Discussion
I know theres a lot of talk about de-cating a Cerbie ( mines a late 2001 S6 ). Am I best removing the cats, or getting a de-cated exhaust? If so , wheres the best place and how much are they? I know it wont get through the MOT without them, so how much of a job is it to re-install them for that?
Also I believe they are worth approx 10% on fuel economy, and a bit on performance . Any advice or thoughts would be appreciated as to pros & cons -thanks in advance
Also I believe they are worth approx 10% on fuel economy, and a bit on performance . Any advice or thoughts would be appreciated as to pros & cons -thanks in advance
You could worse than to talk to Joolz at www.track-car-solutions.co.uk - he sorted mine - de-cats with a standard back box - sound great.
philcerbera said:
You could worse than to talk to Joolz at www.track-car-solutions.co.uk - he sorted mine - de-cats with a standard back box - sound great.
I agree - Just had mine done, de-cats and standard back box, not much noiser than standard, a nice agressive 'POWER' sound to the exhaust, not like the 'LOOK AT ME IM LOUD' noise of decats and sports exhaust.
De-cats are realtively easy to re-fit, and by the way theres no such thing as a 'special' de-cat exhaust, you just remove the decats
jensena said:
. . . and by the way theres no such thing as a 'special' de-cat exhaust, you just remove the decats
What about the linked decat pipes then
I thought they were special (i.e. not your run of the mill replacement) or am I missing something? 
Edited by keithyboy on Monday 11th December 00:17
Wilder said:
Oki sounds interesting - whats the benefit of linked de-cat pipes over normal?
Theres some differing opinions on these, and I'm not enough of an expert to say which is better. I had mine non-linked ones fitted at Euphoria Tacing, and is he is against Linked ones. His argument being that the AJP V8 beinga flat plane crank is basically 2 four cylinder engines bolted together, and they should be kept totally seperate.
jensena said:
Wilder said:
Oki sounds interesting - whats the benefit of linked de-cat pipes over normal?
Theres some differing opinions on these, and I'm not enough of an expert to say which is better. I had mine non-linked ones fitted at Euphoria Tacing, and is he is against Linked ones. His argument being that the AJP V8 beinga flat plane crank is basically 2 four cylinder engines bolted together, and they should be kept totally seperate.
Then again my exhaust expert (who used to work for cosworth) and the dyno figures say otherwise.. as a by-product they're also quieter on part throttle than straight decat pipes.
jensena said:
Wilder said:
Oki sounds interesting - whats the benefit of linked de-cat pipes over normal?
Theres some differing opinions on these, and I'm not enough of an expert to say which is better. I had mine non-linked ones fitted at Euphoria Tacing, and is he is against Linked ones. His argument being that the AJP V8 beinga flat plane crank is basically 2 four cylinder engines bolted together, and they should be kept totally seperate.
As a direct replacement I saw an average of 5bhp through the rev range improvement, but the torque curve stayed pretty much the same, however, the fueling characteristics had changed (not massively), once this had been mapped then there was an increase in Torque upto around 10lb/ft through the rev range.
So as a direct replacement the linked de-cats will give you at least a 5bhp increase and will leave the torque the same (fueling slightly different but fine), with a remap you will gain more torque, but it would be not cost effective to have a remap with just linked de-cats.
Normal de-cat pipes tend to give a slight decrease in bhp and torque (poss 5bhp / lb-ft) so for me the best route would always be linked de-cats.
Jules.
Steve_T said:
Cyclone1 said:
...
Normal de-cat pipes tend to give a slight decrease in bhp and torque (poss 5bhp / lb-ft) so for me the best route would always be linked de-cats.
Jules.
So I'd be better off putting my cats back in?
Your choice.......but as the gains / losses are so negligable either way, then for noise alone the de-cats (of any type) are worth it.
Just putting my two-pence in.
Linked pipes are theoretically designed to use the negative back-pulse in the pipes from connected cylinders to improve scavenging from the exhaust port, improve flow during valve overlap and, therefore, aid filling of the cylinder charge. I have been led to believe that the distance and volume of the crossover pipe is crucial as to which part of the rev-range is most affected.
Whatever the theory, Jules and Jools have proved that power, torque and noise appreciation are improved.
The straight decat pipe, as far as I know, is just a substitute pipe of similar length that is bolted in place of the cats whereas the 'sports' exhaust is a straight-through pipe that continues back from the cats to the back of the car negating the need (?) for a silencer box.
As I say, all theory. I bought a pair of sports pipes when I bought the car but they are still sitting in the wrapping waiting for me to jack the car up high enough to be fitted. Don't hold your breath !
Oops, and a question from me. Has anyone noticed a difference in temperature in the cabin after fitting decats ? The cats are right under the gear lever and run at about a million degrees so wondered what would happen when they're gone ?
Oops ! just mis-typed gear lever as "fear" lever. Arf arf !!
Linked pipes are theoretically designed to use the negative back-pulse in the pipes from connected cylinders to improve scavenging from the exhaust port, improve flow during valve overlap and, therefore, aid filling of the cylinder charge. I have been led to believe that the distance and volume of the crossover pipe is crucial as to which part of the rev-range is most affected.
Whatever the theory, Jules and Jools have proved that power, torque and noise appreciation are improved.
The straight decat pipe, as far as I know, is just a substitute pipe of similar length that is bolted in place of the cats whereas the 'sports' exhaust is a straight-through pipe that continues back from the cats to the back of the car negating the need (?) for a silencer box.
As I say, all theory. I bought a pair of sports pipes when I bought the car but they are still sitting in the wrapping waiting for me to jack the car up high enough to be fitted. Don't hold your breath !
Oops, and a question from me. Has anyone noticed a difference in temperature in the cabin after fitting decats ? The cats are right under the gear lever and run at about a million degrees so wondered what would happen when they're gone ?
Oops ! just mis-typed gear lever as "fear" lever. Arf arf !!
Edited by Mr.Cerbera on Monday 11th December 10:56
The chap who kindly took me for a test drive on Saturday reckoned the cabin temperatures were massively reduced once the cats were removed.
Also, if you get the car remapped (properly) you will probably find to gain the best power output your engine will need to run richer, which is not good for cats. I'm not sure whether the standard MBE runs in closed loop mode or not but a standard lambda can only measure a very small percentage either side of stoic, which in turn is only achieved by running the mixture too lean to make proper power.
So, remove them for longevity. Pop them back on for MoT.
Also, if you get the car remapped (properly) you will probably find to gain the best power output your engine will need to run richer, which is not good for cats. I'm not sure whether the standard MBE runs in closed loop mode or not but a standard lambda can only measure a very small percentage either side of stoic, which in turn is only achieved by running the mixture too lean to make proper power.
So, remove them for longevity. Pop them back on for MoT.
Mr.Cerbera said:
Oops, and a question from me. Has anyone noticed a difference in temperature in the cabin after fitting decats ? The cats are right under the gear lever and run at about a million degrees so wondered what would happen when they're gone ?
Mine certainly started runing a lot cooler in the cabin when I had the decats fitted. It's not impossible that Jools did some heat shield jiggery-pokery too but I'm sure it's mostly down to the decats.
Cyclone1 said:
Steve_T said:
Cyclone1 said:
...
Normal de-cat pipes tend to give a slight decrease in bhp and torque (poss 5bhp / lb-ft) so for me the best route would always be linked de-cats.
Jules.
So I'd be better off putting my cats back in?
Your choice.......but as the gains / losses are so negligable either way, then for noise alone the de-cats (of any type) are worth it.
Well thats the first I've heard that fitting Cats will actualy boost power!!
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