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Old 01-02-2013, 02:29 PM   #1 (permalink)
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vx poor mpg at highway speeds

It seems I cant stay in lean burn at highway speeds.
If i attempt to stay in leanburn I can't keep up with traffic.
I have no problem with side streets as I can get 80mpg doing 35, I can get about 45mpg at 55 on the highway, but I cant sustain this without bumping the throttle.
Just seems like the car has a big parachute behind it

My engine is newly rebuilt (about 1000 miles on it now), tranny seems fine (~2k at 60mpg), all new tune up stuff, rolls easily, new oxygen sensor, new fuel filter, new fuel pump.. Just don't know what to check next.

Timing seems fine, valve lash fine, bald front tires

Replacing vacuum lines and PVC valve when its warmer out.

My guino tank mpg is 35. What am i missing or should recheck?

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Old 01-02-2013, 04:27 PM   #2 (permalink)
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Some VX's had dealer option mud flaps and passenger side view mirrors that will add drag, the first VX I had had all that extra stuff and I noticed it.
Tire pressure, wider wider then stock tires, wheel alinement, to thick of oil and of course brake drag are all things that I would check.
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Old 01-02-2013, 04:58 PM   #3 (permalink)
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While you're sorting out possible mechanical issues, get a partial grille block on there as well. Every effort at drag reduction equals higher speeds before lean burn kicks out.
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Old 01-02-2013, 05:35 PM   #4 (permalink)
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The grill block might help in two ways, lean burn stops if the engine gets to cold as well, when you rebuilt your engine did you put a ~180F or a ~195 thermostat in?
The VX came with a factory grill block behind the grill, if your car did not come with A/C then the grill opening was just a few square inches.
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Old 01-02-2013, 07:34 PM   #5 (permalink)
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Double check timing, too.
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Old 01-02-2013, 07:41 PM   #6 (permalink)
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Quote:
Originally Posted by nbleak21 View Post
Double check timing, too.
Right... the VX cam shaft timing is not set with the pulley marks inline with the head, instead it's set with the pulley marks inline with another set of marks on the head that are about 6 degrees off.
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Old 01-03-2013, 12:31 AM   #7 (permalink)
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thanks, i'll start checking things.

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