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mnstrvx 05-04-2009 09:52 PM

new 94' VX owner, several "advanced" questions!!! lol...
Hi everyone, here is what I've done so far, and some of the questions that i have...

I have briefly spent some time thumbing through this site and I am quite excited to see the enthusiasm of saving fuel!

Okay, so i just purchase this VX about three weeks ago from an older guy in Tucson, AZ and right after purchase, i ran over to the local walmart to dump seafoam into the gas tank and engine oil. It took me about 200 miles to get back home. Teal Green, with grey interior, everything is stock except the stereo. 204,000 miles when purchased. the car was remarkably clean, and well maintained! The engine bay is BONE DRY not a drop of oil or grease from anywhere! Once home I did the following:

Plugs (NGK)
wires (OEM)
cap (OEM)
rotor (OEM)
fuel filter (OEM)
pcv valve (haven't done the nifty PCV valve mod yet, is it worth it?)
drive belts
topped off brake fluid
topped off and bled clutch hyd. system
checked timing belt (looked great)
checked transmission fluid (looked great)
checked air filter (clean)
checking coolant (awesome)
changed oil out with conventional 5w-30
changed out oil filter
disconnected the EGR valve (was EXTREMELY rough when cold, and was starting hard, so i disconnected the EGR as well as the vaccum line to it-problem solved, of course it's a temporary fix) read the thread abouting cleaning EGR, wasn't to excited about the effort involved.

After reading some posted in the search section and some current active threads:

removed and cleaned my temp. sensor (behind the intake manifold on the driver side, white plastic sensor).
removed and cleaned idle are control valve
removed and Wd-40'd some of the connectors
removed and cleaned the MAF or MAS sensor, black sensor right above TB.

Okay, so now for some questions...

I don't know how some of you folks are getting incredibly high MPG figures? I went through a tank of gas already, but for a good duration of time the car was idling as i was "diagnosing" things under the hood (also changed fuel filter and spilled some fuel). not to mention the fact that the tire pressure was incredibly low. I still got about 420 miles to the tank (I was kind of disappointed). this was all primarily city driving. I was doing a lot of above 2,000-2,500rpm shifting (until i read some more threads regarding shift points).

so, any advice would be greatly appreciated? I would love to see ABOVE 50mpg (500+ per tank full).

some things that i am considering, add more seafoam to the tank and engine oil before changing out this oil... once it's time to change the oil I want to do the following; 0w-20 royal purple in the engine, royal purple synchromax in the transmission (unless of course something else is recommended-like engine oil in the tranny- and what's the capacity), new tires (mine are relatively old, and need to be changed. what's an ideal tire pressure for these cars).

was considering 155/80-13's or 175/70-13's... both of which are reasonably priced locally.

thanks for any advice, direction, support!

jmf 05-05-2009 02:47 AM

How much gas is "a tank"? Start using the gas log so you can keep track of how changes help your FE. A new oxygen sensor is allways a good idea if you don't know the age of the current one(this made the bigest difference on mine). My vx was running rough when I bought it the previous owner said it was the EGR but i replaced the O2 sensor and that fixed it. 175/70's seem to work great for me, I have them at 48psi any higher and the ride is really hard.


theholycow 05-05-2009 05:02 AM

Welcome! It's nice to see your enthusiasm, too. Congrats on finding a clean VX.

I would not expect the Royal Purple to pay for itself in FE (fuel economy) or any other way.

What size tires are on the car right now?

The VX is particularly sensitive to the oxygen sensor, so as jmf said, you may need a new one. When buying a replacement, beware that the VX uses an expensive and rare wideband sensor rather than the common narrowband type. The link he gave you, which appears to be the same one as in my sig, is the only known place to get one at a decent price.

jmf is also 100% correct about the gas log. Miles per tank is so inaccurate that it's meaningless for trying to improve your FE. You need decent accuracy before you can experiment and try things to see what works, or else you'll get bad information.

Finally, to answer your question of what we do to get incredibly high MPG figures: We modify our driving, more than our cars. Most car modifications don't pay for themselves in FE. Driving modifications are free (except those that put more wear on the car; but those tend to pay for themselves anyway).

Basic stuff starts with conserving momentum by driving as if you have no brakes. Try to time traffic lights so you don't have to brake, cruising through a green light instead. Enjoy going fast around turns. Any time you brake, you discard energy that you already paid for with gas. Any time you go faster than necessary, you end up braking and discarding that energy, so try to go the right speed in non-highway driving.

If you have patience, drive slower all the time. I don't personally do this one as much as other members here, because I just don't have enough patience.

Experiment and adjust your shift patterns. In my VW Rabbit, I've found that there is no limit to how low I can shift to save gas. If I run it up to 1100rpm and then shift, I get great FE, though I generally have to get up to 1300-1500rpm or else my acceleration is too slow. My VW also has a wideband O2 sensor, and that is credited with allowing me to use WOT (Wide Open Throttle - gas pedal on the floor) without throwing the computer into Open Loop, a mode where most cars will run with a rich air/fuel ratio. Low RPM + WOT = good FE for me. The VX may be the same way. However, the VX also has Lean Burn, which I think happens during low throttle cruising conditions, so that's something else to consider when choosing gears and shift points.

Advanced strategies include stuff like Pulse & Glide, and Engine-Off Coasting.

mnstrvx 05-05-2009 10:33 AM

thanks a lot for the information! I recently (within this week-after reading some threads) have been driving much more slowly, and doing several of the adviced methods that you two have mentioned.

After i cleaned up several components last night, i also happened to adjust the idle screw. it's idling now at less than 500rpm! It's smooth as silk right now!

I checked the oxygen sensor, as that was my first thought when it was running rough, but the sensor "looked" new from the outside, and I even took it out and cleaned it with WD-40 and brake cleaner. It looks relatively new, must have been replaced recently. (I will keep this in mind further down the road).

Royal Purple and Amsoil seem to "out perform" other leading oils... that's why i thought it "might" be a good idea to get a "better" engine oill. Although i don' thave a problem running Mobil 1 or Valvoline. I typically run Mobil 1 syn. in my Vette'. I'll give that a shot first, still sticking with 0w-20, 0w-30.

I can't think of any other method to get an accurate idea of how much fuel I am putting into this thing other than filling the tank after it goes completely empty? I know this is a weak method of measure, since I tend to Top off occiasionally, and it that in mind, the "full tank" amount can very.

mnstrvx 05-05-2009 10:35 AM

****by the way****

my current tires are 165/80-13 and I am ONLY at 33-35 psi!!!!! This can be a HUGE problem! I will get the tires inflated ASAP. I can't beleive running suck High Pressures though?

GasSavers_TomO 05-05-2009 11:06 AM

I run 50psi in my Sumitomo HTR200 during the summer and 45psi in my Goodyears for the winter. just as long as you aren't inflating past the max psi indicated on the sidewall, there is nothing to worry about.

theholycow 05-05-2009 11:42 AM

The way to measure your fuel economy is as follows:
  1. Fill tank. It doesn't matter if it's empty or not. Reset your trip odometer. Don't top off after the pump automatically stops.
  2. Next time you fill, try to use the same pump with the car facing the same direction. Divide your trip odometer by the gallons you put in. Now you have the most accurate MPG measurement that you can easily get.
  3. Enter the data into a gaslog here and the site will automatically calculate your MPG and graph it for you, as well as letting you enter notes to keep track of it.
You can view my gaslogs by clicking on the MPG figures below my username to the left of this post.

As for tire pressure, there's more information than you'll ever want to read, in the link in my sig about tire pressure. To put it succinctly:
  • You have to experiment to find the right pressure for you. The minimum is the pressure that's marked on your car, the maximum is the pressure that's stamped on the side of the tire. I usually end up at the maximum.
  • The usual fears do not happen. The tires don't explode, don't break more easily, and usually don't wear worse in the center. In fact, those things improve. Handling usually improves. Ride may get noticeably worse or you may not feel the difference.
  • If handling or ride is bad, you know you've gone too high and should back it off a few PSI.

R.I.D.E. 05-05-2009 01:32 PM

I would consider getting the EGR working properly.

Try the max pressure listed on your sidewalls. Your car should be very easy to push. I could move mine on flat ground with one thumb.

I am running 44 PSI on my Insight, on the original 7 year old tires (sidewall max recommendation). The previous owner had them at 26 PSI. His lifetime mileage was 43. I reset the lifetime mileage and now its at 62.3.

My only other mod is a 40% grille block on the Insight.


mnstrvx 05-05-2009 09:45 PM

Would a front air dam, lowering the car, getting "air dams" for the front wheels make any difference?

I wouldn't mind blocking off some of the frontal area, but I don't know if it's wise here in AZ.

I will get around to the EGR eventually. At this point, it's running REALLY well, without any engine light or issues.

My tires are (once again) slightly older (dried out, showing some cracks in the tread)... I should be replacing those sooner than anything else. The alignment is also slightly off... it's pulling to the right. I'll get that done, once i get the tires.

I was thinking of getting a set of lowering springs (just a slight "drop", nothing major) and replacing the tired shocks/struts

whats hypermilling everyone?

jmf 05-06-2009 03:33 AM

I haven't done any modds yet. I wanted to see how high i could get the FE on driving alone. I installed a lean burn monitor which has been a great help. I use my car for work and haul tools, wood, workers and anything that will fit. My last fillup was 57mpg and I hope to improve that. I drive alot of back roads and hills, I have no doupt that this car could get 70mpg on all interstate driving with no modds.

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