Vacuum and its importance to engine performance (1 Viewer)

[21NDone]

Vacuum as it pertains to engines and their performance intrigues me. I know enough about vacuum to stumble my way through using it as a diagnostic tool. I’m a data guy because.. data doesn’t lie. Readily available data is best.

From my peanut – What is the best approach to monitoring, in real time, engine vacuum on a FJ40 with a F engine? I would guess the answer is a vacuum gauge. If, going down that path, what is the desired location? In the cabin of the truck? Engine bay? Both? What have you done? How do you use the information from the gauge? Are there better options than a gauge?

Few questions – appreciate any feedback - Cheers!

 

[charliemeyer007]

I have a vac gauge hanging on my dash since about 1986. Helps with fuel economy. Throttle position placement is determined by listening to engine and looking at the speedometer and the vac gauge. There is point where no more speed is obtained but the noise increases and the vac drops.

 

[mattressking]

Vacuum is a measurement of engine health. The lower the vacuum, the less ability an engine has to pull fuel into combustion chamber. This is very important on carbureted engines because vacuum pulls the fuel through the circuits to create combustion. Poor vacuum causes rough running, hesitation, poor idle, misfire, etc.

The reason folks think fuel injection conversions are great (sniper for example) is because fuel is pressurized into the venturi and air fuel is computer controlled to compensate for poor mixture via O2 sensor.....therefore fuel injection masks a majority of issues by overcompensating for poor engine health (to a point).

Put a gauge on an unused port that is about close to center on the manifold and watch. A gauge is not necessary in the cab, if you are that nervous about vacuum measurement, your truck is poorly maintained. A quick connection and measurement when the truck is cold and hot is a great check to perform during oil changes or if you noticed a difference in idle/performance.

 

[GA Architect]

Vacuum as it pertains to engines and their performance intrigues me. I know enough about vacuum to stumble my way through using it as a diagnostic tool. I’m a data guy because.. data doesn’t lie. Readily available data is best.

From my peanut – What is the best approach to monitoring, in real time, engine vacuum on a FJ40 with a F engine? I would guess the answer is a vacuum gauge. If, going down that path, what is the desired location? In the cabin of the truck? Engine bay? Both? What have you done? How do you use the information from the gauge? Are there better options than a gauge?

Few questions – appreciate any feedback - Cheers!

With an unnecessary ash receptacle, I just purchased a dual 2" gauge plate and these vintage gauges. I have since installed some of the autometer angle bezels for a better visual from the seat and ordered some new Veethree gauges. Once they get installed, I'll update my thread accordingly.

As for using the vacuum gauge, below is a Stewart Warner Motor Minder Gauge, aka Vacuum Gauge. I believe keeping the FJ40's 2F in green while driving would be the equivalent of how the 'eco mode' light works on my Corolla. (Yes, I'm aware it isn't the same gas mileage/nor the same engine/nor the same vehicle....just showing how the gauge works.)

 

[21NDone]

Vacuum is a measurement of engine health. The lower the vacuum, the less ability an engine has to pull fuel into combustion chamber. This is very important on carbureted engines because vacuum pulls the fuel through the circuits to create combustion. Poor vacuum causes rough running, hesitation, poor idle, misfire, etc.

The reason folks think fuel injection conversions are great (sniper for example) is because fuel is pressurized into the venturi and air fuel is computer controlled to compensate for poor mixture via O2 sensor.....therefore fuel injection masks a majority of issues by overcompensating for poor engine health (to a point).

Put a gauge on an unused port that is about close to center on the manifold and watch. A gauge is not necessary in the cab, if you are that nervous about vacuum measurement, your truck is poorly maintained. A quick connection and measurement when the truck is cold and hot is a great check to perform during oil changes or if you noticed a difference in idle/performance.

Not nervous yet, but do appreciate the importance of vacuum wrt engine performance. The idea of checking at oil change intervals is a solid recommendation - Thanks.

 

[21NDone]

With an unnecessary ash receptacle, I just purchased a dual 2" gauge plate and these vintage gauges. I have since installed some of the autometer angle bezels for a better visual from the seat and ordered some new Veethree gauges. Once they get installed, I'll update my thread accordingly.

View attachment 3537013

View attachment 3537014

As for using the vacuum gauge, below is a Stewart Warner Motor Minder Gauge, aka Vacuum Gauge. I believe keeping the FJ40's 2F in green while driving would be the equivalent of how the 'eco mode' light works on my Corolla. (Yes, I'm aware it isn't the same gas mileage/nor the same engine/nor the same vehicle....just showing how the gauge works.)

View attachment 3537025

Something about that motor minder gauge I like. Interested seeing the Veethree gauges installed on your rig.

 

[Pighead]

I have a vacuum gauge hanging off under the dash, used an unused port towards the rear of the intake manifold.
I find it quite usefull in tuning the engine and when climbing hills. Keep the vacuum above 1 and it won't ping. If it drops to 0, downshift