Air Intake Restrictor with A-B test
 

Ok, so the thought here was that if the engine gets less air it will have to lower the amount of fuel it uses to maintain normal air/fuel ratio.
Less gas will be less power but possibly higher mpgs at cruising speed.

So here is my mass airflow sensor.
http://img638.imageshack.us/img638/9...sairsensor.jpg

My thinking is that all I would have to do is block up the air filter box to do the trick.
So out comes the box cutter and the coroplast and a hacking I go and come out with this abomination.

http://img225.imageshack.us/img225/5...restrictor.jpg

Sorry about the pic quality, it was 1am at a gas station. :\
So on the right side you see the top of the air intake is being blocked about 3/4 by a piece of coroplast.
Then on top of that is the big piece of coroplast with a small hole in the center about 1/3 the side of the air intake tube.
Then on top of that mess I put the air filter and then latch the box closed.
The box was still air tight and with the filter on tip I didn't have to worry about anything getting sucked into the engine.

I did my runs between 1 - 2 am so traffic was no issue, though I probably confused the hell out of the guy at the gas station I used to stop and record numbers at.
Temps were 45 - 47F and I did my best to hold 45 mph though my car doesn't have cruise control so it was a bit hard.

Had a 1.5 - 2 mile stretch of road with gentle ups and down.


Heading west with my restricted air intake my runs were 52.4, 53.0, 53.4 for an average of 52.93 mpg.

Heading west with the normal air intake my runs were 52.9, 52.9, 53.7, 53.3 for an average of 53.2 mpg.

Heading east with my restricted air intake my runs were 50.6, 51.7, 51.5, 52.5 for an average of 51.57 mpg.

Heading east with the normal air intake my runs were 52.7, 52.1, 53.3 for an average of 52.7 mpg.

Variance heading west was 0.9 mpg but the variance heading east was much larger at 1.55 mpg.

Heading west the standard air intake was 0.27 mpgs better then the restricted intake.
Heading east the standard air intake was 1.13 mpgs better then the restricted intake.

I know the sample size was very small that that it looks like the restricted air intake didn't work but going both directions the variance was larger then the difference of averages.

I plan on giving it a try again on a different road once I need to replace my air filter so I can mod the filter itself and then run a comparison between a clean filter and a dirty one modded to be more restrictive.

Thing I don't know is how long does it take for the cars CPU to modify the air/fuel ratio?
I did do a quick 5 minute drive between normal air intake and restrictive air intake but I'm not sure if that was enough for the CPU to actually change the mix.

That's one hell of a good job for no cruise (and no scangauge?)

My gut tells me that while the idea seem good, it's not going to work.
But let's get some of the smart guys in here.

My gut tells me to feed it.

But it always says that. If I listen closer it also tells me that the throttle plate takes care of ALL the engine's intake restriction needs... and it's fully adjustable too!

Does your car have a MAP or MAF sensor ?

I think Frank pretty much called it, the only effect your mod has is a different throttle position reading for the same total restriction.

no change in FE per the EPA 2x and IATn at least 1x
 

Props for posting results that didn't align with expectations. Science!

The car has a built in instant and average mpg display and while probably not as accurate as a scangauge it's good enough to easily detect a change of 3% or greater.

Not sure if I have a MAP or MAF. If it's important I can look it up.

I don't mind posting results that didn't work out. But right now I feel there isn't enough proof one way or the other. Even though I'm now expecting that it either won't make a difference or it will actually make things worse I feel obligated to do a second set of tests in the future.

Reason I tried this is due to a bad layout for setting up a warm air intake so I figured instead of getting less dense warmer air I would just reduce the amount of more dense cold air.

Idea sounded good at one in the morning ;P

If I had a nickel for every brilliant idea I had at 1 in the morning!

Man, you had me.......rightr before the last SENTENCE!!!!!!;)

It's all good.
Keep thinkin and keep tryin.

Those tests were on new throttle body or fuel injected gasoline powered cars. A clean air filter does improve mileage on diesels and cars with a carburetor.

Just wondered about a WAI to do the same, less dense air = less fuel, or so the theory goes at least. As unproven as air tabs, but maybe slightly more potential.

by reducing the size of the intake, do you not reduce horsepower?

reducing horsepower would be more beneficial at idle i would think. if you could test to see how your gph changes when sitting at a stop light with your restricted intake. this may not be worth anything at speed but may be beneficial at idle

not on a diesel and how many carberated systems remain
 

the new diesel common rail systems use intake restriction to improve EGR flow at cruise , so partially restricted air filters will have little to no detrimental effect on FE .

there are so few cars with carbs remaining that it does not matter ,ALL cars with carbs get poor FE compared to systems with fuel injection and engine management .

maximum horse power
 

Would you need something like these to aid the higher intake speed ?

http://www.e30m3project.com/e30m3per.../trumpets2.jpg

EDIT - or of course a single one.

To the contrary, what auto makers must do to meet EPA mandates for emissions is very detrimental to fuel economy. To claim otherwise is a very poor argument.
There Are lots of cars with carbs still. Go to any car parts store and they have brand new carbs for sale. It it is irrelevant that cars with carbs get worse fuel economy than cars with fuel injection. What is relevant is cars with carbs exist and get better fuel economy with a clean airfilter.

Someone has claimed that with a Ford Focus...removing the tube going to the front of the hood (fresh air) and allowing air to directly go into the bottom of the filter box resulted in increased mpg. Less restriction and warmer air.

I'll eventually try this...but won't like the noise when it's punched....the throttle that is.

It's true on my Cruze too. The airbox opens right to the engine bay without all the fresh air crap in the way. I can also hear the turbo spool with the excessive intake stuff removed, so it's an auditory reminder to get out of boost when possible. :turtle:

You're adding a very inefficient air restriction in front of another very inefficient (variable) air restriction.

Ideally, you'd want to have a variable venturi to meter airflow, but such things tend to be very expensive to create. There'd still be the issue of pumping losses due to intake vacuum formation, but the variable venturi would pretty much remove losses due to throttling.

Nice try, though.

I'm trying this with my Aygo at the moment by blocking the front nostrils which (theory tells me) feeds cold air to the intake. The intake is on the left of the box on top of the engine :

http://1.bp.blogspot.com/__kjL7rUis0...oyota+Aygo.jpg

EDIT - Apologies is some people got an email of nonsense, I got the image link wrong.

This has made no difference to the intake temps so far though because this is heated anyway by the fact it sits on top of the warm engine. A guy I link to in my thread measured temps with a CAI and found that made no difference either because of the heated manifold effect.

So I have a warm intake anyway :D

On some of my older cars they had a water heated inlet manifold too.

While I agree this is true for american made cars there are exceptions and the 70s is a bad time frame to pick because of the gas crisis there were a LOT of very FE cars in the 70s. Additionally carbs and TBI were not that different FE wise in the 80s, we really only saw improvements with injectors and tuning improvements heading in to the 90s. Carbs actually vaporize fuel and I believe overall required less maintenance, injectors are just cheaper and easier to tune now.

http://datsun1200.com/uploads/photos/1661.jpg

http://store.valueweb.com/vintagepap...alog/WW015.jpg
I know this is the 80s, but I think it's worth noting this is 52MPG from a carb while GM was busy throwing a TBI on everything and still getting worse FE.

Anyway I agree with you overall, just wanted to point out that carbs could be quite amazing and while cars produce less pollution per unit of exhaust volume, I do not believe overall we're getting that much less pollution per mile.

Actually if you want to really go back you should look at when they first removed lead from fuel, only in the past 15-20 years have we really reclaimed that lost HP and FE from having to severally lower our compression ratios and tune for a cat that wouldn't really be necessary with the correctly build engine or tune.

Yes, but those are the old-old unadjusted epa ratings. Knock 25% off that to compare with today's cars. Old 50 = (about) 38 new. We have a whole crop of new econocars that beat that with a 40 mpg rating.

I was just reading somewhere about the old EPA ratings... you can basically ignore the "highway" number and go by the other one.

carbs are not quite amazing at all
 

i suggested that cars of equal mass were to be compared
a 1600 lb crx with a carb does not compare to a 2500 lb citation or k car with TBi -
when comparing cars of equal mass the system with fuel injection AND engine management wins a contest of fuel economy -

early CIS systems without engine management were only marginally better than carbs , but still , they were measurably better .

carbs are poor 2nd place even with engine management ... such as it was .

Give me ceramic engine block and heads and no restriction on Nox emissions and I'll give you an engine that will spank the rest in FE with a carb.

Note Ceramic engine blocks won't need a cooling system.

Most people can. I've never gotten the "old" EPA city rating (19 MPG) with my Mustang. And since I found ecomodder.com, I only (occasionally) get less than the old "highway" rating on road trips. I must be doing something wrong. :)

EPA #s from the 70s and early 80s
 

i think FL was referring to the EPA claims from the 70s and early 80s - your car is a 2007 and it is not equipped with a carb

we must deal with what exists in the real world
 

i do not suppose such an engine actually exists nor will it ever find it's way to production because of durability issues -

and
in the real world , we do not want to use an engine that has no restriction on NOX production as NOX is very bad for humans , none the less , EGR can be used to limit NOX formation
on
any
engine

real , or imagined

You can download the raw test scores by year. The spreadsheet shows both the raw score and the adjusted window sticker rating.
Download Fuel Economy Data

Air flow, in my experience, can be a somewhat touchy subject. I higher flowing, less restrictive air filter *can* improve engine efficiency, power, and mileage, but it is on an application-by-application basis. My last car was very similar to my current car, but it had a smaller turbo. A local tuner performed extensive tests on Car A with a K&N panel filter and saw no improvements in any area over the stock air filter. When that tuner (and others) did the same test on Car B (with a larger turbo) and the car's power increased by 5-7 whp, the mpgs went up by a small (but noticeable) amount, and the AFR leaned out by about .5 (where the fuel economy came from, IIRC).

But again, this is an application-by-application, so your mileage may vary.

Now, in terms of restricting air flow, if you have an air flow sensor, your car is just going to compensate (but will be down on power). Even if you don't, you have a higher likelihood of "running rich," which can actually hurt your fuel economy and possibly damage your engine (rich knock).

In the early 80's they were working on it and actually built some test engines with at least one being tried in a car. Due to tightening NOx emissions standards all research was abandoned.

Popular Science - Google Books page 64

Popular Science - Google Books page 54

Popular Science - Google Books page 77

Quote:

and in the real world , we do not want to use an engine that has no restriction on NOX production as NOX is very bad for humans , none the less , EGR can be used to limit NOX formation on any engine real , or imagined

yes. I agree that we don't wont unlimited NOx.

However use of EGR does two things to control NOx. One it displaces excess Oxygen. Two it cools the combustion charge by requiring the fuel to heat more mass thus keeping combustion temps below that required to form NOx. One key advantage of a ceramic engine is you can have a much hotter combustion and therefore extract more power. EGR would negate this benefit. EGR also reduces the specific heat ratio of the combustion gases, thus limiting efficiency.

EGR is good , there is no excess 02 , EGR does NOT displace 02
 

first off
EGR is good -

EGR displaces
Air / Fuel mixture by reduce ing available volume in the combustion chamber by partially filling the combustion chamber with an INert gas , exhaust gas ,

so
EGR dilutes the air / fuel mixture , the entire air / fuel mixture , not just the 02 .
EGR does not make the mixture rich or lean , EGR dilutes the air/fuel mixture with an INert gas .

key word is "Dilute"

EGR reduces Combustion Pressure and by so doing reduces combustion temperature and by so doing reduces NOX formation

At Cruise , EGR does not function at WOT or idle on gasoline powered engines , but on Diesel engines - EGR does function at any load at the pleasure of the ECM
so

EGR does not reduce maximum engine performance measured in torque or horsepower .

EGR does increase efficiency by reducing
Suction Throttling loss
as Joe dumb driver just steps down more on the go pedal when EGR is active to get the same go as when EGR is Not active

EGR is good

However use of EGR does two things to control NOx. One it displaces excess Oxygen. Two it cools the combustion charge by requiring the fuel to heat more mass thus keeping combustion temps below that required to form NOx. One key advantage of a ceramic engine is you can have a much hotter combustion and therefore extract more power. EGR would negate this benefit. EGR also reduces the specific heat ratio of the combustion gases, thus limiting efficiency.

In a modern EFI engine, I really don't see how narrowing/restricting anything other than the individual runners to each cylinder will increase efficiency. Even then, that's very dependent on gearing, load, runner length, how well tuned the CSA (Cross Sectional Area) was to begin with, etc.

Anything on the outside of the throttle, and especially on the outside/before the MAF is just increasing pumping losses.

I think a lot of these theories are ones that are valid with old-tech single plenum inlines or high-duration and CSA V8s, etc. They don't translate to modern engines that are much better tuned for cruising speed operation and have far better mixture, emulsion, swirl, etc.

ECMs Intake air, and so on
 

Maybe I'm missing something here, but I don't see your logic leading to better fuel economy, all else held equal.:confused: I think you're taking the lesson of drag due to poorly designed engine area air flow and applying it to the engine air intake. Once cooling air is moving through the radiator, that's enough, it doesn't need more which ends up causing drag hitting a wall in the engine compartment. For the engine intake air, it's a different matter; you want no restrictions there, to avoid running fuel-rich on hills and under moderate acceleration.

The ECM adjusts mixture continuously, thousands of time per second in response to the O2 sensor; that's your "short term fuel trim". If for some reason the ECM sees that you're running rich or lean habitually, it will bias it's commands to the injector pulsewidth so as to achieve the desired 14.7:1 air fuel mix; that's your "long term fuel trim". The ECM stores familiar conditions and matches what it sees to what it remembers, and commands the corresponding mixture. Not thousands of times per second, but it can still respond fairly quickly by stepping to different remembered conditions. It can even learn a new condition in the time you're concerned with.

On the flat you can get by with very little throttle and maintain 45-65 mph. But consider a hill. You're going along flat and gradually slow down given the same throttle position. So to keep some speed, you add more throttle. The restrictions in your air intake can't deliver enough air to keep an economical mixture, so to deliver what you're asking for with your right foot, it runs fuel rich. You go a bit faster but pay a fuel penalty. With less restriction in the air intake, you achieve that speed with a better mixture, and better fuel economy.

So by restricting the air intake on purpose it will run fuel-rich more often when you throttle too much for the (less) air available. At best you end up doing the same thing you could achieve by being lighter on the throttle, and at worst, you're running fuel rich more often. Another change is that you no longer can accelerate as well, which for me would be a safety issue. I can stay off the gas in routine freeway driving, but when at 62-65 mph I slowly pass the vehicles cueing up in the right lane for an exit, I'd rather go to 68-70 mph for a few seconds to be able to get out of the way of those yahoos busting my tailgate than stall in the slow lane and have to accelerate again to get to 62.

My notion is that fuel economy is about driving fewer miles with less weight, keeping inertia (including with aeromods and coastdowns before traffic lights), being light on the throttle from a stop, and running a good air-fuel mix (by letting it breathe).

The irony here is that I was looking at ways to decrease the air drag to the intake, so that the mixture is less often running fuel-rich while towing, or on hills, or worse, both...

no , that is not how the systems work
 

So by restricting the air intake on purpose it will run fuel-rich more often when you throttle too much for the (less) air available. At best you end up doing the same thing you could achieve by being lighter on the throttle, and at worst, you're running fuel rich more often.

no , that is not how it works
if there is less air because of a restriction , the restriction becomes the throttle . the ECM will provide only the amount of fuel to match the amount of air that it counts . the ECM counts the air flow with either a calculation in speed density systems or more directly with the input from the MAF sensor .

the ECM only provides fuel to match the counted air
the system DOES NOT run rich because of intake restrictions .
intake restrictions do reduce maximum power output by reducing the maximum
calculated load value

intake restrictions have zero effect on fuel to air mixture
and
zero effect on fuel trim

the system can change mixture based on load depending on it's design.

And if you put a flat plate (like a throttle plate) right into a given airflow, that itself introduces an element of aerodynamic drag. Minimize that drag (like placing that flat plate parallel with the airflow instead of facing the airflow), and you increase efficiency.

That's in addition to, and separate from, the idea that engine efficiency will be improved from lowering the vacuum inside the intake manifold in order to minimize pumping losses.

From the first page.

That would be a "Mass Air Flow" sensor. A "Manifold Absolute Pressure" sensor would be after the throttle plate.

A MAF sensor works by calculating temperature of the air moving by wires and seeing the resistance change with that temperature. The ECU (thinks it) knows the size of the tube and therefore the volume of air. So if the MAF sees colder air it must have more flow.
A possible confusion caused by this mod is if the temperature of the air at this location is getting colder from expanding after your restrictor plate. Thus tricking the ECU into thinking there is more flow when there is actually less. Any time the ECU gets confused by readings it did not expect, it switches to preset "open loop" mode.

My long term fuel trim is running 0.78-2.34% rich, and I have been considering three suspects. One is restriction from my 25% reduction in my WAI intake tube diameter. This comment suggests that's not the issue. My other suspects are my O2 sensors (very old they are) or dirty injectors.

But I have a question still about the restriction: what if the ECU does not have MAF sensor data and can't "count" the air? Many of the cars listed here at EM, such as mine, only have the throttle position sensor, IAT sensor, and the MAP sensor. Doesn't that change your argument about how the ECU reacts? And does it mean restriction could force the car to run rich more often?