If you don't have a vacuum gauge, you're missing out!

[Dieselman]

Originally Posted by RandomFact314

lol, are none of these pics good enough for someone to tell me where to hook up a vacuum gauge, ....

No, as none show the throttle body and intake manifold area. Maximum vacuum is produced after the throttle flaps and before the intake valves. look for a pipe in that area and check it is a dead end at the other end and you have true manifold vacuum.

[gone-ot]

...does the car have vacuum-assisted power brakes?

...if so, then simply "T"-into the hose leading to the power brake diaphragm assembly.

[Dieselman]

Originally Posted by Old Tele man

...does the car have vacuum-assisted power brakes?

...if so, then simply "T"-into the hose leading to the power brake diaphragm assembly.

That's not true vacuum as the servo has a bleed off when the brakes are not being used. A pipe to a MAP sensor or similar is true vacuum as it is a dead end with no leak off.

[CoastRider]

My vac gauge is like a third eye to me, showed me how eccesive i was with the throttle. The guage came off a mityvac vacuum pump I bought years ago for engine testing and repair. Unfortunatly it doesnt have a light so its hard to read at night, but its what I had around so I used it. The upside is that the needle has a large sweep radius compared to what I found in stores.

saving funds for a 4th eye, a MPGuino.

Various readings i get with a 4.9 inline 6
idle 27
flat cruising 20+
hills 15

Only thing I havent figured out yet is when its best to use 5th gear vs 4th during low speeds. At 45 mph 4th gear less than 2k rpm's I can keep the vacuum at 20in. If I shift to 5th the rpm's drop and so does the vac down to 15in since the engine is working harder. I'm just not sure if the rpm drop offsets the increased load. The 4th eye will tell me just dont have it yet

[orange4boy]

Only thing I havent figured out yet is when its best to use 5th gear vs 4th during low speeds. At 45 mph 4th gear less than 2k rpm's I can keep the vacuum at 20in. If I shift to 5th the rpm's drop and so does the vac down to 15in since the engine is working harder. I'm just not sure if the rpm drop offsets the increased load. The 4th eye will tell me just dont have it yet

The motor is at a lower RPM and higher gearing so MPG is almost surely better in the higher gear. You can't compare vacuum readings at different RPMs. Just look at a BSFC chart to see how different the efficiencies are at different RPMs.

At lower RPM, bigger throttle opening, higher gearing you have:
1) lower pumping losses
2) lower frictional losses
3) other advantages I can't remember

I've observed this with my mpguino. Git'er up into those high gears ASAP

[elhigh]

Originally Posted by Dieselman

That's not true vacuum as the servo has a bleed off when the brakes are not being used. A pipe to a MAP sensor or similar is true vacuum as it is a dead end with no leak off.

Are you sure about that? My system has a check valve to hold vacuum in there when I'm not using brakes. I T'd into that very line to hook mine up, it pulls a really deep vacuum. Pegs the needle on the top end, decel in gear.

[RH77]

I have always used TPS and MPG to get this kind of idea with the SG.

Where I have always been puzzled, is acceleration with a crazy torque converter that engages to 3 levels of lockup force at will. More pressure locks it up harder and increases load, but a lighter foot gives better FE (but don't press too hard, or it unlocks completely). Then harder accel to a more efficient speed sometimes makes up for it. I remain confused...

I assume MAP will offer a better number than the wavering LOD figure.

Is this or another number good for accel, and where should it be?

RH77

[99prizm]

I ordered the Auto Meter gauge, waiting on shipping. Anyone installed one on a 99 Prizm / Corolla? I got 37.6mpg last tank!! Hoping to break 40mpg with help of the vacuum gauge...

[gone-ot]

Originally Posted by 99prizm

I ordered the Auto Meter gauge, waiting on shipping. Hoping to break 40mpg with help of the vacuum gauge...

...which? did you buy an Auto Meter VACUUM GAUGE? or an Auto Meter model 9100 ecometer?

[bgd73]

Originally Posted by solarguy

Cough...I drive a diesel...cough...neither one works...cough.

Seriously, neither option works for me. MPGuino is unsuitable for VW diesel , right?

Other options? I got the basic '04 Jetta TDI PD, without the fancy schmancy gauge cluster, so no readout of FE of any kind. I don't feel like doing the junkyard thing to replace the cluster.

I do have very good diagnostic software that lets me snoop through the diagnostic port, but very clunky to try using a laptop while driving.

Finest regards,

troy

I run a carb progressive two barrel, I could only guess a vacuum gauge would work for something.

just feel it out like a diesel..