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Old 04-28-2014, 02:50 PM   #1 (permalink)
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Default Lower MPG at 45'ish deg F air temps

Anyone else experience lower mpg with the air down in the 45 deg F range compared to the 60's (dry pavement but higher Rel Humidity) running down the free way at 60 mph? It seemed I was struggling to get in the mid to high 60's this morning in 45 deg F, where normally at this point of the commute I am usually a couple higher MPG. Still ended up at 70 mpg so I can't complain.

In one sense I can see lower MPG since the air is more dense from an aero dynamic perspective.

In another sense, I can see the air is denser and you'd think you'd get a little better mpg, albeit I suspect this car is closed loop fuel injection so maybe the air density doesn't matter.. and its intake air is warmed by the engine compartment anyways.. so maybe this is more a function of air resistance?

Anywho.. just curious on folks thoughts from a learning perspective with the car.

Stock MT.
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Lifetime MPG: 64.8

Last edited by andrewdonald1; 04-28-2014 at 02:53 PM.
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Old 04-30-2014, 10:02 PM   #2 (permalink)
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Cool damp air drops my mpg too. I still have winter warm air mods installed (grill blocks, warm air inlet). I check tire pressure frequently too, with varying temps, tire pressure varies as well.
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Old 05-01-2014, 07:42 AM   #3 (permalink)
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Quote:
Originally Posted by Mountain driver View Post
Cool damp air drops my mpg too. I still have winter warm air mods installed (grill blocks, warm air inlet). I check tire pressure frequently too, with varying temps, tire pressure varies as well.
I'll have to look into those mods for next year.

I am very happy with the car in general.. what's not to be happy about getting 70 -85 mpg on the free way and combined 61mpg on tanks of gas?
My lifetime right now is around 63.5 - 64 mpg...

Do those mods help that much to maintain mpg at those cooling more humid temps?
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RE-92 Tires.
Best: 85.3 MPG for 71.7 miles @ 60 mph - NO drafting the big rigs!
Lifetime MPG: 64.8
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Old 05-02-2014, 12:04 AM   #4 (permalink)
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A lot of mixed opinion on warm air and grill mods. Overall, they do keep some heat in the engine. I also try not to use heat in the cabin (until the outside temps get real cold).

Lower grill block helps some, radiator block helps more but you need to know actual engine coolant temp (ect) to be safe with that one, the temp indicator on the dash is slow to respond and the car will be overheated by the time the dash indicator shows red.

Warm air mod also helps some.

With mild temps, 40's give or take, I get back about 5-6% of mpg lost.
Temps in the 20's-30, I get about 2-3% back.
Teens and below, no difference in mpg on my car. Engine does warm quicker though.

A lot of info in different threads. Here's a link with some pics of mine: https://www.insightcentral.net/forums...no-lie-28.html
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Last edited by Mountain driver; 05-02-2014 at 12:07 AM.
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Old 05-03-2014, 04:01 PM   #5 (permalink)
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Quote:
Originally Posted by Mountain driver View Post
A lot of mixed opinion on warm air and grill mods. Overall, they do keep some heat in the engine. I also try not to use heat in the cabin (until the outside temps get real cold).

Lower grill block helps some, radiator block helps more but you need to know actual engine coolant temp (ect) to be safe with that one, the temp indicator on the dash is slow to respond and the car will be overheated by the time the dash indicator shows red.

Warm air mod also helps some.

With mild temps, 40's give or take, I get back about 5-6% of mpg lost.
Temps in the 20's-30, I get about 2-3% back.
Teens and below, no difference in mpg on my car. Engine does warm quicker though.

A lot of info in different threads. Here's a link with some pics of mine: https://www.insightcentral.net/forums...no-lie-28.html
Thanks bro! I do really appreciate your ingenuity especially the cables etc for the radiator blocking! That's some good work!
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Rostra Cruise Control
Hybrid Automotive Grid Charger
Sony DSX-S310BTX Digital Media Receiver
Kicker 40CS654 6.5" Coaxial Speakers
RE-92 Tires.
Best: 85.3 MPG for 71.7 miles @ 60 mph - NO drafting the big rigs!
Lifetime MPG: 64.8
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Old 05-03-2014, 06:33 PM   #6 (permalink)
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The Gen1 loves heat-fuel economy wise.
-loves high warm intake air temp(IAT)
-loves high water temp
-loves high road surface temps

Re IAT, some methodical member a few years back conducted experiments to find the optimum IAT. I can't find the thread at the moment, but if memory serves, he found that 115 degrees was ideal. From my own warm air experiments I believe he was pretty much right.

Re H2O temp, my testing convinces me that the engine is more efficient, MPG wise, above 200F. But, as Mountain driver says, you must closely monitor the temp with a good gauge, such as the OBD II C&C, or a Scangauge. The dash gauge is far from accurate. The service manual says that the thermostat starts to open at 197F and is completely open a 212F. One could infer that this is an acceptable operating range. In northern climates, the coolant temp will hug the 197 mark. It seems to me that this means that the first little trickle of normal radiator flow cools the engine below optimum. Of course, grill blocks are needed to raise the coolant temperature. Incidentally, they also slightly improve aerodynamics.

Re road surface temp, warm tires have less rolling resistance that cold tires. Anyone can prove this by comparing the roll down distances between cold road and warm road over the same course.

So the car loves hot weather. It is an observation not original with me.
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Old 05-03-2014, 06:51 PM   #7 (permalink)
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andrew: thanks for the compliment on my 'ugly' air mods. The folk with the ingenuity made automatic systems that self regulate. Many before me have posted several articles on their warm air mods and other ideas. Check out posts by Joecvt and AbCaRed00 just for starters. There are many more.

The OP for the thread link above is Insightful Trekker, some other posters in that thread have links to other good ideas. A little lenghty, but interesting browing in the whole thread.
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Last edited by Mountain driver; 05-03-2014 at 06:54 PM.
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Old 05-06-2014, 08:15 AM   #8 (permalink)
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Right now I am just driving it pretty well stock..
Until I get a good feel for the car MPG wise thru different conditions.. plus I am pretty busy.. I really am not much of a modification guy anymore.. time is more valuable on my weekends then a couple bucks of fuel savings...
But as I slow down and get some more free time, maybe I'll do it.
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2002 silver MT 86K miles
Rostra Cruise Control
Hybrid Automotive Grid Charger
Sony DSX-S310BTX Digital Media Receiver
Kicker 40CS654 6.5" Coaxial Speakers
RE-92 Tires.
Best: 85.3 MPG for 71.7 miles @ 60 mph - NO drafting the big rigs!
Lifetime MPG: 64.8
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Old 05-06-2014, 01:13 PM   #9 (permalink)
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My mileage. Yours may vary. Pink is temperature, blue is MPG.


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Old 05-06-2014, 01:19 PM   #10 (permalink)
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Quote:
Originally Posted by Need4Speed View Post
My mileage. Yours may vary. Pink is temperature, blue is MPG.


Damn dude.. I am continually impressed by the owners on this board..
Assuming all equivalent other than temperature, that is a great graph!!!
Thanks for sharing kind sir.

Andrew
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2002 silver MT 86K miles
Rostra Cruise Control
Hybrid Automotive Grid Charger
Sony DSX-S310BTX Digital Media Receiver
Kicker 40CS654 6.5" Coaxial Speakers
RE-92 Tires.
Best: 85.3 MPG for 71.7 miles @ 60 mph - NO drafting the big rigs!
Lifetime MPG: 64.8
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