When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Like you are alluding to, It is literally just a vacuum gauge. In general they are hooked up to the throttle body, and measure vacuum from there. They could put mmHg or BAR markings on it and it would be exactly accurate all the time. But because higher vacuum constitutes greater efficiency at a given engine speed, calibrating the scale can give you a "roughly right" estimate of fuel economy when cruising. It's wildly inaccurate when accelerating hard or engine braking, but since the gauge is mostly useful at steady speed anyway that's a worthwhile tradeoff.
To be accurate in more broad conditions, the vacuum reading would have to be tied to the tach and speedo.
is this how almost all instantaneous mpg gauges work or just older ones?
is this how almost all instantaneous mpg gauges work or just older ones?
Like Striker said, just older ones. Newer ones will actually calculate it using data collected from various sensors, and should be much more accurate in a wider variety of conditions.
The old-school way wouldn't even work on my two most recent cars, whose throttle bodies are--by design--100% open any time the engine is running.
Like Striker said, just older ones. Newer ones will actually calculate it using data collected from various sensors, and should be much more accurate in a wider variety of conditions.
The old-school way wouldn't even work on my two most recent cars, whose throttle bodies are--by design--100% open any time the engine is running.
ok thanks to you both
is a general rule that analogue gauge = vacuum? my LS is definitely an older car but it has a digital instantaneous mpg reading
is a general rule that analogue gauge = vacuum? my LS is definitely an older car but it has a digital instantaneous mpg reading
No. For example, BMW has had an electronically-driven fuel economy gauge with a sweeping analog needle for decades, including on my 2000 E46. (Pic isn't my car, but same gauge):
I thought the BMW ones were vacuum too because they act just like my gauge in the old Benz.
Also, remember when YEARS ago I said you could get close to 25MPG in a Suburban? (I'm sure as part of a bitching tirade against V8 pushback...) And people said I was crazy?
Almost hit it. Flat roads and between 50 and 60mph about 45 minutes each way.
It would appear that cylinder deactivation (AFM) may actually work. As long as it doesn't affect drivability or reliability I'm fine with it. It is absolutely positively imperceptible.
Also, remember when YEARS ago I said you could get close to 25MPG in a Suburban? (I'm sure as part of a bitching tirade against V8 pushback...) And people said I was crazy?
Almost hit it. Flat roads and between 50 and 60mph about 45 minutes each way.
It would appear that cylinder deactivation (AFM) may actually work. As long as it doesn't affect drivability or reliability I'm fine with it. It is absolutely positively imperceptible.
not bad! that's still about 2 mpg better than i could possibly squeeze out of the benz lol... i dread to think what the mpgs would be if the supercharger pulley wasn't on a magnetically clutched pulley with an air bypass valve (in cruising the blower isn't engaged and the intake air follows a separate path)... well i guess just look at a 2005 ford GT and there's your answer
I thought the BMW ones were vacuum too because they act just like my gauge in the old Benz.
Also, remember when YEARS ago I said you could get close to 25MPG in a Suburban? (I'm sure as part of a bitching tirade against V8 pushback...) And people said I was crazy?
Almost hit it. Flat roads and between 50 and 60mph about 45 minutes each way.
It would appear that cylinder deactivation (AFM) may actually work. As long as it doesn't affect drivability or reliability I'm fine with it. It is absolutely positively imperceptible.
Oh it totally does work, I have two cars with it and owned 2 5.7 Hemis before with it and you will see 2-3 more mpg.
Issue I had with it was it kills the spark plugs REALLY fast in my 4.0 so I disabled it. Now mpg is the same as the D4 W12, that one can also use a version of deactivation but it's a totally different strategy that alternates banks.....
It works and doesn't seem to cause issues but it's only worth 1.5 mpg.
24.5 mpg is insane for a a 6.2L V8 in a huge truck, all 8 cylinders couldn't have been firing much of the time.
Part of that is because today's automatics are geared so tall in the upper gears. At most sane cruising-speeds, the engines are basically turning fast-idle RPM on the highway. That's one reason why I also get excellent MPG on the highway.
We all know I don't care about fuel economy but sure, as long as that doesn't give me trouble that's nice!!!
24.5 mpg is insane for a a 6.2L V8 in a huge truck, all 8 cylinders couldn't have been firing much of the time.
Can you do a hand calc on the way back? I'm very curious if you are actually getting ever somewhat close to that as that would mean you are beating the TTV6s with ease
Part of that is because today's automatics are geared so tall in the upper gears. At most sane cruising-speeds, the engines are basically turning fast-idle RPM on the highway. That's one reason why I also get excellent MPG on the highway.
The 10 speed automatic no doubt also helps with fuel economy.
I must say at least as far as that vehicle is concerned, the 10 speed auto is fantastic. It is lightning, lightning fast and shifts are imperceptible.
They. say the ZF 8 speed is even better, I'd love to sample that one.
Can you do a hand calc on the way back? I'm very curious if you are actually getting ever somewhat close to that as that would mean you are beating the TTV6s with ease
Yes I will try to remember. I'm sure I'm beating the tt6s. The engine is barely working thanks to good ole fashioned displacement. Big engines always overdeliver when loafing around at decent speeds. Like your W12s do.
It's great, but old and nothing special. Works great though. These cars with tons of gears drive sort of differently. When it works, it works great.
Originally Posted by Toys4RJill
the horror
LMAO I actually had to put it in 4WD earlier bc I got stuck in the sand in the driveway of the house we are renting. I'm sure if I gunned it back and forth I could have gotten out in 2WD but I didn't want to make a mess. Nevertheless, the LX I wouldn't have had to do anything because it's FT4WD.
