vaccum and effiency...

[HISSIN50]

Maybe some one who has read the Probst book more than once, can answer this?

jason

Since I am the only one to have mentioned this book, I guess this was directed at me. I have read it more than once, so feel free to point out answers and page numbers for info found.

I still stand by my previous answers, but others will obviously differ. Perhaps Daggar or someone with a WB or who datalogs can provide more inclusive stoichiometry info for given situations. The nature of the stock lambdas are to maintain stoich; I would not infer much from the toggling of the voltages. That is just me.

 

[vristang]

Since I am the only one to have mentioned this book, I guess this was directed at me. I have read it more than once, so feel free to point out answers and page numbers for info found.

I still stand by my previous answers, but others will obviously differ. Perhaps Daggar or someone with a WB or who datalogs can provide more inclusive stoichiometry info for given situations. The nature of the stock lambdas are to maintain stoich; I would not infer much from the toggling of the voltages. That is just me.

JT
thanks again for taking the time for this discussion, its always a pleasure.

I will keep kicking these thoughs around in my mind, hoping to come up with something, however unlikely.
I wish I had a reliable way to test economy in small distances so I could work some of these issues out.

Best of luck to all:Word:

 

[Look Its Aaron]

lambdas

Lambda Lambda Lambda?

 

[TheUser]

Rich=Lower air/fuel ratio; not enough air to support complete combustion of fuel
Lean=Higher air/fuel ratio
So anyway, it seems to me that the lower vac would mean an increase in throttle, which increases gasoline usage..not necessarily causing a rich condition because the fuel is burnt, but just uses more gas than a part throttle, lower rpm, more vacuum approach because there is more air present. It kinda seems like you're interchanging "running lean" with "more fuel economy" and I don't think they're completely interchangeable. What I'm saying is that just because you're still running lean (more oxygen than needed for complete combustion) at a lower vac (higher rpm), you're still using more fuel because you're using more air than you would if you shifted, decreased rpms, raised vacuum, and kept the same speed. Efficient? Maybe not the MOST efficient, but I really don't think there's a way to run with more throttle and BETTER economy than part throttle.

Seriously man, not trying to be a dick...I've never really thought about this stuff a whole lot until now, but this is what makes sense to me. I too own the probst book - and have for over a year I'd say - just never have gotten around to reading it; I figure if I have time to read, I should probably be studying for the classes I'm paying big bucks for.
If anything I said was off-base, please correct me.

 

[vristang]

The User-
No offense taken. This is what the forum is all about. (Actually you mention shifting, which is crucial to this topic, and has yet to be mentioned )
I get what you are saying and you are right, with an increase in throttle there will be an increase in fuel to match the increased air flow (even if stoich is maintained). So the argument that you, Hissin, and others have made is that the throttle should be kept closed for economy driving.
My point is that the engine will operate more efficiently when the throttle is wide open compared to low throttle (one of many reasons for the increased efficiency of a diesel motor).
Neither of these 2 arguments are wrong, but I am trying to understand this a little better, in relation to real world driving.
It seems to me that there would be a crossover point between these 2 philosophies.

On the way home from work today I did an experiment. At 55mph in 4th gear the engine was turning at ~2300rpm and the vac was between 18-20". At the same speed in 5th gear the rpms were ~1650 and the vac was 14-16". Will I get better fuel economy with higher rpms/ vac, OR with lower rpms/vac? (I recorded the above numbers while trying to maintain a steady speed with constant throttle position. In both scenarios the a/f ratio was reading similarly.)

I would like to test this somehow but I tend to have a heavy right foot, which would corrupt any data I would collect from fuel economy calculations.

:Word:
jason