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

[ConnClark]

Originally Posted by Christ

1. Why won't a vacuum gauge work for you? Even if you're boosted, you're still in vacuum before the turbo spools, so the idea would be to keep out of boost as much as possible.

Diesels don't have a throttle and hence don't have a vacuum. Any thing that requires a vacuum is driven off of a vacuum pump.

Unlike a gas engine, diesels do not require a fixed fuel mixture to run right. In fact they run better the leaner the combustion gasses. Boost actually raises the efficiency of a diesel engine and will do so up until the point air starts to liquify. There is a break even point however where it takes more energy to create the boost than is recovered by the efficiency increase and thus boost beyond this point reduces net efficiency.

Generally however, if you drive so that your engine is generating the least amount of boost it is an indication that your pistons are extracting the most energy they can. This does not mean that you should modify your engine to reduce boost or try and prevent your intercooler from reducing intake manifold temps in any way.

[Christ]

Originally Posted by ConnClark

Diesels don't have a throttle and hence don't have a vacuum. Any thing that requires a vacuum is driven off of a vacuum pump.

Unlike a gas engine, diesels do not require a fixed fuel mixture to run right. In fact they run better the leaner the combustion gasses. Boost actually raises the efficiency of a diesel engine and will do so up until the point air starts to liquify. There is a break even point however where it takes more energy to create the boost than is recovered by the efficiency increase and thus boost beyond this point reduces net efficiency.

Generally however, if you drive so that your engine is generating the least amount of boost it is an indication that your pistons are extracting the most energy they can. This does not mean that you should modify your engine to reduce boost or try and prevent your intercooler from reducing intake manifold temps in any way.

I really should stop posting so early in the morning... or get some sleep at some point.. - I already knew this. Thanks though LOL.

[Unforgiven]

My old Fury had a vacuum gauge. Interesting that most vehicles today dont have a vacuum gauge. Someday the Impala will hopefully benefit from Scangauge.

[elhigh]

Originally Posted by EXPIOWA

*Cough*MPGuino*Cough*Same price*Cough*

*cough*carbureted*cough*hack*gasp

[Unforgiven]

<chuckles> Yes, the old Fury was carburated, a classic old 2 barrel that did a good job in fuel economy considering the size of the vehicle moved, the weight (old classic IRON) and a 3 speed, non overdrive transmission.

[cottonfox]

Originally Posted by Clev

It measures the vacuum at the intake manifold. As engine power increases, the engine generates less vacuum. The upshot is that a vacuum gauge can show you approximately how much the engine is putting out.

Sorry for the insultingly new question, but what is the advantage of this over the tach, which shows how hard the engine is working in RPM's?

[vtec-e]

The vac gauge shows how much the accelerator is pressed and therefore how much fuel is going into the engine.

ollie

[hypermiler01]

Originally Posted by Clev

I'd see between 0 and 3 inches on the gauge. By adjusting my speed and throttle a little bit, I'm able to climb at about 6 inches at nearly the same speed.

I thought lower was better, no?

[Clev]

Originally Posted by hypermiler01

I thought lower was better, no?

Nope. Higher vacuum is better (at least for a given gear. Lower vacuum can be acceptable in a higher gear for the same speed.)

[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.