sbridgey
ClioSport Club Member
disco 4, 182, Meglio
Stolen from a PH article but I think its actually quite good.
Exhausts - The Rules
In-line engines
Single pipe only, sided to reflect the location of the exhaust manifold where appropriate. A Caterham is the most extreme example of this rule but the same applies whether the exhaust is inside or outside of the bodywork. Double barrel exhaust tips are only acceptable for engines of more than four cylinders. Centre exits acceptable for transverse engines where the exhaust is routed thus for the line of least resistance, eg, old Minis.
Vee engines
Unless using a shared turbo V6s are permitted a single-exit pipe per cylinder bank, paired centrally like the Jaguar F-Type or at any distance apart as required by aesthetic demands. Quad pipes are ONLY acceptable for engines of eight cylinders or more, spacing again at manufacturer's discretion so grouped together (eg. Corvette Stingray, Pagani Zonda) or in pairs. Any more than four pipes looks daft. If even Ferrari at the height of 70s excess thought so (ref. 365 GT4 BB and subsequent 512BB).
Boxer engines
Normally aspirated horizontally opposed engines may, in extreme examples (ie, VW Beetle) be permitted more than one pipe. Single turbo boxer engines should only use a single exit pipe, location as appropriate. Twin turbo flat-sixes may be permitted two single-exit pipes but only if individual turbo and manifold assemblies are used on each cylinder bank. Porsche 911s ALWAYS look cooler with a single corner-exit pipe.
Trims, diameters and other details
The diameter of the pipe exit should reflect that of the exhaust system as a whole; artificially flared pipes are to be avoided at all costs. Likewise, the exhaust tip should be part of the system as a whole - 'free floating' trim details with 'hidden' exits contained within are unacceptable. Straight-cut, plain gauge tubing (stainless steel or titanium) will always look cooler than 'rolled' or chromed trims. Chamfering is acceptable, especially if it matches the angle of the bumper or diffuser.
Quirks and traditions
Triple-exit pipes are as thorny an issue as three-spoke alloys and to be treated with extreme caution. Where dictated by the exhaust system - eg, Ferrari F40 and Porsche 911 RS 3.0, with its capped straight through track exits and corner 'road' system - it can be sub-zero cool. The 458's F40 homage triple-exit system treads a fine line but is acceptable.
Only Italian cars, specifically Alfa Romeos, can get away with the off-centre, angled single pipe that looks like a wizened old gent nonchalantly smoking a fag out of the corner of his mouth.
Noise
Should be consistent across the rev range and not artificially augmented; contrived start-up blips with the system fully open before closing the valves and settling down to a quiet idle are especially objectionable (see Porsche, Ferrari, etc). If you need to temporarily quieten your exhaust slip-on cans are acceptable.
Pops, bangs and crackles should only occur 'naturally' and not due to contrived ECU controlled 'misfires'. Ditto flames.
Side exhausts
Always cool, subject to abiding by regulations with regard to engine configuration, aspiration and location. End of.
And the actual article
http://www.pistonheads.com/gassing/...+Exhaust+fakery:+Tell+Me+I'm+Wrong&mid=374945
Exhausts - The Rules
In-line engines
Single pipe only, sided to reflect the location of the exhaust manifold where appropriate. A Caterham is the most extreme example of this rule but the same applies whether the exhaust is inside or outside of the bodywork. Double barrel exhaust tips are only acceptable for engines of more than four cylinders. Centre exits acceptable for transverse engines where the exhaust is routed thus for the line of least resistance, eg, old Minis.
Vee engines
Unless using a shared turbo V6s are permitted a single-exit pipe per cylinder bank, paired centrally like the Jaguar F-Type or at any distance apart as required by aesthetic demands. Quad pipes are ONLY acceptable for engines of eight cylinders or more, spacing again at manufacturer's discretion so grouped together (eg. Corvette Stingray, Pagani Zonda) or in pairs. Any more than four pipes looks daft. If even Ferrari at the height of 70s excess thought so (ref. 365 GT4 BB and subsequent 512BB).
Boxer engines
Normally aspirated horizontally opposed engines may, in extreme examples (ie, VW Beetle) be permitted more than one pipe. Single turbo boxer engines should only use a single exit pipe, location as appropriate. Twin turbo flat-sixes may be permitted two single-exit pipes but only if individual turbo and manifold assemblies are used on each cylinder bank. Porsche 911s ALWAYS look cooler with a single corner-exit pipe.
Trims, diameters and other details
The diameter of the pipe exit should reflect that of the exhaust system as a whole; artificially flared pipes are to be avoided at all costs. Likewise, the exhaust tip should be part of the system as a whole - 'free floating' trim details with 'hidden' exits contained within are unacceptable. Straight-cut, plain gauge tubing (stainless steel or titanium) will always look cooler than 'rolled' or chromed trims. Chamfering is acceptable, especially if it matches the angle of the bumper or diffuser.
Quirks and traditions
Triple-exit pipes are as thorny an issue as three-spoke alloys and to be treated with extreme caution. Where dictated by the exhaust system - eg, Ferrari F40 and Porsche 911 RS 3.0, with its capped straight through track exits and corner 'road' system - it can be sub-zero cool. The 458's F40 homage triple-exit system treads a fine line but is acceptable.
Only Italian cars, specifically Alfa Romeos, can get away with the off-centre, angled single pipe that looks like a wizened old gent nonchalantly smoking a fag out of the corner of his mouth.
Noise
Should be consistent across the rev range and not artificially augmented; contrived start-up blips with the system fully open before closing the valves and settling down to a quiet idle are especially objectionable (see Porsche, Ferrari, etc). If you need to temporarily quieten your exhaust slip-on cans are acceptable.
Pops, bangs and crackles should only occur 'naturally' and not due to contrived ECU controlled 'misfires'. Ditto flames.
Side exhausts
Always cool, subject to abiding by regulations with regard to engine configuration, aspiration and location. End of.
And the actual article
http://www.pistonheads.com/gassing/...+Exhaust+fakery:+Tell+Me+I'm+Wrong&mid=374945
