K&N Performance Air Filter

[ptjones]

I agree with the above - maybe a less restrictive filter will yield a little more power...maybe...but along with that power will come more fuel burned.

What is important here is the ICE doesn't have to work as hard sucking air in so less gas is used.

 

Paul

Edited November 14, 2013 by ptjones

[ptjones]

   Old filter is in box and new is sitting on the box.

 

Well I did it, Changed The CMAX AIR FILTER. What a pain in you know what! It can be done, but not without patience and blood. There are sharp things down there in the ICE compartment. FORD instructions are marginal at best, they don't want you doing this. You need to unplug Mass air flow sensor not in instructions and wire strap I broke around PCV tube. I think you can get this at AutoZone, but don't see why you need it. Wear good gloves to prevent from giving blood. LOL

 

I tested all three filters on my very simple (KIS) test. Here is how it works. You take a box and tape it up good. Then make holes for filter(tight fit) and shop vacuum. Then I setup Dial Indicator on side of box to measure compression of box. Only took a few minutes to setup. Here are the results.

 

1. No filter .000"

2. K&N filter .0005"

3. Ford new filter .0025"

4. Ford 42K old filter .005

 

I'm thinking that the difference is significant and maybe 1 mile per gal. We will see. I don't think there has been very many CMAX's air filters changed. I think you can guess what filter I'm using. :)

 

Paul

Edited November 14, 2013 by ptjones

[marshtex2]

Driving to maximize fuel economy means minimize throttle opening which minimizes air flow needs.  High flow air filters will provide more air within a pressure drop range which will support higher throttle openings and more fuel flow which equals more power but less FE.  At modest throttle openings for best FE, OEM air filters likely are just fine and they've been researched and flow capabilities documented by the OEM.  Paying extra for a high flow air filter just to let air go through at rates needed for high FE?  Make sense?

 

Recalling my Mercedes Benz service manuals from the 1950's and '60's: Tap filter while blowing shop air through the filter in the reverse direction every 10,000 miles.  Doing this it seemed a filter would serve well forever when we are not needing a lot of wide open throttle, max power output (low FE).  Of course this works best with dry filters.

[ptjones]

Driving to maximize fuel economy means minimize throttle opening which minimizes air flow needs.  High flow air filters will provide more air within a pressure drop range which will support higher throttle openings and more fuel flow which equals more power but less FE.  At modest throttle openings for best FE, OEM air filters likely are just fine and they've been researched and flow capabilities documented by the OEM.  Paying extra for a high flow air filter just to let air go through at rates needed for high FE?  Make sense?

 

Recalling my Mercedes Benz service manuals from the 1950's and '60's: Tap filter while blowing shop air through the filter in the reverse direction every 10,000 miles.  Doing this it seemed a filter would serve well forever when we are not needing a lot of wide open throttle, max power output (low FE).  Of course this works best with dry filters.

I had a 2007 Focus that I sold a year ago. I installed a Steeda filter system and gained at least 3mpg and what a difference in power. The Ford system was very restrictive and designed to muffle intake noises or make engine quieter.  Hybrid is not like regular car because you use significant throttle for short periods and then go back to EV. You need nonrestrictive air filter for this application. I'm expecting around 1MPG improvement which is only 2%. If you can make several 2% improvements all of a sudden you gained 5MPG or 60 more miles on a tank. :) 

 

Paul   

[fbov]

As the autospeed article I linked to earlier showed, there can be significant gains available on the intake side. Hwever, the author found the air filter was not a source of pressure drop, and so no gains were available.

 

I will also note that he found the Japanese hybrids to have benchmark intake restrictions, as I expect will Ford. But, it never hurts to test...

 

As to the MB advice, it's not as crazy at it seems. Paper air filters improve their filtration with use. The 10K service removes most of the big stuff that's restricting air flow, but can't dislodge the fine particles that increase fine particle efficiency. Eventually, the paper fails, but until then, you take one step closer to a HEPA filter every time you clean it.

 

Have fun,

Frank

[ptjones]

As the autospeed article I linked to earlier showed, there can be significant gains available on the intake side. Hwever, the author found the air filter was not a source of pressure drop, and so no gains were available.

 

I will also note that he found the Japanese hybrids to have benchmark intake restrictions, as I expect will Ford. But, it never hurts to test...

 

As to the MB advice, it's not as crazy at it seems. Paper air filters improve their filtration with use. The 10K service removes most of the big stuff that's restricting air flow, but can't dislodge the fine particles that increase fine particle efficiency. Eventually, the paper fails, but until then, you take one step closer to a HEPA filter every time you clean it.

 

Have fun,

Frank

I tried the water test but It's not very sensitive. Got 3/8" for dirty filter, 1/4" for clean and would have got nothing for K&N. My test was a lot more sensitive. Paul

[fbov]

Actually, engine vacuum is one place where the water manometer works fairly well, as engine vacuum can reach 30 in/water. Low numbers are sign of overall good flow.

 

Conversely, are you quoting manometer measurements from your test box? in that case, the CFM of your vacuum matters. The engine's pulling about 32 cu ft per 1000 revolutions....

 

Have fun,

Frank

[ptjones]

Actually, engine vacuum is one place where the water manometer works fairly well, as engine vacuum can reach 30 in/water. Low numbers are sign of overall good flow.

 

Conversely, are you quoting manometer measurements from your test box? in that case, the CFM of your vacuum matters. The engine's pulling about 32 cu ft per 1000 revolutions....

 

Have fun,

Frank

The dial indicator test was very sensitive, but the two do correlate closely. Thinking about doing some tuff testing and adding chin spoiler.

 

Paul

[Recumpence]

The chin spoiler is something I am very interested in as well. Problem is, I would like to make a new totally flat belly pan from the new chin spoiler rearward. However, I do not want the dealer freaking out when I bring it in for oil changes. That being said, the solution seems to be to make the new pan easily removeable with the stock pan still above it. That way I can remove my simple flat pan when the car goes in for an oil change.

 

I have considered many designes for chin spoilers ranging from a simple flat panel running straight down to a nicely radiused edge like the stock spoiler has. As a general rule, to maximize drag, the leading edge of a moving object should be rounded (radiused) and the trailing edge should be sharp.

 

Matt

Edited November 17, 2013 by Recumpence

[fbov]

I'm waiting for Spring to do anything close to the ground... but that doesn't mean I haven't thought about it! From what I've read, the pressure gradients along the centerline are very telling, and Autospeed's vacuum methods will work well here, albeit not with water; you need fractions of an inch. I've got 2 Magnehelic gauges.

 

I look forward to see what you come up with!

Frank

[Alex Sams]

I haven't looked under my hood because I can't get my wife out of the car when I'm not working. We have opposite schedules. If anyone changes to a oil/cloth filter like the K&N- it's been my experience that the MAF needs to be cleaned regularly, and I would say weekly for a month until the excess oil stops getting collecting on the MAF. Excess oil reduces the amount of air sensed, and makes the engine run as rich as it can in most situations until the O2 catches up with it. It has always negatively affected fuel economy, but that was on Focus' (or Focis) which have HO2S but not WHO2S. I'm assuming the C-Max is wideband since that would be more fuel efficient. 

 

I recently tried some easy ICE FE trick, like the high flow filter, and it didn't work. I've always found that Lucas FI treatment gave me about 3 more MPG on average in all my vehicles. For this to be economical, I bought by the gallon, and a quart bottle for treatments because it was graduated. This brought the cost of a tank treatment down to about $1. I also found- but forgot- that their recommended dosage was too high. They recommend 1 oz per 2.5 gal. I found that my fuel economy dropped at that rate, but increased at 1oz per 5 gal. Now I remember why I quit messing with it, because the Focus has a 4 gallon reserve, and after 4 tanks or so I had to not treat a tank in order to maintain fuel economy. PITA. Now we own a hybrid..... 

 

I'll have to see how the K&N works as well. Hopefully before the spring comes so I'm not comparing oranges to apples. For now our first modification is side moldings. I may do it after that. We still have essentials- floor mats, and 2nd key to purchase. 

[ptjones]

I haven't looked under my hood because I can't get my wife out of the car when I'm not working. We have opposite schedules. If anyone changes to a oil/cloth filter like the K&N- it's been my experience that the MAF needs to be cleaned regularly, and I would say weekly for a month until the excess oil stops getting collecting on the MAF. Excess oil reduces the amount of air sensed, and makes the engine run as rich as it can in most situations until the O2 catches up with it. It has always negatively affected fuel economy, but that was on Focus' (or Focis) which have HO2S but not WHO2S. I'm assuming the C-Max is wideband since that would be more fuel efficient. 

 

I recently tried some easy ICE FE trick, like the high flow filter, and it didn't work. I've always found that Lucas FI treatment gave me about 3 more MPG on average in all my vehicles. For this to be economical, I bought by the gallon, and a quart bottle for treatments because it was graduated. This brought the cost of a tank treatment down to about $1. I also found- but forgot- that their recommended dosage was too high. They recommend 1 oz per 2.5 gal. I found that my fuel economy dropped at that rate, but increased at 1oz per 5 gal. Now I remember why I quit messing with it, because the Focus has a 4 gallon reserve, and after 4 tanks or so I had to not treat a tank in order to maintain fuel economy. PITA. Now we own a hybrid..... 

 

I'll have to see how the K&N works as well. Hopefully before the spring comes so I'm not comparing oranges to apples. For now our first modification is side moldings. I may do it after that. We still have essentials- floor mats, and 2nd key to purchase. 

I never cleaned my 2007 Focus MAF after installing Steeda air filter system. I usually got between 40-45mpg on the HWY and it is the only car I've owned that had no carbon deposits in the exhaust pipe after 60k miles and it was a five speed manual. I can't say I have seen any noticeable improvement in mpg's from K&N filter change and it was a bear to change. I will say that with temps in the 30-50*F range I'm getting almost 50mpg on the Smart Gauge with over 425mi on this tank. :)

 

Paul

[Alex Sams]

Well, we tend to only hear from people who had issues with fuel economy. Maybe your filter didn't have excess oil. I get 30 in my wagon, but that's mostly in-town driving. Highway is about 36 mpg. I was getting better than that until I changed the exhaust. I'll never do that again for fuel economy. Diesels see fuel economy benefit from less restrictive exhaust, but not gasoline engines! At least not until it's clogged up. There's a difference between 07 and 05's like the one I have- 07s have a second engine temp sensor on the thermostat, and have always gotten better averages than the 05. Thanks though- I wish I got 40 mpg in my wagon!

[Joseph B Howle]

unfortunately I wouldn't believe the hype when it come to these filters. Not only are they expensive, but that have to be cleaner regularly to be effective. Another piece to consider is that how a modern cars engine works with the computer monitoring everything. Basically, every car has this thing called a mass air sensor. What this sensor does is read the air volume and temperature coming into the engine. The computer uses the data gathered by the mass air sensor to control the fuel burn. it also reads from the oxygen sensor. In normal operation, as stated the computer regulates the fuel mixture based on the sensor reading. If to much air is coming, more fuel is spent, if excess air is in the exhaust, more fuel is burnt.

 

The K&N filters are supposed to allow more free air flow which they do. The problem is that in a modern engine, the computer compensates for the increased air flow by increasing the amount of fuel and it does this to prevent a lean condition. Hence making them ineffective at saving fuel. Some may argue that they do but what likely happens is that people install these to save gas and use a lighter accelerator foot along with it.

[ptjones]

unfortunately I wouldn't believe the hype when it come to these filters. Not only are they expensive, but that have to be cleaner regularly to be effective. Another piece to consider is that how a modern cars engine works with the computer monitoring everything. Basically, every car has this thing called a mass air sensor. What this sensor does is read the air volume and temperature coming into the engine. The computer uses the data gathered by the mass air sensor to control the fuel burn. it also reads from the oxygen sensor. In normal operation, as stated the computer regulates the fuel mixture based on the sensor reading. If to much air is coming, more fuel is spent, if excess air is in the exhaust, more fuel is burnt.

 

The K&N filters are supposed to allow more free air flow which they do. The problem is that in a modern engine, the computer compensates for the increased air flow by increasing the amount of fuel and it does this to prevent a lean condition. Hence making them ineffective at saving fuel. Some may argue that they do but what likely happens is that people install these to save gas and use a lighter accelerator foot along with it.

What you say is true, but you are missing one important fact that the ICE is an air pump. If you restrict the air flow it takes horse power(GAS/mpg) to over come the restriction. It would appear in the case of the CMAX the restriction is minor, but my test did show the K&N filter was the least restrictive. As I have mentioned before my 2007FOCUS/manual trans was a dramatic example of a very restrictive/noise suppressive air filtering system.  I went from 34mpg to 40-45mpg with Sneeda air intake filter system ScanGauge and GoodYear Gas Miser tires. :)

 

Paul

[Joseph B Howle]

Basically what I am saying is that in a computer controlled engine, the computer seeks to run at a programmed mixture based on air temp, barometric pressure, throttle position etc. The part that I think you are overlooking is that fuel is not injected into the engine at one set rate. It is constantly varying in rate a pressure due to the computers program and in essence, if you put more air into your motor, you are creating a lean fuel mixture condition which will cause the engine to run rough and over heat unless it counteracts by inject more fuel to get back to that correct fuel mixture.

 

Also, as stated, with all the (supposed) fuel saving products on the market. I personally believe the to be in the same realm as the so called miracle diets pills. The pills themselves really do nothing for but because your taking them, your subconsciously tries to be more active and eat better which is actually what's making you loose weights. With fuel saving products, I believe the same is true. Yeah, perhaps some may save you a gallon or two here and there but the cost of investing in them does not offset the savings if any. Think of it this way, (Hypothetically) one or two extra miles per gallon, would save you about  5- 7 cents per tank but if you weight that against a $100 dollar intake. How long would it take you to recoup just what you spent on the intake and remember, until you recouped the $100, you haven't saved 1 penny. Spending money, doesn't save it.

[ptjones]

Basically what I am saying is that in a computer controlled engine, the computer seeks to run at a programmed mixture based on air temp, barometric pressure, throttle position etc. The part that I think you are overlooking is that fuel is not injected into the engine at one set rate. It is constantly varying in rate a pressure due to the computers program and in essence, if you put more air into your motor, you are creating a lean fuel mixture condition which will cause the engine to run rough and over heat unless it counteracts by inject more fuel to get back to that correct fuel mixture.

 

Also, as stated, with all the (supposed) fuel saving products on the market. I personally believe the to be in the same realm as the so called miracle diets pills. The pills themselves really do nothing for but because your taking them, your subconsciously tries to be more active and eat better which is actually what's making you loose weights. With fuel saving products, I believe the same is true. Yeah, perhaps some may save you a gallon or two here and there but the cost of investing in them does not offset the savings if any. Think of it this way, (Hypothetically) one or two extra miles per gallon, would save you about  5- 7 cents per tank but if you weight that against a $100 dollar intake. How long would it take you to recoup just what you spent on the intake and remember, until you recouped the $100, you haven't saved 1 penny. Spending money, doesn't save it.

Using your example you should never replace your air filter because you will never recoup your investment. Unfortunately air filters are a maintenance requirement so you have a choice of what filter you can use. I went with the K&M filter because of the least restriction/better mpg's and it should last the lifetime of the CMAX, save money by not having to buy anymore filters. WIN,WIN situation. It's all about the MPG's for me. :happy feet:

 

CMAX is my hobby with the goal being able to get 75mpg and 1,000mi. on a tank of gas. I'm currently at about 67mpg and 935mi on a tank. With new aero improvements I'm working on I will be able to make my goal. :yahoo: :)

 

Paul

[Joseph B Howle]

The only effect a lease restrictive intake has is allows the engine to spin up quicker and that's all. The boasted benefit is from solely the fact that the car will get the desired speed easier. You can achieve the same simply using the empower feature on the left hand side of the dash. All you have to do is keep the bar blue and below the blue frame. You obviously drive and energy, me I have just the regular hybrid. In the area I live, its wide open between two mountain ranges and going places usually includes a 15 plus miles journey. Its in this case that I felt the energy was not effective because the time it take the battery to recharge. In my hybrid, I can stretch to 4 miles on battery alone and after the battery is depleted, it will charge again in another 4 - 5 miles giving me the benefit of split gas/electric operation. With the energy, the battery would run out on the way to work and I would not be able to use it again until after it had a full nights charge. I have used K&N filter before, especially on my Harley but what I found with using them was me having to change the intake manifold gaskets frequently because of the lean condition being caused when I got to highway speed and having a carb. I have also had them in other vehicles too but had similar results, no noticeable change and malfunctioning 02 sensors within 15k to 20k miles. I wont buy them anymore.

 

Something else to consider is vehicle weight, the energy weighs more because of the bigger battery. If your making aero dynamic improvements I am not sure the difference will be great but you can do it the other way and take out weight and achieve the same. remove the rear seats, only fill the tank to half full would be examples of weight savings. Adding the things for fuel savings again, will you recoup the cost would be the question ask yourself. Also, is attaching things to the body worth potential paint and sheet metal damage buy adhesives and drilling holes. All these things may sound good because of the MPG number you may be able to achieve but realistically, what does it really save in the end. Plus, if you ever had to sell the car, how does all that affect the resale value.

 

I went through all of this years ago with a car that I wanted more MPG and I went as far as to by one of those bubbler kits. It save me a little on fuel but after 2 years with it, I never got my investment back.

[Joseph B Howle]

oh if you want to stretch your mileage that far. Drop your driving speeds to 50 in a 55 and 59 is a 65. This is how I drive and I am achieving the printed MPG rating from ford without ANY change to my car.

[fbov]

Joe, we like to play with our cars. Members try things and report back what they find. Paul is one of the most successful in increasing mileage with his mods, and he hasn't rested on his achievements; he keeps trying new things.

 

The fuel consumption dependence on speed and temperature are well documented, so the question becomes: What can we do to move the temp- and speed-dependent fuel consumption curves? Paul's grill block is a nice example of a documented change with known collateral issues (mainly ICE temp rise, not a bad thing this time of year).

 

If you have experiences, please share. You may find the C-Max is a fun car to play with because Ford got a lot of things right, so small changes can yield measureable improvements. The cars also behave quite differently from non-hybrids, and differently than most hybrids, too. As scubadadmiami put it, (paraphrasing at best) it's an expert system, and once you learn to use the expert features, there's a lot you can play with.

 

Have fun,

Frank

 

PS I've used K&N, and they represent a tradeoff between filter pressure loss and filtering efficiency. Given the C-Max has very little pressure loss across the filter, and will spend very little time at high RPM, I can't see enough advantage to balance the risk. As Bob the Oil Guy put it:

"the stock OEM type filters perform very well in filtration and don't inhibit flow nearly as much as some think"

Edited January 22, 2014 by fbov

[Joseph B Howle]

Nicely put!!! I just hate when people boast money saving when they are truly non existent. However if they state the real reason for doing so which is basically so they can say I am hitting this mileage as bragging rights if you will. I can completely understand the motivation to want to push the car but when it comes to doing it for money saving, lets face it ford has already done that for us. The little gains you may get after trying some new things, come at a cost which more than offsets your menial savings. I went through a whole gambit of this stuff with a previous vehicle. I did aero dynamic mods, intake mods and even a water bubbler system. I track my fuel expenditures and mileage for a solid year prior to doing this stuff. Then the next year I made the changes and ran it all keeping track of everything in the same manner. The cost of the mods was $393.64. My fuel expenditures were only about $25 less then the previous years. I averaged 27k miles both years. To put it in perspective the if you subtract the fuel saving from the money saving mods. I was left with paying more than the previous year; which amounts to no savings.

 

 

Now, I don't believe in debunking anyone but what I am stating is tested fact and in reality if you want to save money without spending it, the best thing to do is lighten the vehicle. The cars weigh in at a hefty 3000 lbs plus so anything you can do to ease the load on the vehicle is key. Even if you block off the grill, the car still has to push through the same volume of air. Its the volume of air that is causing your vehicles drag. The only way to reduce this volume of air is to make the car smaller.. it's simple physics. What your left with is what can be done to ease the burden of this volume of air. Unfortunately, very few things can be done. Of the available options, you have lightening the car or streamlining it. Ford did an excellent job with the aero dynamics of this car, even with putting the radiator low in the chassis so the air basically blows right through and out the underside of the car. Adding a grill cover has side affects of which we both can agree are not so great. Plus with the type of engine used, ( Atkinson Cycle ), they are designed to maximize thermal efficiency which by blocking the radiator you away taking away from the thermal efficiency because the engine can't cool itself. About the only place the it suitable for aerodynamic change is the under carriage and if it is anything like my 2012 fiesta, the bottom is pretty flat already from the factory. The only thing I would change in any vehicle and that includes my C-Max is the under the car and in the rear. Car manufacturers overlook this area, except in sport cars and they put a plate that directs the air from under the car in continuous flow under the bumper. In all other cars, this plate does not exists and what you are left with is basically a massive cup shape (back side of the rear bumper) facing forward which acts like a big air damn.

Edited January 22, 2014 by Joseph B Howle

[ptjones]

The only effect a lease restrictive intake has is allows the engine to spin up quicker and that's all. The boasted benefit is from solely the fact that the car will get the desired speed easier. You can achieve the same simply using the empower feature on the left hand side of the dash. All you have to do is keep the bar blue and below the blue frame. You obviously drive and energy, me I have just the regular hybrid. In the area I live, its wide open between two mountain ranges and going places usually includes a 15 plus miles journey. Its in this case that I felt the energy was not effective because the time it take the battery to recharge. In my hybrid, I can stretch to 4 miles on battery alone and after the battery is depleted, it will charge again in another 4 - 5 miles giving me the benefit of split gas/electric operation. With the energy, the battery would run out on the way to work and I would not be able to use it again until after it had a full nights charge. I have used K&N filter before, especially on my Harley but what I found with using them was me having to change the intake manifold gaskets frequently because of the lean condition being caused when I got to highway speed and having a carb. I have also had them in other vehicles too but had similar results, no noticeable change and malfunctioning 02 sensors within 15k to 20k miles. I wont buy them anymore.

 

Something else to consider is vehicle weight, the energy weighs more because of the bigger battery. If your making aero dynamic improvements I am not sure the difference will be great but you can do it the other way and take out weight and achieve the same. remove the rear seats, only fill the tank to half full would be examples of weight savings. Adding the things for fuel savings again, will you recoup the cost would be the question ask yourself. Also, is attaching things to the body worth potential paint and sheet metal damage buy adhesives and drilling holes. All these things may sound good because of the MPG number you may be able to achieve but realistically, what does it really save in the end. Plus, if you ever had to sell the car, how does all that affect the resale value.

 

I went through all of this years ago with a car that I wanted more MPG and I went as far as to by one of those bubbler kits. It save me a little on fuel but after 2 years with it, I never got my investment back.

Just for the record I drive Hybrid, not Energi and I haven't done anything to damage my car, holes etc so at anytime I can go back to stock.  The Goal is to go faster and get great MPG's not slower.  I have been working at fuel mileage since I put Grill Covers, Front air dam, light weight fan, headers and dual-port intake manifold on 1974 24mpg Pinto wagon into a 30mpg car in 1974. There are bunch of us on this forum that look at our cars and think how can I make it better. :) 

 

Paul

[Joseph B Howle]

No knocking that all,, I'm just being the voice of reason here. As mention before, I did the same kinds of mods. Especially on my Harley 2004 XL-1200C. 69HP and 55 ft lbs of torque stock power with about 55mpg expected from a 4.5 gallon tank. All the following work I did myself and did increase mileage, it increased power and fuel consumption. I have the factory heads to achieve 18 to 1 compression, port and polished to a mirror finish the factory intake and carb and opened them up by a 16th of an inch ( Flow bench the set and noticed a 10% flow increase), Installed vance and hines short shot exhaust, screaming eagle heavy breather with K&N filter, screaming eagle ignition, stage one cams.

 

Dyno tested the bike at 105.6 HP with 121 Ft Lbs of torque on 92 octane fuel. The bike from a dead stop could achieve 80 mph in less than 11 car lengths and while only shifting to second gear. The fuel cost for the mods was cutting my range per tank to about 120 miles from over 250 from the 4.6 gallon tank.

 

 The fact of the matter is increased flow mean increased fuel burn. How are you calculating your mileage? There is a guy at work who drive a crappy old Honda civic that tells me all the time he gets better mileage than I do simply because he says I used this much, and I divide this by how many miles I went on that gas. But we drive the same distance everyday, and have the same size tank but I goes two weeks on a fill and he barely goes 1 week. When you do the math, it computes that he does, but in physical proof, my tank last longer than his. How is that possible?

[fbov]

Nicely put!!!...

 

Now, I don't believe in debunking anyone but what I am stating is tested fact and in reality if you want to save money without spending it, the best thing to do is lighten the vehicle. ...The only way to reduce this volume of air is to make the car smaller.. ...Plus with the type of engine used, ( Atkinson Cycle ), they are designed to maximize thermal efficiency which by blocking the radiator you away taking away ... The only thing I would change in any vehicle and that includes my C-Max is the under the car and in the rear. ...

Interesting story; you ever post on Ecomodder? Seems right up your alley... back then, at least. I certainly understand changing interests!

 

That said, you're thinking like a conventional ICE car, not a hybrid.

- cars make excess heat in engine and brakes that must be removed or bad things happen

- hybrid need to conserve heat in engine, due to low burn duty cycle, and have little heat in brakes due to regen energy dissipation.

 

Paul's done the temp rise tests and the C-Max has far better cooling than it needs during the summer, and it absolutely struggles to keep the heat working in winter (much less engine temp near optimum) without high ICE usage. Front end mods are limited, but reduced air infiltration is the one that universally reduces drag.

 

Your focus on weight is again an effective conventional car technique, as there is substantial loss in acceleration/braking. Once you see mass as a source of energy, a place to store it, your thinking changes. My mental model of a hybrid looks at energy storage and transfer, something like this:

(link)

 

You turn fuel into energy, then conserve it. The biggest loss is the engine itself; my 30% is high reflecting Atkinson design and optimized brake specific fuel consumption (BSFC), and assuming an engine temperature in the optimum range, you'll agree. From there, it's where you put it - charge the battery or accelerate the car - and what you do with it - climb hills or regenerate the battery.

 

While mass is an impediment to acceleration, once you're at speed, parasitic losses (RR and drag) dominate. Rolling resistance has a very weak speed dependence and there's little to do beyond tire brand/size changes. Aerodynamic drag has a second order dependence macroscopically, and a fourth order dependence locally. Therefore, you're seeing experiments in aerodynamics, as there is more payback to be had than normal.

 

And, yes, that means that a smaller cross section would help, but I like my side mirrors and I'm not about to lower the roofline.

 

Have fun,

Frank

Edited February 5, 2014 by fbov

[sjsquire]

Glad to know they're available.  I'm a big fan of K&N, been using them since the 70's.  Always found an increase in performance and gas mileage (usually about 10%).  Stopped once I started leasing.  I don't think you will see 10% on a modern car, but anything that makes it easier for an engine to function, will give a performance and mileage boost.  If I keep the Energi when it needs a new filter, I will surely put one in.

 

Very pleased with the Energi so far (2 months, 2,000 miles, 80 miles per gallon)

 

Solid German feel.  One of the best cars overall that I've owned (Fiat 128, BMW 2002tii, Mercedes 250, 2 Fords - Mystique (great) and Sable (garbage), and a lot of Passats and Golfs.