CMAX Grill Cover Testing, 2-5 MPG Gain

[ptjones]

Trying some new things to get better mpgs!

Bought roll of protective carpet tape at Lowe's for $14 and covered the whole front of MadMax including over the grill covers.

Bought NAPA Oil Pan Heater 150 watt, 120v for about $45 and glued with contact cement to the bottom of the oil pan. You can see the plug hanging out the right side of top gill.

Having wonderful freezing test weather here in Atlanta! Brrrrr!

Paul

Edited January 9, 2014 by ptjones

[ptjones]

With mods I got my best MPG's to work ever from a cold start of 44mpg, previous record was 38mpg during the summer. I started and ended with 50% SOC.  Yesterday I probably got my worst of 29mpg caused by being unable to go into EV because of traffic and starting with 20%SOC and ending up with 75%SOC. It takes a lot of gas to charge the HVB . My lunch time loop I averaged 59mpg at 38*F OT.  It looks like the oil pan heater is worth 2-4mpg on your first trip maybe up to 6mi. anyway. Probably go down a little as your trip got longer.   :) 

 

Paul

[ptjones]

Yesterday I went to North Atlanta to check out a 2014 CMAX Energi at Sandy Springs Ford to take pics of improvements to 2014 model. Atlanta had a high of 65*F yesterday, it was great. I decided to see if I could get the Smart Gauge overheat warning and find out what the actual temp. is for that warning.  I drove on the Fwy's the whole time between 60-75MPH and the highest temp. I got to was 238*F , never got the overheat message and Smart Gauge still had 4-6 degrees F to get to the top White line. This is with the whole front of the car covered grill covers and carpet tape.  It would appear the only way to get this warning is to have a long steep grade and use three bars to be able to get hot enough like Jus did. I averaged at least 50mpg for the 115mi. trip. :yahoo:

 

Paul

[hybridbear]

hybridbear

 

I read the tread on the FFH site.. Good stuff.  My question is, do you need to shift from D to L to D to "trick" the computer, or could you just start off in L? The reason I am asking is I am not proficient at differentiating engine sounds.

After starting out driving in just EV, I will often shift to L while stopped when I know that upon acceleration I'll make the ICE start for the first time. You'll clearly hear the difference as in L the ICE will rev to 3000+ RPM whereas you'd be around 2000 RPM in D. Once the revs increase you can shift back to D. With time you'll be able to pick up on when the computer changes patterns and starts to increase the RPM before the RPM actually goes up so then it's much more smooth.

 

Now that the holidays are over, I need to get back to interrogating the car... It'll take me some time to understand hybridbear's analysis, especially since I have access to the same data and can replicate the results.

 

I've seen 1-bar EV limit ever since the PCM update, and agree that it's there just to bring ICE back on sooner, but Saturday I got a 1/2 bar EV limit despite very high SOC. Granted, the low temperature that morning had been -4F, and the back of the car had seen no sun, but it was in the 20's when it occurred, and I'd been driving, so the ICE wasn't cold.

 

Thoughts? where might this fit?

 

HAve fun,

Frank

Perhaps the heater setting was causing it. How warm was the coolant when this happened? When the coolant temp is dropping where it's really close to the threshold for making the ICE run for heat I've seen the EV threshold drop very low to get the ICE on for heat, even when the SOC is high. Turning off the heat for a few minutes will usually get the EV threshold back to normal.

[hybridbear]

When the HVB is extremely cold your EV power is limited. While the dealer fixed the trunk on our new white FFH Friday, they gave me our old black FFH to drive. The HVB temp when I left the dealer was 4.5 F according to the ScanGauge. The HVB would not run the car in EV mode at all. Any touch of the gas pedal would make the ICE come on. I didn't think to get a pic showing the low threshold. Once the HVB warmed up above 15F I was able to get 1/2 bar of EV as shown in the pic below. Once the HVB hit 20F I was able to get 1 bar of EV. I did not get normal EV operation back until the HVB was warmer than 32F. The HVB fans came on right away and ran non-stop to funnel heated cabin air across the HVB.

Edited January 19, 2014 by hybridbear

[hybridbear]

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

How does grille blocking make the car unstable at speed? I didn't quite follow that portion of your post. Thanks!

[fbov]

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

Edited January 20, 2014 by fbov

[ptjones]

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

I have gone 90mph and CMAX still feels very stable with Grill Covers on. The car is very heavy for it's size and I haven't noticed the car getting light feeling. If anything I would think Grill Covers would cause more air going over the top of car and not under it creating more down force. Besides I just don't we are going fast enough.IMO :)

 

Paul

[fbov]

I have gone 90mph and CMAX still feels very stable with Grill Covers on. The car is very heavy for it's size and I haven't noticed the car getting light feeling. If anything I would think Grill Covers would cause more air going over the top of car and not under it creating more down force. Besides I just don't we are going fast enough.IMO :)

 

Paul

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

Edited January 21, 2014 by fbov

[ptjones]

Filled up last night and even with cold temps (20's-40's*F) 50% Hwy I got (Smart Gauge)49.6mpg, 618.5mi and 12.46gal. Actual 49.3mpg.,627.8mi. and 12.74gal., I can say I'm averaging 4-5mpg better than last year at this time and it was warmer then. All the Mods have made a serious improvement. :yahoo:

 

Paul

[hybridbear]

Frank - very interesting. Thanks! I imagine that the grille blocking pushes more air over the top of the car, thus resulting in less downforce. There would also be some additional air pushed underneath the car, but I agree that the majority would go up and over. I wish I had access to a wind tunnel to see the changes.

[ptjones]

To me I think the underside is becoming  an increasing low pressure area sucking the car down. Also from the Cord line(behind the driver seat) is generally a higher pressure area with air slowing down changing direction and compressing at the base of the windshield. NASCAR teams use that area to feed the fuel injection systems. From the Cord line back air is speeding up to fill the gap caused by the 4inch drop in elevation and causing lift. The Question is are we gaining more lift than down force. ;) :detective:

 

Paul

[ptjones]

Beautiful snowy day in Hotlanta area...LOL! MadMax ain't too thrilled about it and temps in low 20s. Grill covers keep snow out and oil pan heater plugged in at my shop. Got 47mpg on lunch trip!

[ptjones]

Today Hwy's got better so I made a 50mile trip to North Atlanta got 50.1mpg with temp of 32*F going 80-50mph and returned 2hrs later with temp of 40*F going 50-75mph and got 53.6mpg. In 25min. temps got up to 231*F so I turned on heater and then temps were running 215-225*F  I was amazed that there as still around 100 cars parked on the side of the Fwys from the snow storm. :)

 

Paul

Edited January 30, 2014 by ptjones

[fbov]

... and returned 2yrs later ...

Well that explains it... you found the secret time travel button!

Edited January 30, 2014 by fbov

[ptjones]

I have been telling you the Grill Covers are great and this proves it! LOL Thanks for catching before my wife saw it, she loves giving me a hard time.LOL :drop: 

 

Paul

[ScubaDadMiami]

Are you suggesting the grill covers for all highway travel, not just in cold weather?  I'll be driving up to New Hampshire in June.  I am looking to increase my highway FE, but I would have thought that using grill covers during the summer would cause overheating.  If anything, I would only use them for the interstate driving portion of my trip.

[Jus-A-CMax]

Are you suggesting the grill covers for all highway travel, not just in cold weather?  I'll be driving up to New Hampshire in June.  I am looking to increase my highway FE, but I would have thought that using grill covers during the summer would cause overheating.  If anything, I would only use them for the interstate driving portion of my trip.

 

I don't think using the grill covers will cause you to overheat (Yeah sure - coming from the ONLY guy here with self-made grill covers that managed to overheat...but the laugh is on me) under normal driving conditions. Its got to around 75-85F last week and the covers & engine temps were fine. The ONLY time I overheated and the car warned me, was when I was climbing a "super" grade at 66mph with the car fully loaded, FWA on (thanks to the wifey) and it was a long sustained 3 to 4 bar burn at times. No damage done and as soon as I dropped speed back to 2 bar (speed dropped to 50-55mph), the engine immediately started cooling down back to normal. At NO time, did the engine shut off. So I won't sweat it...but I know next time not to push the engine this hard with the covers. Jus my 2c.

 

I am still running with my covers on.

Edited January 31, 2014 by Jus-A-CMax

[plus 3 golfer]

Are you suggesting the grill covers for all highway travel, not just in cold weather?  I'll be driving up to New Hampshire in June.  I am looking to increase my highway FE, but I would have thought that using grill covers during the summer would cause overheating.  If anything, I would only use them for the interstate driving portion of my trip.

Here's my thoughts on full grille covers when you are using AC.  You want air flow through the condenser to remove heat.  Otherwise, the electric compressor has to work harder.  IIRC, the grille shutters are normally operated during normal AC operation allowing air flow through the condenser and radiator.  The electric fan may also come on to lower coolant temperature especially during AC operation and higher coolant temperature and also would have to work harder because of the air flow restriction of the grille covers.   So, is the net effect of grille covers worth it in terms of FE savings and potential earlier replacement of equipment?

 

I have a set of grille covers and planned to use them on our trips across country normally made in late October / November time frame when not using AC.  But this year we went in late August and returned in mid September.  My intent was to run with the full covers once I got out of the valley of the sun. So, in Show Low, AZ (6000') and temps in the 70s about 10:30 PM, I put the full covers on and shut the ac off.  I have DashCommand and Engine Link loaded on my IPad so I could monitor coolant temperature (along with other stuff).  This is what I noted.

 

1) Gold Canyon (1835' elevation) to Show Low (150 miles of up and down mountains to 6000' elevation) ambient about 90F at start with AC on - coolant temperature ran around 200F going downhill and about 212 going uphill at speed of around 65 mph.  This to me indicates that the shutters were likely operating.  In Show Low, I put both full covers on and turned AC off as ambient was in the 70s and it was nighttime.

 

2) Show Low to Quemado, NM still climbing to the 7000'+ elevation with ambient in the upper 60s - low 70s with grille covers on.  Coolant temperature was between 222F and 235F depending on downhill vs uphill speed about 65+ mph except through towns. About 15 miles outside of Quemado, I stopped and took off covers as I was about to head  to I 40 (about 75 miles) at higher speeds on a very good two lane, fairly flat, rarely traveled road as I didn't want to continue running with average coolant temps around 230F once I got on I 40.  Coolant temps immediately dropped to the 200+F range at about 70 mph.

 

3) Once I got on I 40, I ran at with Eco-Cruise set at 78 mph (Garmin GPS) and still going up / down mountains.  Coolant temperature averaged around 210F.

 

4) About 7am (East of Albuquerque)  I needed to turn AC back on and coolant temps dropped on average 10*F+ degrees to around 200F.  So it appears that the PCM was likely regulating grille shutters to keep coolant temperature around 200*F with AC on.

 

In any event, I don't want to run full covers when I'm using the AC. Also, I don't want to run covers with coolant temperature averaging 230F even though there in no alarm message. 

 

On the trip East I got overall 40.4 mpg - door to door with an average speed of 68.4 mph (gps miles / gps moving time). My average speed on interstates (about 1600 miles) was 72.3 mph.  On the trip back home, I averaged nearly 74 mph on interstates mainly because I drove very little during darkness so I set eco-cruise about 1-2 mph higher. I also battled a strong quartering wind from MO into AZ and rain in AZ high country and my overall return mpg dropped to 38.3 mpg.  Overall, door to door round trip, I averaged 69.1 mph and 39.2 mpg with me, wife, our black lab and luggage (maybe 450 - 475 pounds). 

 

As far as the economics, I assume that had I run the grille covers for the entire trip I would average no more than 2 mpg better.  So, (4080 miles / 39.2 mpg) = 104 gallons actual fuel put in the tank with no covers vs. (4080 / 41.2) = 99 gallons estimated had I used full covers.  So,  is the cost of saving at most 5 gallons of fuel worth the risk of running  the coolant at 230F for 4k miles?  It may be for some but not for me. 

[fbov]

I believe that grill covers are doing two things.

- reducing air infiltration

- smoothing out the air flow as it splits left and right at the car's centerline

 

One can envision an adjustable cover, were you can easily increase air infiltration when cooling needs increase, without much damage to the air flow. In Winter, or in rural driving, you'd minimize infiltration because you have excess cooling capacity. When your driving style changes so the coolant temp starts to rise, stop and open the vents. I know for my part, this would be a rare event.

 

Have fun,

Frank

 

PS nice data Plus!

[ptjones]

Are you suggesting the grill covers for all highway travel, not just in cold weather?  I'll be driving up to New Hampshire in June.  I am looking to increase my highway FE, but I would have thought that using grill covers during the summer would cause overheating.  If anything, I would only use them for the interstate driving portion of my trip.

I had my covers on all year long and the only time temps go up is at high speeds and long up hill climbs. I did supply a Grill Cover with cut out for Summertime use that solves this problem. At Fwy speeds it's worth  2mpg aero improvement. There is no reason to take off for City driving. :)

 

Paul

[ScubaDadMiami]

I had my covers on all year long and the only time temps go up is at high speeds and long up hill climbs. I did supply a Grill Cover with cut out for Summertime use that solves this problem. At Fwy speeds it's worth  2mpg aero improvement. There is no reason to take off for City driving. :)

 

Paul

I might be interested in that design.  Are they easy to clean (road bugs, etc.)?

 

I will be making a 4,000 mile trip in June to July.  So, I am looking to boost highway speed mileage.

Edited February 1, 2014 by ScubaDadMiami

[ptjones]

I might be interested in that design.  Are they easy to clean (road bugs, etc.)?

 

I will be making a 4,000 mile trip in June to July.  So, I am looking to boost highway speed mileage.

Grill Covers are easy to clean, install and remove.

 

Just got back from trip to SF (6k miles, 11 days and 50k total miles now) with all kinds of bad weather snow and ice with temps from -9*F to 70*F.  MADMAX did very well with careful driving in icy and snow packed roads.

 

Things I learned on this trip: 1. I hit 240*F climbing out of Camp Verde, AZ steep grade and still had away to go to the white line on Smart temp gauge so 245*F is approx. the top limit before warning message.

                                             2. With Grill Covers on you run 10*F cooler with P&G vs cruise control plus better MPG's.

 

                                             3. Top Grill is worth 5*F cooler when open.

 

                                             4. Lower Grill cover is worth about 10*F higher when installed

                                            

                                               Averaged about 42MPG's actual, not bad considering conditions. :)

 

Paul

Edited February 16, 2014 by ptjones

[ptjones]

MPG's are going up with slight improvement in average temps. Feb 21 fill up 47.9mpg and Mar 6 fill up 49.9mpg. This is with Grill Covers, Oil pan heater, GasPods, wheel covers, tires 49psi. and ScaGauge. Should be in middle 50's by end of Apr. :shift:  :) 

Paul

[mtb9153]

MPG's are going up with slight improvement in average temps. Feb 21 fill up 47.9mpg and Mar 6 fill up 49.9mpg. This is with Grill Covers, Oil pan heater, GasPods, wheel covers, tires 49psi. and ScaGauge. Should be in middle 50's by end of Apr. :shift:  :) 

 

Paul

I got to get one of those Scan Gauges it seems, to better understand what is going on under the hood.