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Old 07-07-2012, 10:01 PM
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Blue area on tach

Just noticed (light was rite) my Pentastar tach has a blue band from about 900 rpm to 2000 rpm. That is low even for a diesel and particularly for a high winder like the V6. Anyone know what it is for ? (Steering wheel will block for most people).
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Old 07-07-2012, 10:26 PM
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Re: Blue area on tach

are you a hyper-miler?
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Old 07-07-2012, 10:32 PM
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Re: Blue area on tach

I think it's the range where it apparently gets the best fuel economy. Sucks because the Jeep does everything it can to keep it in that range even if it means shifting at a ridiculously too early rpm. I so hate the shift point on this Jeep.
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Old 07-07-2012, 10:32 PM
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Re: Blue area on tach

I believe its the RPM range to maximize efficiency or something similar but a fairly quick revving, NA V6 in a 2.5 ton SUV isn't going to spend much time in that range.
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Old 07-08-2012, 01:20 AM
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Re: Blue area on tach

With the V8, it's blue from 900-2900 rpm's. As others mentioned, it's for the most efficient operating range.
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Old 07-08-2012, 02:44 AM
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Re: Blue area on tach

In the old days a vacuum gauge indicated if you were in the best range for mileage...

1965 Chevrolet Impala 327 came standard with an economy gauge, called manifold vacuum.... I used to watch that needle go back and forth in my Grandpa's car when I was like nine years old. It never stayed in the green area because he always had his foot in it.

I wonder what newbee engineer thought if you keep the RPMs in a certain range it improves gas mileage. Ohh wait, maybe it means you get blue balls if you keep the RPMs in that range...

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Old 07-08-2012, 06:44 AM
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Re: Blue area on tach

Actually the vacuum gage was a GM gimmick, marketing fluff. It didn't come close to indicating best economy and really didn't provide much useful information except when you had a vacuum leak... and sometimes the gage or sensor or hose leaked .

Best mileage in general is keeping the engine at its peak torque, which is also typically where the exhaust is the most resonant. The EFI instant mpg indication is much better indicator of fuel economy, however.
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Old 07-08-2012, 08:49 AM
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Re: Blue area on tach

Quote:
Originally Posted by mr_bots View Post
I believe its the RPM range to maximize efficiency or something similar but a fairly quick revving, NA V6 in a 2.5 ton SUV isn't going to spend much time in that range.
You would be surprised, with the grand cherokees ridiculous shift points it's in that green section a LOT more than I would like.
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Old 07-08-2012, 09:05 AM
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Re: Blue area on tach

Quote:
Originally Posted by JTS97Z28 View Post
You would be surprised, with the grand cherokees ridiculous shift points it's in that green section a LOT more than I would like.
i too dislike the shift points, like when i want to accelerate and there's a delay then suddenly it revs so hard it scares my passengers - not a smooth transition at all.
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Old 07-08-2012, 11:37 AM
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Re: Blue area on tach

learn how to drive it
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Old 07-08-2012, 01:23 PM
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Re: Blue area on tach

When tach is in the blue the Eco light comes on I think
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Old 07-08-2012, 01:55 PM
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Re: Blue area on tach

Quote:
Originally Posted by JTS97Z28 View Post
You would be surprised, with the grand cherokees ridiculous shift points it's in that green section a LOT more than I would like.
My 2011 3.6 is hardly ever there, usually up-shifting between 2500 and 3000rpm. Maybe I've just adapted to it and keep my foot in it more.

The Eco light bugged me too, I turned it off the day I bought it.
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