Econometer/Vacuum Gauge Installation Guide

[Johnny Mullet]

This is also posted in my Metro thread, but I wanted to post it here in the instrumentation section for those interested in using a vacuum/boost gauge in their vehicle. This guide is for a 1998 Metro, but installation would be similar on most vehicles.

The new gauge is a "Vacuum/Boost" gauge made by Sunpro, but the only scale I can use on a non-turbo vehicle will be the vacuum side of the gauge.



The first thing I had to do is find a proper mounting location and on my car, the spot on the column was perfect for a 2" gauge. I simply used the supplied self tapping screws and secured the mount to the top half of the column cover...............



I then placed the gauge in place through the mount and ran the vacuum tubing and electrical wires for the gauge illumination behind the cluster cover so nothing is exposed.



I simply removed the heater control cover plate and unplugged the bulb and spliced the illumination wires right into the harness so the gauge lights up when the cluster lights up.............



The mounting and illumination is now complete. The last thing to do is to run the vacuum hose provided with the gauge through the firewall to find a vacuum source. I ran a long screwdriver through the main wiring harness boot and fed the tubing through the gap made by the screwdriver.



I then adapted the connector to a vacuum source to monitor my fuel economy.



Here it is all installed and in the normal driving position, nothing on the cluster is blocked................



NOTE: The vacuum line was spliced into the large vacuum line at the booster originally shown in the picture, however, this was causing poor readings. I later spliced into the vacuum source very close to the engine for instant readings of the engine vacuum. After driving with the gauge, it actually tells you when to shift if you know how to monitor it and will also make it easier to stay easy on the throttle.

[cfg83]

Johnny Mullet -

Most excellent! I just had my mechanic install one this week :

Vacuum Line Connection :


Cheapy JC-Whitney Gauge


It's on a cheezy Glow-Shift Gauge Pod, and then zip-tied to the dashboard cover.

At idle or in steady-state 5th, it reads a steady 10 In Hg. Is that correct? What should it be? Also, my cheapy gauge doesn't go negative like your Sunpro. I don't really know how to use it for shifting. I mostly got it to watch for engine problems.

CarloSW2

[Johnny Mullet]

The way mine operates is kinda weird, but I have it figured out and use it to save gas.

Starting the car, the gauge reads about 15 at idle and as you accelerate the vacuum drops and the gauge can read almost zero at hard acceleration. During upshifting, you can actually watch the needle slightly raise in vacuum right at the ideal shift point and it's pretty closely timed with the dashboard shift light. When letting off the gas, the gauge will read around 20-25 depending on speed.

Once you are up to normal driving speed, it's up to you to find the sweet spot. On my particular setup, I get the best fuel economy at around 55 MPH and the vacuum gauge reading around 10 on the dial. I try to keep it there steady. The gauge is sensitive and will change with throttle position/load. I use this to keep a steady throttle position to save fuel.

[Vince-HX]

engine vacuum is also a good indication of how healthy your engine is.

Mine read 21 @ idle, 15-17 @ 45mph, and 12-14 @ 65 mph, 23-25 under engine braking. It really helps because I can dial in the right amount of throttle very quickly for the speed I want to travel.

Negative boost FTW

[getnpsi]

I sprang for the autometer vacuum only one so it would match the oil pressure and other gauges ive collected along the way from modding cars. it was $45 on ebay. I think this is a great direct feedback tool for the driver who doesnt want to spend for the scangauge.

[azlar]

cfg83,

If you're getting 10 inches of mercury, either your engine is sick, or it's a bad vacuum source. Should be getting 15-18 at idle.

Is the needle steady? Does it bounce up and down, or slowly fluctuate? This gauge is a great indicator of both engine health and economy. Check a service manual or on-line reference for details about the readings.

The boost side is a waste of money, unless you have a turbocharger. Not a popular ecomod option...

I've run that gauge for 20 years and it's about the best fuel efficiency meter there is (for ICE).

[cfg83]

azlar -

Originally Posted by azlar

cfg83,

If you're getting 10 inches of mercury, either your engine is sick, or it's a bad vacuum source. Should be getting 15-18 at idle.

Is the needle steady? Does it bounce up and down, or slowly fluctuate? This gauge is a great indicator of both engine health and economy. Check a service manual or on-line reference for details about the readings.

The boost side is a waste of money, unless you have a turbocharger. Not a popular ecomod option...

I've run that gauge for 20 years and it's about the best fuel efficiency meter there is (for ICE).

Thanks for the info. The needle is rock-steady so I am hoping it's a bad source. I'll do some homework and see what's up.

CarloSW2

[Johnny Mullet]

Looks like the mechanic who did yours hooked to the PCV valve? I would find a source directly to the intake or closer to it.

[cfg83]

Hello -

My mechanic used his professional vacuum gauge and it read 17 in. Hg at idle RPM. He tapped into the same connection my vacuum gauge is using.

Verdict: My vacuum gauge is crummy.

The Lesson: Don't buy cheapy Garage-Pro vacuum gauge from JC Whitney or you'll get what you pay for.

I'm working on getting a better V-Gauge.

CarloSW2

[Johnny Mullet]

Wow. The old vacuum gauge I was using was an older one offered by JC Whitney and it did not even have a number scale on it, just a green "Economy" and a red "Power" display in it. I had no issues with it after 10 years of use in multiple vehicles until the needle fell off.