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!

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.

justinor

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.

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.

****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?

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.

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.

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.

regards
gary

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?

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.
justin

Possibly.

They'll never pay for themselves in FE gains. If you want them for fun, enjoy.

It's the practice of trying to exceed the EPA FE ratings. It includes the modifications you're asking about, but mainly it consists of the driving style changes we discuss here.

Overinflation issues?
 

I'm always reading on hypermilling suggestions about over-inflation of tires, but so often I read about the downsides on "recommended tire inflation" instructions. And that is that over-inflation can cause some erratic and dangerous handling issues in wet weather. Have any of you who commonly inflate the tires to the sidewall max had any problems like that? Rainstorms can come up quickly, and I don't see myself getting out of the car and lowering pressures when a downpour saturates the highway. Also, having been in a 10 car pileup when the roads were slick has tended to make me more cautious. Any thoughts?

Scott

I've been "over"-inflating for 400,000 of my >600,000 miles of driving experience. I experimented and found it to solve many of my tire problems and concerns long before I had any interest in saving gas. The common fears usually do not materialize. It does differ from one driver/car combination to the next.

The best way to find out what works for you is to experiment. Try different pressures. The car's posted pressure is the minimum safe pressure and the pressure stamped on the side of the tire is the maximum (there are some exceptions but maximum safety is between those two pressures). Each time you adjust it, try to gauge how it's working for you; feel the ride and handling and pay special attention when it rains.

It is usually said that the center of the tire tread will balloon out when overinflated. If that's truly the case, then it will improve hydroplaning-resistance, becoming safer for your particular concern with sudden downpours.

The only time I've found wet traction to suffer from additional inflation is with the rear tires on my pickup. The truck is labeled 35psi, and the LT245/75R16E tires are rated for up to 80psi. With no load in the bed and the tires up to 80psi, the rear tires can spin under moderate acceleration from low speeds. At 70psi they're fine. What do you drive, and what size tires does it have?

I haven't noticed much of a difference with my tires at 44psi when its wet, but when there is snow on the roads, I definitely do. I routinely lower my tire pressure when I have to drive in the snow. That also leads me to believe that even though I might not notice any difference in the rain, there nevertheless is one.

i forgot to mention that the AC has been on constantly since I purchased the VX. Here in Phoenix, it's already approaching temp's of 100 degrees!

A nasa study concluded that hydroplaning decreases as tire pressure increases. The speed at which hydroplaning occurs is higher with higher tire pressures.

https://www.tirerack.com/tires/tirete...e.jsp?techid=3
They only explore inflation below the specified 35 psi, but physics doesn't know any such limits. If it's worse below, you can extrapolate that it's better above.

Snow, on the other hand... see above.

Everyone should be slowing down in bad rain storms. That solves hydroplaning.
justin

tire inflation
 

Hey everyone, thanks for your input on the inflation issue. I'm driving a '92 Honda Civic VX with P165/70R-13 Sumitomo HTR T4. The sidewalls state an inflation of 51 lbs max. That seems like a lot. I have traditionally overinflated 4 lbs with no problems but with your comments, will push that and try more.

And a message to our original poster mnstrvx in this thread. Congrats on the new VX!!!!!!! Didn't mean to take away from your questions.

Scott

scott- the inflation thing was news to me too! I always ran "about" 32-35psi in my car tires... my girlfriend has a yukon with LARGE tires, i might try to inflate those to or near the recommended max.

If the Yukon has the stock tire size, it can almost surely go to 44psi without any adverse effects.

Okay... you do know that your tank is 10.0 gallons, right? So 420 miles on a tank (how many gallons did you fill up with? Probably less than 10) is probably mid 40s. It's very easy to get good gas mileage in the VX. You don't have to do anything too fancy and there are some key things you should know.

0. The more you brake, the more fuel you use. Try to drive in such a manner to avoid slowing the car down more than necessary. Fuel saving is all about conservation of forward momentum. Roll baby roll! (Coasting in gear is less efficient than coasting in neutral. Leave it in gear if you are coming to as top.)

1. When the engine is cold, the VX gets piss poor gas mileage. If you are doing lots of short trips and you're not seeing the temp needle get close to the little thermometer picture thing then you're never going into lean burn and are generally using lots of fuel.

2. Once the engine is warmed up (the temp gauge needle is just below the temp picture) accelerate slowly and shift at RPMs that will have you pulling from 1000 or 1050rpms after you have shifted. No reason to shift at higher RPMs, unless going up hills.
On flat here are my shift points:
1st and 2nd gear @ 1500rpm
3rd and 4th gear @ 1200rpm
5th gear @ 1100rpm.

3. Don't drive over 65mph. Speeds between 30mph and 55mph in 5th gear will get you the best mpg.

If you follow the above points while accelerating with a feather foot you will have mid 50s or I'm a Scottish terrier (unless you do lots of short trips and lots of city driving). The VX does not shine in the city, unless you learn some more advanced techniques.

Okay, on to more advanced and high falutin' feats of fuel savings beyond feather footing for when you are doing lots of short trips with cold starts and/or city driving.

The first five minutes your engine is warming up uses tons of fuel. One way I fight this is by employing the tried and true technique of pulse and glide (tried and true at least for this car). I'll get up to slightly higher than my desired speed and then turn my car off and coast for awhile, then I'll bump start the car and repeat the process. I'll do this until my temp is up, at which point, if your car is running right and your head lights and A/C aren't on, you should idle at 500rpm in neutral negating the need for turning your engine off and coasting to save fuel. Coasting in neutral when the car is warm is an easy way to save fuel.

In the film Wall-E there is a scene that makes a very nice and simple analogy of pulse and glide. Wall-E is in outer space holding onto a Fire Extinguisher. He fires the extinguisher to propel himself forward.. then glides for awhile.. and then repeats to propel himself forward again. Same principle on the road.

To save fuel while the engine is cold employ the pulse and glide method:
Accelerate in the highest gear possible to just above your desired speed, then put in the clutch, wait a half a second or so, kill the engine, wait another half a second, turn it back to ON position (leaving the engine off) and coast in neutral for as long as prevailing traffic and your patience will allow. Then bump start it. You should avoid bump starting in 2nd gear, and definitely not in 1st gear! There are certain speeds that correspond to certain gears you should bump start in.

Speeds that correspond to the appropriate gear to bump start in:

5th gear; any speed above 13mph.
4th gear; between 9 and 13mph.
3rd gear; between 4 and 8mph.
2nd gear; between 2 and 3mph.
1st gear; never.

It's tricky to bump start in 2nd gear without causing a knock or lurch so I advise against it. Use your starter if you are going this slow.

If there is any kind of lurch or knock sound when you bump start you are doing it at too high a speed for the gear you are trying to do it in and/or letting the clutch out to quickly!

To bump start: make sure your ignition is in the ON position. Put in the desired gear and let the clutch out as if you were doing a normal shift. If you do it too slow it will not work and if you do it too fast it will cause a knock or lurch which I don't think is good for the engine or tranny. As soon as the ignition catches, IMMEDIATELY put the clutch back in and engage the appropriate gear for your driving speed. Immediately putting the clutch back in will help prevent any damage being done to your engine or tranny.

Disclaimer:
I have no knowledge of the ill effects on the engine or related components from bump starting properly on a cold engine. I've been doing it for a year (even in winter) and while I had some undesirable effects for a short while (I was having faulty alternator issues), in the last several months the car has been purring like a kitten.

City driving.
1. Saving fuel in the city environment is all about LOOKING AHEAD and paying vigilant attention to what the traffic lights ahead of you are doing and more importantly what traffic ahead of you is doing. The better you can predict what's going to happen in front of you the more fuel you have the potential to save. It's all about ROLLING up to the traffic lights! Let the other cars accelerate by you only to have to slam on the breaks for the red light. Half the time you'll roll through the green light that you gave enough time for the red light to become, while the other cars have to get going from a stop. Avoid non thinking REACTIONARY driving. Employ the PROACTIVE model of responding ahead of time to what people in front of you are doing. Keep as much distance between you and the cars in front of you without keeping enough distance for someone to pull out in front of you. ;):thumbup:

2. Accelerate slowly and shift at 1500rpm from 1st and 2nd gears. When you are going fast enough to keep up with traffic coast in neutral for a bit (or with the engine off if your engine isn't warm yet) until you need to accelerate again to keep up with traffic.

3. Remove any extra weight from your car that you don't absolutely need to haul around with you. The VX is a very light car. Any extra weight has more negative effect on gas mileage than in other cars.

I encourage others to challenge, disagree or revise any of my points!
Thanks.

I would revise the terminology used above. Each person's opinion of exactly how to describe things differs, but above it seems that "Pulse & Glide" is applied, without further qualification, to both engine-on P&G and engine-off P&G. I prefer to describe engine-on P&G as merely P&G, and engine-off P&G as EOC P&G or just EOC (Engine-Off Coasting).

Also, I don't recommend EOC for new hypermilers unless they are already comfortable with P&G first.

One technical point I'd question is being light on the throttle during acceleration. Unless you're trying to use lean burn (can you, during acceleration?), wouldn't you want to reduce pumping losses by laying on the gas pretty hard (and shifting even lower if you're accelerating too fast)? That strategy is very effective in my car, but I don't know if it would be in a VX.

I would recomend a lean burn monitor. You can accelerate quite well in lean burn if you can see where the limit is. Alot of the time I only have to back off the thottle a little to stay in LB, and still accelerate. I haven't had any luck with P&G or EOC, I try to just stay steady, slow a little on the hills and brake as little as possible.
justin

Thanks for your reply holycow. I abstained from the acronym terminology cause I didn't want to scare off the new poster given the whole business of EOC itself can be pretty intimidating.

Yes, you can lean burn while accelerating. I used to accelerate harder but found that I wasn't getting as good gas mileage as feather footing acceleration, even though getting up to speed takes longer. I don't have an mpg scanner, but in my experience combining slow accelerations with excessive EOC is how I achieved 67mpg over three tanks (1600 miles or so).

This is really the best way to go. You don't need a lean burn monitor, you just gotta "feel" it :). Which is more fun imo. But it would be cool to have a monitor.

thanks again for the info. i just stepped back into this section briefly and noticed more posts! lol...

I am currently attempting more P&G (not EOC). I don't feel "comfortable" with EOC since I have a heavy traffic commute both ways (to and from work), and I don't believe the wear and tear on the drivetrain is "worth" it. although i might try this in the future.

in AZ heat, the engine running cold isn't much of an issue.

I ahve been noticing better MPG lately. With more attention to driving habbits... I have been "busy" with the gas log, as I find it to be a nice little tool.

BTW, the yukon has the "stock" tire size, but not the stock tires. The tires state "max" psi at 35!! and that is what the car is set at

I am pleased with the ability to "compare" my current MPG log with the vehicles stated city mpg rating, actually I am doing slightly better. Keep in mind that AZ is already seeing temperatures in the 105-110 range so the AC has been on ALL the time since I purchased the VX... i would imagine that I would see an increase in MPG if i was not using the AC. (although definately not an option right now).

I cannot imagine that this car will do "better" on the highway? With say, 65-75mph speeds? Anyone care to share their highway driving MPG experiences? the mpg rating is suppose to be 55 highway.

There is nothing at all wrong with that. Nobody should do it if they don't feel comfortable with it.

There would be an increase, but there's more important things than fuel economy -- like not having heat-related health problems, and not feeling too uncomfortable. With the temperature that high you get a large benefit to fuel economy anyway, at worst it is canceled out by the AC.

Most cars do better on the highway. While they're subjected to higher speeds which increase aerodynamic drag and engine RPM, they don't have to stop and go. When you brake you discard energy that you've already made out of fuel and is a huge effect on FE. Plus, the VX has lean burn, which I'm sure works a lot better for steady cruising than it does for city traffic. I think many VX drivers go really slow on the highway though, so I don't know how well it does at 65-75mph.

If the maximum is truly 35psi (and if the Yukon recommends 35psi), that means they are probably near their maximum load rating too. I would not want want to run those tires on that vehicle.

However, it may be ok to use 44 or 51 psi as your maximum. I would not recommend it and I would not do it - not for worry about the tire or any practical effect, but for legal ramifications if there was a tire failure during (or causing) an accident. I suspect that exceeding the stamped maximum could put you in a position of liability that you wouldn't be in had the tire failed at a pressure not exceeding the sidewall stamp.

https://www.geocities.com/barrystiretech/loadtables.html
Edited for brevity, more detail at the link...

vx mpg at 60 mph
 

I cannot imagine that this car will do "better" on the highway? With say, 65-75mph speeds? Anyone care to share their highway driving MPG experiences? the mpg rating is suppose to be 55 highway.[/QUOTE]

At a true 60 mph ( GPS speed ) with a flat road and zero wind my vx does 56 mpg measured with my Mpguino. I would think 65-75 mph would be a good bit less. I also would like to here what others get at highway speeds.

turbothrush- thanks for the info. I think the VX's "sweet spot" is probably 60mph. Keeping the engine "at/near/below" the 2,000rpm mark "seems" to produce the "best" return (in mpgs).

holycow- I actually looked on the tire the night we spoke about increasing tires pressures, and the tire actually says "maximum psi, 35". these are not the stock tires that came with the vehicle, and they are "slightly" more aggressive tread than what the stock tires would have had. I can't really complain of the results that I get from the yukon, as it get's roughly the 16-18mpg that it's listed to get (it's the 4.8L v8). Plus my girlfriend is much more impatient that I am with driving habbits. She drives the thing like it's a tiny sports car (I don't approve of it, but what are ya' gonna' do?)

Not to mention the fact that I purchased those four tires nearly new (mounted/balanced/installed) for $200 dollars (for the yukon). I figured I would get 30k miles out of them, and than worry about swapping for something else down the road.