Exhaust System
Discussion
There was a bespoke 4 pipe one before (there is a picture around somewhere) - details here
http://autos.groups.yahoo.com/group/noble-m12/message/419
I'd check with the factory though, as I'd imagine if it changes the back pressure the mapping may get thrown out.....
J
http://autos.groups.yahoo.com/group/noble-m12/message/419
I'd check with the factory though, as I'd imagine if it changes the back pressure the mapping may get thrown out.....
J
Most turbocharged cars that have their CAT removed are renowned for boost increases, so be careful.
Generally speaking, an exhaust system that flows more freely causes lower backpressure. With lower backpressure the exhaust gasses leave the engine too quickly and as a result the engine runs a little ‘cooler’ than usual at lower revs. This causes the engines performance to suffer a little, but what is lost low-down is usually more than reclaimed at higher revs.
Some exhaust manufacturers design exhausts so they restrict exhaust gasses at lower revs to generate more heat, and then open up once the turbo starts to generate significant pressure to combat this problem.
To summarise, a simple free-flowing exhaust will probably loose you some of the low-down grunt you had, but in return, you will see some good gains further up the revs. Oh and the noise
I hope this is of some use to you
Laurence
Generally speaking, an exhaust system that flows more freely causes lower backpressure. With lower backpressure the exhaust gasses leave the engine too quickly and as a result the engine runs a little ‘cooler’ than usual at lower revs. This causes the engines performance to suffer a little, but what is lost low-down is usually more than reclaimed at higher revs.
Some exhaust manufacturers design exhausts so they restrict exhaust gasses at lower revs to generate more heat, and then open up once the turbo starts to generate significant pressure to combat this problem.
To summarise, a simple free-flowing exhaust will probably loose you some of the low-down grunt you had, but in return, you will see some good gains further up the revs. Oh and the noise
I hope this is of some use to you
Laurence
Well I have my twin rear exit exhaust system for sale if anyone's interested - only suitable for a 2.5 litre car (mines now a 3). Cost me around 400 (150 would be fair) - it will fit straight into a car without any mods (except two holes in the black grill) - you may need to remove the KAT pipe and have a KAT replacement pipe however.
>> Edited by guysh on Friday 21st November 16:54
>> Edited by guysh on Friday 21st November 16:54
Hi Lawrence,
While that can be true for a normally aspirated car (decrease backpressure too much, and your low-end will suffer), the same is not the case for a turbocharged car.
There's really no such thing as "too big an exhaust" for a turbocharged engine. The more the exhaust flows, the better the turbo will spool up. Certainly, at some point you reach diminishing returns where the turbo won't spool any faster (the Noble is close to that point already), but you will not hurt your bottom end power by improving exhaust flow. The turbo itself provides all the backpressure the engine could need.
Best,
Marc
While that can be true for a normally aspirated car (decrease backpressure too much, and your low-end will suffer), the same is not the case for a turbocharged car.
There's really no such thing as "too big an exhaust" for a turbocharged engine. The more the exhaust flows, the better the turbo will spool up. Certainly, at some point you reach diminishing returns where the turbo won't spool any faster (the Noble is close to that point already), but you will not hurt your bottom end power by improving exhaust flow. The turbo itself provides all the backpressure the engine could need.
Best,
Marc
Yup, if you increase the pressure differential across the exhaust impellor you decrease it's response time. The noble has mapped wastegate anyway and relatively small turbos on the earlier 2.5 cars and they're controlling the boost off the ecu. They also spool up very quickly so not too much to worry about there.
I work about 2 miles from John Nobles so get to see all sorts of lovely things being played with on the rollers.. although trying to get serious power from the catted cars looks a bit difficult at the mo, but the power figures I was seeing down there the other day means you guys have some pretty serious pieces of kit to look forward to.
The noble is a great car
I work about 2 miles from John Nobles so get to see all sorts of lovely things being played with on the rollers.. although trying to get serious power from the catted cars looks a bit difficult at the mo, but the power figures I was seeing down there the other day means you guys have some pretty serious pieces of kit to look forward to.
The noble is a great car
SpeedDemon said:
There's really no such thing as "too big an exhaust" for a turbocharged engine. The more the exhaust flows, the better the turbo will spool up. Certainly, at some point you reach diminishing returns where the turbo won't spool any faster (the Noble is close to that point already), but you will not hurt your bottom end power by improving exhaust flow. The turbo itself provides all the backpressure the engine could need.
This is interesting, because every turbocharged car I have ever driven with an aftermarket exhaust has never felt quite as brawny BEFORE the car makes any boost as with the standard exhaust.
Most of my friends agree with this. Perhaps it's just a mental thing
Laurence
Quick google seems to suggest the best exhaust for a turbo car is none at all....
www.extrememotorsports.com/g2stage/stage1.htm
www.fullboost.com.au/articles/techinfo/exhausts.html
www.zhaust.com/tech/0201/exhaust/
and this one seems quite comprehensive
www.vishnutuning.com/exhaust101.htm
J
www.extrememotorsports.com/g2stage/stage1.htm
www.fullboost.com.au/articles/techinfo/exhausts.html
www.zhaust.com/tech/0201/exhaust/
and this one seems quite comprehensive
www.vishnutuning.com/exhaust101.htm
J
Thanks for the links Joust they are really interesting.
I was led to believe that, "The best exhaust for a turbocharged car is none at all!" But then I read a post from an automotive engineer who is very clued up in the topic area indeed. This is his answer to the question, "Is the best exhaust for a turbo no exhaust at all?":
"No, but if you want an uncontrollable turbine-effect motor that would be only any good as a drag car then maybe yes... even then I doubt it.
You need exhaust piping to provide good control and balance to the turbines output.
If the turbos are allowed to 'run free' then they will not heat up until say 4000rpm at that point the massive heat shock (simple BTU quantities will heat the Turbine unevenly and kill it quite quickly."
Looks like we have an interesting debate on our hands...
P.S. Joust: I haven't seen your car about for a long time now. Has the wet weather put you off
I was led to believe that, "The best exhaust for a turbocharged car is none at all!" But then I read a post from an automotive engineer who is very clued up in the topic area indeed. This is his answer to the question, "Is the best exhaust for a turbo no exhaust at all?":
"No, but if you want an uncontrollable turbine-effect motor that would be only any good as a drag car then maybe yes... even then I doubt it.
You need exhaust piping to provide good control and balance to the turbines output.
If the turbos are allowed to 'run free' then they will not heat up until say 4000rpm at that point the massive heat shock (simple BTU quantities will heat the Turbine unevenly and kill it quite quickly."
Looks like we have an interesting debate on our hands...
P.S. Joust: I haven't seen your car about for a long time now. Has the wet weather put you off
LaurenceFrost said:No problems - it's amazing what you can find with a bit of googling - unfortunatly I haven't time to read any of them!
Thanks for the links Joust they are really interesting.
LaurenceFrost said:Must be said that in my "engineer mode" it would be my first assumption, that to have a controlled system you need a bit of positive feedback, and an exhaust gives you that. I'd always thought the reason Tubi et. all were not just "a pipe and a bunch of boxes" was to optimise the back pressure whilst removing nasty effects of the "normal" exhaust.
You need exhaust piping to provide good control and balance to the turbines output.
LaurenceFrost said:Not sure what you mean here. The turbo surely heats up due to two effects - the outcoming exhaust gasses, and the normal compression of a gas raising it's temprature. I'd imagine the latter is the "worse" one - is that what you mean?
If the turbos are allowed to 'run free' then they will not heat up until say 4000rpm at that point the massive heat shock (simple BTU quantities will heat the Turbine unevenly and kill it quite quickly."
LaurenceFrost said:No - I'm around. I drive it into work every day at the moment - but then that's mainly "North"
P.S. Joust: I haven't seen your car about for a long time now. Has the wet weather put you off
J
As Justin pointed out - 2 but the way in which it's setup you could probably have two either side it you wanted - just by replacing the pipe that the tailpipes come from with a longer one.
ibroker said:
guysh
One pipe either side or two. Any pics of the back of the car you could mail me
Thanks
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