18 replies to this topic

[finch661]

has anyone fitted a vacuum gauge to their mini, http://www.minispare...=...AUGE BY TIM

are they useful at all, and if so, how do you fit one?

thanks

finch

[Guess-Works.com]

Vac' gauges are very useful if you want to reduce the amount of petrol you're sticking in your tank... which is why they are also commonly called economy gauges.

You can attach them in two ways, put a T piece in the vac line from the carb to the dizzy and run it off there, or drill a hole ( or use the existing hole if present ) in the inlet manifold and with an adaptor, run it off that..

What you then need to do is understand what the gauge is telling you... it measures the vac in the inlet manifold, which is directly related to how far the butterfly is open. The higher the vac, the less air/fuel mixture is entering the engine, therefore less fuel is being used... When cruising the art is to get the needle as far in the 'green' as possible while maintaining road speed.

I have one on my 1330, which drinks juice like there's no tomorrow when on full throttle, but when cruising, I can easily return 30+ mpg, by being thrifty with the right foot.

[dklawson]

I run a vacuum gauge (VDO) on my Mini and (AutoMeter) on my daily driver Honda. As John said, their best function is helping you improve fuel economy. However, they also offer some information that is helpful in diagnosing engine problems.

I have mine connected to a "T" in line with the brake servo hose. You can "T" into the carb to dizzy vacuum line as John suggests, however, those readings will be slightly different while cruising. If you use that connection method the reading at idle may be very different depending on which side of the throttle butterfly the carb vacuum port is.

A third connection method is to buy the carb spacers from Mini Spares designed for this purpose. They replace the normal spacer and include a tapped hole with a barbed fitting to attach the vacuum hose.

[stormintrooper]

iv heard that putting the gauge into the vacuum advance line with a T piece gives incorrect readings?

[lrostoke]

I actually use a vacuum gauge for setting the timing...read about it on a classic car website..it based on the theory that as engines wear the standard timing marks can be out.

You basically start the car let it tickover and advance the timing untill the gauge shows its highest reading, you then retard the timing so that the gauge reading drops by 1/2" of vacuum.

Used it on 3 minis works a treat.

[jaydee]

Thats actually interesting, have to get a gauge and try this.

[liirge]

look at this of your interested

[GreaseMonkey]

Does the restrictor have to be used with Smiths gauges? Or does the restrictor come along with the carb spacer take off? I have a Smiths Vacuum but it didn't come with the restrictor, I think.

Edited by GreaseMonkey, 23 April 2009 - 02:54 PM.

[liirge]

Im not sure mate, i dont thin anyone uses them for minis, probably not enough vacuum...but i could be terribly wrong!

[dklawson]

The purpose of the restrictor is to dampen slightly the bouncing needle that can occur in a vacuum gauge. You can operate the gauge fine without it. I think as a diagnostic tool the gauge is more useful without a restrictor. As for the Mini "not having enough" vacuum, there is no flow through the gauge itself, just in and out of the connection hose/tube. All engines when in proper tune and good condition will generate about 20" of vacuum at idle. Vacuum is not a function of the engine size or type.

The following are a few links I keep for reading and using vacuum gauges:
http://www.users.big...ergoff/vac1.htm (be sure to click on the forward links... there's more than one page)
http://www.secondcha.../public/186.cfm (be sure to click on the green "scenario" links)
http://www.classictr...cts/vac/uum.htm
http://www.centurype...ge-spg-148.html

[liirge]

Yup, sorry about that misinformation.
Good links you got there Doug, you favorites list must be enormous.

[Ozymandias]

Would I be able to use a vacuum gauge on an SPi (no carb!) If so, where would I connect it?

[gazza82]

You should be able to get a new spacer with an adaptor so that fits between carb and inlet ... like this http://www.minispare...ngs.aspx?130207

 

On an SPi .. no idea, sorry.

[dklawson]

The SPI and MPI engines will still have intake manifolds and therefore, vacuum to measure.  I have no first hand experience with them so I cannot tell you if there is a pre-existing tap for you to connect the vacuum hose to.  If you don't find one, look at placing a T fitting between the manifold and any brake servo that is fitted.  You will have to make sure that the T is located between the servo's check valve and the manifold.  If you locate the T on the "wrong" side of the check valve the vacuum reading will hardly change at all... rendering the gauge useless.

[Ol timer]

Am looking at the idea of a vacuum gauge however I really don't want to faf around removing the carb and fitting a vacuum plate. Where can I get a T piece so I can run between the dizzy and the carb?