Let's talk WAI - Gas Savers

drifttec101 · 01-22-2010, 07:45 PM

Alright I've read all about WAI's on this forum and I really do believe that people are seeing gains from them, but I really want to know why. My theory is this:

I believe that everyone is seeing gains because the warm air intake temperature that the computer sees is prompting a leaner air-fuel ratio from the computer. Basically, the computer is just squirting less fuel into the engine. I don't think anyone will disagree with me on that, so what's my point here?

Why spend the money on dryer vent hoses when we could all just relocate the air intake sensor? The whole idea of the WAI is just to detune the car so it's making less power. What I'd like to do is seal off the hole that my AIT sensor is located in, and then just allow the sensor to read underhood temps, which reach into the 150 F range easily according to my scan gauge. Meanwhile, I'll continue to allow ambient air to come into my engine. Yeah, I realize this is just a trick, but like I said the whole idea is just to detune your engine.

Any thoughts? Also, I'm going to block the openings in the front bumper because they are huge, and useless for the most part.

As a side note, I would be really interested to see dyno results between WAI and CAI and stock, then compare the numbers to fuel consumption. I propose that the setup with the least amount of power will yield the best fuel consumption. Notice I said fuel consumption, not fuel efficiency. Efficiency is what you get out divided by what you put in. We are all looking to reduce fuel use, not make our cars run with maximum efficiency (like an F1 car haha).

BEEF · 01-22-2010, 09:21 PM

the A/F ratio on a car is fixed, you can't fool the computer (easily anyway). what you propose would be seen by the oxygen sensor as a lean condition and it would do either two things. it would A) compensate for the situation and spray the correct amount of fuel or B) ignore all sensors and go to an internal fuel curve similar to the open loop situation (my a/f in open loop is ~12 vs the 14.5 in closed). either situation is not good.

the reasons behind why the WAI intake work have been debated time and time again. I personally feel like the reasoning is because warm air is less dense. less dense air has less oxygen. less oxygen requires less gas. the a/f ratio is the same but you are inputing less oxygen so to keep the a/f ratio the same, you use less gas. in essence you are decreasing your displacement. several others talk about better mixing of the mixture. some also talk about giving you more play in the pedal. what used to take 1/2 inch of pedal may now take 1 inch of pedal so you can meter your throttle position better. it does cut off top end though.

as far as cost, mine ran me around $10 total and I have leftover material in case I want to change it around. the cost isn't really an issue.

be careful with the grill block. one good purchase may be a scangauge as well to monitor all this stuff a little closer. I personally watch my IAT and my WT (incoming air temp, water temp respectively)

**theholycow** · 01-23-2010, 05:37 AM

Theories vary, but I think it's pretty well agreed that the A/F ratio doesn't change, as the O2 sensor will read the lean condition and cause the computer to compensate. Also, most modern cars have a Mass Air Flow sensor that tells them how much air comes in, regardless of its density (it's not a Volume Air Flow sensor).

Here's my guess (taking cues from BEEF to jog my memory, it's been a while since a major WAI discussion):
Less dense air still has the same ratio of oxygen, and since you're still getting the same mass of air you'll still use the same amount of fuel. You save in reduced pumping losses when you're forced to open the throttle more. You save by recycling some of the heat energy that you were otherwise going to waste into the atmosphere; now, instead, that goes back into your engine. By using less dense air, you are effectively decreasing your displacement because you just can't get as much air (and therefore fuel) into the cylinder.

drifttec101, what kind of car do you drive? Some cars respond well to WAI, some don't. The same goes for grille blocking...my current vehicles are safe with 100% blocking, some people can't get away with blocking much at all.

drifttec101 · 01-23-2010, 07:38 AM

2004 Dodge Neon... You say that some cars respond to WAI, and some don't. That's interesting. The air fuel ratio shouldn't change much, it needs to stay within proper operating conditions for the car to run correctly... that's the whole point. The air intake temp. sensor will see the warmer air coming into the engine which is less dense, therefore less fuel is required for the proper air-fuel ratio. That's why the sensor is there.

If the computer didn't adjust its parameters according to air intake temperature, then there would be no reason for that sensor to exist. I agree that air always has the same ratio oxygen for whatever temperature, but for the same volume of air, warmer air will have fewer oxygen molecules (fewer nitrogen molecules also etc...). So to avoid a rich mixture (melting pistons), the computer will lessen the fuel flow.

So, at this point there is less oxygen, and less petrol mixing.... and we can go further on a tank of fuel. All we've done is reduce the power of our cars because we're burning less volume of air-fuel mixture. AKA we've detuned our cars.

This talk of decreasing your displacement is odd to me. Displacement is a defined volume of your engine, and will not change unless you machine your heads or change pistons etc... Let's not overcomplicate the WAI idea.

As far as $10 to make it is concerned, that's half a tank of fuel! I'd rather do it for free. What I'm going to try is this... remove the fenderwell air box and close the hole that is left there between the engine and the fender. Then take the stock underhood airbox top off. Now my filter will be exposed to underhood air. The only problem with that is the the crankcase valve line requires suction that will be reduced if I unseal the top of the underhood box. Will that be a problem?

BEEF · 01-23-2010, 10:50 AM

when I said in essence you are reducing your displacement, it is the same example as a turbo guy saying that in essence a turbo increases displacement. it doesn't actually change, it just uses less fuel as if it was a smaller displacement motor.

also, I thought rich wasn't a problem. I was under the impression that lean was where you have problems with melting pistons because of detonation. a true explosion and not a controlled burn. many turbo guys have problems because their stock fuel pumps and fuel injectors can't supply the extra need of the turbo (or the increased need of a higher boost turbo)

also, you can do it the way you are talking but you won't get the temps that the rest of us are seeing. the issue is that the temps under the hood really aren't that hot. you have to get to a heat source in order to really heat the intake air (most use the exhaust manifold). when I first did mine, I only saw around a 30 degree delta from outside temp. after putting a heat shield on it, I now see close to a 70 degree delta. (the delta changes as temp increases so there is more of a difference in the summer time).

something easy you can do is to take out your air box and drill a hole in the side going to your engine with a hole saw. reinstall the airbox in the car and cover the original opening with tape. that will accomplish what you want without compromising anything else in the system. I did this on my car but added a piece of flexible exhaust tubing that went to the header and a heat shield to direct the heated air into the intake.

also, as far as cost, depending on what you have laying around you really could do it for free. I just decided to purchase a few things and I still have a lot of material left. I could probably do 10 cars with the material that I have (other than the flexible tubing which was less than $5)

I do have a picture in my garage of my intake if interested.

good luck to you

drifttec101 · 01-23-2010, 11:54 AM

Right on, I had the lean rich piston burning thing backwards. I like the idea of the hole in the air box, I might give that a try when it stops raining one of these days.

Really, my whole goal is to detune the engine by messing with external parameters without spending money. The best way to go is with megasquirt but it's not worth $600 to save gas. I have a long drive from school to home, and if I can get 47 mpg I can do the drive on one tank of fuel. I don't think I can really get that much out of the car practically, but I'll give it a shot anyways.

BEEF · 01-23-2010, 02:40 PM

the expensive parts of my setup (if you want to call it expensive) were:

-the flexible exhaust tube
-the window flashing (you may be able to buy a smaller piece)
-and the metal tape (may be able to use duct tape depending on how much heat it can handle)

as you can see, depending on what you have laying around, you could make it a really cheap project. the tube can just be a metal tube. not sure if you can get away with pvc (do a lot of research before you even consider a plastic tube)

when I was a kid, my dad built a shop out back and we threw out loads of metal flashing. if I knew now what I knew then I would have snagged some.

the gains from the WAI are better the higher the temp. there have been debates also about what the optimum temp is. some go over 200f. I personally cap myself at 180 or so. highest I have seen on my setup is 179 and that is in the heat of the summer in the high 90s (don't really see over 100 around here)

unless you can monitor these temps, I would be very cautios with what you do. maybe the hole in the airbox might be best for you since you aren't monitoring the temps. fyi, the scangauge 2 will show you these temps and other stuff. www.scangauge.com

why don't you start a garage and that way you can log your mileage and keep a running talley of how you are doing.

welcome to the forum (a few posts late)

drifttec101 · 01-23-2010, 02:52 PM

Thanks for the welcome, I already have a scangauge. I've been using it for quite some time now. From the information I've logged my Neon is right inline with what the EPA site says.

**theholycow** · 01-23-2010, 02:55 PM

Quote:

Originally Posted by drifttec101

I agree that air always has the same ratio oxygen for whatever temperature, but for the same volume of air, warmer air will have fewer oxygen molecules (fewer nitrogen molecules also etc...).

The problem we're having here is semantics, not a lack of understanding. We know the same thing but we're saying it differently. You're talking volume, I'm talking mass.

On the no-budget WAI thing...Since you're going to be hacking it up anyway, you should be able to get dryer hose from someone who delivers or repairs dryers; clean the lint and hack away. Or, use something else salvaged (small HVAC duct, maybe).

BEEF · 01-23-2010, 03:45 PM

if you have a scangauge, you're good to go on this project.

the grill block is another good one too. you could start with cardboard or even coroplast. both of which are readily available and free.

maybe one project at a time would be better. 47 mpg out of a neon would be impressive but that may be a strech. ODK, maybe it is closer to your reach than you know. even if you only increase a few MPG, that is still money in your pocket.

I have a spread sheet at work that shows how much money I have saved. been a while since I played with it but I think it was around $500 or so when I hit the 1 year mark on this site.

interesting fun fact, the PT cruiser is built on the same frame as the neon. strange isn't it.

drifttec101 · 01-23-2010, 04:25 PM

The PT cruiser and the Neon share basically everything including engine blocks! Good job on saving the $$. Yeah 47 is a lot, it would be about a 33% increase over EPA. Plus, I can't really reduce weight because I have to carry supplies back and forth when I make the trip. At the very least monitoring my fuel consumption while driving the long distance keeps me awake.

**theholycow** · 01-23-2010, 04:56 PM

Reducing weight won't necessarily help anyway. There's a link in my sig about it. In short, most cars do not gain any FE from weight loss, especially if driven by a hypermiler.

33% over EPA is easy in my VW, and not impossible in my GMC (which has an automatic).

**Jay2TheRescue** · 01-23-2010, 06:23 PM

Quote:

Originally Posted by drifttec101

What I'm going to try is this... remove the fenderwell air box and close the hole that is left there between the engine and the fender. Then take the stock underhood airbox top off. Now my filter will be exposed to underhood air. The only problem with that is the the crankcase valve line requires suction that will be reduced if I unseal the top of the underhood box. Will that be a problem?

I did this on my 98 Sierra. Better than nothing, and the only expense was a few pieces of duct tape to cover the original intake. I've been meaning to fab up a better WAI, but I've been lazy.

Ford Man · 01-23-2010, 06:56 PM

I've seen people reroute the intake air tube from the fender well to a warmer area underneath the hood and use that as their WAI.

Project84 · 01-24-2010, 04:43 PM

I got 46mpg for a tank average after a HAI and interstate driving. The SG was reading like 47.7 or something before the off ramp, but then a little city driving pulled me down to 46 for the tank.

My car is supposed to do like 31 highway... so quite a jump. I was driving from Cleveland to Cincinnati which geographically is a slight downhill slope I think. I did mild drafting and kept the car in gear the whole time. No A/C and ambient temp was like 80-85 w/ AIT being 140's I think?

The detailed info is in my gaslog.

severach · 01-25-2010, 12:25 AM

My two theories are:

1) The increased temperature makes more of the fuel charge burn early in the stroke making a higher percentage of the energy produce forward motion.

2) The increased temperature shifts the Scangauge MPG higher even though there is no real increase.

Why move the IAT sensor? Run it with a variable resistor and set the temperature to anything you want. It won't take long to figure out what the IAT does.

BEEF · 01-25-2010, 06:07 AM

many of us use the scangauge as an indicator but use our gaslogs to verify a change (negative or positive) of a particular modification.

many things throw the scangauge off but pen and paper calculations are pretty accurate (especially over many tanks)

the IAT sensor reading doesn't mean much. it is part of a closed loop system where the 02 sensor adjusts the feedback. regardless of what the IAT is reading, the 02 will adjust the A/F ratio to a stoich mixture (or go to open loop where you are running rich)

**Jay2TheRescue** · 01-25-2010, 06:08 AM

I think the intake air temp sensor just helps the engine cope with varying temperatures more quickly. Adding a resistor will only produce a short term gain as the engine computer will start to get lean readings from the O2 sensor, and it will relearn how to operate with the skewed data.

**theholycow** · 01-25-2010, 08:05 AM

Quote:

Originally Posted by BEEF

many of us use the scangauge as an indicator but use our gaslogs to verify a change (negative or positive) of a particular modification.

many things throw the scangauge off but pen and paper calculations are pretty accurate (especially over many tanks)

The Scangauge is great for giving you live data and encouraging you, but it is NOT an dependable way to record your fuel economy.

Pen and paper calculations are not merely "pretty accurate" over many tanks; they are 100% accurate. After all, they are based on the actual fuel you used and the actual miles you drove. What could be more important than the fuel you used and the miles you drove?

BEEF · 01-25-2010, 08:34 AM

nothing is 100% accurate.

the gas pump only goes down so many significant digits as does the trip odometer. the degree of error is very, very small but there is still degree of error.

some portion of the gas is either not accounted for or fabricated and some mileage the same. even though it is 0.000X of a gallon and 0.0X of a mile

the assumption is that in averaging the numbers, they will even out but there is always some small fraction of a percentage that you are off from the actual.

sorry for overthinking this one

**Jay2TheRescue** · 01-25-2010, 09:14 AM

Yes, but the more fuel you purchase at one time (ie, wait till the tank is pretty empty) this margin of error gets smaller & smaller.

drifttec101 · 01-25-2010, 03:13 PM

There's an app for that actually haha. To anyone here who has an ipod or iphone look up Fram Gas Cubby. It just does the pen and paper thing for you.

Okay, here's another idea... Would restricting the air intake opening reduce fuel consumption? I think it will reduce throttle response, basically detuning the car. Less air = less fuel.

Dr. Jerryrigger · 01-25-2010, 03:35 PM

Quote:

Originally Posted by Jay2TheRescue

Yes, but the more fuel you purchase at one time (ie, wait till the tank is pretty empty) this margin of error gets smaller & smaller.

Very true

The largest margin of error is not the gas pumps decimal place, but how much you fill your tank. I try to top every tank off the same, but I know of no exact method of doing so. I do try to use the same pump, but this only helps a little. But if you think about 50 fill ups, this +- .02gal per fill will obviously balance out, as you only take fuel out one way (hopefully) and your tank doesn't change size.

Back to the WAI (i haven't been online for a wile, so i'm jumping back several posts here)
WAI shouldn't effect burn ratio at all, if you what to lean it out you should bust you O2 sensor reading by 30mV or so (not recommended if you don't have a EGR)
The intake temp matters very little to the computer, just a way of making sure everything is okay.

The benefits as i see them:
1)As stated several times, less air mass needs less fuel to burn in the way that will make your O2 sensor happy.
2)Theoretically (probably true, but may not give mensurable improvements) Hot air will hold fuel vapors better. Thereby your injectors work a little better. This is even more a factor when you think about injected fuel boiling before combustion, which must happen to some degree with a warm block, and high vacume.

tjts1 · 01-25-2010, 03:59 PM

WAI doesn't work.

**Jay2TheRescue** · 01-25-2010, 05:16 PM

On a modern fuel injected vehicle blocking off part of the air intake will only save gas as well as a block of wood screwed to the back of your accelerator pedal would.

drifttec101 · 01-25-2010, 06:35 PM

Care to expand on that Jay?

**theholycow** · 01-25-2010, 07:14 PM

Blocking your intake is doing exactly the same thing is closing the throttle. The only difference is that it's doing it further from the engine.

The throttle is already very good at its job of throttling.

What's more effective in many cars is to shift lower and open the throttle more, so the engine isn't wasting energy on the extra work required to get air past the closed throttle. You produce the same amount of work, accelerate the same, but you use a little less gas because you waste a little less energy.

**Jay2TheRescue** · 01-25-2010, 08:36 PM

Thanks HC, that's exactly why blocking off the throttle is like a block on the back of the pedal.

drifttec101 · 01-26-2010, 01:14 PM

I'm really leaning toward the warm air intake not really doing anything except cutting power to your engine. Just like restricting the air intake inlet will cut power... just like not opening the throttle as much. So really, instead of spending any money on modifications lets all just not accelerate as quickly.

If you want to make your engine truly more efficient then you should reduce rotating intertia within your drivetrain. Lightweight flywheel, gun drilled camshaft, smaller cluth, lightweight pistons etc. All of that is way too expensive to even consider if your goal is to save money on fuel cost.

Reducing friction with exotic ceramic coatins and what not would also help a bunch, but once again it's not practical. The factory engineers already optimized the desgin of aerodynamics with regaurds to functionality and performance, so any gains there are minimal. (Just put tape on your grille for long drives).

Really the only practical thing to do is not drive as much and drive slower when you do drive. Hypermiling is tough on equipment. Like not letting your car warm up on those cold winter mornings is AWFUL for your engine. Maybe you'll save a few bucks but if your engine fails then all that money you've saved goes into repair.

**Jay2TheRescue** · 01-26-2010, 01:27 PM

I agree that hypermiling can be hard on the vehicle. I suspect that my transmission problems in my 98 K1500 were due to me hypermiling in a 10 year old vehicle with over 150,000 miles. My Torque Converter started slipping, and that was after a few months of inducing DFCO by downshifting, shifting into Neural at lights, etc. I am now not as extreme in my efforts, balancing economy with wear & tear on the vehicle. The new torque converter + flush & fill the tranny with synthetic ATF cost me about $1,000. I still manage to do a percent or two over EPA estimates with most of my driving being short trip city.