ScanGauge shows FJ gets 104 MPG!

[White Rim]

.. coasting fast down a steep hill in neutral

OK so I was coasting down Route 141 from Mt Adams.

What was interesting was that I was coasting at 60, and the Gallons per HOur was fluttering between 0.5 and 0.6 GPH.

NOw normally if the rig is idling while stationary it consumes 0.3 or 0.4 or maybe 0.5 GPH if the air conditioning is on.

So I ask myself, "Self: Why TF is the FJ cosuming 0.6 GPH in neutral when it is going 60 MPH and only .3 when stopped?" Because if I was consumin 0.3 GPH and going 60 MPH that would be 200 MPG! ANd I want my 200 MPG going down hill. Basically the FJ is consuming ALMOST DOUBLE the fuel when idling while coasting vs idling while stopped!!

Well so I notice the tach is showing ~1200 RPM. Ah but is the air conditioning on? NO.

So why is it running 1200 RPM when coasting at 60 in neutral (manual)?

SO I get to the bottom of the big hill and it flattens out at Trout lake and I thought well I will just let it coast to a stop and watch the RPMS with the scangauge. Switching the scangauge to read RPMS I see it is running ~1250 RPMs as I coast slower and slower..... 50, 40, 30, 20, 15...
At 15 MPH the RPMs begin to go down, and reach the normal idling speed of ~750 - 800 RPMS at 5 MPH. I repeat this test several times on other hills, and just coasting to a stop on flats. Sure enough, the exact behavior each time. THe RPMw ramp down from 1250 to 750 between 15 and 5 mph.

So the engine computer is upreving the engine according to the vehicle speed.

Why?

I struggle to understand the emissions or other rationale behind this.

Plus it is killing my mileage in coast!

Maybe it is to ensure adequate power steering pressure?? But that really doesn't make sense either because adequate steering can easily be supplied at 750 RPM.

Any idea why this does this?

[fjcruzer123]

My first guess is to keep the tranny from having to jump gears if you decide to accelerate. That and maintaining engine power for things power assisted steering, brake assist, etc.

I know the Heep I drive for work drops to idle whenever it can, but when I tap the accelerator the tranny has to jump to keep up (and it shows at 85K since it now clunks in and out of every gear...) .02

[Steve_53]

This is another manifestation of the same issue that has been discussed in other threads, including this one:
http://www.fjcruiserforums.com/forum...hifts-6mt.html

Trust me, the mpg penalty when coasting is nothing compared to the thrill factor this contibutes to stop and go driving in heavy traffic on an icy road.