MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: craigy123 on February 12, 2012, 03:34:23 pm
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Ive had a price to get my new de-cat downpipe ceramic coated, is it really worth it? Compared to just heat wrap? It's not a lot of money at £80, but it is £80 that could be spent else where I guess. Whats you views?
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Why a de-cat DP?
Why ceramic coating it?
:signIWS:
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Why a de-cat DP?
Why ceramic coating it?
:signIWS:
De-cat purely for more power and noise : and ceramic coating as it should in theory let the hot gases escape quicker and flow out easier.
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Ive had a price to get my new de-cat downpipe ceramic coated, is it really worth it? Compared to just heat wrap? It's not a lot of money at £80, but it is £80 that could be spent else where I guess. Whats you views?
I was quoted quite a bit more from zircotec (have a good reputation) but am getting BCS to wrap mine for £50 as part of a new system I'm having :smiley:
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How should ceramic coating improve gas flow? It's pointless.
Wrapping it with heat tape will reduced heat transfer to the engine bay. That's worth
considering.
De-cat is stupid. It seriously does harm to the environment without being neccessary.
A proper 100 or 200 cpsi doesn't affect power significiently.
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Ceramic coating will improve gas flow as heat loss from exhaust gasses mean the gasses slow down.
For downpipes of manifolds its worth coating inside and outside of the tube.
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Ceramic coating will improve gas flow as heat loss from exhaust gasses mean the gasses slow down.
For downpipes of manifolds its worth coating inside and outside of the tube.
Thanks for that. What I was getting at in my first reply.
So you recommend it PDT?
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We do it on a lot of high spec / motorsport projects. Its not massively expensive and certainly helps, moreso on cars that have front mounted turbos or mid/rear engined where component position restricts cooling.
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
My DP is actually Blueflame 3" decat but nige is making the rest of the system to match up :happy2:
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
My DP is actually Blueflame 3" decat but nige is making the rest of the system to match up :happy2:
Haha, I'm the they way about. It's mating up to a 3" car back blueflame. Bring on the noise.
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
My DP is actually Blueflame 3" decat but nige is making the rest of the system to match up :happy2:
Haha, I'm the they way about. It's mating up to a 3" car back blueflame. Bring on the noise.
Haha weird coincidence
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
My DP is actually Blueflame 3" decat but nige is making the rest of the system to match up :happy2:
You do know that if you get pulled by the police or vosa and they see you have a decat they can give you a gv9 and have the powers to take the car from you as it would be deemed unroadworthy. Just letting ya'll know
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Think I might get this done then. Can't be bothered farting about with heat wrap.
Mike, it's a BCS downpipe I got :party: top
Quality.
My DP is actually Blueflame 3" decat but nige is making the rest of the system to match up :happy2:
You do know that if you get pulled by the police or vosa and they see you have a decat they can give you a gv9 and have the powers to take the car from you as it would be deemed unroadworthy. Just letting ya'll know
It will be flanged with 100 or 20cell sports cat like my current miltek setup :happy2:
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Ceramic coating will improve gas flow as heat loss from exhaust gasses mean the gasses slow down.
Sorry, sounds like complete nonsense. Any prove on this or at least a theory?
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Ceramic is far better than wrap and lasts forever unlike wrap which lasts a year at best before crumbling away. Wrap allows water to become trapped between it and the pipe and over time the pipe rusts.
The ceramic keeps the hot exhaust gasses in the pipe which allows the gasses to travel faster while keeping the heat away from the rest of the engine bay.
Does the same job as wrap, but lasts and looks better. Doesn't just come in white, but loads of different colours now.
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Ceramic is far better than wrap and lasts forever unlike wrap which lasts a year at best before crumbling away. Wrap allows water to become trapped between it and the pipe and over time the pipe rusts.
The ceramic keeps the hot exhaust gasses in the pipe which allows the gasses to travel faster while keeping the heat away from the rest of the engine bay.
Does the same job as wrap, but lasts and looks better. Doesn't just come in white, but loads of different colours now.
Alex, you use Zircotec? cant remember. Would it be more cost effective to coat the inside of the DP to keep the heat form escaping rather than wrap? £50 - £60 to wrap using good quality stuff
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Sorry, sounds like complete nonsense. Any prove on this or at least a theory?
:popcornsoda:
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Used to use a local place, but the white ceramic kept flaking off. The grey they do is fine but not rated as high on the temps so I use that on charge pipes and intakes.
Zircotec for manifolds and downpipes. More expensive and longer turn around, but it lasts and they do more colours.
I would just go for the outside coating on a downpipe on our cars. On the mega power stuff then do inside and out.
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Used to use a local place, but the white ceramic kept flaking off. The grey they do is fine but not rated as high on the temps so I use that on charge pipes and intakes.
Zircotec for manifolds and downpipes. More expensive and longer turn around, but it lasts and they do more colours.
I would just go for the outside coating on a downpipe on our cars. On the mega power stuff then do inside and out.
Thanks again mate, top man :happy2:
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Ceramic coating will improve gas flow as heat loss from exhaust gasses mean the gasses slow down.
Sorry, sounds like complete nonsense. Any prove on this or at least a theory?
Hotter gases are easier to force through the exhaust system than cool gases due to density. Ceramic coating keeps gasses hotter within the exhaust system helping to decrease exhaust density & increases exhaust flow.
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Hotter gases are easier to force through the exhaust system than cool gases due to density. Ceramic coating keeps gasses hotter within the exhaust system helping to decrease exhaust density & increases exhaust flow.
The opposite is true. :wink:
Cooler gases have less volume, so they pass the exhaust system easier.
Hotter gases requiere larger diameter and cause increased back pressure.
Simply physics. :innocent:
In the end only one aspect is really significient: taping the downpipe will
reduce thermal radiation to the engine bay and intake system and increase
power on prolongued full throttle.
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So why do high powered cars coat both inside and outside of the manifold/exhaust system??
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The Ex F1 technician and engine builder that I speak to 3-4 times a week must be wrong then. So must the guys at Zircotec and The authors of numerous books that cover the subject I.e 4 stroke tuning by A.G Bell.
Also the EFI university must be using incorrect information during their training seminars.
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Hotter gases are less dense than cold gases so the hotter gasses travel faster.
http://www.cartuningtips.com/112-ceramic-exhaust-coatings
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Google Boyles Law and Daniel Bernoulli
Same principal for dynamic passage of air over a wing creating lift CL=1/2 Rho V Squared, a smoother surface also creates a better boundary layer against the surface over which it passes = less drag = better breathing
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Simple physics :innocent:
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Ceramic is far better than wrap and lasts forever unlike wrap which lasts a year at best before crumbling away. Wrap allows water to become trapped between it and the pipe and over time the pipe rusts.
I agree ceramic is abetter option, but I really don't buy the rust issue. The temperatures of the exhaust would dispose of sny water residue.
I did a lot of research into this as the 'rust' issue gets thrown around alot on the forums. As it happens I found no truth or proof of it. I actually found the opposite. I found lots of images of guys who had their DPs wrapped for a couple+ years and the DP looked like new.
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Ceramic is far better than wrap and lasts forever unlike wrap which lasts a year at best before crumbling away. Wrap allows water to become trapped between it and the pipe and over time the pipe rusts.
I agree ceramic is abetter option, but I really don't buy the rust issue. The temperatures of the exhaust would dispose of sny water residue.
I did a lot of research into this as the 'rust' issue gets thrown around alot on the forums. As it happens I found no truth or proof of it. I actually found the opposite. I found lots of images of guys who had their DPs wrapped for a couple+ years and the DP looked like new.
If it lasts a year ill be happy. :happy2: The downpipe is like new now so we will see (eventually)
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What a wee debate. :grin:
I think I'll get this done now. Satin black was what the price was quoted for. So I'll just go with that. No point in getting it any other colour really.
Cheers for the input from the pro's :happy2:
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On cars where the downpipe/ manifold is at the front of the engine and then comes under the sump (often with no under tray I.e many vauxhalls) then the wrap does take lots Of abuse from water etc... If the wrap and item to be wrapped is of a good quality then you won't have any issues. If you try and wrap your cheap eBay mild steel manifold with eBay wrap then it will probably rust.
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Stainless Blueflame DP with wrap & stainless clamps used in motorsports & noble exhaust systems. Not sure if adhesive & sealant are used too but I trust it will be done properly. Im sure it will be fine on my humble Leon :smiley:
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So why do high powered cars coat both inside and outside of the manifold/exhaust system??
Do they? Are we talking about special requirements of race cars? No Porsche and no
Ferrari sportscar needs gmiimicks like this. Are these slow?
The Ex F1 technician and engine builder that I speak to 3-4 times a week must be wrong then. So must the guys at Zircotec and The authors of numerous books that cover the subject I.e 4 stroke tuning by A.G Bell.
Also the EFI university must be using incorrect information during their training seminars.
That's why I asked for information and I still miss it.
But of course ''hoter gasses flow better'' still remains nonsense in case of an exhaust system.
Google Boyles Law and Daniel Bernoulli
Same principal for dynamic passage of air over a wing creating lift CL=1/2 Rho V Squared, a smoother surface also creates a better boundary layer against the surface over which it passes = less drag = better breathing
Dave, if you had read what I've written in other topics about aerodynamics you'd know
that I have read enough about Bernoulli, Hucho and others.
I did not negate in any way smoothing the surface will improve flow. :wink:
Until now some guys told about isolation and better flow of hotter gases which is crap.
Also smoothing the inner surface doesn't need any coating at all.
At least on a cheapo DP. :stupid: This seems like putting a F1 tyre on a Tin Lizzy.
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Air density increases when temperature drops, so coating/wrapping should help:
http://en.wikipedia.org/wiki/Density_of_air
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Surely if the hot gases can't escape through heat soak through the downpipe then they will be forced out quicker?
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This is getting interesting now!
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:pomppomp: Have a fight see who's the best :pomppomp:
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:pomppomp: Have a fight see who's the best :pomppomp:
Using ceramic coated broad swords......? :popcornsoda:
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:pomppomp: Have a fight see who's the best :pomppomp:
Using ceramic coated brown swords......? :popcornsoda:
That's :sick:
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Air density increases when temperature drops, so coating/wrapping should help:
http://en.wikipedia.org/wiki/Density_of_air
That's not the point.
In this case (exhaust gases) the gas mass remains the same, just the volume differs. :wink:
So your example is a different matter.
The cooler the gases the lesser the volume and the easier it will flow through the exhaust.
So preserving the heat can not increase flow.
The only advantages of wrapping are to prevent heating up the engine bay (and so take in)
and a faster heat up of the cat from cold start (if you still have a cat).
The last is the reason why VW and others use a DP with an air gap on some models (both
Diesels and gas engines).
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Zircotec have lots of useful info on their website, lots of technical studies etc...
I have sent an email to a specialist that I know, see if he can provide some definitive technical reports that support the claims by Zircotec (and almost all other exhaust coating specialists worldwide, as well as F1 techs and authors of tuning manuals and technical studies) that state that maintaining the gas temps aids velocity.
see what they come back with. ......
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Ask sheldon from the big bang theory, he would know :grin:
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:popcornsoda: I believe the ceramic coating should increase the speed of the exhaust gases. :happy2:
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...... that state that maintaining the gas temps aids velocity.
Of course, the same exhaust gas mass with higher temp and more volume
needs to flow faster to get the same gas mass flow through the system.
That's why drag increases and so back pressure as well.
So what? Faster gases doesn't mean lower drag - it means increased drag !!
:wink:
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I think you have mostly been outgunned on this one.
Its OK to be wrong :innocent:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F_qoTL-iRC8LM%2FSScik8-6HhI%2FAAAAAAAAJz0%2F8Ap1VudMgEk%2Fs320%2Fhumblepie-logo.gif&hash=77ed283c0367ce47b30916bc0a93d9fa5eff6680)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimgs.xkcd.com%2Fcomics%2Fduty_calls.png&hash=6dbf0181e2f77f38534936cb760d170fde1c06a7)
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Didn't you understand my tellings or didn't you even read it? If you didn't understand it you
better ask a specific question.
Many of the postings on this topic are based of half-whisdom and misunderstanding of physics,
some are commercial.
Hotter gasses improve flow? I explained why it's nonsense. It doesn't help reading retailers'
sites who want to sell their stuff. You better read a proper scientific book (and understand it).
:wink:
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(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimgs.xkcd.com%2Fcomics%2Fduty_calls.png&hash=6dbf0181e2f77f38534936cb760d170fde1c06a7)
I love it!! :notworthy:
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Didn't you understand my tellings or didn't you even read it? If you didn't understand it you
better ask a specific question.
Many of the postings on this topic are based of half-whisdom and misunderstanding of physics,
some are commercial.
Hotter gasses improve flow? I explained why it's nonsense. It doesn't help reading retailers'
sites who want to sell their stuff. You better read a proper scientific book (and understand it).
:wink:
I too have studied physics at degree level as part of an engineering degree. I agree with everyone on here but you :P
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Didn't you understand my tellings or didn't you even read it? If you didn't understand it you
better ask a specific question.
Many of the postings on this topic are based of half-whisdom and misunderstanding of physics,
some are commercial.
Hotter gasses improve flow? I explained why it's nonsense. It doesn't help reading retailers'
sites who want to sell their stuff. You better read a proper scientific book (and understand it).
:wink:
None of the retailers or tuners in this topic have tried to sell anything. They have been kind enough to take there time to answer my question and give some advice. :happy2:
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Hmm I was always under the impression too that keeping heat in the exhaust is beneficial for increasing gas speed. Watching this thread with interest :happy2:
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I too have studied physics at degree level as part of an engineering degree. I agree with everyone on here but you :P
What's wrong?
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I too have studied physics at degree level as part of an engineering degree. I agree with everyone on here but you :P
What's wrong?
you :grin:
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The Bruce, what do you reckon to this statement: "If you imagine how hot the gases are as they pass the exhaust valve, they need to be kept as close to that temperature as possible for the length of the tuned header pipe in order to maintain laminar flow".
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it would still have a laminar flow even if cooler unless the flow is disrupted by something else to some how to turn it turbulant. That said there are specific velocities of certain fluids where the flow stays laminar. Outside of this and it becomes turbulant. No idea what that would be on an exhaust gas, I know what it is with fluids in H/CWS pipework
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"If you imagine how hot the gases are as they pass the exhaust valve, they need to
be kept as close to that temperature as possible for the length of the tuned header
pipe in order to maintain laminar flow".
If you look a page or so back I already answered this, Luke. :wink:
The hotter the exhaust gas the more it is expanded (I guess there is no doubt and
no different opinion on this). The more it is expanded the more volume. The more gas
volume (the more expanded) a pipe has to transport in the same time the higher is
gas speed and so drag and the higher the back pressure.
Still a simple thing. So:
There is no advantage in keeping high temperatures. They even disturb gas flow as
hotter gases ( = expanded gases ) are harder to flow in a limited diameter pipe.
There is even no need to think about laminar vs turbulent flow etc.. All the turbulence
issues increase with more flowing gas volume because gas speed increases.
If someone would say hotter gases will flow better ( = lower drag ) he would also
say that a car has lower drag at 200 mph than at 50 mph.
What's wrong?
you :grin:
Very interesting posting. :happy2:
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What would pour faster, cold custard or hot custard? It's the same amount of custard therefore the same amount of molecules. With the hot custard your molecules are further apart (as previously agreed) and therefore "looser" and therefore easier to pour.
Same goes for exhaust gases. Everything IS further apart but its still the same volume coming through the engine. It doesn't magicaly suck extra exhaust gases out just because its hotter.
And whilst we are on the subject, can you tell me what's heavier...a ton of bricks or a ton of feathers?
Oh, and would you prefer to be attacked by one horse sized duck or ten duck sized horses? :signLOL:
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^^^^^^^ :signLOL:
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10 duck sized horses every time.... :signLOL:
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Awaiting Bruce's reply :popcornsoda:
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My memory of reading exhaust design books years ago is that the post turbo exhaust design fundementals can be (relatively) easily simplified as there's not the same level of complication to the pulse tuning / scavenging issues that one has to contend with on a NA engine.
In gist, my memory of maximising on boost performance is:
- maximise differential pressure across the exhaust turbine
do this by:
- minimising pressure drop in post turbo pipework
- keep heat (within reason) in the exhaust pre turbo to assist working the gas as hard as possible across the turbo
so:
- don't fit a 1.5" pea shooter on a Veyron.....
- minimise pressure drop by getting heat out of the exhaust ASAP post turbo - lower the volumetric flow rate, and as a by-product lower the gas velocity.
Roughly, pressure drop for a body of area A moving in a fluid of density rho can be calculated by:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fhyperphysics.phy-astr.gsu.edu%2Fhbase%2Ffluids%2Fimgflu%2Fairfri2.gif&hash=2a022b514f8f05786f77e1ea8ed421af2161e7be)
If you've got a high velocity fluid you have a high pressure drop per metre of pipe, if you have a high temperature fluid you have a higher molar volume which dictates a higher velocity flow. Post turbo, temperature is bad, high velocity is bad, high back pressure is bad.
It's not quite as simple as the ideal gas law, as there are simultaneous elements to calculations governing exhaust gas flow, but very crudely... double the temp, double the volume. Double the volume, double the velocity (for a given molar flow). Double the velocity, quadruple the pressure drop.
My 2 p worth.
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2p worth? ^^^ ??? about 14 quids worth there :P
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2p worth? ^^^ ??? about 14 quids worth there :P
Bite me! :signLOL: :happy2:
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What have I started..........? :popcornsoda:
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2p worth? ^^^ ??? about 14 quids worth there :P
Bite me! :signLOL: :happy2:
:ashamed: :signLOL:
What have I started..........? :popcornsoda:
War !!
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What have I started..........? :popcornsoda:
A distraction from the pain of trying to find a replacement engine for one I killed on Sunday..... so thanks for that!
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What would pour faster, cold custard or hot custard?
[pendantic barstewards mode :signLOL:]
bad choice - custard is a non Newtonian fluid, like ketchup and blood, and simple fluid dynamics equations don't define their behavior.
Hot custard does pour faster however....
[/pedantic barstewards mode]
Quite fancy some custard and cake come to think of it :drool:. :evilgrin:
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Awaiting Bruce's reply :popcornsoda:
I already thought it's pointless, but I hope 'alackofspeed' has made things clearer:
If you've got a high velocity fluid you have a high pressure drop per metre of pipe, if you have a high temperature fluid you have a higher molar volume which dictates a higher velocity flow. Post turbo, temperature is bad, high velocity is bad, high back pressure is bad.
It's not quite as simple as the ideal gas law, as there are simultaneous elements to calculations governing exhaust gas flow, but very crudely... double the temp, double the volume. Double the volume, double the velocity (for a given molar flow). Double the velocity, quadruple the pressure drop.
My 2 p worth.
:happy2:
What would pour faster, cold custard or hot custard?
bad choice - custard is a non Newtonian fluid, like ketchup and blood, and simple fluid dynamics equations don't define their behavior.
Hot custard does pour faster however....
again: :happy2:
Nice example, but different thing though, Alex. :wink: Custard changes viscosity, gases mainly change volume with temperature.
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(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwhitsblog.com%2Fwp-content%2Fuploads%2F2011%2F12%2Fdarth-vader-epic-fail.jpg&hash=2d80c0deb6afb697ee6183f1cd3824fe6b6549b5)
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I am utterly confused. Have you got a link to a web page or book explaining/backing up what you're saying Bruce?
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You won't be able to read most of my books. :rolleye: (they aren't english of course)
Thought everbody here agrees that gases expand when they get hot.
Think of your tyres when you drive fast. Tyre pressure will increase.
I guess that's the point. :wink:
Of course both larger diameter and smoothening sharp edges will improve flow.
I never would say anything against that.
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So what you are saying is that the pressure of the exhaust gases increases as does the volume?
With a tyre, there is no where for the gases to escape to so its going to gain pressure in a different way to an exhaust with an open end. So surely the higher pressure will force the exhaust gases out faster?
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Day 3 of the exhaust wrapping saga :popcornsoda:
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I never thought id see a willy waving thread in physics, my formulas bigger than your formular :surprised: :grin:
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All this for a 2.0tfsi lol.
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All this for a 2.0tfsi lol.
The engine the forum is based on....
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All this for a 2.0tfsi lol.
The engine the forum is based on....
Was going to say same thing
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Rob, we don't need any formulas for a basic understanding. :wink:
So what you are saying is that the pressure of the exhaust gases increases as does the
volume?
Not exactly. The volume itself causes that 'more' gas that has to pass the pipe.
More gas at the same time > increased speed > more drag and more work for
the engine to spill the gases out.
Why are aftermarked downpipes better? They are bigger. Larger diameter means
slower gas speed. Irritated? More diameter means that the same amount of gas
passes easier and less forced > lower speed required to let the same amount of
gas passing through it.
Even more - this is irony of fate - larger diameter means (much) larger surface and
larger surface provides increased cooling. That's (one reason) why Volkswagen
uses smaller diameters: they want to force cat heat up after start.
With a tyre, there is no where for the gases to escape to so its going to gain pressure in a
different way to an exhaust with an open end. So surely the higher pressure will force the
exhaust gases out faster?
Alex, my example was just to explain that heating up gas (air) will gain an icrease in
volume (and pressure). It doesn't matter if there's something closed or if there's leak.
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All this for a 2.0tfsi lol.
The engine the forum is based on....
Took the words right out of my mouth! :chicken:
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Had a response from one of the companies I emailed regarding the subject (they manufacture/design/develop exhaust systems for various applications from F1, WRC, World Gt and also helicopters) their response to the question I asked regarding coatings and their purpose in their applications highlighted 3 main factors:
Aiding gas flow
Controlling gas velocity and turbulence
Temperature control
Longevity of components
I did not mention that I would be posting their resonse online and their email response did state that all information held in their emails were strictly confidential, so I wont mention their name. They do however use Zircotec :smiley:
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In gas, there is already low intermolecular interaction or force, but with an increase in temperature, each molecule has a greater momentum, and thus more momentum can be lost/transferred in a collision (e.g. molecular collision with the containment).
Gas molecules travel in straight lines and bounce off each other and objects. The hotter the gas the faster they travel. But the faster they travel slows down how fast they travel in a certain direction as they are bouncing around more. This is shown in the link
http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html (http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html).
However for the purpose of cars we are talking very little difference in the actual performance impact on the engine, as the gas exit pressures are much higher. With the gas in the photo it was more to show a demonstration that hotter gas does travel slower.
Usually smaller exhausts help get rid of gases quicker using the scavenge effect. This only really applies to N/A engines as the turbine wheel on a turbo/supercharger interferes with the gas pulses. Once a pulse of gas is released into the exhaust it moves forward but there is a small gap left between each pulse. We are talking microns here. That gap is enough to act like a draft and help suck the next pulse along quicker. Its the same theory that racing cars use with 'drafting'.
Heat wrap or ceramic coating does help keep the intake temps down and thus keeps the incoming (intake) gas more dense. Its a trade off really. I am having my downpipe wrapped by BCS purely to keep the intake temps down.
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All this for a 2.0tfsi lol.
:indifferent: :stupid:
All this for a 2.0tfsi lol.
The engine the forum is based on....
Took the words right out of my mouth! :chicken:
Apparently no other engines exist apart from the 2.5TFSi. :chicken:
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In gas, there is already low intermolecular interaction or force, but with an increase in temperature, each molecule has a greater momentum, and thus more momentum can be lost/transferred in a collision (e.g. molecular collision with the containment).
Gas molecules travel in straight lines and bounce off each other and objects. The hotter the gas the faster they travel. But the faster they travel slows down how fast they travel in a certain direction as they are bouncing around more. This is shown in the link
http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html (http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html).
However for the purpose of cars we are talking very little difference in the actual performance impact on the engine, as the gas exit pressures are much higher. With the gas in the photo it was more to show a demonstration that hotter gas does travel slower.
Usually smaller exhausts help get rid of gases quicker using the scavenge effect. This only really applies to N/A engines as the turbine wheel on a turbo/supercharger interferes with the gas pulses. Once a pulse of gas is released into the exhaust it moves forward but there is a small gap left between each pulse. We are talking microns here. That gap is enough to act like a draft and help suck the next pulse along quicker. Its the same theory that racing cars use with 'drafting'.
Heat wrap or ceramic coating does help keep the intake temps down and thus keeps the incoming (intake) gas more dense. Its a trade off really. I am having my downpipe wrapped by BCS purely to keep the intake temps down.
I read that article myself this morning.
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All this for a 2.0tfsi lol.
:indifferent: :stupid:
All this for a 2.0tfsi lol.
The engine the forum is based on....
Took the words right out of my mouth! :chicken:
Apparently no other engines exist apart from the 2.5TFSi. :chicken:
:grin:
KNew you guys would either bite, or miss the point. Instead you have done both.
It's a roadcar, whilst the scientific discussion behind it has got interesting, I'm not sure why it's turned so heated. At 80 pounds I'd say go for it not gonna break the bank, but will you notice the benefit on a stock turbo 2.0tfsi, or even the much much superior 2.5tfsi (which incidentally runs alot hotter) I doubt it.
More important things in life, but carry on anyway.
Blouse and skirt geezers lol.
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In gas, there is already low intermolecular interaction or force, but with an increase in temperature, each molecule has a greater momentum, and thus more momentum can be lost/transferred in a collision (e.g. molecular collision with the containment).
Gas molecules travel in straight lines and bounce off each other and objects. The hotter the gas the faster they travel. But the faster they travel slows down how fast they travel in a certain direction as they are bouncing around more. This is shown in the link
http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html (http://www.physics.montana.edu/demonstrations/video/4_thermodynamics/demos/gasviscositychangewithtemperature.html).
However for the purpose of cars we are talking very little difference in the actual performance impact on the engine, as the gas exit pressures are much higher. With the gas in the photo it was more to show a demonstration that hotter gas does travel slower.
Usually smaller exhausts help get rid of gases quicker using the scavenge effect. This only really applies to N/A engines as the turbine wheel on a turbo/supercharger interferes with the gas pulses. Once a pulse of gas is released into the exhaust it moves forward but there is a small gap left between each pulse. We are talking microns here. That gap is enough to act like a draft and help suck the next pulse along quicker. Its the same theory that racing cars use with 'drafting'.
Heat wrap or ceramic coating does help keep the intake temps down and thus keeps the incoming (intake) gas more dense. Its a trade off really. I am having my downpipe wrapped by BCS purely to keep the intake temps down.
I read that article myself this morning.
[/quote
Hopefully it simplifies things for people with a visual demonstration and explanation about gas and the effects of heat.
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Aye mate get it done :happy2:.
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Heat wrap or ceramic coating does help keep the intake temps down and thus keeps the incoming (intake) gas more dense.
Its a trade off really. I am having my downpipe wrapped by BCS purely to keep the intake temps down.
That's the point and as I said before the only reason I thought of wrapping my DP as well.
:happy2:
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A couple of images showing with and without wrap on our downpipes...
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi66.photobucket.com%2Falbums%2Fh269%2Fnigeblueflame%2FVW%2FMotorSportCat.jpg&hash=e2ca257baba115e5a071f41ea6ea4037128779ba)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi66.photobucket.com%2Falbums%2Fh269%2Fnigeblueflame%2FVW%2F_DSC1490.jpg&hash=c40923ad6fa759e30f8e5958c8db0efd3529a4d2)
Cheers
Nige
:happy2:
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A couple of images showing with and without wrap on our downpipes...
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi66.photobucket.com%2Falbums%2Fh269%2Fnigeblueflame%2FVW%2FMotorSportCat.jpg&hash=e2ca257baba115e5a071f41ea6ea4037128779ba)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi66.photobucket.com%2Falbums%2Fh269%2Fnigeblueflame%2FVW%2F_DSC1490.jpg&hash=c40923ad6fa759e30f8e5958c8db0efd3529a4d2)
Cheers
Nige
:happy2:
Would that one be going on a certain Leon Cupra today? :)
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Yours is already on mate !! :jumpmove:
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Yours is already on mate !! :jumpmove:
You just made a mess in your pants Mike ? :signLOL: