If you don't have a vacuum gauge, you're missing out! - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Clev · 01-28-2009, 11:05 PM

Quote:

Originally Posted by Christ

I thought lower was better as well... since opening the throttle more increases VE by lessening restriction via the throttle plate, which reduces vacuum... I was under the impression that regardless of gear or engine speed, less vacuum would create better efficiency.

On my car, the more throttle, the lower the vacuum. When I'm climbing the hill, if I give it slightly less gas, the vacuum goes from 3 to 6. Does that mean I'm using more gas by using less throttle?

Christ · 01-28-2009, 11:14 PM

I see now... I didn't realize you were talking about going up hills and such.. so is higher vacuum generally better? How can you tell when to use higher or lower vacuum for a given situation? Sorry - I'm doing my taxes right now too.

Clev · 01-28-2009, 11:18 PM

I go for the highest gear first, and the highest vacuum second. The vacuum gauge helps me because often I can ever-so-slightly let up on the throttle and still maintain the same speed. It allows me to drive without taking my shoes off. :-)

Christ · 01-28-2009, 11:21 PM

So keep it in 5th whenever possible, and keep the vacuum as high as the engine will allow - right?

How does this methodology apply to forced induction? Am I still trying to keep a high vacuum number? (Or as low boost as possible, given certain situations). If you don't know, it's no biggie, I was just wondering.

azlar · 05-25-2009, 01:39 AM

I know this is an old post, but I'm catching up on the forum and wanted to weigh in.

Vacuum gauges are a great and simple item to add to your ecomodding. But you can't get too wrapped around numbers. 18-20 are good for idle, 3-5 for acceleration, 25+ for decel. Book values.

What it really provides is INSTANT feedback about where your throttle is. If you're accelerating from a stoplight at 10 in/Hg, ease your foot a bit at you'll get 12" and better economy with no noticeable speed differential. None of the electronic doodads give you that feedback that quick. A tach tells you how fast the crankshaft is turning, but has nothing to do with fuel consumption.

But the best part of a vac gauge, is the diagnostics. Is it low at idle (restricted exhaust?), have a regular drop (burnt valve?), wandering needle (carb probs?)

They are relatively cheap and easy to install. Initially ignore the numbers and just see where your car fits. Once you understand your engine's personality you can truly tweak it for max mpg

kstruve · 07-20-2009, 04:25 PM

I had wondered about how vacuum gauges help with efficiency myself. I just realized that my car (Subaru WRX) already has one installed! It's my turbo boost gauge - duh. I never really paid much attention to its behavior below 0 until recently. My gauge's units is in MPa (megapascals) instead of inches of mercury, but I found an online converter and found that 15 inHG is about .05 MPa on my gauge. So now I should keep it well under 0 from now on.

The Atomic Ass · 07-21-2009, 02:09 PM

Quote:

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 know it's a late reply, but if a diesel engine has electric injectors as opposed to mechanical, wouldn't it still be a candidate for an MPGuino?

RandomFact314 · 07-21-2009, 05:21 PM

Yeah I am really thinking about getting a vacuum gauge but I still am not sure where to plug up the pipe?

The Atomic Ass · 07-21-2009, 09:19 PM

Quote:

Originally Posted by RandomFact314

Yeah I am really thinking about getting a vacuum gauge but I still am not sure where to plug up the pipe?

Need some more shots of your engine a little further right. Easiest place is going to be on the throttle body, then you can take basically any small rubber line and it will be vacuum.

RandomFact314 · 07-21-2009, 10:38 PM

Quote:

Originally Posted by The Atomic Ass

Need some more shots of your engine a little further right. Easiest place is going to be on the throttle body, then you can take basically any small rubber line and it will be vacuum.

Its hard with this 127 limit, Besides, I thought it was suppose to come from the intake box? and that is the very far right of my engine bay...