Air Intake Restrictor with A-B test

[PaleMelanesian]

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

[Ladogaboy]

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).

[ConnClark]

Originally Posted by mwebb

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

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

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.

[mwebb]

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.

[johnunit]

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.

[mcrafarm]

Maybe I'm missing something here, but I don't see your logic leading to better fuel economy, all else held equal. 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...

[mwebb]

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.

[t vago]

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.

[hamsterpower]

Originally Posted by Arragonis

Does your car have a MAP or MAF sensor ?

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.

[California98Civic]

Originally Posted by mwebb

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.

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?