Aftermarket intake questions - Page 2

No. Why don't you first read the thread before replying to it.


Yes.  It is a simple similarity (or dimensional, if you want) argument.

Leon
--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

 rammm@REMOVE_THIS_TAGdommelen.net (Leon van Dommelen) wrote:


If you argue that admitting colder air would decrease flow efficiency
then you're also arguing that admitting warmer air would increase it.


Please feel free to quote anything you think I should have read.


Sorry. That's obfuscation, not explanation.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."

There is simply too much obfuscation so, I'm starting with a clean slate.
What I hear Leon saying is that at any given velocity of a car, lets say a
Miata for interest of this group, the power output from the engine is the
same, assuming all other external factors are the same (e.g., engine
modifications don't change the profile and thus the drag of the car).
Also, assuming similar fuel mixture in the combustion chamber (which is
controlled by the ECU to meet exhaust and performance criteria), the amount
of air entering through the intake system stays the same (e.g., same power,
same fuel to air ratio, and therefore same air volume).   Thus, the throttle
plate in the air intake will be further closed in a less restrictive air
intake system compared to stock.

Now for the difficult part.  I believe Leon is stating that at constant
power output, the engine with the less restrictive intake system will need
to work harder to pull in the air due to lower vacuum needed to pull the
same volume across the trottle plate.  Put another way, more fuel is needed
to the same net power output to the wheels since more power is used to pull
air into the enginer.  If this is the case, then I can understand Leon's
argument.  For maximum fuel efficiency, the intake system should be designed
to minimize pumping losses at the designed optimum speed.

What I don't understand, is why moving restriction from the intake system to
the throttle plate results in the engine having more pumping losses.  I
understand that the pressure loss across the throttle plate will increase,
but at the same time, the pressure loss across the rest of the system is
less.  Therefore, couldn't the vacuum down stream of the throttle plate to
be the same in both cases.  Why isn't it the other way around where the
restriction across the throttle plate actually results in less total
pressure drop than the restricted intake system?

Now, of course, this entire argument is only valid for the steady state case
(e.g., the car at constant velocity and the engine at constant power
output).  From my experience, even at what appears to be constant velocity
(e.g., driving on the highway at say 65 miles per hour), the engine output
varies to adjust for other factors (e.g., incline of the road, wind, passing
cars, etc.).  Average fuel consumption is thus the average overtime as the
engine output and thus fuel efficiency vary to maintain constant speed.

Gus

Yes, let's get the facts straight.  You NEED to get an aftermarket
intake system otherwise the manufacturers won't make money and the
world economy will collapse so get one right away, do your part to
avoid the end of civilization.

That should be clear and free of obfuscation, right?



--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

I couldn't agree with you more.  After all, that's what a free market
economy is all about.  The choice whether to spend hard earned cash on a
product is 100% up to the buyer.  And since we are all individuals with free
choice, our individual decisions may be different with neither being better
than another, just different.  The best we can do is make sure that facts
are available for people to make wise decisions.  The worst would be for
everyone to stop make decisions to wisely spend their money because the
facts were obfuscated.  That is when our economy and the world would
collapse.  So yes, go out and spend your hard earned cash today for the good
of the country and the world, but first do the research, learn the facts,
and spend our money wisely.

Gus

Oh, LORD NO!  If we were spending our money wisely nobody would have a
Miata at all!!!!  We'd all be driving vanilla 4 door sedans with wimpy
4cyl engines and avoiding all luxuries of all kinds.... if people knew
the facts nobody would buy 90% of the products available today so.....
let's just keep on buying ignorantly, the economy NEEDS unwise buyers
and people who don't understand the economy, that's what keeps the
lottery healthy, that's  what keeps the payday loan business afloat,
thats what maintains finance companies......

Geez, man, stop preaching intelligence, our economy is designed to run
w/o it and cannot survive educated consumers.




--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

You know, I think you are right.  I should have suggested maximizing
personal satisfaction and enjoyment not the use of wisdom.  Forgive my poor
choice of words.

Gus

Yes so far.


No, this misses the exact point.  It is the *amount of oxygen*, not the *volume*
that stays the same.  By design a Miata engine wants to take in 1.8 L air by
volume every cycle.   When it really needs only a fraction of that, during
highway cruise, say, the throttle keeps out the excessive air.   That means
that the engine fights the throttle, which costs power, hence fuel.  Now if the
intake air goes down say 30 C in temperature, the volume that the engine needs
becomes even smaller by about 10 percent.  So the throttle must let the engine
get even less volume, so they fight harder, so fuel consumption goes up.

Leon



--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

 rammm@REMOVE_THIS_TAGdommelen.net (Leon van Dommelen) wrote:


Because while resistance goes up, the speed of the flow goes down. And
power required to overcome the resistance to the flow is proportional to
the *square* of the speed of the flow, but only directly proportional to
the friction.

IOW, double the density of the air, you halve the required flow by
doubling the resistance. Thus you get an increase by a factor of two
from change in resistance, but a decrease by a factor of four from
change in flow, for an overall decrease in pumping losses by a factor of
two.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."

No.  This is an internal flow, not flow around a car.  Speed is irrelevant
here, it is total pressure that counts.  The total pressure loss must be
greater for the smaller flow volume.

And resistance is a meaningless term here also.  The throttle is not trying
to move through the air.  What counts is head loss, not force.  (Although
the head loss of course finally shows up as a reduction in pressure on
the top piston surfaces.)


Think of taking the Miata to Denver.  If it takes in the same number of
molecules of oxygen, in Denver the throttle might be wide open, and there
will be no real pumping losses.  In Florida it will be partly closed at exactly
the same produced power.  Pumping losses, here we come.

Then consider the fact that for *the air resistance of the car*, your argument
above *does* apply.  The air resistance in Denver will be much smaller too, and
you are probably going at a good clip on this highway if your throttle is wide
open in Denver.  We in Florida suffer.  :(

But then, we do not freeze to dead in winter as they do in most of the rest of
the country.  :)   But then we freeze to dead in Summer.  :(  But you can always
go outside to warm up some in your Miata.  :))

Leon
--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

 rammm@REMOVE_THIS_TAGdommelen.net (Leon van Dommelen) wrote:


Internal flow follows the same laws of fluid dynamics as external flow
does.


No, but the pistons are trying to draw air through the throttle. In
doing so, they must use power.


In Denver, the resistance will be less (not none, BTW), but the air must
be moving much faster to make up for the change in density. Power
expended goes up in proportion to resistance (which has fallen) and up
in proportion to the square of the velocity (which has risen).


--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."

 rammm@REMOVE_THIS_TAGdommelen.net (Leon van Dommelen) wrote:


if you're in a non-FI Miata, no. Your throttle will indeed be wide open,
but you'll be in third or fourth gear, engine gasping for breath.

We now resume the counting of pinhead-dancing angels, already in
progress...

Actually, when I was in Denver, I spend hours in endless traffic jams.
Fuel efficiency was most definitely *not* enhanced.  The rest of Colorado
was great, though.

Leon


--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

You are right, the important variable is mass of oxygen not volume of air.
I was being lazy in my analysis and basically assuming the conditions were
similar enough that the density didn't change signficantly.  I also
understand that the same mass of oxygen requires less volume of dense air.
How significant is the reduction in fuel efficiency with lower intake air
temperature?  Do cars get lower gas mileage in the winter in cooler
climates?

I still do not understand your point for the case when the temperature is
the same and the only change is a less restrictive intake leading to more
restriction across the throttle plate.  I do understand that fuel efficiency
is impacted by pumping loses, which a greater at low power when the throttle
is closed, and by friction loses which increase with engine speed.  I also
understand that more restriction across the intake system (e.g., closing the
throttle) results in more pumping loses.  What I don't understand is why it
matters where the restriction is in the intake system.  I'd think that what
would matter is the restriction across the entire intake system not just the
throttle.  What am I missing?

Gus

Common sense says that it should be very small.  30 degrees Centigrade
is about 50 or so Fahrenheit, and that changes the density, so the pumping
losses, by about the same percentage.  That limits it to just a few miles
per gallon, and then pumping loss is only one item for which fuel is used.

I was not saying it is something to worry about, just responding to
suggestions that common sense says an aftermarket intake would improve
fuel mileage.


I have no clue.  There must be lots of much more important variables.


I am somewhat mystified what you are asking here.   Did I not already note
in another post exactly the same that you are saying here?  Your final
sentence seems to be exactly what I said there.   If the intake air temperature
is the same, the effect of the intake should be the same, except for effects
that would take a fanatic to measure.

Leon


--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

Since when does closing a throttle increase fuel consumption? Cooler air
into an engine simply means combustion will be more complete because of the
higher amount of oxygen in the air per unit volume. It doesn't affect the
throttle at all. If the ambient O2 in the air is too high (virtually
impossible unless you are injecting it), the oxygen sensor in the exhaust
will sense any unburned oxygen in the exhaust gas and send this info to the
ECM to adjust timing/mixture, etc., but that is again uncombusted oxygen in
the exhaust, not incoming oxygen at the intake side. The MAS on the intake
attempts to measure air volume and temperature, but doesn't measure actual
oxygen content.


This statement must assume that the "explicit airflow restrictions"
(whatever they are) are not hindering the system's performance in the
control situation. But if airflow restrictions in the control setting are
choking the combustion air to the system causing it to underperform, then
allowing the air through by reducing the restrictions would allow the system
to perform better, would it not? This is the assumption the ram intake
manufacturers make - that the stock system has inherent restrictions that
keep the engine from performing at optimal levels.


So, as my stock air cleaner element becomes more clogged with dirt,
(reducing airflow - agreed?) I will need to reduce my throttle to keep
performance the same?? Put another way, the more restricted my airflow, the
better?!?



I agree that most auto manufacturers are going to tune their entire
drivetrains to achieve a particular goal in many categories, ie. fuel
economy, driveability, torque curve, horsepower, noise emissions,
hydrocarbon emissions, etc. However, that doesn't mean that you still can't
improve some parameters, albeit at the possible reduction of others.  My
initial question to the group was, who has tried an aftermarket intake, and
what was the result? My intention was to get actual information from people
who have actually tried these systems, not to spend a bunch of everyone's
time mentally masturbating in a virtual circle jerk.

No, it doesn't mean "combustion will be more complete".

It means there will be more combustion, as there is more air and thus
more oxygen; provided, of course, that the sensors can recognize this
fact (which they almost certainly can), and the injectors can provide
enough fuel.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."

Since pretty much the beginning of internal combustion engines.  As
long as it is at given power.


No.  On a modern engine, the ECU adjusts the fuel to the amount of
oxygen present.   So it would increase performance.  Hence the need
to reduce throttle if performance is to be the same.


Head losses due to the basic geometry, i.e. at constant throttle.

Head loss is the official word for the effect of flow restrictions.  (Which
are most of the time differences in pressure, rather than velocity, as you
seemed to think in an earlier post.)


Please read again all my original posts.  The performance was to be held
*constant*.  If you want to drive a given speed, performance (or to be precise,
engine horsepower output) is given, not something to be optimized.  Fuel
consumption is then to be optimized, and that is a very different matter.


In your original post you stated,

"Logic tells me that the intake would increase the fuel economy even more."
and I asked "What logic?"

If you check the subthread you are responding to, you will find that this is
the issue under discussion, not maximum horsepower that the engine can produce.


I did not make any personal remarks at your address.  Why do you do it at mine?

Leon
--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

Leon,


True. What you did was obfuscate a simple question by attempting to send the
discussion in several directions that do nothing to answer the inital
question(s). If you don't have an answer to the question(s) asked, why do
you hinder the process by confusing the isuue - answering simple questions
with divergent questions? I have plenty of my own reasons for not purchasing
a system to date;  I am simply trying to get real-life information/data from
owners who have actually tried the systems and have opinions on the results.


I was talking about myself starting a useless thread - why would YOU take
the comment personally?
--
Boreal
2001 LS 6 speed Silver/tan, Sport Suspension w/hard rear sway bar

You posted the above remark in a public newsgroup.  It is definitely wrong.
You get the facts.  Thanks are not necessary since I too post to a public
newsgroup.


I think it would not be obvious to everybody that you were addressing
this to yourself.   Note the reference to spending people's time.  That was
the thing I was doing, remember?   With good justification, and this is
a public newsgroup, so I can.  But anyway.

Leon
--
Leon van Dommelen :)  Bess, the Miata :)  Bozo, the Miata :)
rammm@dommelen.net             http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas