quite a few), who have suffered any noticable deterioration in performance.
chimster said:Yes, you'll grin even harder than you do currently, when you pop and crackle through town. Your ears will get wet as a result and your face may start to ache. Removing said grin is not easy!
5)Any other down sides to this mod other than possible annoying the neighbours?
chimster said:
6)Best place to get this done in East Anglia area?
Dunno guv...
To conclude, I had mine done by Austec back in January and without doubt it's the best thing I could have done. It sounds (IMHO) amazing, and never fails to make me grin. The addition of vicious pops and crackles to the hardened V8 soundtrack is amazing and not something I could live without now.
In short...
JUST DO IT!!! chimster said:
1)I was just wondering does the modification cause any uncomfortable droning within the cars cabin whilst driving at speed?
Yes, at about 50-60 in 5th it can get a little loud and drony
chimster said:
2)Does the cutting open and re-welding of the rear box compromise the strength and integrity of the box or exhaust system in general with regards to introducing any weak points for blowing or the possible on-set of corrosion etc?
If anything it makes it stronger as some stronger pipes are inserted. The exhaust is not a load bearing part, so as long as the weld is done correctly its fine. Mine was done 18 months ago and there are no problems so far.
chimster said:
3)Is the aforementioned modification effectively the only difference between a standard Chim exhaust system and commercially available "Sports exhaust"?
I've heard someone elses sports exhaust and it sounded less bassy but with more pops and crackles. I prefer mine, plus it was 1/3 the price of a sports exhaust
chimster said:
4)Does the exhaust mod have any effect on engine performance?
Had mine on a rolling road for a re-chip and it turned in some pretty good figures for a 4.5
chimster said:
5)Any other down sides to this mod other than possible annoying the neighbours?
Decreased fuel economy and aching face muscles due to changing down on just for the noise on the overrun
chimster said:
6)Best place to get this done in East Anglia area?
Sorry, no idea, but definitely get it done!
Rob
chimster said:
2)Does the cutting open and re-welding of the rear box compromise the strength and integrity of the box or exhaust system in general with regards to introducing any weak points for blowing or the possible on-set of corrosion etc?
If anything it makes it stronger as some stronger pipes are inserted. The exhaust is not a load bearing part, so as long as the weld is done correctly its fine. Mine was done 18 months ago and there are no problems so far.
[/quote]
I'd disagree - every cut and shut I've seen (including mine) has suffered as the exhaust bends and doesn't sit correctly.
chris_chim said:
Re 5 - forget about doing trackdays at Castle Coombe!
That's a very good point. You may well have trouble getting below the acceptable dB thresholds for trackdays (and I mean generally, not just at CC).
However, ACT do a pair of removable tailpipe silencers, which may help in such situations...
zippee said:
Do check on this....I get a nasty whistle sound when foot is flat to the floor above 3k revs.
Hence the reason I mentioned Offords solution with the cherry bombs. According to Simon this should eliminate this noise.
Excuse my ignorance...but what's cherry bombs????
trackdays for you if you do. Hi peeps, New member to ph, had a Chimaera for about a year and now started playing with it.
I thought you may be interested to note that i had a problem with blowing exhaust manifold gaskets, took them off to replace and found one of the pre cats had started to break up. Spoke to Act and they refurbed my manifolds removing the pre cats. Just had the mot yesterday and passed no problems CO reading 0.03%, still got main cat in place though.
At the same time of fixing the manifolds, found the pipes had cracked into and out of the centre silencer box, so had some flared pipes made up to replace the box, welded these in place to produce an absolutely awesome exhaust note, total cost about £60 plus work at ACT. Interestingly although it nows scares small children around town, the noise is not intrusive at speed, just seems to be left behind!
I thought you may be interested to note that i had a problem with blowing exhaust manifold gaskets, took them off to replace and found one of the pre cats had started to break up. Spoke to Act and they refurbed my manifolds removing the pre cats. Just had the mot yesterday and passed no problems CO reading 0.03%, still got main cat in place though.
At the same time of fixing the manifolds, found the pipes had cracked into and out of the centre silencer box, so had some flared pipes made up to replace the box, welded these in place to produce an absolutely awesome exhaust note, total cost about £60 plus work at ACT. Interestingly although it nows scares small children around town, the noise is not intrusive at speed, just seems to be left behind!
evilc said:
Hi peeps, New member to ph, had a Chimaera for about a year and now started playing with it.
I thought you may be interested to note that i had a problem with blowing exhaust manifold gaskets, took them off to replace and found one of the pre cats had started to break up. Spoke to Act and they refurbed my manifolds removing the pre cats. Just had the mot yesterday and passed no problems CO reading 0.03%, still got main cat in place though.
At the same time of fixing the manifolds, found the pipes had cracked into and out of the centre silencer box, so had some flared pipes made up to replace the box, welded these in place to produce an absolutely awesome exhaust note, total cost about £60 plus work at ACT. Interestingly although it nows scares small children around town, the noise is not intrusive at speed, just seems to be left behind!
So does this mean that effectively you have no silencer, just straight through?
With reference to the "sports exhaust" mine has a factory fit, sports pipe and the only difference I can see is that it increases in diameter for the last few feet. I wouldn't expect any perfromance gain but it certainly gives it a deeper (and louder) sound track than the standard pipe.
Not compared it to someone who has had the standard pipe modified, so I can't comment on the difference here.
Not compared it to someone who has had the standard pipe modified, so I can't comment on the difference here.
I bought a "modified" exhaust a couple of months ago but beware. I wasn't happy with the sound it made so I opened the silencer up (with disc grinder) and i found 2 bits of old scaffold pipe just sort of tacked in place. They didn't fit the original pipes i.e. slightly too small and were cut too short so there were gaps all around. Needless to say i got some pipe that was slightly bigger than the originals and cut them so they would slide over the stubs that were left in the silencer and i then welded them in place properly. I also repacked the box with exhaust wadding before i welded it back together. Its got a much better crisper sound and i don't get any droning at certain revs like i used to. 
Still got the standard exhaust for track days, although its a PITA to change just for one day every now and then.
Still got the standard exhaust for track days, although its a PITA to change just for one day every now and then.
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