"Economy" meter

[dan filipi]

I had a car once with a vacuum meter in the dash.
It had a scale on it red, yellow, green. For best fuel economy keep it in the green.

A recent thread here got me to thinking how I could put something like this on the bike.

Without some kind of gauge and relying only on feel, sound and throttle twist it's hard to know what the best speed and rpm is to be running on the highway for best mpg.

I had a vacuum operated cruise control on mine in the past.
I tapped vacuum hose fittings into the intake pipes so I think I'm part way there but how would I make this so the vacuum needle would be smooth and could I tie 2 intakes together with a tee without affecting mixtures.

 

[mcgovern61]

I was taught in driver education class (1978) the best economy is achieved by putting an egg between your foot and the gas pedal. Don't break the egg and your MPG will be the best you can achieve. I apply the same principal to the throttle on the bike. It would be nice to see a gauge to prove that. My Ford Focus has a digital bar graph that performs the same function.

 

[dan filipi]

I was taught in driver education class (1978) the best economy is achieved by putting an egg between your foot and the gas pedal. Don't break the egg and your MPG will be the best you can achieve. I apply the same principal to the throttle on the bike. It would be nice to see a gauge to prove that. My Ford Focus has a digital bar graph that performs the same function.

That's the way I drove too, that and using the brakes as little as possible. I've been able to raise mpg on my service van from 10 to 12 mpg.

On the bike though, as well as the car, it's impossible to know at what speed say above 55-60 when the wind resistance is starting to lower mpg. Only way I can think of is tracking the mpg for a couple hundred miles at different speeds or by a vacuum meter.
Also sometimes it might be better to down shift on a grade and slow down a bit.
I think if the vacuum is held at it's highest would be best.

 

[slabghost]

Assuming you have not altered your air box and have a good filter you should be able to get an overall vacuum reading from the plenum under the air filter. This would require drilling and installing a nipple or fitting of some kind. Since this is before the carbs I'm not sure how well it would work.

 

[AApple]

A TRUE vacuum reading would need to be taken from below the throttle plate(s). On a multi-carb set-up like the one on the 'Wings, that's not gonna be easy at all, since the carbs mount directly to the heads(basically). Taking vacuum for a gauge from only one carb with this design will inherently have a "pulse" to it. That's why the manometers have a liquid in them...to smooth those pulses out so you can get an "average" on the vacuum reading.
I have several types of vac gauges..I may try a few things to see what happens when connected here or there....this might be interesting. Of course, it won't be as interesting as trying to rid with an egg in my hand, on the throttle, but interesting none the less. :mrgreen: :smilie_happy:
I wonder if you could connect a hose to each carb, connect those to a 4-way fitting, and then take a gauge hose from there?

 

[slabghost]

Connecting a can to two of the vacuum ports and the guage from there might be fairly accurate. If you can find a way to seal up an opened soup can.

 

[dan filipi]

I'm going to try one gauge to one of the vac fittings I already tapped in with one of the carb sync valves inline an see how that looks.
I do have a plastic vacuum canister I made up for the cruise control, maybe that inline would smooth the pulses better.
Looks like a good excuse to go play in the garage and do a video :builder:

 

[dan filipi]

I hooked up one carb to the canister I made and it smooths the pulses out real nice, without it the needle bangs stop to stop lol.
The canister fits in below the right fairing storage, just gotta figger a way to mount the gauge and make a test run.

 

[mike in idaho]

Just hook the gauge line to one of the intake branches, with the carbs properly synched all four will show the same vacuum level anyway. Use an aquarium valve in the line(like the valves used in a carb-sync tool) to dampen the pulses in the gauge. On the GL1100, a tee inserted in the vacuum advance hose would do nicely for a hookup spot.

 

[dan filipi]

I thought about using one of the valves from my sync gauges but they turn too easily and will probably need to be fiddled with occasionally to keep the needle moving and not fluttering.
The vac storage container works good so that's what I'll use for hookup to manifold vacuum.

The vac advance port has vacuum only on acceleration and seems to render steady needle movement so that might be a better place to tap in even without needing a canister or valve inline.
The target gauge reading should be 0 I would think which would make reading the gauge easy. Any reading above 0 would indicate a load on the engine.

I'll do some test riding this weekend both ways.

 

[AApple]

NOOOO!!! :swoon:
You'll wanna see the HIGHEST vac reading...."0" would indicate a load on the engine...a heavy load, such as acceleration from a stop, or passing someone. The higher the reading, the better. See what it shows at idle...you should see the same(or really close) at cruising speed. :rtfm:
:mrgreen: :wave:

Then again...IF you tap into the vac advance, it would be different, but I don't know how accurate that would be... :headscratch:

 

[dan filipi]

NOOOO!!! :swoon:
You'll wanna see the HIGHEST vac reading...."0" would indicate a load on the engine...a heavy load, such as acceleration from a stop, or passing someone. The higher the reading, the better. See what it shows at idle...you should see the same(or really close) at cruising speed. :rtfm:
:mrgreen: :wave:

Then again...IF you tap into the vac advance, it would be different, but I don't know how accurate that would be... :headscratch:

Right, higher vacuum is better if tapped in on the manifold vacuum on the head side of the throttle plate like the sync screws but lower if tapped on the other side of the throttle plate where the vac advance gets it's vacuum.

 

[dan filipi]

I get only 3" vacuum from the advance port, too little to gauge where my throttle is at so I hooked up to the intake through the vacuum storage container.

Maybe have a chance this weekend to try it out.

In the video, while reving it's in 5th gear with light pressure on the brake pedal.

 

[dan filipi]

About 125 mile ride showed that running at 55 mph on the flats gave me the highest vacuum.

On 5% grades I'd get higher vacuum buy going into 4th.
It seems like my target vacuum is 5-8", it's hard to get 10" unless going down hill of course.

Since I had varying winds I have to test some more but for the most part keeping a light twist on the throttle and not lugging the engine seems to yield the highest vacuum, pretty much what I thought and the way I usually ride anyhow.