cancel
Showing results for 
Search instead for 
Did you mean: 

One that may even exhaust pierre!

Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

One that may even exhaust pierre!

While sitting in nose to tail slow traffic this morning. Although some do -many don't- contain twin exhaust pipes, is there any technical advantage to the flattened oval tail-pipes seen on many -particularly- up-market German cars. Or is it purely a dubious attempt at automotive bling?
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
17 REPLIES
nadger
Rising Star
Posts: 4,498
Thanks: 46
Registered: 13-04-2007

Re: One that may even exhaust pierre!

Amazing how the mind wanders when one is stuck in a traffic jam  Roll eyes
Moderator
Moderator
Posts: 25,766
Thanks: 1,124
Fixes: 47
Registered: 14-04-2007

Re: One that may even exhaust pierre!

Presumably twin exhausts have twin cats...twice the price. Is it a cost saving exercise?
Now you've got me at it Roll eyes
Customer and Forum Moderator.
Product of the Tyrell Corporation
Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

Re: One that may even exhaust pierre!

I do some of my best thinking in traffic jams...
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
Moderator
Moderator
Posts: 25,766
Thanks: 1,124
Fixes: 47
Registered: 14-04-2007

Re: One that may even exhaust pierre!

Presumably you have one of these. Ok on the motorway but not so good on 'B' roads.
Customer and Forum Moderator.
Product of the Tyrell Corporation
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: One that may even exhaust pierre!

Got one that clips over the top of the wheel and a flap drops down, got a cup hole and pen tray, only trouble is, cant drop the flap when anyone is sitting in the seat,might have been OK in the White Van, think thats when I first got it, now it is just taking up space in the garage
Back to the Exhaust, makes you wonder with some of the go faste boxs, all fart and no go
With the bigger cars, i would assume that they are V engines and one exhaust for each bank, been a long time since I looked under the hood.  Also some makers have small bore (The BMC range did) that makes the gas flow faster.  The only work I did on exhaust was measure the CO around the vehicle to make sure it didnt get into the vehicle.  And to gradularly shorten the pipe and measure the floor temperature to make sure your feet didnt get burnt
Community Veteran
Posts: 6,735
Thanks: 12
Registered: 02-02-2008

Re: One that may even exhaust pierre!

Quote from: pierre_pierre
i would assume that they are V engines and one exhaust for each bank

Pure bling.  Grin
I've got a 4.2 V8 and it does have twin final exhausts (together, not on opposite sides) but this is only, as far as I can tell, to fit neatly under the bumper.
There is one (big fat) exhaust and one (massive) catalyst, it's just the final box that exits in 2 very short smaller pipes.
But it's a pretty large car with loads of room for "stuff" incluiding all the Quattro gubbins. I imagine some models would fit 2 smaller exhaust systems underneath more easily - at a price.
Community Veteran
Posts: 38,249
Thanks: 936
Fixes: 56
Registered: 15-06-2007

Re: One that may even exhaust pierre!

My V6 has twin pipes and twin cats and twin silencers but then the pipes come together for the final major silencer.
I think the reason why there are twin cats is that the v6 is transverse mounted and it wouldn't be practical to have one cat with the feed pipes being of dramatically different lengths
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: One that may even exhaust pierre!

this is the tray, name on it is Autopilot, it also has a message, dont use while driving, fat chance of that
Do you like the Mug?
edit
Oh and the seat is right back
Community Veteran
Posts: 13,921
Thanks: 514
Fixes: 7
Registered: 01-08-2007

Re: One that may even exhaust pierre!

As I understood it was so that the exhaust gasses could escape quicker (IE less pressure) which allows the engine to pick up RPM faster than a single exhaust.
Basic principle being the faster the emissions get out, the faster the engine can go faster.
I need a new signature... i'm bored of the old one!
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: One that may even exhaust pierre!

fast flow up a small pipe reduces the pressure - Bernoulli  theory http://en.wikipedia.org/wiki/Bernoulli%27s_principle
Quote
fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.Bernoulli's principle is named after the Dutch-Swiss mathematician Daniel Bernoulli who published his principle in his book Hydrodynamica in 1738

Community Veteran
Posts: 38,249
Thanks: 936
Fixes: 56
Registered: 15-06-2007

Re: One that may even exhaust pierre!

Which actually means that fast flow up a small pipe gives a greater pressure drop than slow flow down a big pipe (with the same total flow)
Basically small diameter pipes, bends, restrictions cause a drop in flow for the same pressure differential.
This is why tuned performance cars use large pipes with as few bends as possible.
However there are two more factors - with all the gubbins stuck at the back of the exhaust nowadays the actual pipe size and configuration is a bit less critical within sensible limits and the other is that if an exhaust pipe has its length/diameter changed from the original design it can cause the flow to reduce by setting up a standing wave as the flow is pulsed not steady.
And no I don't remember enough fluid dynamics to explain the actual theory.
Community Veteran
Posts: 13,921
Thanks: 514
Fixes: 7
Registered: 01-08-2007

Re: One that may even exhaust pierre!

Quote from: pierre_pierre
fast flow up a small pipe reduces the pressure - Bernoulli   theory http://en.wikipedia.org/wiki/Bernoulli%27s_principle
Quote
fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.Bernoulli's principle is named after the Dutch-Swiss mathematician Daniel Bernoulli who published his principle in his book Hydrodynamica in 1738


Certainly true but then at the same time in order to push those gasses through faster requires energy from the engine resulting in a resistive force against its RPM pickup surely?
The fast flow thing is true, the faster something flows through a pipe the less pressure there will be because there is less particles in the confined space. As OldJim has said though, surely bends in the pipe (which is typical of all exhausts) will create pressure points which slow it all down again. Thats my understanding of it anyway.
I need a new signature... i'm bored of the old one!
Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

Re: One that may even exhaust pierre!

In the jam again this morning (see OP) in almost the same place. Observed that lateish Vauxhall's are also sporting the must-have flattened oval tail-pipe, but with a single exhaust pipe inside. But of course, the antecedence of Vauxhall is German (Opel) so perhaps that accounts for it.
What do Kwik Fit do when faced with these articles of Bling I wonder...
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
Community Veteran
Posts: 16,834
Thanks: 1,124
Fixes: 13
Registered: 06-11-2007

Re: One that may even exhaust pierre!

Quote from: Petlew
While sitting in nose to tail slow traffic this morning.

I hope you remembered to turn your heater fan off...........   Undecided   . to save you having "forced" co1 emissions in your cab ! !...  Shocked