RE: Exhaust fakery: Tell Me I'm Wrong
Discussion
Captain Muppet said:
PH said:
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).
It's kind of hard to close a vacuum operated solenoid valve before building up vacuum from running the engine. Unless we want a few seconds of listening to a vaccum pump before start up?The start up noise is also a consequence of the fail safe mode being open. Unless you want to risk your engine melting you pretty much have to have an entirely non-contrived start up yelp. I suppose you could just have a silencer large enough to handle peak gas flow, but then the EU won't let you fit an exhaust valve just for noise any more, so it'll be quiet all the time.
Do we still hate the noise now we understand why it's there?
Captain Muppet said:
PH said:
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).
It's kind of hard to close a vacuum operated solenoid valve before building up vacuum from running the engine. Unless we want a few seconds of listening to a vaccum pump before start up?The start up noise is also a consequence of the fail safe mode being open. Unless you want to risk your engine melting you pretty much have to have an entirely non-contrived start up yelp. I suppose you could just have a silencer large enough to handle peak gas flow, but then the EU won't let you fit an exhaust valve just for noise any more, so it'll be quiet all the time.
Do we still hate the noise now we understand why it's there?
I think the spacing is ok and a 6 pot 3 litre is allowed 2 exhausts. However, from there is starts to go a little wrong for the purists as we have engine noise being pumped into the car:
Before
http://www.youtube.com/watch?v=xI1g9blvCp8
After
http://www.youtube.com/watch?v=WyxGyhIobjM
The pipes on my clio make me chuckle- there's a plastic chrome finisher in the bumper and a smaller pipe inside; fair enough you think- lots of people do it.. but then look closer and there is an even smaller 'real' pipe inside the other one!
It's like some sort of exhaust Russian-doll
It's like some sort of exhaust Russian-doll
brasse said:
Best aftermarket exhaust, if design (inline, single exit) and sound are the conditions (all natural hoonery): The Pugsport.
http://www.youtube.com/watch?v=F5Ab7i9yqeA
Yep, that's smart. Those wheels are vile though.http://www.youtube.com/watch?v=F5Ab7i9yqeA
I don't think the number of cylinders matters; it's all about layout and orientation.
No inline engine should ever have exhaust tips on both sides of the car. An inline engine should have them on the exhaust valve side of the head only; a transverse front mounted engine should have them on whichever side if most convenient for routing, but not both. Transverse rear-mounted is a bit harder because often the back-box runs across the back of the car through packaging necessity so there is no extra metalwork involved in having pipes on both sides, but it still smacks of form over function to me (and yes, that includes my car).
Longitudinal Vs and Boxers can have two pipes if they're normally aspirated, SC or have parallel turbochargers. Single or sequential turbos should be one-side only.
Transverse Vs can do whatever the hell they like because the plumbing is horrible.
Personally, I'm of the opinion that the tail pipe should always be the same diameter as the exhaust itself, but since that's so rare these days it's probably rather controversial.
I always thought the quad pipes on six-pot BMW M-cars were the epitome of tackiness.
No inline engine should ever have exhaust tips on both sides of the car. An inline engine should have them on the exhaust valve side of the head only; a transverse front mounted engine should have them on whichever side if most convenient for routing, but not both. Transverse rear-mounted is a bit harder because often the back-box runs across the back of the car through packaging necessity so there is no extra metalwork involved in having pipes on both sides, but it still smacks of form over function to me (and yes, that includes my car).
Longitudinal Vs and Boxers can have two pipes if they're normally aspirated, SC or have parallel turbochargers. Single or sequential turbos should be one-side only.
Transverse Vs can do whatever the hell they like because the plumbing is horrible.
Personally, I'm of the opinion that the tail pipe should always be the same diameter as the exhaust itself, but since that's so rare these days it's probably rather controversial.
I always thought the quad pipes on six-pot BMW M-cars were the epitome of tackiness.
Edited by kambites on Wednesday 19th June 14:09
I hate the silly centre exhaust on my Megane.
Not only does it have an annoying plastic chrome-alike surround, but the central position completely prevents the car from being used to tow anything. Boo to the new Focus ST and Astra VXR too.
Can't complain about the Caterham's exhaust. I've yet to properly burn my leg against it, though I'm sure my time will come!
Not only does it have an annoying plastic chrome-alike surround, but the central position completely prevents the car from being used to tow anything. Boo to the new Focus ST and Astra VXR too.
Can't complain about the Caterham's exhaust. I've yet to properly burn my leg against it, though I'm sure my time will come!
kambites said:
I don't think the number of cylinders matters; it's all about layout and orientation.
No inline engine should ever have exhaust tips on both sides of the car. An inline engine should have them on the exhaust valve side of the head only; a transverse front mounted engine should have them on whichever side if most convenient for routing, but not both. Transverse rear-mounted is a bit harder because often the back-box runs across the back of the car through packaging necessity so there is no extra metalwork involved in having pipes on both sides, but it still smacks of form over function to me (and yes, that includes my car).
Longitudinal Vs and Boxers can have two pipes if they're normally aspirated, SC or have parallel turbochargers. Single or sequential turbos should be one-side only.
Transverse Vs can do whatever the hell they like because the plumbing is horrible.
Exhaust size should be related to power and exhaust gas flow. David Vizard states you need 2.2cfm of flow per 1hp for a restriction free exhaust.No inline engine should ever have exhaust tips on both sides of the car. An inline engine should have them on the exhaust valve side of the head only; a transverse front mounted engine should have them on whichever side if most convenient for routing, but not both. Transverse rear-mounted is a bit harder because often the back-box runs across the back of the car through packaging necessity so there is no extra metalwork involved in having pipes on both sides, but it still smacks of form over function to me (and yes, that includes my car).
Longitudinal Vs and Boxers can have two pipes if they're normally aspirated, SC or have parallel turbochargers. Single or sequential turbos should be one-side only.
Transverse Vs can do whatever the hell they like because the plumbing is horrible.
On Vee engines this isn't normally too bad as you run basically two exhaust systems. But 4 cylinder cars making 300bhp it is more of a problem and a 2.5" pipe will be restrictive and even this size can be difficult to route under the car, so splitting the pipe into two 2" pipes will increase flow, reduce restriction and maybe be easier to route.
Turbocharged and diesels run higher EGT's, so a large exhaust is good for flow and allows more rapid expansion of the gases to aid cooling and lower EGT's.
300bhp/ton said:
Exhaust size should be related to power and exhaust gas flow. David Vizard states you need 2.2cfm of flow per 1hp for a restriction free exhaust.
Exhaust size should, yes, exhaust tip size should not, except insofar as is necessary to support the actual exhaust bore. Trying to make a car look more powerful by making it look like it has a larger exhaust by fitting a few inches of huge chrome pipe to the back is daft (and again, yes I include my own car in this). Edited by kambites on Wednesday 19th June 14:12
Otispunkmeyer said:
Quick fun fact (not!) the derv models have exhausts that turn down to point at the floor before they reach the triangles. The triangles are purely for show.petrols exit through the triangles and as a consequence you can often tell what model is what because the diesel has perfectly clean triangles and the petrols eventually get covered in black.
Really? Mine is a 2.2 diesel and has both the pipes popping straight out the exits. (It's an Si). The cheap diesels have the point down and the triangle of chrome is blanked off.300bhp/ton said:
...a 2.5" pipe will be restrictive and even this size can be difficult to route under the car, so splitting the pipe into two 2" pipes will increase flow, reduce restriction and maybe be easier to route.
Plus in terms of tuning the sound a single large pipe will boom horribly. Which is why two small pipes is so often a good way to exit a back box when the rest of the system has been a single pipe. Less boom for less weight and less cost.
300bhp/ton said:
Captain Muppet said:
PH said:
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).
It's kind of hard to close a vacuum operated solenoid valve before building up vacuum from running the engine. Unless we want a few seconds of listening to a vaccum pump before start up?The start up noise is also a consequence of the fail safe mode being open. Unless you want to risk your engine melting you pretty much have to have an entirely non-contrived start up yelp. I suppose you could just have a silencer large enough to handle peak gas flow, but then the EU won't let you fit an exhaust valve just for noise any more, so it'll be quiet all the time.
Do we still hate the noise now we understand why it's there?
Dan
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