how much difference did MPGuino or vacuum gauge make for you?
 

i've been on the fence about installing either a vacuum gauge or mpguino in my '90 4wd corolla wagon for quite a while. been giving it more thought lately and wanted to know what sort of real life returns people have seen. for example, what did you average before and after installing it? did it help you adjust your driving habits?

also, i see the FAQ says the mpguino is much more useful than a vacuum gauge but i'm curious about how people feel about one versus the other. is the mpguino really that much better? i am used to carbs so i have a real soft spot for vacuum-related stuff. also, the mpguino is about 3x the cost of a vacuum gauge so i'd like to know if it's really 3x better.

sorry if this is a common question around here. i did a search but couldn't find quite the info i am looking for.

I like the MPGuino. In fact, I liked it so much I made a bunch of improvements to make even more useful. I've got one installed in the Karen-Mobile, which is a real neat trick - considering that people owning such a car would generally go with a ScanGauge II or UltraGauge. Planning to install one in my Caravan soon, as soon as I can figure out how and where to take the vehicle speed signal.

thanks, t vago. did you keep track of your mileage before adding an mpguino? i wonder how much difference it has made to your driving habits and fuel economy.

It makes a difference, it works and it's fun!
 

i like measuring manifold pressure, aka vacuum, with a big fat analog gauge. It's quick and easy--put a tee in a line coming off the throttle body and run a hose to the dash and it's working.

i drive a bigass van that got 14 mpg for years and years before i got saved. After i got converted to the ecomod religion my mileage is closer to 17 mpg using all the tricks: pulse and glide, coasting in neutral, staying off the brakes, and quickly accelerating with high load as indicated by the vacuum gauge.

i don't always accelerate, but when i do i drink dosx... i make sure the engine is pulling hard at or near it's most fuel efficient region (i.e high manifold pressure = low vacuum).

When driving i don't need to know or read any numbers in real-time, just look at the needle and adjust the throttle such that it's either floating up in the high vac, or i bury that thang down low when under load.

My Best tank without the vacuum gauge was 34.56MPG (added bay pan) and second full tank using vacuum gauge was 36.12MPG (without bay pan still from changing oil, smog, etc) and I could still probably fine tune my use. That is a 4.5% increase. I accelerate at 5"hg vac at 2~2.5k rpm thanks to BSFC Chart.

I can't say that it helped a whole bunch, as I had already fine-tuned my driving habits prior to installing my MPGuino. I rather installed it to see the effects of hardware modifications to fuel economy. For instance, I could measure about a 5.5% increase in fuel economy due to installing aero wheel covers, and I can see an improvement in fuel economy whenever my EGR valve opens up. It's rather interesting to see my UltraGauge and my MPGuino track each other when the EGR valve remains closed, but see up to 15% difference when it opens up. The MPGuino, which actually measures fuel pulses, is more accurate.

+1 The Best part about MPGuino is it really is close to real time, my SG2 is really laggy by comparison (yes it's set to 'Fast' comm). After getting used to 'Guino the SG2 is only slightly better than OE FE instumention.

I can't say it's made a big difference to my number as I've already had the techniques mastered, it mostly reaffirms if what I've been doing was right or not. The fuel log doesn't have any real blip when instumentation went in, because in the summer heat A/C use is the biggest factor (3l/100km!) for me.

The real gains can be made with instant feedback urging you to keep up the good work, or to try harder ;) FE instrumentation far outshines a vacuum gauge in this regard.

The analog manifold pressure gauge (vacuum) actually provides instant feedback sooner and quicker than the digitical stuff can, since the ECU must read airflow/massflow/pressure to calculate injection pulsewidth, then the instrumentation must read the output pulsewidth and engine rpm in order to calculate and display FE.

Technically true, but functionally & realistically a "draw."

Why? Because the movement of air pressure (vacuum) is relatively much SLOWER (millisecond) than the speed of electrons (microsecond)...even though those electrons have to functionally navigate the physical distances (and timing gates) between the sensor, computer, OBD-II CAN-bus, and lastly the SGII or UG.

Thus, my bet is on the electron over the physically moving bourdon-tube needle for pure "speed."

Never really used a Vac gauge, but with an Ultragauge for instant fuel economy I went from a consistant 38 up to a consistent 42mpg on a 99 escort. I was already fairly good at the hypermiling thing from my previous experience with my civic and an MPGuino.

just came across this excellent page that shows how useful a vacuum gauge can be in diagnosing a wide variety of engine issues. the interactive graphic at the bottom of the page is great.

How to Use and Interpret a Vacuum Gauge

The point has already been made that seeing an actual number is a bonus as it is more effective encouragement to max out mpg. It is like having a cheering section in the car with you.

i got a USA-made vacuum gauge off ebay for $25 including shipping. installed it about a month ago and have been really pleased with the results. over the last 3 tanks i've averaged an increase in fuel economy of about 10%. i even smashed my personal best from a year ago: my best tank had been 14.1 km/L (33 mpg), and this was all hwy, just me in the car, windows up. yesterday i got 15.7 km/L (37 mpg) and that was with 3 passengers, all our camping gear, and the windows down. i definitely drove a bit slower than i would have without the gauge but i'm ok with that.

the biggest driving habits i've changed are accelerating at 5-7" of vacuum, backing off the throttle while climbing hills to keep the vacuum steady until cresting the hill and then accelerating at 5-7" vac back up to cruising speed, and using 4th gear a bit more often (5th is a bad choice for climbing anything but the slightest hills).

i drive a stock '90 4wd corolla wagon. never thought i'd see 37 mpg in a 4wd. pretty happy with the little gauge.

an addendum to this post. we have a gas-guzzling 7.5L '91 f350 that we use for our work truck and hauling the camper. it averaged 8 mpg. back in the early summer i installed the same vacuum gauge that i put in my car and have since been averaging 10 mpg. that's only 2 mpg but it's a mileage increase of 25%.

i love vacuum gauges!