Discussion
Allegedly you save some fuel. Decat & sports exhaust is LOUD. Decat alone sounds nice - better than a sports exhaust I'd say. Power wise, hard to say- there's more natural variation between engines to notice a definite difference, but you definitely get better transient throttle response.
Do it !
Sounds amazing with sports pipes and car pulls much (well noticebly) harder at higher revs. No need for any changes either. They're simple for the dealer to remove (and put back at MOT).
-- Dont be a twat cats, are fitted for a reason.
Cat's cause more damage to the atmosphere when the car
is cold that lead in petrol does.
Andy
>> Edited by dyb on Friday 28th June 20:12
Sounds amazing with sports pipes and car pulls much (well noticebly) harder at higher revs. No need for any changes either. They're simple for the dealer to remove (and put back at MOT).
-- Dont be a twat cats, are fitted for a reason.
Cat's cause more damage to the atmosphere when the car
is cold that lead in petrol does.
Andy
>> Edited by dyb on Friday 28th June 20:12
Just got the car back from it's service and also had the de-cat done - sounds 
great!
Good thing is that it can be docile when you want it to be (by selecting a higher gear, lower revs), but when you reach 4500rpm and upwards
.
Decat and sports exhaust I've been told are LOUD ALL OF THE TIME, which I suppose could become irritating after a while. Have yet to hear a Cerbera with a sports exhaust so couldn't comment on that option. However general consensus (members here, dealers, garages) are that the decat is best option.
Don't really know how it affects performance, running etc (due to service being done - would expect it to run better anyway)
P.S. Dealer said he's never seen such long flames coming out the exhaust - over 1ft!
great! Good thing is that it can be docile when you want it to be (by selecting a higher gear, lower revs), but when you reach 4500rpm and upwards
. Decat and sports exhaust I've been told are LOUD ALL OF THE TIME, which I suppose could become irritating after a while. Have yet to hear a Cerbera with a sports exhaust so couldn't comment on that option. However general consensus (members here, dealers, garages) are that the decat is best option.
Don't really know how it affects performance, running etc (due to service being done - would expect it to run better anyway)
P.S. Dealer said he's never seen such long flames coming out the exhaust - over 1ft!
I've already got the sports exhausts fitted to my 2002 4.5 Cerb, but my dealer has offered me the de-cat option at no cost. It would seem rude not to take them up on their offer, but from what I can gather on this and previous threads I'm going to have a FCUKING LOUD car all of the time. Is there anybody out there in PH land who has had this mod done who lives close-ish to me (S.E. London), so that I can get to hear what its going to be like before I commit to the work? If so can you e-mail me direct - Thanx in advance.
Removing a cat will save no fuel at all, the front hego sensor is fitted in front of the cat for the reason of monitoring and control fuelling around stoichiometry, the fuelling is driven rich and lean to give the optimum catalyst conversion conditions to convert the NOX, HC and CO, only way of improving fuel consumption is to have the calibration modified within the PCM, but then why drive a Cerb if you want fuel improvement? Iv been in two de-catted Cerbs with Sports exhaust systems, and they are superb, great improvemnt at higher rev range and sound amasing, the popping and banging is the un burnt fuel igniting within the exhaust system, flames are caused by this also when dropping down through gears in a tunnel, as soon as I get the Cerb im saving up for, de-cat and sports exhaust will go staright on, beware of having a made up stainless exhaust system by outside companies as a to bigger bore will cause an exhaust slug to bounce back through the pipe and actaully prevent the exhaust gases exiting as quick, this will decrease power through certain rev bands. On another note, when MOT's come round, cats have to go back on, so dont bin em.
Iv seen the figures with engines dyno tested, to bigger bore and power is actually reduced, same reason as having no exhaust or manifold at all, no back pressure or to little is not the way to go, sounds to me like you have had a number of cars with big bore and big diameter exhaust systems which are purchased from car specialists, these companies do not and have not the money to purchase every engine and stick it on a dyno with different exhausts (for engine only) to see if the manufacturers given power figures are improved. Exhaust slug is a return of some sort, vibration or sound that travells back up the pipe on return of exhaust gas exiting, it happens on all cars, big bore pipe can cause loads of issues with this, its a true fact which accessory places know nothing about, only how to sell exhausts that look good.
Yes by removing the cats, obviously there are changes that take place, but not that the HEGO sensor can see and then cannot monitor these cahnges as the hego is in front of the cat, so fuelling is un affected.
Yes by removing the cats, obviously there are changes that take place, but not that the HEGO sensor can see and then cannot monitor these cahnges as the hego is in front of the cat, so fuelling is un affected.
mr 8 . sounds like you're getting a little bit confused on the exhaust tuning thingy .
the exhaust slug you refer to is the name given to each exhaust pulse leaving the individual cylinders, these have momentum and are less prone to reverse flowing back into the chamber at high velocities.you can use this effect to scavenge the chamber and draw in fresh charge on overlap, indeed coupled with the inlet charge momentum it's possible on certain engines to exceed 100 percent cylinder volumetric efficiency. By having smaller pipes you increase the velocity of the slug, but going too small limits the pipe's outright flow rate, generally slightly small is the way to go (never heard that before ...!!)to gain torque through the rev range.
the bouncing back bit refers to the pressure wave reversal in the pipe, this happens whenever a pressure wave reaches a significant change in area, ie the end of the pipe or a suitably large expansion chamber.
back pressure .. lowest is best. period. er - except where you can use back pressure to alter the torque curve. back pressure never increased outright maximum power of an engine, but it can move it so you make better use of available gearing.
the exhaust slug you refer to is the name given to each exhaust pulse leaving the individual cylinders, these have momentum and are less prone to reverse flowing back into the chamber at high velocities.you can use this effect to scavenge the chamber and draw in fresh charge on overlap, indeed coupled with the inlet charge momentum it's possible on certain engines to exceed 100 percent cylinder volumetric efficiency. By having smaller pipes you increase the velocity of the slug, but going too small limits the pipe's outright flow rate, generally slightly small is the way to go (never heard that before ...!!)to gain torque through the rev range.
the bouncing back bit refers to the pressure wave reversal in the pipe, this happens whenever a pressure wave reaches a significant change in area, ie the end of the pipe or a suitably large expansion chamber.
back pressure .. lowest is best. period. er - except where you can use back pressure to alter the torque curve. back pressure never increased outright maximum power of an engine, but it can move it so you make better use of available gearing.
Joospeed, knew you would reply, and yes, your much more experineced in this field then I am, its been 10 years since Iv dealt with back pressure etc, cannot recall saying that smaller diameter is the way to go, lowest back pressure is better, but what I meant was that to bigger bore pipe can have the reverse effect, not always, but these pipes are also not tested always, just built to fit and many manufacturers hope for the best. Can you see my point?
On another note, many TVR owners are currently moaning that their TVR once on a dyno outputs less power than TVR are stating, the 360 and 420BHP figures are obviosly from flywheel, the 320bhp to 350 seen on rolling roads are from wheels, do you happen to know what transmission losses are once power is through to the wheels quoted by TVR? average manufacturer says about 5% losses, but others loose as much as 10% but still show the flywheel figures which they are entitled to. The 420bhp at flywheel is probably what was shown during developmnent at TVR, but the actual calibration and hardware has probaly been chaged for production since. Any ideas?
On another note, many TVR owners are currently moaning that their TVR once on a dyno outputs less power than TVR are stating, the 360 and 420BHP figures are obviosly from flywheel, the 320bhp to 350 seen on rolling roads are from wheels, do you happen to know what transmission losses are once power is through to the wheels quoted by TVR? average manufacturer says about 5% losses, but others loose as much as 10% but still show the flywheel figures which they are entitled to. The 420bhp at flywheel is probably what was shown during developmnent at TVR, but the actual calibration and hardware has probaly been chaged for production since. Any ideas?
I was under the impression that most rolling roads could measure transmission losses and take these into account to calculate the flywheel power. Typical scenario is for rolling road to 'drive' the car wheels while car in gear and clutch presses, therefore power used equals transmission losses.
Dunno if this method was used on any of the reported TVR HP tests though.
WB
Dunno if this method was used on any of the reported TVR HP tests though.
WB
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