Mountain driving with Honda VX

[oldertech]

We just got back from the mountains of Colorado. With no MPG reading devices, I'm wondering... I know that coasting in idle is a way to make maximum efficiency down hills, but when the hills are mountains, you have to stay in a gear to hold the car from going too fast, and not burning up your brakes.

My question: Coasting down a mountain in gear in a '92 VX - are you burning gas? Or is gas shut off to the injectors if no power is needed?

As it was, we got 47 MPG driving home to Kansas at 75 MPH with AC on a lot of the way. Sure need to add a MPG computer to know what it really is doing all the time.

Scott

[SVOboy]

If you're engine braking you will not be using gas.

Have you thought about picking up an MPGuino yet?

[bestclimb]

you can feel the deceleration fuel cut off. As you are coasting down in gear with (3rd is shows up well in the honda) as you get down to about 1000 rpm you will feel the decelration from the engine braking stop. you can pick up a replacement instrument cluster with a tach for 30 bucks from a u pick a part, and install a wire off the speedo when you install it for the mpguino. It literaly takes less than 1 hour to both. Assuming you have a 5th gen honda.

[Old Mechanic]

Considering the average speed and AC use, I would consider 47 MPG to be about the optimum mileage you would get.

I would probably get about the same around here where it's fairly flat.

With AC on fuel shut off is about 1200 RPM, so you want to use the proper gear to maintain your downhill speed. Probably 4th or 5th depending on the grade.

When climbing you can stay in lean burn if you can maintain a manifold vacuum of over 5 inches. On grades that require downshifting for the down slope, the corresponding up slope would be difficult to climb at any decent speed while maintaining 6 inches of vac.

I would say the major factor in your mileage was your high average speed, much more so than the grades you encountered.

PS VX had a factory tach.

regards
Mech

[oldertech]

Sure have thought about MPGuino. Where do I get one and where is the most comprehensive info on how to install/use?

Scott

[oldertech]

The prime reason I'd like a mileage computer is that gas tank. For a car that is so carefully thought out to get high mileage, the regular means of checking, by dividing the gallons filled by the mileage driving is really, really hard to consistently do. If you stop filling the tank as soon as the pump clicks off, you are short about 2 gallons. If you trickle, trickle, trickle, you can go to a place that I named, "hyperfill." When I "hyperfill" the tank, I can go 200+ miles before the gauge drops from F.

I've looked at the tank design and it seems the filler tube is below the top of the tank. So when we trickle, we are kind of forcing fuel into the expansion area? Has anyone else acknowledge this in the VX? We had a Del Sol, and never had wacky filling issues.

By the way, I've read that the '92 VX has a 12 gallon tank, and the '93-'95 has a 10 gallon tank. Can anyone verify that?

Scott

[NachtRitter]

I can verify that my '94 has a 10 gallon tank, according to the manual that came with.

[bestclimb]

Originally Posted by oldertech

Sure have thought about MPGuino. Where do I get one and where is the most comprehensive info on how to install/use?

Scott

http://opengauge.org/mpguino/

The install is pretty easy, there are a few of us using them in 5th gen civics, the install is pretty painless. If you require a bit of guidance just do a search in the DIY or instrumentation forums or ask.


in my DX filling to the first click, I can go about 150 miles (50+mpg) before I come off the full mark. The tank 11.9 gallons. the first 3 gallons gets it off the full mark. The next 3 brings it to the half way point. 3 more drops it to the empty mark. and the last three just about on E to sputter.

[Old Mechanic]

I cut a piece of 2X4 with a angled edge. When I pull up to the pump I drop it in front of the left rear tire, and raise that end up slightly.

Consistent fill ups and about 50-60 miles range to the same point on the gauge when it gets to about 400 miles on the odometer.

One day I will carry some extra fuel and run it out to see what the gauge reads, but the way the needle oscillates, you can probably get a pretty good idea when it stops moving altogether. I think one time I got over 9 gallons in it but I don't like to run in tank electric fuel pumps dry. In my opinion since they are cooled by the fuel, it could shorten the life of the pump.

regards
Mech