Choose Your Weapon - Armed With ScanGauge

[2TonJellyBean]

Comparing FE readings of a 2007 V6/A5 Santa Fe and 2001 I4/5M Accord

We were going 250kms (155 miles) away through the heart of cottage country this past weekend. We had a choice to take our new Santa Fe or trusty Accord and better economy primarily at the expense of my front seat legroom (4 people and the trunk 2/3rds). Best yet, it gave me a chance to try the ScanGauge on the Accord - it was originally bought to help me try and make the Santa Fe about 10% more economical.

Going up I was mostly doing things like comparing speeds and efficiencies and testing glides. I averaged somewhere around 7 LHK but was driving using many styles. Coming home I drove consistent and fast when traffic permitted with a bit of coasting including one to 130 on a long downhill, but next to no load driving up and down hills and lots of stop and go as evidenced by a 67 kph average with most open highway driving done at 100 to 112.

The Accord did a respectable 7 LHK / 33? MPG at a high sustained speeds with the AC on combined with about 20-20 kms of slow stop and go traffic. The Santa Fe would have been hardpressed to do it any lower than 9 LHK (plus 28 MPG), and even that might have been doubtful with the stop and go.

The differences between the manual Accord and the Santa Fe are very interesting. I could never see how P&G meant anything to Santa Fe unless the speed was always under 60 kph - otherwise you could sneak into 5th at 63kph/39mph and then letting it slide as low as 50/31. In the Accord the potential for P&G was very obvious. In rolling terrain the most efficient cruise speed was actually above 88kph/55mph - and it would hold around 10 - 12 LHK max on any grade and could easily clear most hilltops at well under 10 LHK when DWL instead of trying to stay with the flow and avoid or be a cause of the late day traffic jams coming back from up north on long weekends.

The biggest plus in my opinion of throwing the ScanGauge on the Accord was understanding why the Santa Fe doesn't show much potential for P&G techniques. I thought it was me - probably is to some degree however with the Accord, it was obvious that it would be very beneficial to P&G ICE-Off when the hills rolled up and down or when travelling under 90 KPH.

The Accord's engine couldn't efficiently match the load under hilly or slower conditions and the ScanGauge made that pretty obvious - otherwise I can't see how I would have ever known.

The Santa Fe gets very good steady state KPH/MPG using CC on the flatter sections from about 60 to 70 KPH / 37 - 43? MPH because it matches load better - the computer seems to keep the LOD lower overall and steadier than my foot no matter how hard I try.

It makes me think about modern modulating condensing boilers used in hydronic/radiant heated homes. The boiler computer controller modulates the air intake fan speed (and by venturi effect the flow of natural gas) up and down to match the heatloss of the home. Once the heatloss of the home goes below the minimum modulation range, the boiler fires intermittently on calculated cycles to match the load of the home by varying firing times at minimum power. In effect it becomes a true pulse and glide system.

Anyway, the Honda could get amazing mileage doing a P&G at an average of 60 to 70 KPH / 37 - 43? MPH while the Santa Fe doesn't seem to show any room for improvement over using CC and steady speeds while using the plus minus buttons to flatten the load when the terrain rolls at these same speeds. The Santa Fe's engine simply seems pretty matched to the load at low RPM driving once you're in 5th.

I probably saved about 20-30 litres / $20-30 in gas for the round trip by taking Honda.

[SVOboy]

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[ZugyNA]

Originally Posted by 2TonJellyBean

Anyway, the Honda could get amazing mileage doing a P&G at an average of 60 to 70 KPH / 37 - 43? MPH while the Santa Fe doesn't seem to show any room for improvement over using CC and steady speeds while using the plus minus buttons to flatten the load when the terrain rolls at these same speeds. The Santa Fe's engine simply seems pretty matched to the load at low RPM driving once you're in 5th.

I probably saved about 20-30 litres / $20-30 in gas for the round trip by taking Honda.

Honda = lower CD and 2WD

SantaFe = higher CD and 4WD

Can't glide so well with drivetrain and wind drag?

[2TonJellyBean]

SVOboy, I'm actually not very happy with Honda, so I'll be doing them no favors until they start selling cars that I fit in (right now only the Odyssey fits and it doesn't fit my legs or budget as well as the SF and it's too big for our needs). BTW, the Fit was the first car I looked at and then realized it was misnamed! ;-)

Originally Posted by ZugyNA

Honda = lower CD and 2WD

SantaFe = higher CD and 4WD

Can't glide so well with drivetrain and wind drag?

The Cd for that Accord was 0.33 and it's 0.37 for the SF (no idea of frontal area on the SF is to compare overall Cdx factors). I don't think the added drivetrain drag has as much affect on FE as having to accelerate an additional 300 pounds each and every time.

I actually think it glides quite well. I just don't see much or any gain from pulsing when it's flat vs steady state unless my speed is under 63kph (can't get into 5th) or speeds fall below 50kph and I drop into 4th.

My daily drive commute is dropping kids off at school and then driving to the commuter train - short trips with 50 kph max / all low speed and I check trip averages and the best thing I've found is to sneak up to grab 5th if I can and then do a fairly steady state speed / DWL and maximize coasting when I can - traffic permitting.

The Accord doesn't seem to use much more gas pulsing than steady state at speeds under 90 kph. The SF on the other hand has a major drop in MPG whenever pulsing - even mild pulsing. I would expect that mass and the slushbox are what hurts its P&G potential the most and it hurts it on the pulse side. A paradox...