De-cat a bad thing?
Discussion
after fiddling with my adaptives and pots and messing it all up I phoned dreadnought to see how much they charge for an engine tune up as any work they have done for me has been a little expensive, but top notch so i trust them
Spoke to one of the guys and he was saying that having de-cats fitted is a bag thing as it messes with the pulse on the exhaust etc and that the cerbera runns better with them fitted, I have just fitted joo's new short induction kit and chip so thought my linked de-cat woul be a good thing?
Anyone got anything on this or been told this before?
Spoke to one of the guys and he was saying that having de-cats fitted is a bag thing as it messes with the pulse on the exhaust etc and that the cerbera runns better with them fitted, I have just fitted joo's new short induction kit and chip so thought my linked de-cat woul be a good thing?
Anyone got anything on this or been told this before?
Is this on 4.5's then? as I took them out on my 4.2 and didn't notice any change on driving or on the before/after diagnostics comparison.
I took mine out as I really wasn't happy with that heat source next to the gearbox/clutch. The gearchange lever used to get red hot in summer and so did the cabin/tunnel.
I took mine out as I really wasn't happy with that heat source next to the gearbox/clutch. The gearchange lever used to get red hot in summer and so did the cabin/tunnel.
sorry should clarify on this
she's a 4.5, The cats were taken out 2 years ago and I have never had any problems but dreadnought says they may not help and can even reduce power.
recently fitted the short induction kit and tried to sort my adaptives and made a mess of it, will have another go next week.
Im looking for middle ground really as she's my daily drive along with my R1 so want good road manners normally, but a big kick in the back when i want it.
I know what you mean about the heat, it did used to get bad in the summer!
she's a 4.5, The cats were taken out 2 years ago and I have never had any problems but dreadnought says they may not help and can even reduce power.
recently fitted the short induction kit and tried to sort my adaptives and made a mess of it, will have another go next week.
Im looking for middle ground really as she's my daily drive along with my R1 so want good road manners normally, but a big kick in the back when i want it.
I know what you mean about the heat, it did used to get bad in the summer!
As I see it the adapatives are actually a reflection of the oxygen sensors. The Cerb has no more engine control than those sensors. It has no independant idea of airflow.
The adaptives are just telling you if a suitable mixture of air and fuel are heading into the catalyst.
The problem is the catalyst has a very short life in the presence of unburnt fuel going in. A very short life indeed.
This is compounded by the fact that the Cerb has quite an overlap on the valves, such that there is almost always unburnt fuel going into the cats.
The MBE on the Cerb is trying to hold you to a compromise between knackering your cats in a very short time, but still having a fuel happy overlapped performance engine.
Unfortunately this is a compromise. Removing the cats, removes the need for the air fuel mix to be compromised to anything other than performance, and maintaining a healthy margin for anti-knock. The Air Fuel mix for a catalyst and for a maximum performance engine is a little way apart.
I doubt mappers ever set your car up so that its producing max power over the whole of the rev range as it would likely make the car around town a bit snatchy and peaky to drive. I think it likely they set max power above 4000, and below that dial it back to make it less powerful but more smooth.
I see no reason that cats in your car improve any aspect of your performance, apart from fuel economy as a side issue of the different map.
I have never been convinced that any form of back pressure has ever helped any engine. The closest I have ever had explained is in motorcycles where an exup valve in the exhaust narrows the exhaust to change a standing wave in an otherwise fixed length exhaust. Several times I've been told it works by applying back pressure but never heard of a convincing argument as to why this helps, so I choose to ignore it.
I don't like unneccesarily loud engines, but jools linked decats are very nice sounding that seem to past all the various track day noise limits when combined with a standard rear box.
The adaptives are just telling you if a suitable mixture of air and fuel are heading into the catalyst.
The problem is the catalyst has a very short life in the presence of unburnt fuel going in. A very short life indeed.
This is compounded by the fact that the Cerb has quite an overlap on the valves, such that there is almost always unburnt fuel going into the cats.
The MBE on the Cerb is trying to hold you to a compromise between knackering your cats in a very short time, but still having a fuel happy overlapped performance engine.
Unfortunately this is a compromise. Removing the cats, removes the need for the air fuel mix to be compromised to anything other than performance, and maintaining a healthy margin for anti-knock. The Air Fuel mix for a catalyst and for a maximum performance engine is a little way apart.
I doubt mappers ever set your car up so that its producing max power over the whole of the rev range as it would likely make the car around town a bit snatchy and peaky to drive. I think it likely they set max power above 4000, and below that dial it back to make it less powerful but more smooth.
I see no reason that cats in your car improve any aspect of your performance, apart from fuel economy as a side issue of the different map.
I have never been convinced that any form of back pressure has ever helped any engine. The closest I have ever had explained is in motorcycles where an exup valve in the exhaust narrows the exhaust to change a standing wave in an otherwise fixed length exhaust. Several times I've been told it works by applying back pressure but never heard of a convincing argument as to why this helps, so I choose to ignore it.
I don't like unneccesarily loud engines, but jools linked decats are very nice sounding that seem to past all the various track day noise limits when combined with a standard rear box.
julian64 said:
As I see it the adapatives are actually a reflection of the oxygen sensors. The Cerb has no more engine control than those sensors. It has no independant idea of airflow.
The adaptives are just telling you if a suitable mixture of air and fuel are heading into the catalyst.
The problem is the catalyst has a very short life in the presence of unburnt fuel going in. A very short life indeed.
This is compounded by the fact that the Cerb has quite an overlap on the valves, such that there is almost always unburnt fuel going into the cats.
The MBE on the Cerb is trying to hold you to a compromise between knackering your cats in a very short time, but still having a fuel happy overlapped performance engine.
Unfortunately this is a compromise. Removing the cats, removes the need for the air fuel mix to be compromised to anything other than performance, and maintaining a healthy margin for anti-knock. The Air Fuel mix for a catalyst and for a maximum performance engine is a little way apart.
I doubt mappers ever set your car up so that its producing max power over the whole of the rev range as it would likely make the car around town a bit snatchy and peaky to drive. I think it likely they set max power above 4000, and below that dial it back to make it less powerful but more smooth.
I see no reason that cats in your car improve any aspect of your performance, apart from fuel economy as a side issue of the different map.
I have never been convinced that any form of back pressure has ever helped any engine. The closest I have ever had explained is in motorcycles where an exup valve in the exhaust narrows the exhaust to change a standing wave in an otherwise fixed length exhaust. Several times I've been told it works by applying back pressure but never heard of a convincing argument as to why this helps, so I choose to ignore it.
I don't like unneccesarily loud engines, but jools linked decats are very nice sounding that seem to past all the various track day noise limits when combined with a standard rear box.
Cheers for that Julian, that clears a lot up for me.The adaptives are just telling you if a suitable mixture of air and fuel are heading into the catalyst.
The problem is the catalyst has a very short life in the presence of unburnt fuel going in. A very short life indeed.
This is compounded by the fact that the Cerb has quite an overlap on the valves, such that there is almost always unburnt fuel going into the cats.
The MBE on the Cerb is trying to hold you to a compromise between knackering your cats in a very short time, but still having a fuel happy overlapped performance engine.
Unfortunately this is a compromise. Removing the cats, removes the need for the air fuel mix to be compromised to anything other than performance, and maintaining a healthy margin for anti-knock. The Air Fuel mix for a catalyst and for a maximum performance engine is a little way apart.
I doubt mappers ever set your car up so that its producing max power over the whole of the rev range as it would likely make the car around town a bit snatchy and peaky to drive. I think it likely they set max power above 4000, and below that dial it back to make it less powerful but more smooth.
I see no reason that cats in your car improve any aspect of your performance, apart from fuel economy as a side issue of the different map.
I have never been convinced that any form of back pressure has ever helped any engine. The closest I have ever had explained is in motorcycles where an exup valve in the exhaust narrows the exhaust to change a standing wave in an otherwise fixed length exhaust. Several times I've been told it works by applying back pressure but never heard of a convincing argument as to why this helps, so I choose to ignore it.
I don't like unneccesarily loud engines, but jools linked decats are very nice sounding that seem to past all the various track day noise limits when combined with a standard rear box.
Will focus more on my adaptives when im setting her up next! I may just bite the bullet this time and get dreadnought to set her up for £65 this once as im hardly here this summer due to going to afghan in Aug so want to enjoy her as much as I can before i go
I'm trying to learn a little about induction and exhaust system design. As I understand it the inlet plenum reflects the induction wave, thus pushing more air and fuel into the cylinder. Thus, I assumed the exhaust manifold design would be the reverse, using the flow from one cylinder to create a vacuum in the exhaust port of another cylinder. If that is the case, I can't see how restricting the flow with a cat could possible help.
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