Aftermarket Cold Air Intake pros & cons (long)
#1
01-27-2006, 11:56 AM
Aftermarket Cold Air Intake pros & cons (long)
{last revised 1-27-2006)
This post has more information rather than less.
It is designed to give you tools to spend money effectively.
If you have already made a purchase
there is a chance that reading this
may make you unhappy or emotional.
Don't blame the aftermarket air intake for not giving you a MPG increase.
There has been lots of careful scientific testing of all kinds of air intakes
and the result is that they neither increase/decrease MPG on gasoline engines.
But you can also reliably predict that if 100 customers buy an air intake that
DOES ABSOLUTELY NOTHING
and then these customers check their next tank to see if it improves MPG,
then 50 of these customers will see an improvement,
50 customers will see a decrease,
and ONLY if you could collect and average all 100 of the next tanks
of gasolines would you find a true average of zero.
If less restrictive air inlet system improved MPG,
after the last 20 yrs of C.A.F.E.
(Corporate Average Fuel Economy)
government MPG standards,
you would now see massive air intakes with 2 foot high by 4 foot wide
openings - even on the smallest 4 cyl compact.
Honda in a spirit of fierce pride, told its student engineers to do everything
possible on the Insight Hybrid to get the greatest possible MPG - they were
in a competition with Audi CEO and Porsche's grandson Ferdinand Piech
who was having his engineers build the A3
aluminum body/3 cyl diesel as the world's highest MPG car.
Honda used every known trick in the gasoline engineering book to get over 70
MPG to beat Audi's fuel economy of 3 liters per 100 km on diesel. Notice that
Honda was starting out about 20% behind because they were trying to make a
gasoline engine powered vehicle beat a diesel power vehicle for 'world
bragging rights.'
Go look at the air intake of a Honda Insight.
What do you see?
If you don't want to trust just the Honda,
go check out the Toyota Prius, Lexus 400H and Ford Escape Hybrid air intakes.
See a trend?
Check out the 2006 Corvette Z06 air intake for a 'ram air' design on a
vehicle that can reach 'only' 198 mph. You can bet several engineers
spent hours trying to tweak this inlet to get an extra 2 mph.
It would be easy to do a RELIABLE test of any two air intakes at the
dragstrip.
The way to do it would be to get two nearly identical trucks. They don't
have to be exactly identical but the closer the better.
The two trucks would line up against each other at least 4 times and
preferably 8 or more.
The first half of the runs one truck would have the air intake
and the other would have the stock air intake. After each pass
the drivers swap trucks. Then for the second half of the passes
the two trucks would swap intakes.
In making comparisons it is better to look at terminal speed rather than ET,
but subtracting 60 foot times from ET and comparing those is worthwhile too.
If the air intake really makes a average gain in terminal speed on both trucks
when installed that is pretty reasonable proof.
You might ask yourself:
Why doesn't each air intake maker hire an independent lab to do this and
verify that their intake is superior?
If you do 20 runs instead of 8,
and if the air intake makes a gain in terminal speed on 19 of those 20 runs,
then you are approaching the kind of proof scientists and MD's are supposed to
have before they 'publish' a fact in a magazine.
They wouldn't even have to hire a 'lab'.
Two of the following 'straight shooting' automotive writers (James Dulley,
Dan Neil, Steve Dulich, Rick Ehrenberg) have records that prove their
opinions can't be bought and could probably be paid a nominal
fee & travel expenses to face off against one another in a test.
A side benefit of the above test is that you could also settle bets as to
which of the two drivers was better, which can be fun. Killing two birds with
the same stone, so to speak.
A properly designed air intake can give modest increases of torque and
horsepower at wide open throttle - but sometimes this comes at the cost of
increased noise or filters that get clogged with bugs and dirt faster.
If you are willing to tolerate more noise, in nearly every case you can
build a better air intake than you can buy.
This post has a Part II about the cheapest way to test any air intake.
Don't want to do testing and want a shortcut toward an effective
air intake?
Well, in a nutshell just remount your stock air box so that it will suck air
out of the cavity behind the firewall and below the windshield where your air
vents presently get their air. This spot will give you cooler air, higher
pressure air, and it will not pickup bugs/road grit as badly as an inlet near
the front grill.
Why didn't your vehicle suck air from this spot in the first place?
Because with the interior cab air vent inlets there it allows A LOT of NOISE
to go into the vehicle's cabin.
As a matter of fact, most aftermarket air intakes
JUST MAKE EXTRA NOISE.
This extra noise convinces most owners
that they are making more horsepower - no kidding.
If you read enough auto postings you come to the conclusion that many young
owners are really after 'Excitement' not true vehicle performance you
can time with a stopwatch. The loud mufflers, the loud stereos, the
vibrations of hard shock absorbers, the unstable feeling while driving high
lifted suspensions - it is really more about excitement than performance. Note
many of these same vehicle owners are heavy players of video games.
In addition to the spot at the base of the windshield, at the front of the
radiator grille, and - surprise - a scoop at the top of the tire in the fender
interior are spots where high velocity air can be converted to high pressure.
Notice that I have NOT said to rely on dyno testing of air intakes...I have
said do road tests.
Why?
Because you can't really test an aftermarket air intake system on a dyno where
the vehicle is not moving and an electric fan is blowing air at the radiator.
This makes it SO EASY TO CHEAT that you can make any air intake show a HP
increase on the dyno graph. Don't trust any dyno graph that claims to show an
aftermarket air intake horsepower gain. Realistic airflow around the vehicle
is critical to seeing whether it really works.
Note that KN Filters lists how independent laboratories verify their air
flow claims and their performance claims, but there is not a link to where an
independent lab has verified any MPG improvement claim. That is because the
engineers at KN Filters know that any MPG gain or loss that a customer reports
is really just 'random variation.' But that does not keep KN from quotes such
as 'Customers report 1-2 better MPG.' Note how that is 'literally true' but
not 'scientifically valid.' Those are known as 'Weasel Words' in the
advertising trade.
http://www.knfilters.com/testmethod.htm
http://www.knfilters.com/powertesting.htm
Even with all the warnings about how easy it is to cheat or make mistakes in
dyno testing, this series of posts by Dodge 5.7 Hemi owners is worth reading.
Note how well the stock air inlet system worked.
http://www.lxforums.com/board/showthread.php?t=14140
For examples about how one lone automotive enthusiast went about (imperfectly)
doing some home air filter element testing similar to that described above, go
to this link:
http://www.bobistheoilguy.com/airfilter/airtest2.htm
If you have read this far and presently think that the author
'Hates Cold Air Intakes' or thinks not a single one provides any gain
you have misunderstood and are urged to reconsider.
The author would also like to state for the record that if the maker
of any aftermarket air intake would run the 'Two Truck Test'
described and publish the result - then this FAQ would name that
air intake and describe it as 'Better Tested than its Competitors'.
Part II
If you want a real answer you can trust about an air intake design,
then.......
Go down to Sears and buy one of the $30-70 multimeters with the temperature
probe. Sometimes they are on sale for $19
http://www.sears.com/sr/javasr/produ...26+Accessories
Later you can use this relatively cheap multimeter and its Type K thermocouple
to 'balance' your exhaust gas temperatures by swapping around the highest
flowing fuel injectors to the highest flowing intake ports....but that is
another story.
Then buy one of these $30 gauges that can measure low pressures and buy a
length of plastic tubing about 10 feet long to attach to it:
http://flw.com/olash2.htm#1490
Get the 30/30" pressure model.
If you don't want to spend this money you can also make a simple "U tube
manometer" with just a 20 foot length of clear plastic tubing and a yardstick:
Now drill small 1/16 th inch diameter holes in your stock air filter housing
and air inlet tubing,
like at:
1. at the begining of the inlet tube
2. in front of the air filter element
3. behind the air filter element
4. near the throttle body connection
Put a fresh new air filter element in your stock filter box. Go out on a road
with little traffic and measure the temperature and pressures at your small
hole test points of the stock system when the engine is at wide open throttle
through the 2000 to 6000 rpm range.
If you find between two points that the temperature goes up, then the air is
picking up heat in that length between the two points. (i predict you won't
find much heat pickup)
If you find that the pressures go down between two points then there is
restriction in that section, like across the filter element ( i predict you
will only find a small restriction across the paper element of the filter)
Now try moving the air inlet to the stock filter box from its stock location
to other places - like the grille top or bottom. Look for a place where the
pressure is highest and the temperature is lowest. (I predict you will find
that the cavity behind the firewall and below the windshield will be best -
this is also where your air vents pick up air to ventilate the truck's cabin)
Now, if you are a bit more adventurous try the following experiment:
With all the stock air system in place, put the truck in 2nd gear and measure
with a stop watch how many seconds it takes to accelerate from 3000 rpm to
6000 rpm with wide open throttle. Do this test 3 times and average the
result.
Now if you are a little more daring and have found a clean road with little
dust in the air, think about doing the following 2 tests (it is optional but
informative)
Do the same test from 3000 to 6000 rpm, but with the paper air filter removed
from the box, and the box closed back up. This is the 'no filter but cool air
pickup' test.
Then do the same test, but with the air intake system removed and the throttle
body opening sucking the hot air from underneath the hood. This is the 'no
filter hot air pickup test.'
{The above tests sound dangerous without an air filter, but I can tell you
that many highway patrol officers removed the air filters on their cars in the
1970s. I have personally seen people pour uncooked rice down carburetors to
scour out carbon deposits. Lack of an air filter over long periods will cause
the bore walls and piston rings to wear out much quicker, but a quick test has
little effect unless you are unlucky enough to get a large chunk of something
down the throttle. If you are worried you can cover the throttle opening with
some eighth inch hole window screen material or mesh stocking}
Now go order the aftermarket air inlet systems of your choice and repeat the
pressure, temperature and 3000-6000 rpm acceleration tests in 2nd gear. Send
back the systems that don't do as well as the best for a refund of your money.
Report your results to automotive forums.
You will be a hero to some,
the worst possible news to others selling junk.
This post has more information rather than less.
It is designed to give you tools to spend money effectively.
If you have already made a purchase
there is a chance that reading this
may make you unhappy or emotional.
Don't blame the aftermarket air intake for not giving you a MPG increase.
There has been lots of careful scientific testing of all kinds of air intakes
and the result is that they neither increase/decrease MPG on gasoline engines.
But you can also reliably predict that if 100 customers buy an air intake that
DOES ABSOLUTELY NOTHING
and then these customers check their next tank to see if it improves MPG,
then 50 of these customers will see an improvement,
50 customers will see a decrease,
and ONLY if you could collect and average all 100 of the next tanks
of gasolines would you find a true average of zero.
If less restrictive air inlet system improved MPG,
after the last 20 yrs of C.A.F.E.
(Corporate Average Fuel Economy)
government MPG standards,
you would now see massive air intakes with 2 foot high by 4 foot wide
openings - even on the smallest 4 cyl compact.
Honda in a spirit of fierce pride, told its student engineers to do everything
possible on the Insight Hybrid to get the greatest possible MPG - they were
in a competition with Audi CEO and Porsche's grandson Ferdinand Piech
who was having his engineers build the A3
aluminum body/3 cyl diesel as the world's highest MPG car.
Honda used every known trick in the gasoline engineering book to get over 70
MPG to beat Audi's fuel economy of 3 liters per 100 km on diesel. Notice that
Honda was starting out about 20% behind because they were trying to make a
gasoline engine powered vehicle beat a diesel power vehicle for 'world
bragging rights.'
Go look at the air intake of a Honda Insight.
What do you see?
If you don't want to trust just the Honda,
go check out the Toyota Prius, Lexus 400H and Ford Escape Hybrid air intakes.
See a trend?
Check out the 2006 Corvette Z06 air intake for a 'ram air' design on a
vehicle that can reach 'only' 198 mph. You can bet several engineers
spent hours trying to tweak this inlet to get an extra 2 mph.
It would be easy to do a RELIABLE test of any two air intakes at the
dragstrip.
The way to do it would be to get two nearly identical trucks. They don't
have to be exactly identical but the closer the better.
The two trucks would line up against each other at least 4 times and
preferably 8 or more.
The first half of the runs one truck would have the air intake
and the other would have the stock air intake. After each pass
the drivers swap trucks. Then for the second half of the passes
the two trucks would swap intakes.
In making comparisons it is better to look at terminal speed rather than ET,
but subtracting 60 foot times from ET and comparing those is worthwhile too.
If the air intake really makes a average gain in terminal speed on both trucks
when installed that is pretty reasonable proof.
You might ask yourself:
Why doesn't each air intake maker hire an independent lab to do this and
verify that their intake is superior?
If you do 20 runs instead of 8,
and if the air intake makes a gain in terminal speed on 19 of those 20 runs,
then you are approaching the kind of proof scientists and MD's are supposed to
have before they 'publish' a fact in a magazine.
They wouldn't even have to hire a 'lab'.
Two of the following 'straight shooting' automotive writers (James Dulley,
Dan Neil, Steve Dulich, Rick Ehrenberg) have records that prove their
opinions can't be bought and could probably be paid a nominal
fee & travel expenses to face off against one another in a test.
A side benefit of the above test is that you could also settle bets as to
which of the two drivers was better, which can be fun. Killing two birds with
the same stone, so to speak.
A properly designed air intake can give modest increases of torque and
horsepower at wide open throttle - but sometimes this comes at the cost of
increased noise or filters that get clogged with bugs and dirt faster.
If you are willing to tolerate more noise, in nearly every case you can
build a better air intake than you can buy.
This post has a Part II about the cheapest way to test any air intake.
Don't want to do testing and want a shortcut toward an effective
air intake?
Well, in a nutshell just remount your stock air box so that it will suck air
out of the cavity behind the firewall and below the windshield where your air
vents presently get their air. This spot will give you cooler air, higher
pressure air, and it will not pickup bugs/road grit as badly as an inlet near
the front grill.
Why didn't your vehicle suck air from this spot in the first place?
Because with the interior cab air vent inlets there it allows A LOT of NOISE
to go into the vehicle's cabin.
As a matter of fact, most aftermarket air intakes
JUST MAKE EXTRA NOISE.
This extra noise convinces most owners
that they are making more horsepower - no kidding.
If you read enough auto postings you come to the conclusion that many young
owners are really after 'Excitement' not true vehicle performance you
can time with a stopwatch. The loud mufflers, the loud stereos, the
vibrations of hard shock absorbers, the unstable feeling while driving high
lifted suspensions - it is really more about excitement than performance. Note
many of these same vehicle owners are heavy players of video games.
In addition to the spot at the base of the windshield, at the front of the
radiator grille, and - surprise - a scoop at the top of the tire in the fender
interior are spots where high velocity air can be converted to high pressure.
Notice that I have NOT said to rely on dyno testing of air intakes...I have
said do road tests.
Why?
Because you can't really test an aftermarket air intake system on a dyno where
the vehicle is not moving and an electric fan is blowing air at the radiator.
This makes it SO EASY TO CHEAT that you can make any air intake show a HP
increase on the dyno graph. Don't trust any dyno graph that claims to show an
aftermarket air intake horsepower gain. Realistic airflow around the vehicle
is critical to seeing whether it really works.
Note that KN Filters lists how independent laboratories verify their air
flow claims and their performance claims, but there is not a link to where an
independent lab has verified any MPG improvement claim. That is because the
engineers at KN Filters know that any MPG gain or loss that a customer reports
is really just 'random variation.' But that does not keep KN from quotes such
as 'Customers report 1-2 better MPG.' Note how that is 'literally true' but
not 'scientifically valid.' Those are known as 'Weasel Words' in the
advertising trade.
http://www.knfilters.com/testmethod.htm
http://www.knfilters.com/powertesting.htm
Even with all the warnings about how easy it is to cheat or make mistakes in
dyno testing, this series of posts by Dodge 5.7 Hemi owners is worth reading.
Note how well the stock air inlet system worked.
http://www.lxforums.com/board/showthread.php?t=14140
For examples about how one lone automotive enthusiast went about (imperfectly)
doing some home air filter element testing similar to that described above, go
to this link:
http://www.bobistheoilguy.com/airfilter/airtest2.htm
If you have read this far and presently think that the author
'Hates Cold Air Intakes' or thinks not a single one provides any gain
you have misunderstood and are urged to reconsider.
The author would also like to state for the record that if the maker
of any aftermarket air intake would run the 'Two Truck Test'
described and publish the result - then this FAQ would name that
air intake and describe it as 'Better Tested than its Competitors'.
Part II
If you want a real answer you can trust about an air intake design,
then.......
Go down to Sears and buy one of the $30-70 multimeters with the temperature
probe. Sometimes they are on sale for $19
http://www.sears.com/sr/javasr/produ...26+Accessories
Later you can use this relatively cheap multimeter and its Type K thermocouple
to 'balance' your exhaust gas temperatures by swapping around the highest
flowing fuel injectors to the highest flowing intake ports....but that is
another story.
Then buy one of these $30 gauges that can measure low pressures and buy a
length of plastic tubing about 10 feet long to attach to it:
http://flw.com/olash2.htm#1490
Get the 30/30" pressure model.
If you don't want to spend this money you can also make a simple "U tube
manometer" with just a 20 foot length of clear plastic tubing and a yardstick:
Now drill small 1/16 th inch diameter holes in your stock air filter housing
and air inlet tubing,
like at:
1. at the begining of the inlet tube
2. in front of the air filter element
3. behind the air filter element
4. near the throttle body connection
Put a fresh new air filter element in your stock filter box. Go out on a road
with little traffic and measure the temperature and pressures at your small
hole test points of the stock system when the engine is at wide open throttle
through the 2000 to 6000 rpm range.
If you find between two points that the temperature goes up, then the air is
picking up heat in that length between the two points. (i predict you won't
find much heat pickup)
If you find that the pressures go down between two points then there is
restriction in that section, like across the filter element ( i predict you
will only find a small restriction across the paper element of the filter)
Now try moving the air inlet to the stock filter box from its stock location
to other places - like the grille top or bottom. Look for a place where the
pressure is highest and the temperature is lowest. (I predict you will find
that the cavity behind the firewall and below the windshield will be best -
this is also where your air vents pick up air to ventilate the truck's cabin)
Now, if you are a bit more adventurous try the following experiment:
With all the stock air system in place, put the truck in 2nd gear and measure
with a stop watch how many seconds it takes to accelerate from 3000 rpm to
6000 rpm with wide open throttle. Do this test 3 times and average the
result.
Now if you are a little more daring and have found a clean road with little
dust in the air, think about doing the following 2 tests (it is optional but
informative)
Do the same test from 3000 to 6000 rpm, but with the paper air filter removed
from the box, and the box closed back up. This is the 'no filter but cool air
pickup' test.
Then do the same test, but with the air intake system removed and the throttle
body opening sucking the hot air from underneath the hood. This is the 'no
filter hot air pickup test.'
{The above tests sound dangerous without an air filter, but I can tell you
that many highway patrol officers removed the air filters on their cars in the
1970s. I have personally seen people pour uncooked rice down carburetors to
scour out carbon deposits. Lack of an air filter over long periods will cause
the bore walls and piston rings to wear out much quicker, but a quick test has
little effect unless you are unlucky enough to get a large chunk of something
down the throttle. If you are worried you can cover the throttle opening with
some eighth inch hole window screen material or mesh stocking}
Now go order the aftermarket air inlet systems of your choice and repeat the
pressure, temperature and 3000-6000 rpm acceleration tests in 2nd gear. Send
back the systems that don't do as well as the best for a refund of your money.
Report your results to automotive forums.
You will be a hero to some,
the worst possible news to others selling junk.
#3
01-31-2006, 03:34 PM
RE: Aftermarket Cold Air Intake pros & cons (long)
HankL, I know you've posted this info in numerous posts on this site and others. It is interesting reading. However, it does get annoying paging down through it to get to the next person's post. As a suggestion, close this thread so no one else can reply, then paste the link to this thread when you are replying to a post and you want to relay this information. That way a person can get the information if they want it, but others won't have to scroll through information that they have seen before.
You do an amazing amount of research and have a nice collection of data. However, when you reply to posts, think of it as an executive summary to the president of your company. Provide footnotes (links) to the data that helped you draw your conclusion, but do not include it in the main body of your reply.
You do an amazing amount of research and have a nice collection of data. However, when you reply to posts, think of it as an executive summary to the president of your company. Provide footnotes (links) to the data that helped you draw your conclusion, but do not include it in the main body of your reply.