Just bought and installed a vacuum gauge!
 

I finally got around to buying and installing a vacuum gauge! Well, it's a boost gauge, but my turbo won't go in for a few more months, so for now I am only using the left side of the gauge. lol

By the way, I bought it from Dax, thanks again!

My goal right now is to go for a whole tank and never go under 10 in/hg. It takes a lot of throttle control and I really have to pay attention to my RPMs, engine load, gear etc. But I believe that staying above 10 in/hg will help me reach my goal of 40mpg.

Any of you experimented with the use of a vacuum gauge? Are you able to keep it above 10 in/hg all the time?

above is better for fuel economy? i thought the motor injects less fuel then the pressure is lower....

Yessir, welll.. strictly speaking, the lower the pressure the more efficiently the engine is operating. Now if the driver uses P&G, then shuts off and coasts, minimal pressure while accelerating is good. But I can have efficient engine operation and inefficient/fast driving, which can lead to worse mileage compared to inefficient engine operation and efficient/slow driving. By breaking everything up into an acceleration/deceleration phase, the hope is to combine efficient engine operation with efficient/slow driving.

I was speaking in terms of vacuum, measured in inches of mercury, which is how a vacuum gauge reads it.

Basically the higher the vacuum (higher the In/Hg) the better fuel economy. When the throttle plate is all the way open, there is near zero vacuum. When you decelerate the vacuum goes way up because the engine is trying to pull air through the throttle body.

Anyways, I was looking at my fuel maps the other day and they showed that the higher the vacuum, the less fuel that is used.

thats what i was thinking when i went to bed after responding...hahaha

for some reason i thought 'under' was left when its definitely right when measuring vacuum.

I haven't used, or seen, a vacuum gauge in years! My first car, a 1983 Holden Commodore wagon with a 202 ci I6, 2 barrel carb and 3 speed auto, had one. Once I learnt how to use it I always tried to get the most vacuum possible. I'm planning to add a vacuum gauge to the Charade soon.

I've got a vacume gauge I've been running on my 89 Honda Wagon, for the last couple of month's. It would be nice to have a real readout of the mileage, at any point in time, however since cash is a big challenge, the gauge is what I have.

Where I find the gauge seems to help, is I have noticed that their seem to be a number of circumstances where I can back off the throttle, just a little and get the vacume to go to around 15 inch's, without losing much or any speed. Once my speed starts to drop significantly, or if I can see I'm pulling a slight grade, I try to pull just enough throttle to maintain the speed. When I find I am going to go down a slight grade, I try to use that to accelerate.

I generally try to run either 5 inch's, for acceleration, or I try to back off the throttle to pull the 15 inch's. Where it is really helpful is the difference between 12 and 15 inch's is very minute, on the throttle, but it seem's to make a significant contribution to the mileage. It seem's to me like, when I am diligent, that I can make a very noticable, positive effect on my fuel use. However it get's difficult to keep myself focused on what I am doing. This is another place the gauge really help's because as soon as I look at the gauge, I realize I am running at more like 10-12 inch's but as soon as I notice, most of the time, I remember to back off on the throttle.

This is probably just a crude imitation of pulse and glide, but it is where the vacume gauge seems to help me, the most.

If you remember on that gauge it had those colored sections on the dial , with the red band on the left side.
That red portion (maybe labled accelerate or power) should prety well coincide with the vacuum level required to activate the high load enrichment circuit in the carburettor.
Keeping the needle just on the orange scale border of the red , but not going into the red , should give the most efficient acceleration but with the least amount of fuel used.
I had a 173 VB commodore manual and when driven like this was suprisingly fuel efficient - well , for a big car anyway.

My SG2 has it.

I usually ride around 8.8

When I coast in gear it hits 2.3-2.4

I have and it's a great way to save gas and spot engine problems. I bought a new one I found at https://ideamaster.com/mm.htm for only $5. Great service, good people.