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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

What, no love for my tuft test? Or would you prefer an upright image? Picky, picky... It would be interesting to see if someone else sees what I did! I've also got some interesting salt pics... C-Max vs. Volt, when I get time. Frank

What autocrossing taught me was that it was more important to mount the optimum size tire for your wheels than it was to mount a wider tire on it's narrowest recommended rim. Running Yoko 001R in 185/70 and Yoko 008Rs in 205/60 on a 13x5.5" wheel, the 185s cornered better, but the 205's were smaller diameter, resulting in better acceleration. I used the 205's at track events, and the 185's for autocrossing. Now, I'll admit the 001 and 008 were distinctly different tires, but the trend applies - best cornering comes when wheel and tire are selected so they work well together. As to why P225/50-17s, one big source of rolling resistance is sidewall deflection. The shorter the contact patch, the less deflection occurs. If you look at speed-record tires, they're tall and thin, for less drag, but run very high pressures so the contact patch is still short. Passenger cars can't make that large a tradeoff, especially when they carry a substantial load, so we get wider tire, but still with a short contact patch. Have fun, Frank

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"

But the last thing I need is another display to look at instead of traffic! That's why I'm not looking for a smart phone holder, as I've seen some folks do, and hoping I can log the data and review offline. Then again, I drove my high-MPG rural route today with the middle grill blocked, but without cycling heat, and hit 30.0... I could barely get 1/3 of my mileage in EV, vs. 2/3 in warm weather. Highway nets me 33-38 at these temps. Have fun, Frank

Paul, I can't argue with your results, but must with your rationale. "Grill Covers would cause more air going over the top of car... creating more down force." But more air going over the top of the car means more lift... your thinking is backwards in this regard. (And please don't take this as a general comment.) Bernouilli's Law states that the faster air moves over a surface, the lower the pressure it exerts on that surface. - The flat surface on the bottom of an airfoil is a minimum-distance path. - The curved surface over the top of an airpoil is a longer distance, so... ... the airfoil exhibits lift, just like your car. That's one reason I wanted to read Hucho; empirical results trump any theoretical understanding (as the late Halton Arp steadfastly maintained), especially those of the Aristotelian variety. At the same time, one thing I'm sure Ford did was engineer some latitude into the car's aero stability, as we of the user community will do some crazy stuff and expect to end up none the worse for the experience. What I'm looking forward to is the possibility that the combination of an air dam, grill blocks, hood seals, fog light covers, rocker panel air dams, tire spoilers, smooth wheel covers and a Kamm-back (without a lift-modifying diffuser) will push the CP forward and increase rear lift enough that with all your tools behind the back seat, a strong sidewind would result in some excitement. There are posters on Ecomodder that have modified their cars into instability, or at least recognize that the car's not as safe as one might expect, and so don't let others drive it. If you want to go there, I won't object, but I want to be sure you know it beforehand. No surprises. HAve fun, Frank

Scan Gauge ordered over the weekend, and Torque for my new smart phone... about $20 total. Of course, this is from someone who hasn't remembered to involk Test Mode yet... not even once. HAve fun, Frank

comments below... Most of my performance tire experience also comes from autocrossing. By way of credentials, I have the complete runner-up set - 2nd, 3rd, and 4th - in H-Stock at Nationals in the 1980's to early 1990's. I ran a BMW 320iS, 1.8L 5-speed. 13x5.5" wheels and no suspenstion adjustability, so positive camber up front and negative camber, semi-trailing arm in back. I ran everything from 175/50 P7's to Yoko 008R/001R and the Goodrich autocrossers, leaving the pursuit about the time Goodrich came out with their asymetric carcasses, and dropped everyone's tire pressures 10-15 lb. That's where I see link #2 failing in the rationale side, even as he presents a functional process for optimizing pressures. Gotta run, Frank

I believe what makes sense. That's why I asked for rationale - what are you thinking? I'm more interested in that discussion than finding what's recommended, as all recommendations are the same... thanks to our legal system. Frank

Rapier, I'd like to hear your logic, as there's a strong argument that a narrower contact patch improves braking. Pascal's Law says the contact area is equal, so a narrower contact patch must also be longer, which favors braking. And same for you, dc. How does higher tire pressure hurt traction? What's your logic, as there's again a strong argument to the contrary. Pascal's Law says that the higher PSI has a smaller contact patch, but it's carrying the same load, so the contact pressure is also increased. This gives the tread better bite into the road surface, so the net tractive force available is the same. Where you really see this is in winter driving, as modern snow tires need contact pressure to distort the tread blocks, raising edges within the tread block. Now, reducing tire section will reduce drag, and changing tire diameter will change effective gearing, but the available effect is small unless there's a lot of room for really big tires. Plus, you now need to apply correction factors, as your mileage will be a wash unless you calculate actual miles driven. But then, the only way to improve an optimized system is with a buch of little improvements that add up. HAve fun, Frank

http://ecomodder.com/forum/fuel-economy-mpg-modifications.php#22 Second to roof racks on ecomodder's list of things to remove if you want to use less gas. Frank

It's all in Center of Pressure (CP), where all aero forces act, relative to Center of Mass (CM). As long as the CP is behind the CM, aerodynamic forces will tend to turn the car into the wind - align CP directly behind the CM. Since the car's motion is responsible for the majority of the "wind" the driver is comfortable when the car steers into it. However, the CP moves forward as the car speeds up. When it gets ahead of the CM, the effect of aero forces no longer turns the car into the wind, but rather, turns the car away from the wind. Again, the wind is the direction of travel, so turning away from the wind is usually steering for the guardrail, or the trees beyond. Put the feathers on the front of an arrow and see how well it flies... that's what we're doing when we modify airflow at the front of the car. Like I said, it's not as simple as reducing drag. Have fun, Frank

Neat Site! Thanks!!

Too late for your C-Max. RSC (roll stability control) and traction control already apply the brakes without operator input. Frank

I can't imaginge what you must have seen!!! Glad to have your experience on the forum. As to fat feet, I once bent the brake pedal arm on an old Volvo when it caught on the sole of my boot. Bent it up, as I was getting out of the car... not your normal foot-hooked-on-pedal, I admit! Frank

I suspect that you may balance one with the other... and I'm on the airdam/grill block bandwagon, just working slowly to understand the elements of a change. Frank

Perhaps you can appreicate that there is a huge difference between hitting the wrong pedal, and hitting no pedal. "...I took my foot off the accelerator (emphasis added), but the C-Max kept accelerating. I applied the brakes - car still kept accelerating." Audi's problem was a pedal arrangement that differed from other luxury cars of the day. People really were pressing the wrong pedal by mistake, because it was in about the same place as the brake pedal in their old caddy or town car. FWD was new at the time, and required different pedal and firewall layout for packaging reasons. But who in their right mind is going to tell a grieving mother that she just killed her child! Here, LW was not making any input, and then applies the brakes which fail. Are you saying LW is mistaken in recalling that he lifted his foot, and was really flooring it the whole time? I've had the car apply the brakes when my feet were not touching the pedals, and I am absolutely certain of that fact, because I was moving my foot from the brakes to the gas, and the brakes were applied when I was mid-transfer. This car is very sophisticated, very complex, and with a large number of new and (for the great unwashed public) untested safety features that may or may not reduce driver risk. Everything described here is plausible, while in the Audi, it was physically impossible without pedal error. Granted, it's possible to accelerate without using pedals (cruise) but that would be malfunctioning if it didn't drop out when you hit the brakes. And remember, brakes always win. Self-acceleration accompanied by brake failure is a potent problem. I say investigate and fix, rather than hide the danger so your car's worth more. Have fun, Frank

First off, Mike, you are the man; thanks for the spoiler detail as that had to be dity work! I had Hucho's Aerodynamics of Road Vehicle on my Christmas list, and Santa was good to me...The two lessons I've gleaned after paging through the whole thing, and reading the first few chapters: Aerodymanic optimization involves a lot more than drag reduction, as drag has benefits that are critical to car design. Minimum drag cars are undrivable, and DIY drag reduciton can be dangerous. Equivalent drag coefficient for cars can be achieved by starting with the right shape (like the C-Max) or by optimizing the details of a less intuitive, albeit more aesthetic shape. From this perspective, Ford is doing detail optimization in 2014. - The rear window bumps look like an attempt to reduce energy transferred to the trailing vortices coming off the roof. - the front and rear wheel spoilers are a common way of reducing wheel drag - we haven't seen the hood mods, but there's a lot of room for improvement, so let's assume they did. You'll recall that tuft testing showed a very sharp break at the window edge - air flow on the glass was nearly perpendicular to the high-speed flow coming off the C-pillar. Rear window mods should serve to move that break farther back, reducing the area of the back window that's experiencing low pressure. It may also reduce the energy lost to the trailing vortices coming off the roofline. Both reduce drag without upsetting stability (lift and center of pressure substantiall unchanged) The tire spoilers were already there, and I have to wonder why they didn't integrate the additions; they really look tacked-on. But, moving tires are one of the big sources of drag, and if you part the air in from of them, they have less. Again, you'd need a wind tunnel to be sure it's an improvement, but detail optimization proceeds by trial and error. At the same time, I'm intrigued to learn what they didn't do. - front air dam - reduced cooling airflow - side skirts, not just a bump before the tire - rear diffuser - any sort of vortex generator, anywhere. I can understand the last on aesthetic grounds, but members here have seem real improvements from the first couple things... It has to do with lift and stability at speed, if I read things right. A deeper air dam reduces drag, but it also reduces front lift. I suspect the grill blocks are doing the same thing, lowering both drag and lift. Sounds like real improvement, until you research aerodynamics and learn that you've also made the car unstable at speed. Stability has to do with the "centers" where the forces act. For gravity, it's the "center of mass" (CM) where all forces can be assumed to act on the body. For aerodynamics, it's "center of pressure" (CP), where all the aerodymanic forces pressing on the car's skin can be assumed to act. Anything you do to reduce front drag moves the CP forward, and since drag increases with speed, driving faster increases the magnitude of that force. CP behind CM is stable as the aero forces tend to align the car into the wind. CP in front of CM is unstable, as aero forces try force the car across the wind. A combination of high load (moves CM back), front aero mods, and high speed can result in a car that wants to crash. Ford has to avoid that. It's a good thing for us to do, too. HAve fun, Frank

I can't speak to more than what I did. Removing/replacing the SD card caused the nav to reset and the GPS to turn on (if I've interpreted the icon properly). It was on the left of the nav screen, forming a fourth quadrant with the zoom and pointer config buttons. Frank

+1 No car should be able to move, much less accelerate, if the brakes are applied. That you could not apply brakes is just as serious as the unintended acceleration. Have fun, Frank

I must have big cups...

+1 Build Date: 19.09.2012

Should I feel honored that you failed to insult me for asking the same question? I'll thank the other posters for explaining things, but I still don't see a purpose to this item. Now that it's clear there's only one for sale (another area lacking clarity), I will assume that you don't either! Have fun, Frank

This would explain why my car thought it was taking back roads when I was on the expressway this morning... It was a little spooky as I have 2 routes to work, highway and surface. I was driving on one, but the car was on the other. Turns out GPS was OFF - GPS with a red X - so the car really was lost. I removed and reinserted the SD card and the resulting reset brought GPS back up. Have others seen the GPS turn off? I never noticed it before! Have fun, Frank

+1 to heat on the hwy, Rifleman I'm taking the expressway to work so I get heat, and because hwy driving doesn't seem as temperature sensitive. I got 33MPG today at 10F, and that's with no EV available for most of the trip, regardles WT, and full EV only when EV+ turned on near work. Not as much fun, at all! Have fun, Frank