Recumpence

Bill, You gotta run it out to 13 gallons. You would have broken 675 on this tank if you had. :) Matt

The tapering hatch that is truncated is called a Kammback. This is an ideal body design if you cannot taper down fully (like the Aptera). The first generation Insight took this to the extreme by narrowing the rear track to allow a further tapering that would be possible with a full width rear end. Matt

The worse tank I ever had was an expresswway trip out of state. I saw 38.6mpg (IIRC). Matt

I honestly think that the best I will be able to achieve with my current driving area is about 59mpg. So, Jus is destined to break 800 first. :) Matt

Ya, I can see it now......... Well, son, I remember getting huge mileage out of my car. It was awesome, I drove soooo slooowww..... :) Matt

Well, here is my best effort so far. Man, it is NOT easy hitting these numbers. Of course, the tank Jus is currently working on will completely BLOW this away......... I cannot wait to see his results on this tank. Matt

Yup, I mention this in my opening post. The design is a compromise which is what nearly all auto designs are. :) Matt

The pack is fan cooled through grilles inside the cargo area in the car, not under it. :) Matt

I can say in a hybrid, brake cooling is a non-issue. :) Matt

Hey Guys, This thread (as titled) is a discussion of the basics of aerodynamics and how they relate to our beloved Mighty-Max. My apologies to anyone reading this who is an engineer trying to read my jibberish. :) Disclaimer (you have to have a disclaimer, you know); I am not an aerodynamic engineer. The principals I am sharing with you were gleaned from years of RC helicopter experience, top speed RC car building (120mph is my highest speed attained), years of recumbent E-bike manufacturing, and research into hypermiling over the last couple years. Some of the terms I use may be incorrect or incorrectly applied. But, I will do my best to communicate my thoughts as clearly as possible. Here are some general principals. Later I will apply these to the C-Max and point out some highlights of the car's design and some "Problems" with the design that can be improved upon. Bear in mind, this car was not originally designed as an efficient hybrid. It was designed in Europe as a minivan/people mover with a standard gas engine or diesel, not a hybrid. So, Ford was not looking at absolute perfection in the aero department. This is what leads me to the "Problems" with the C-Max's aerodynamics. I will discuss the good points of the design as well. Here are the general principals; #1 Drag is your enemy. Generating airflow around a moving body is not necessarily a bad thing, but drag is very bad. #2 Smooth (laminar) airflow is ideal. Turbulence is not as good as laminar flow. But, a certain amount of turbulence can be a good thing (I will discuss this later). The Vortex is your enemy. It is far better to generate turbulence than vortices. This is an important principal I will discuss shortly. #3 The front of any body moving through any fliud (air is, essentially, a fluid) should be rounded, while the trailing edge should be sharp. This sharp trailing edge helps the laminar flow rejoin at the rear of the moving body. A rounded rear section creates vortices, while a sharp edged rear section creates turbulence. Remember, turbulence is not always a bad thing. #4 Laminar (smooth) airflow over a surface is not always the best. A smooth surface with air flowing over it generates minor vortices between the surface and the moving sheet of air. This vortex generation can be mitigated in many circumstances by generating a small amount of turbulence at the leading edge of the body. This added turbulence eliminates or reduces the vortices and allows the airflow to move more smoothly over the body surface. This is the "Golf Ball" affect. The small dimples in the golfball reduce the votices over the surface of the ball and increase the ball flight range due to the reduced drag (back spin also adds lift, but that is another story). ________________________________________________________________________________ Now, I will apply these principals to the C-Max and we can discuss ways to take advantage of the positives and discuss ways mitigate the negatives of the design. ________________________________________________________________________________ The front of any body moving through the air should be rounded, while the rear should be sharp. The nose of the C-Max is wonderfully rounded. However, the rear of the body is also somewhat rounded especially at the side edges. If you look at the tail-lights of the C-Max, there is a flared section molded into the lense. If you picture that flare continuing all the way down the side of the car. This would give a sharp edge for the air to cleanly separate from the body of the car. The Volt and the Prius have this edge down their sides. A body style that tapers to the rear, then is sharply cut off is generally referred to as a "Kammback" design. This name is derived from an aerodynamic engineer whos last name was Kamm, who did extensive research into this phenominon back in the 1930s. The C-Max has mostly rounded edges at the rear. These rounded edges encourage vortices (remember, vortices are a bad thing. They increase drag substancially). So, this is one major drawback to the C-Max body design. The nose of the C-Max is rounded. This is generally a good thing. There are a few issues with the design, however. First, there are 3 grille openings. This looks cool, but those openings increase drag by taking in air like a small parachute, rather than directing that air around the body of the car smoothly. That is why grille blocks tend to increase MPG. They reduce drag by redirecting air around the body, rather than through the engine compartment. Second, the nose of the car is 3 inches higher than the lowest portion of the belly pan just behind the front wheels. This forces air under the car and compresses it at the lowest area behind the front wheels. This compression increases the airspeed under the car and icnreases drag. Lowering the leading edge of the chin of the car that 3 inches and lowering the front pan to match will reduce the compression of air under the nose as well as drastically reduce the air speed under the car, thus reducing drag. Third, though the nose is overall rounded, it does have a number of areas that trap air and disrupt the otherwise smooth flow around the nose. These are the fog light wells (if equipped), and the previously mentioned grille openings. Ideally, the fog light wells should have lenses molded around them to direct the air around the body, rather than piling it up inside whose wells. The grilles should have partial blocks made as I already mentioned. However, those blocks would be best made to be flush with the edge of the grille openings and rounded to match the curvature of the nose of the car. This will help the air flow more smoothly around the body than if the grilles merely had blocking panels stuck in front of them. Another area of drag on the C-Max is the open section under the cargo area around the muffler. This acts as a loarg parachute. The rest of the car has a basic belly pan, but nothing under that rear section. This section should be covered (the best way to do this is another entire discussion). The wheelwells of the C-Max are well designed in a couple ways. First, they are close to the size of the tires. This improves airflow around the edges of the tires to rejoin the airflow to the sides of the car better than if the wheelwell to tire clearance were larger. Second, they are somewhat rounded. This gives the air a chance to sort of "Jump the gap" between the wheelwell edge and the wheel. One other area that could be improved is the wheels. Smooth wheel covers increase aerodynamics by reducing drag both from the air flowing past the wheels in forward motion as well as eliminating the affect of the rotating wheel acting as a fan. This fan action creates drag also. So, there are at least two areas of aerodynamic improvement available by adding smooth wheel covers. Now, bear in mind, this is just a very elementary 30,000 foot overview of these principals and how they relate to the C-Max. There is FAR more to say. But, this will give everyone a basic understanding of aerodynamics and, hopefully, increase our knowledge of how to obtain the highest possible mileage from our cars. :) Matt

what will happen is, I will top 750, then you will hit 800. :) Its all good. I love driving this car! Matt

Jus, I am pushing REALLY hard to get my MPG up to match yours. But, I am still short on this tank. Right now I am hovering at 58mpg exactly for 490 miles on this tank. For those who may not be aware of this, moving from my 58mpg on this tank to Jus' 58.6 is no easy task. That is 10% higher MPG. That is no small feat. Unless the weather spoils things, this should be a 750+ mile tank. I highly doubt I will match or best your 764, though........ I must say this; Competition is wonderful. It drives us to push harder to achieve better and better results. You know you are a MPG addict when you refuse to turn the AC on and would rather sweat and stick to the seat to gain that extra 1 or 2 mpg. :) At any rate, my driving still contains a lot of 55mph roads and it always will. When I stick to 35mph roads, I am way up at 62.5mpg consistantly. Hmm, maybe for one tank I should absolutely avoid all highways (if that is even possible with my work) just to see how high these numbers can get. I doubt I will beat Jus, though. He is the MAN on this MPG race. I predicted 760 miles on Jus' tank and he hit 764. I predict 780 miles on his next tank. Let's see if I am correct! Matt

800 requires 61.5mpg to achieve. That is really difficult to sustain day after day. For me, not all of my mileage is surface streets. I do have a bit of 65mph driving. I also carry 300+ pounds of equipment all the time. Then there is Illinois weather and horrible roads. Rain kills MPG due to the drag induced by the wetness of the roads and the heavy air. Also, the weekend errands kill my mpg. Like today, my MPG was 59.5. This tank has a 58.4mpg average so far. I bet that will be around 59mpg tank average by the weekend. But, the weekend driving will drop my mpg for this tank at least 1.5mpg or so. Then I will have to fight to get it back up when my work week begins again. These extremely high mpg numbers require a few things; #1 Low overall speed (like 40mph or under average) #2 Relatively flat roads #3 Consistency (you cannot have a single day with poor mileage and expect to hit radical numbers) Now, that being said, I predict an 800 mile tank will happen at some point. I would say Jus will be the man to do it. If his work route remains the same, he will definately be over his 764 on his next tank. I predict (if his route stays the same) he will see 59.5mpg for this next tank. That will put him near 780 miles. I predict I will be over 750 miles on my next tank. But, I highly doubt I will be able to catch Jus...... He has all planets in alignment right now........ Matt

That would still be 4%, not 2.5%. I do not mean to quibble, but that is quite a bit. How many gallons are pumped at that station per year? That is a HUGE amount of money stolen from us........ I will trust my car computer from now on. Matt

That is more than 2.5%. I used, at most, 13 gallons. But, the pump showed 14.1 gallons. Matt

Yup, that gas station has a bad pump, that is what is crazy............... Matt

Ahh, modesty, such a novel thing......... Man, you are going to totally crush me. I predict 760 miles on your tank. I will have a VERY hard time catching that. I will definately give it my all, though. Matt

Yup, me too, premium....... Speaking of gas, I just started a thread on my latest fillup today. Check it out. It is titled "Do NOT trust the gas pumps!" Matt

Hmm, what looks odd about this receipt for gas? Look closely. I am not talking about the difference between the car computer and the gas pump, I am talking about the fact that this car only holds a maximum of 13.5 gallons of gas........ Needless to say, I reported this station to the EPA for fraud........ Matt

This is my best tank yet. Jus is going to CRUSH me, though! Anyway, for a short time, I will be in the lead with this tank........ Congrats, Jus. Remember, I am gunnin for ya! ;) Matt

My best tank was 720 miles. I am on track for a 730 mile tank this time around. Jus has better MPG average on his current tank than mine, however. I am at 56.3mpg on this tank currently. :) Jus, you are going to be in the lead at the end of this tank. I feel it! Matt

Looks like you stand poised to break my record! You should be around (or very close to) 750 miles! Matt

I have found that the optimum speed is 35 mph or under. The car is still very efficient up to about 45mph. Above that, the efficiency begins to drop noticeably. I am a hyper-miler. That being said, much of my high numbers is related to the type of driving I do and the area I live in. Actually, I do not focus as much effort on hyper-miling than I could. My Max is my work car. I am on the phone much of the time I am driving. So, my attention is spent on driving and talking to the client I have on the phone (hands free, of course). So, when I cannot focus on P&G or other hyper-miling techniques, I just drive cautiously. I average around 56 or 57mpg most days I am driving cautiously. When I am dead focussed on Hyper-miling everywhere I go, that rises to a touch over 60mpg. Matt

I like the comment that the Prius is "Appliance like" while the C-Max is a real car. This I like. I had one Prius owner who commented that the doors on my Max are "So solid and heavy. It feels like it is alot more sturdy than my Prius." That sums it up. Now, that being said, I like the Prius. From a pure efficiency standpoint, Toyota got it right. The true Kamback design with sharp rear edges is more aero than the Max. It is also lighter. That being said, we come back to why people are buying the C-Max over the Prius. It is a fun car that is powerful (downright quick), handles wonderfully, is very solid, quiet and still gets very good mileage. I would say it this way; "The C-Max is bigger than the Prius liftback, far more powerful, handles light years better, has far better ergonomics, better interior, and is more solid while keeping mileage quite high. The price is also reasonable and ----- Wait for it ----- it is an American car!" :) Now, lets just hope our beloved Max proves itself reliable......... Matt

Totally awesome! I love it! Matt