SpeedKnight's "experiments"

[theholycow]

Originally Posted by SpeedKnight

Ok, I've been contemplating this lately. I'm a little confused on how reducing power increases FE and vice versa.

Well, just look at a vehicle model with two or more engines available. Almost always, the more powerful engine uses more fuel.

In my mind, more power means the engine holds a given speed with less throttle, which translates to less fuel consumed.

Less throttle does not necessarily mean less fuel consumed. The throttle doesn't consume fuel. All the throttle does is make it more difficult for the engine to get air. By using less throttle at a given RPM, you (through a long chain of explanations) reduce the amount of power you're making, which means you are using less fuel.

If you can keep your RPM low, more throttle will usually be more efficient. By keeping RPM low you prevent the engine from sucking in more air, and by keeping the throttle open you avoid wasting energy sucking that air past a closed throttle. Just imagine the effort you'd expend sucking air through a coffee stirrer vs. a jumbo straw.

I'm confused as to how the opposite could be true.

There are two ways to get more power:
1. Reduce waste. This will increase fuel economy.
2. Use more energy. This will decrease fuel economy.

Something like a Cold Air Intake allows you to pack more air, and therefore more fuel, into the cylinders to make more power. It's making more power but using more fuel.

[GasSavers_BEEF]

less throttle actually means that the cylinder has to suck the air in from a smaller opening as well (pumping losses) it isn't much but it all adds up.

the concept of the warm air intake is that warmer air has less oxygen as warmer air expands more. less oxygen takes less fuel to burn and in a way, reduces the displacement of the motor. it doesn't actually reduce the displacement but the charge of air and fuel are reduced with every cycle as if you were running a smaller displacement motor.

I am actually in the middle of an experiment on my car where I am running a WAI vs the stock setup. hang around for another month or so and I should have the results. it is a really long test. I hope to have close to 2500 miles on this test and some good data to present. it is data on my car (which is unlike yours) but hopefully it will show people the potential.

[SpeedKnight]

Originally Posted by theholycow

Well, just look at a vehicle model with two or more engines available. Almost always, the more powerful engine uses more fuel.

Fair enough.

Originally Posted by theholycow

Less throttle does not necessarily mean less fuel consumed. The throttle doesn't consume fuel. All the throttle does is make it more difficult for the engine to get air. By using less throttle at a given RPM, you (through a long chain of explanations) reduce the amount of power you're making, which means you are using less fuel.

Perhaps I'm not understanding EFI correctly. Does not the ECU determine how much fuel gets injected based on air intake conditions? I'm well aware there are different systems (sadly I can only think of mass airflow sensing systems right now). If the throttle is less open, air movement through the intake tract goes down. The MAF sensor tells the ECU to inject less fuel. Less fuel injected means less fuel used thus improved FE.
If I'm out to lunch on this, I more than appreciate being set straight.

Originally Posted by theholycow

Something like a Cold Air Intake allows you to pack more air, and therefore more fuel, into the cylinders to make more power. It's making more power but using more fuel.

Not to backpeddle in anyway, but assuming warmer intake charges improve my car's FE, perhaps I need to look into a way to easily and quickly switch between a WAI (for daily driving, read economy) and a CAI (for racing).
Or maybe I just need a third car. lol

Originally Posted by BEEF

less throttle actually means that the cylinder has to suck the air in from a smaller opening as well (pumping losses) it isn't much but it all adds up.

This makes sense to me, though I still question whether it makes a visible difference or not.

Originally Posted by BEEF

the concept of the warm air intake is that warmer air has less oxygen as warmer air expands more. less oxygen takes less fuel to burn and in a way, reduces the displacement of the motor. it doesn't actually reduce the displacement but the charge of air and fuel are reduced with every cycle as if you were running a smaller displacement motor.

I understand all of this, but I think the less oxygen dense air will also cause the engine to have to rev higher to maintain a given speed, thus consuming more fuel.

Originally Posted by BEEF

I am actually in the middle of an experiment on my car where I am running a WAI vs the stock setup. hang around for another month or so and I should have the results. it is a really long test. I hope to have close to 2500 miles on this test and some good data to present. it is data on my car (which is unlike yours) but hopefully it will show people the potential.

I look forward to seeing your results.

[R.I.D.E.]

An engine is most effecient when it develops it maximum effective compression, without fuel enrichment.

A typical 4 cylinder engine producing 20 hp at 1500 RPM uses only 50% more fuel to produce 50 hp. That means the last 30 hp cost half as much as the first 20.

WAI increases the effective compression by allowing a larger throttle opening for the same amount of power, because the air is less dense. Air density drops 25% from 32 to 200 degrees temperature.

WAI also enhances fuel atomization. At some point as you reduce the intake temperature fuel atomization will simply not happen. It may be 80 below zero, but the effect of heat is better atomization as a general rule.

Most fuel mixtures in modern engines are ultimately controlled by the oxygen sensor. Other sensors determine a fairly precise mixture, but the untimate arbiter of mixture is the oxygen sensor, which measures the amount of oxygen left in the exhaust after combustion.

Utilizing the knowledge of maximum effective compression is the key to pulse a glide. You must realize that maximum effective compression has nothing to do with wide open throttle. Maximum effective compression can occur a very small throttle openings when the load on the engine is great. That is why pulse and glide works best in the highest gear, especially at low RPM.

regards
gary

[GasSavers_BEEF]

interesting little side note on the WAI that I have observed during my testing so far. at idle (at stoplights) and with the motor warmed up, I have observed that the HP (given by my scangauge) is around 5 hp (usually around 5.3 or so). with the WAI in place, it will go down as far as 4.7 HP. that may not seem like much but it is less wasted energy during the commute. using this knowledge, I would assume that when the car is coasting, it would be using less fuel when using a WAI. that is until the DFCO kicks in. I am assuming the accuracy in my scangauge at least to show the difference between the warm air and stock when the HP is shown differently. just to test this, I can turn on my headlights during idle and see the HP jump by about 3 tenths to show the added drag on the alternator. (I love the scangauge)

also, the fuel injection systems that I know are the MAF (mass air flow) system that you describe and the MAP (manifold absolute pressure) system which I have. it also uses an IAT (incoming air temp) sensor along with the MAP sensor. I have heard that it doesn't work with the MAF sensor type but I don't have one so I can't say either way for sure.

my test is more to show data. I have been running with the WAI for close to a year now (maye over a year) but decided to do a long term test to show more credible data of it working. this is after a particular user (who should remain nameless) decided to debunk it and call all of us stupid. this gives us all more info about the entire thing. I am not proving that it works for everyone but that it works for me and similar cars to my own.

I am on the 4th tank of 6 and am running around 400 miles to a tank. that is a total of around 2400 miles but I always run slightly over so I think it will be closer to 2500 miles total. it will take me at least 2 months to run that far and it is during regular driving because it is pointless to waste the miles just to gather data (my opinion).

(if any of this data has been mentioned before, I didn't read the entire thread)

[theholycow]

Others have already covered this, but I'll put it in some different words...

Originally Posted by SpeedKnight

If the throttle is less open, air movement through the intake tract goes down. The MAF sensor tells the ECU to inject less fuel. Less fuel injected means less fuel used thus improved FE.

You forgot one part of the equation: Work produced. Fuel Economy is about fuel used combined with work done...never just about fuel used or work done. It's easy to get caught up in one or the other.

Not to backpeddle in anyway, but assuming warmer intake charges improve my car's FE, perhaps I need to look into a way to easily and quickly switch between a WAI (for daily driving, read economy) and a CAI (for racing).

If a WAI works for your car, it should be easy to switch. Just have both WAI and CAI installed, and move the intake pipe from one to the other.

I understand all of this, but I think the less oxygen dense air will also cause the engine to have to rev higher to maintain a given speed, thus consuming more fuel.

There you're considering work done but not fuel used.

The easiest way to look at it is to stop looking at fuel used or work done, and instead look for energy wasted/opportunities to waste less. When you look at a technique like Pulse & Glide, you might be concerned that you'll lose for spending the extra fuel on the pulse, or you might think the glide comes for free and will provide more benefit than it does. What you're really doing with P&G is producing work as efficiently as possible then not producing any work at all.

[GasSavers_BEEF]

speedknight,

in your defense, when I came to this site, I was very skeptical and didn't believe a lot of this stuff. I really and truely had to do it for myself.

that being said, I still didn't want to do anything to my car to damage it so I proceeded with the utmost caution. I also cared about the appearance of my car. most of my mods aren't that noticeable unless you know what you are looking for.

we can give you data all day but until you try it for yourself, you won't be satisfied (that was true in my case at least). I am not saying to go and hack up your vehicle even though you don't think something will work. I am more saying to evaluate a particular modification and if you feel that there is merit in it, try it out.

my WAI cost me around $10 from generic parts from autozone, advance, or similar. I can also reverse it with a piece of aluminum tape. that is how I am doing this experiment. I have two openings in my airbox. the factory one and the new one. I simply cover one with tape to run either warm or cool.

[SpeedKnight]

Originally Posted by theholycow

You forgot one part of the equation: Work produced. Fuel Economy is about fuel used combined with work done...never just about fuel used or work done. It's easy to get caught up in one or the other.

Gotcha. It's clearer to me now.
I'll just have to buck up and proev to myself that it all works. Nothing better than imperical (sp?) proof, is there? I think a WAI would be easy enough to set up, and would be easily reversible.

Originally Posted by theholycow

If a WAI works for your car, it should be easy to switch. Just have both WAI and CAI installed, and move the intake pipe from one to the other.

As in two seperate air boxes? That would work, except the VR6 engine uses up the entire engine bay of a GTi. I could do what BEEF mentioned and just cover over the cold air inlet to the box I have now... or more correctly, uncover when I am racing.

Thanks to everyone for the great discussion and for having the patience to have the discussion. Members of other types of forums are far less accomodating.

[GasSavers_BEEF]

I try to spread the knowledge, not corrupt it with my own agendas.

I have had similar experiences with other forums. there is one way, the only way and if you don't do it that way...you are an idiot.

I guess to them, I am the idiot.

also, I have a descent pic in my garage of my setup. you might also want some sort of temperature gauge for the intake. I use the scangauge but you are pre-obd2 so it won't work for you.

[theholycow]

In my VW there's a flex-hose that comes from the airbox (actually the engine cover) and goes to the grille. There it's open both to the engine bay and to the grille. If I block the grille it only pulls engine bay air (and the opening is still larger than the hose); if I block the engine bay side of the opening it would pull just cold air. I could disconnect the hose and bend it to somewhere else for a WAI, too.

Maybe your car is more like my GMC, where the airbox doesn't have a hose or snorkel of any kind coming off of it. However, for a CAI you'd add one (or replace the airbox), and then you could simply hook the hose to the CAI or the WAI.

The "hose" takes up most of the left 30% of this photo: