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20th April 2014
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Know It All
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Join Date: Sep 2013
Location: Glasgow, KY
Posts: 179 Sportster/Buell Model: XL1200R Sportster/Buell Year: 2005
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I am so very pleased with my 1200C spark plug boot breather mods. Thank you, 1200C!
Sarah
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4th June 2015
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Biker
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Join Date: May 2015
Posts: 4 Sportster/Buell Model: XL 883C Sportster/Buell Year: 2007
Reputation: 10

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I put on a k&n and now I need to remap it,started reving way to high if I put it back to stock will it fix the problem or do I got remap it now no matter what?
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26th February 2017
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Biker
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Join Date: Jul 2015
Posts: 27 Sportster/Buell Model: XL883 with a 48 front end Sportster/Buell Year: 2008
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Quote:
Originally Posted by whittlebeast
Here is the math if anyone wants to know
from http://hondaswap.com/forced-inductio...ram-air-41316/
<<< snip >>>
RAM AIR
Operating Conditions
Temperature = Tair = 20C = 293K
Atm. pressure = Pair = 14.7PSIA
Cpair = 1005J/KgK
K = 1.4
The Cpair and K are constants for air.
Case 1 @ 100Kmh (62Mph) = 27.78m/s
Calculating temperature of the ram air
Tramair = ((Vcar^2/2gc)/cp) + Tair
Tramair = (((27.78m/s)^2/2(1kgm/Ns^2)/1005J/kg) + 293K
Tramair = 293.4K
The temperature increased by 0.4K or 0.4C.
Pram = Pair (Tram/Tair)^(k/(k-1))
Pram = 14.7PSIA (293.4K/293K)^(1.4/(1.4-1))
Pram = 14.75PSIA - 14.7PSIA
Pram = 0.05PSIG (gauge pressure)
So as you can see driving 100kmh will only have a gain of 0.05 psi! now lets try for 200kmh.
Case 2 @ 200Kmh (124Mph) = 55.5m/s
Calculating temperature of the ram air
Tramair = ((Vcar^2/2gc)/cp) + Tair
Tramair = (((55.5m/s)^2/2(1kgm/Ns^2)/1005J/kg) + 293K
Tramair = 294.5K
The temperature increased by 1.5K or 1.5C.
Pram = Pair (Tram/Tair)^(k/(k-1))
Pram = 14.7PSIA (294.5K/293K)^(1.4/(1.4-1))
Pram = 14.97PSIA - 14.7PSIA
Pram = 0.27PSIG (gauge pressure)
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I know this is an old post, but this analysis is incorrect. His conclusion is basically right, but that's just luck.
In words, Bernoulli's equation is merely a form of conservation of energy:
Pressure + kinetic energy + potential energy = constant.
After making a few assumptions, we can calculate the pressure rise of the air in the air filter housing. Admittedly, some of these assumptions might be dubious, so this will be a "best case scenario." To make the math easy, we'll assume that the air entering the ham can is brought to rest. Therefore, the gauge pressure rise of the air will be:
P = 1/2 * density * velocity^2
Air density = 1.225 kg/m^3
velocity = 30 m/s (~67 mph)
Therefore, P ~ 550 Pa = .0798 psig pressure increase
Remember, this would be a best case scenario: the air flow into the snorkel is very turbulent, is partially blocked by the stock front header, and the air obviously doesn't come to a complete stop inside the ham can. Therefore, the pressure boost from this "ram air" effect is likely much less. Even it were enough to matter, the largest air restriction in most people's intake tract is - you guessed it! - the throttle valve. Any increase in pressure upstream of the valve would be accompanied by a decrease in throttle usage to maintain a certain speed, but the total amount of air going into the engine would basically be the same. However, it would be interesting if someone ever installed a pressure tap on a ham can and took some measurements.
Rant over. I'm months away from earning a Ph D in mechanical engineering, and the linked analysis really bugged me. Ask yourself: do you think the air entering your intake warms up by nearly half a degree centigrade (roughly a full degree Fahrenheit) just because you're driving through it (the author's first step)??? If this were true, it would mean a carb works by changing the temperature of the air flowing through the throat, rather than changing its velocity (and therefore, pressure).
Also, this is not a jab at whittlebeast. He didn't do the calculations, he just linked them. I very much enjoy (and learn a lot from) reading his posts on tuning.
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26th February 2017
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Senior Chief Know It All
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Join Date: Aug 2016
Location: Space Coast
Posts: 817 Sportster/Buell Model: Sportster XL1200s Sportster/Buell Year: 1999
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Quote:
Originally Posted by msandli
I know this is an old post, but this analysis is incorrect. His conclusion is basically right, but that's just luck.
In words, Bernoulli's equation is merely a form of conservation of energy:
Pressure + kinetic energy + potential energy = constant.
After making a few assumptions, we can calculate the pressure rise of the air in the air filter housing. Admittedly, some of these assumptions might be dubious, so this will be a "best case scenario." To make the math easy, we'll assume that the air entering the ham can is brought to rest. Therefore, the gauge pressure rise of the air will be:
P = 1/2 * density * velocity^2
Air density = 1.225 kg/m^3
velocity = 30 m/s (~67 mph)
Therefore, P ~ 550 Pa = .0798 psig pressure increase
Remember, this would be a best case scenario: the air flow into the snorkel is very turbulent, is partially blocked by the stock front header, and the air obviously doesn't come to a complete stop inside the ham can. Therefore, the pressure boost from this "ram air" effect is likely much less. Even it were enough to matter, the largest air restriction in most people's intake tract is - you guessed it! - the throttle valve. Any increase in pressure upstream of the valve would be accompanied by a decrease in throttle usage to maintain a certain speed, but the total amount of air going into the engine would basically be the same. However, it would be interesting if someone ever installed a pressure tap on a ham can and took some measurements.
Rant over. I'm months away from earning a Ph D in mechanical engineering, and the linked analysis really bugged me. Ask yourself: do you think the air entering your intake warms up by nearly half a degree centigrade (roughly a full degree Fahrenheit) just because you're driving through it (the author's first step)??? If this were true, it would mean a carb works by changing the temperature of the air flowing through the throat, rather than changing its velocity (and therefore, pressure).
Also, this is not a jab at whittlebeast. He didn't do the calculations, he just linked them. I very much enjoy (and learn a lot from) reading his posts on tuning.
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Connie Kalitta, top fuel dragsters...5/6 psi at topend. 300+mph
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27th February 2017
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Biker
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Join Date: Jul 2015
Posts: 27 Sportster/Buell Model: XL883 with a 48 front end Sportster/Buell Year: 2008
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Those intakes don't open into a relatively cavernous air filter housing either. I bet a lot of computer time has been spent on those intakes to maximize every single 0.001 extra psi gain possible, and they definitely are NOT at part throttle. When 0.001 seconds matter, it makes a difference.
Those top fuel dragsters are really impressive pieces of machinery. I know this is off topic, but here are some really impressive pics of a dragster motor:
http://www.motoiq.com/MagazineArticl...orsepower.aspx
Again, the important thing is that there is not enough of a "ram air" effect on a stock sportster air intake to even worry about, and it really doesn't have any effect unless you're at WOT. It's probably greater than zero, but you'd have to have a pretty expensive gauge to measure it. You may as well buy fancy spark plug wires for better performance.
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27th February 2017
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Brass Nut
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Join Date: Feb 2005
Location: Western Weald
Posts: 47,230 Sportster/Buell Model: XL1200CB Sportster/Buell Year: 2015 Other Motorcycle Model: CRF250L Other Motorcycle Year: 2017
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Quote:
Originally Posted by msandli
You may as well buy fancy spark plug wires for better performance.
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True. Some people do actually do that though.
__________________
Folkie
Super Moderator
South East England Riders
There is nothing at the end of any road better than may be found beside it. Edward Thomas (1878 - 1917)
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27th February 2017
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Biker
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Join Date: Jul 2015
Posts: 27 Sportster/Buell Model: XL883 with a 48 front end Sportster/Buell Year: 2008
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At this point, I'm 99% convinced the best way to increase the performance of any bike is for the rider to buy some lessons at a track. I'm 0.9% convinced that it's to do some true wideband O2 dyno tuning. I'm 0.1% convinced that it's for the rider to lose some weight (just by observing who I generally see riding a Harley). On a mainly street driven vehicle of nearly any make, I'm convinced messing with the intake is the last thing someone should do. Again, the throttle blades are the biggest obstruction in a bike or car on the street (on the opposite end, the exhaust is always "wide open," hence why upgrading it first makes sense).
Anyways, enough off topic. I really like the look of ElectricCityIron's setup (post 193). It's very tempting to do that to mine, as it appears to create the most open stock filter housing possible, while still offering good protection from the rain (I ride as long as the roads aren't icy, a rare thing in Atlanta). I'm curious if this design increases inlet temps appreciably, as the stock intake at appears to deal with that fairly well.
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16th June 2019
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Flat Track Racer
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Join Date: Jan 2012
Location: West of Sydney.
Posts: 207 Sportster/Buell Model: 883 Sportster/Buell Year: 1995 Other Motorcycle Model: 101 Scout,68guzzi,250duc
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Hi folks,
I'm doing the breather mod 1200C posted on my 2005 883. a few questions;
1) what size long socket for the breather bolts? I put some callipers on it- seems 14mm is correct, but US bike should be 9/16 ? How big is the hole in the back of the bolt?
2) I've read most of this thread. I think I'll just buy a K&N filter with the stock airbox. It seems they flow better, not worried about filtration as l don't ride on dirt much.
My question is, has anyone actually tested the flow of the stock airbox? It has a hole twice the size of the carburettor and several holes in the bottom. Surely any restriction to airflow into the carb comes from the filter not the housing?
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16th June 2019
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Brass Nut
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Join Date: Feb 2005
Location: Western Weald
Posts: 47,230 Sportster/Buell Model: XL1200CB Sportster/Buell Year: 2015 Other Motorcycle Model: CRF250L Other Motorcycle Year: 2017
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Quote:
Originally Posted by jazzman
1) what size long socket for the breather bolts? I put some callipers on it- seems 14mm is correct, but US bike should be 9/16 ? How big is the hole in the back of the bolt?
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Yes: 9/16". I prefer a 6 point socket: the flats are so shallow it's easy to damage them with a 12 point.
Not sure exactly how big the hole in the back of the bolt is: 1.5mm? 1/16"? The hole in the front is 5/16".
Here's the stock breather bolt:
It's zinc passivated steel. Not sure what sort of steel. It may actually be zinc passivated cream cheese!
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16th June 2019
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Flat Track Racer
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Join Date: Jan 2012
Location: West of Sydney.
Posts: 207 Sportster/Buell Model: 883 Sportster/Buell Year: 1995 Other Motorcycle Model: 101 Scout,68guzzi,250duc
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Thanks for that Folkie!
I wanted to know the hole size as l was worried my new breather tubes may restrict air flow, but no worries there! I'm surprised it is so small.
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