Jaeger/ Smiths gauges: Which cars came with a vacuum-gauge?

[OldDuffer]

Back in the day, cars had myriad gauges; voltmeters, oil-pressure, water-temp, ammeters and a fuel gauge were standard. Some had an oil-temp too. British stuff had Jaeger/ Smiths

A Triumph Stag did well, as did Interceptors. Did any car have the full set? More especially a vacuum-gauge, or was a vacuum-gauge purely a car-accessory shop item?

I ask because eBay will show a helluva lot of used Smiths vacuum-gauges, where are they coming from?

Edited by OldDuffer on Sunday 17th May 10:35

[interloper]

Having seen an aftermarket vac gauge in action, it was possibly the most useless gauge ever, needle flicking all over the place. I can't imagine any manufacturer deciding this was useful to the driver unlike most other dials.

I would be amazed if it was ever a standard fit on a car.....

[2xChevrons]

The only car I know came with a factory vacuum gauge was the A-Body Plymouth Barracuda, which as standard had a 'Performance Indicator' (big vacuum gauge) which was swapped for a tachometer when you specced the appropriate options pack.

I might well be wrong, but IIRC the MPG gauge on older (E30/E34/E36 era) BMWs was just a vacuum (or boost for the turbodiesels) gauge with an appropriately graduated scale. The later ones actually used info from the ECU to measure fuel consumption at the injectors and road speed.

[mph]

The Sinclair C5 was serviced by Hoover - surely a vacuum gauge was an option

[StuntmanMike]

interloper said:

Having seen an aftermarket vac gauge in action, it was possibly the most useless gauge ever, needle flicking all over the place. I can't imagine any manufacturer deciding this was useful to the driver unlike most other dials.

I would be amazed if it was ever a standard fit on a car.....

Aren’t most econometer gauges in BMWs vacuum gauges?

[lowdrag]

Mercedes had an "economy meter". In my 380 SL W107 the only time it was out of the red was a) the engine was switched off or b) going down hill.

[john2443]

What is the value of a vac gauge?

I don't remember anything having one other than as an excuse for an economy gauge.

Mine has Amps, Oil pressure, Fuel, Temp so 6 with Speed and Revs.

[interloper]

StuntmanMike said:

interloper said:

Having seen an aftermarket vac gauge in action, it was possibly the most useless gauge ever, needle flicking all over the place. I can't imagine any manufacturer deciding this was useful to the driver unlike most other dials.

I would be amazed if it was ever a standard fit on a car.....

Aren’t most econometer gauges in BMWs vacuum gauges?

As another poster implies they work on the same lines but are heavily damped. An old school vacuum gauge would be all over the place at idle.

[OldDuffer]

Agreed. Until too late, don't suppose the majority looked at more than the fuel gauge anyway.

Often marked as a economy/performance or mpg gauge, all are essentially vacuum-gauges. Very 'old skool'; way before such things as a Wideband O2 gauge.... and yes, of about the same value to most, ie nil.

But that wasn't the question.

Edited by OldDuffer on Sunday 17th May 17:41

[2xChevrons]

john2443 said:

What is the value of a vac gauge?

I don't remember anything having one other than as an excuse for an economy gauge.

Mine has Amps, Oil pressure, Fuel, Temp so 6 with Speed and Revs.

Economy was always their main supposed purpose (and they were/are mostly marked and coloured to suit). On a simple carb-fed engine a vacuum gauge is as good a proxy for how hard the engine is working as you need, and having a gauge that points to a 'naughty-naughty' red zone when you open the throttle too much was enough to give economy-minded drivers a guide.

A properly calibrated and damped vacuum gauge could also be a diagnostic tool and general indicator of engine condition (since the engine is effectively an air pump) but that really requires noticing changed vacuum readings from the norm. If your engine generated, say, 18inHg at idle when it was new and now you notice it's only pulling 15inHg the rings may be worn. Fluctuating readings on an otherwise damped gauge could point to worn valves on one cylinder etc. You can also use a vacuum gauge to tune a carburettor - adjust the mixture at idle until you get maximum vacuum and then dial it back in a bit.

But yes, largely pointless and at best a relic of the days when you had to dedicate a Sunday a month to keeping your Triumph 1500TC in fine fettle, and at worst only really useful if you make monthly notes of your peak and idle vacuum gauge readings in a little notebook you keep in the glovebox along with every fuel stop and your trip and lifetime running MPG averages...

[OldDuffer]

interloper said:

Having seen an aftermarket vac gauge in action, it was possibly the most useless gauge ever, needle flicking all over the place. I can't imagine any manufacturer deciding this was useful to the driver unlike most other dials.

I would be amazed if it was ever a standard fit on a car.....

Be amazed. Hardly the most useful day-to-day, yet certainly of value if understood, nil if not. That would apply to most gauges. On eBay this moment, the number of Smiths gauges variously marked-up "vacuum/economy/mpg" etc would suggest some Brit-iron had these ex-factory. Anyone know which?

[lowdrag]

In one car I have a speedo, rev counter, oil pressure gauge and temperature gauge. The fuel gauge is a bamboo cane marked off at 5 gallon intervals. Who needs more?

[mog1275]

They make an excellent diagnostic tool if you know how to read it

[OldDuffer]

Yep, only recently had sluggish running. I'd have found it, but the vacuum-gauge had me looking for a leak from the off. Sure enough, a weeping hose at the servo was the cause. How did I know so quickly? Vacuum-gauge stayed low, robbing the dizzy of ignition advance.

Short of a Wideband O2 gauge which I have on one of mine, or a gas analyser, for all manner of DIY woes, it's as good as old skool gets.