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Vacuum Gauge
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FAB Cruiser



Joined: 03 Jul 2008
Posts: 77

PostPosted: Tue Apr 21, 2009 10:47 pm    Post subject: Vacuum Gauge Reply with quote

Is there any point in fitting a vacuum gauge i.e what useful purpose do they serve?

I'm thinking of replacing my vacuum wiper motor for an electric one so I was wondering if it would be worth using the vacuum tube to drive a Gauge instead?

If I have neither a vacuum wiper motor nor guage, how would I terminate the vacuum pump outlet? I think there's a connection on the vacuum pump (which is part of the fuel pump) and the inlet manifold.

Thanks
David
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1254
Location: Nottingham

PostPosted: Tue Apr 21, 2009 10:50 pm    Post subject: Reply with quote

They are excellent for tuning for max economy and driving that way too - there are loads of websites to show how to read these. Can also oick up all sorts of faults

Sometimes are jsut have economy markings eg Red/orage/green/yellow
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ukdave2002



Joined: 23 Nov 2007
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Location: South Cheshire

PostPosted: Wed Apr 22, 2009 8:25 am    Post subject: Reply with quote

As Phil said they are great for tuning and diagnostics, but I find them really irritating and distracting as a dash instrument, maybe thats just me! Rolling Eyes
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peter scott



Joined: 18 Dec 2007
Posts: 6209
Location: Edinburgh

PostPosted: Wed Apr 22, 2009 9:59 am    Post subject: Re: Vacuum Gauge Reply with quote

FAB Cruiser wrote:

If I have neither a vacuum wiper motor nor guage, how would I terminate the vacuum pump outlet? I think there's a connection on the vacuum pump (which is part of the fuel pump) and the inlet manifold.

Thanks
David


Hi David,

You just need to close off the pipe to the inlet manifold. Just stuff a piece of metal rod or wooden doweling up the end of the rubber pipe.

Peter
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Keith D



Joined: 16 Oct 2008
Posts: 967
Location: Upper Swan, Western Australia

PostPosted: Wed Apr 22, 2009 1:13 pm    Post subject: Reply with quote

David,

Why would you want a guage that tells you if you are using a lot of throttle, then you're using more fuel. Or conversely, if you're not using the throttle at all, then you're using less fuel!!!

Keith
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47p2



Joined: 24 Nov 2007
Posts: 2002
Location: Glasgow

PostPosted: Wed Apr 22, 2009 7:11 pm    Post subject: Reply with quote

Vacuum gauge is also excellent for letting you know the condition of your engine. It can show worn piston rings, worn valve guides and as already said a great instrument for tuning the carb
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Rusty



Joined: 10 Feb 2009
Posts: 186
Location: Bunbury, Western Australia

PostPosted: Thu Apr 23, 2009 12:35 am    Post subject: Reply with quote

Someone must think it's a good idea, they put one 4" across in my Holden Commodore from new and I find it very irritating.
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baconsdozen



Joined: 03 Dec 2007
Posts: 1116
Location: Under the car.

PostPosted: Thu Apr 23, 2009 9:13 am    Post subject: Reply with quote

If you set the ignition timing and carb etc to give the highest possible steady vacuum reading then the engine is running at its most efficient.
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FAB Cruiser



Joined: 03 Jul 2008
Posts: 77

PostPosted: Thu Apr 23, 2009 9:23 am    Post subject: Reply with quote

Very mixed opinion on this one!

Am I correct in assuming the tube to my vacuum wiper motor could instead be used to drive one of these?

Thanks
David
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peter scott



Joined: 18 Dec 2007
Posts: 6209
Location: Edinburgh

PostPosted: Thu Apr 23, 2009 10:52 am    Post subject: Reply with quote

As long as it is simply a connection to the inlet manifold, then yes.

Peter
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jessejazza



Joined: 18 Mar 2009
Posts: 75

PostPosted: Sun Jun 14, 2009 11:52 am    Post subject: Reply with quote

Fitting a small vacuum gauge so called economy gauge is a waste of time.

The 52mm type are simply a waste of time other than to let you know when the accelerator pedal is pressed down! The Gunson lo-gauge can be used for tuning reasonably well but as a diagnostic tool a decent 6 ins diameter one is what you need. A barometer made from beer kit tube will provide an excellent DIY diagnostic tool for the garage for virtual nil cash outlay. I got my 6 ins gauge from Canada on ebay after a bit of hunting.

Discussed her on another forum i belong too.
http://www.r3w.co.uk/forum/showthread.php?t=16190&page=2
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Nic Jarman



Joined: 05 Oct 2008
Posts: 1035
Location: Stoke by Clare, Suffolk

PostPosted: Mon Jun 15, 2009 12:42 pm    Post subject: Reply with quote

Another use for vacuum gauges is to balance multiple carbs.

I have 4, so who is the daddy! Laughing
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PAUL BEAUMONT



Joined: 27 Nov 2007
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Location: Barnsley S. Yorks

PostPosted: Mon Jun 15, 2009 1:40 pm    Post subject: Reply with quote

Doesn't you car have a vacuum reserve tank to feed the wipers? if that is the case you need to feed the gauge from the manifold side of the tank or it will probably not do a lot!
Paul
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FAB Cruiser



Joined: 03 Jul 2008
Posts: 77

PostPosted: Mon Jun 15, 2009 3:29 pm    Post subject: Reply with quote

Yes, I was going to replace the Vacuum motor with and electric one and then use the tube to drive a guage. But based on the comments here, it's probably of little worth.

Thanks
David
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Mon Jun 15, 2009 4:58 pm    Post subject: Reply with quote

David,

From memory your car has a double diaphram fuel pump that assists the wipers when accelerating so using a vacuum gauge on the wiper tube would give a false reading.

Art
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