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Old 03-31-2008, 08:10 PM   #11 (permalink)
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Quote:
Originally Posted by LostCause View Post
I think the goal is to never operate at light loads.
To add to what Metro has already said... For highest thermal efficiency - that statement is true... But engines are over sized for that sort of driving. If I operated my engine at peak load all the time, two things would happen

1. I'd get a helluva lot of speeding tickets
2. I'd drastically reduce the operating hours of my engine

It is because the drive train is so big that lower thermal efficiency (lower brake specific fuel consumption) can lead to lower specific fuel consumption.

If I had a 20hp engine in there - it'd be much easier to operate at peak load all the time and maintain a legal speed But, operating a 20hp engine near 20hp for it's entire life will reduce it's service life. The gentleman from wrightspeed motors claimed that your typical car has about a 5,000 engine life. But, that's because these engine live at lower rpm and at low loads for most of their lives....

Quote:
you guys are killing me with these abbreviations..
BSFC ? doesn't take that much more to type it out, stop being lazy..
Hypermilers like abbreviations I don't know why - but it has allowed the term CODFISH to exist Goofy

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Old 03-31-2008, 10:33 PM   #12 (permalink)
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Originally Posted by Chris D. View Post
I still pulled just shy of 30mpg when I filled up.. I even went offroading a bit with my truck club.. I have quite a few 4x4 guys in my club shooting for FE reguardless of their trucks setup, one guy (not on here yet0 went from 15mpg to 20mpg using a few tricks I posted on my fuel log on CustomTacos..

Fixed it

Here and reporting for duty. Just ordered the Vacuum gauge.

FE??? I concur with Chris D. Too many abbreviations

Last edited by Taco Bowl; 03-31-2008 at 10:40 PM..
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Old 03-31-2008, 11:43 PM   #13 (permalink)
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Na, thr can nvr b 2 mny abbr. Welcome to EM!

Quote:
If lower vacuum is seen for a given speed then you know the WAI is working as pumping losses are being reduced.
Quote:
I think the goal is to never operate at light loads.
So I'm so confused right now, I thought that you want high vacuum for better efficiency, not to lower the vacuum. And I also thought that you want to lessen the load, which is where weight-reduction and driving slower to make aerodynamic drag lower come in.
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Old 04-01-2008, 12:21 AM   #14 (permalink)
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in regard to the efficiency of a WOT(wide open throttle) sweep, i am of the opinion, that the most efficiency throttle opening should be vacuum controlled (or ECU) like the secondaries on the old quadajet carb. especially on carb engines.
Fly by vacuum or fly by wire.

The pedal would allow the throttle to open if there was a little vacuum present(high velocity). refering back to post 4. the part where i want the engine to "catchup" with the throttle opening.
I am thinking that all the BSFC(brake specfic fuel comsumption, i think) curves are based on a controlled sweep or even steady state points.
So i am suspicious that a WOT sweep is the most efficient.
Another way of saying it is, the most throttle it will take without getting into fuel enrichment.(old term but still programmed in many fuel maps) In a previous life, i ran an engine test cell and what i observed (although i was not testing for it specifically) was, that, as the engine vacuum dropped to zero in of Hg, opening the throttle all the way up to WOT did not increase the efficiency. (Some engines went into enrichment at 5 in of Hg.) As engine management advanced in the 90's this became less of an issue because the ECU was doing this "feathering" for you. But for a carb'd engine, i don't think you want to get too far ahead of the engine RPM. Now with VVT variable valve timing, lean burn, high swirl HS, fly by wire and all the rest the ECU is able to dial in much closer to the optimal mixture. On the new engines the exhaust temperature would peak when the ECU found the best mixture for each RPM. What is the best way to determine if the ECU is keeping up with the sweep rate?, i don't know. Wide band o2? If it stays in closed loop and vacuum is close to zero? But i think i am close to optimal if i can just see a little vacuum left on the gage as i sweep. BTW.by the way. The highest ex. temp. i ever recorded was 1850 F on a modular truck engine with aluminum heads

So to make a long story short, i couldn't say that a WOT sweep is the best for most engines. Nor would i say that WAI is best for most engines. I think it depends on how technically advanced or retarded the engine management system is.

Last edited by diesel_john; 04-01-2008 at 01:45 AM..
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Old 04-02-2008, 03:56 AM   #15 (permalink)
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Quote:
Originally Posted by MetroMPG
But let's keep this in context. Chris was just asking for advice on what to do with his current setup, at cruise, (my interpretation) to achieve the best efficiency.
Sorry for getting a bit impractical...I just didn't want everyone to get the idea vacuum in and of itself is a good thing. I think too many questions are best answered with, "It depends...".

Quote:
Originally Posted by trebuchet03
To add to what Metro has already said... For highest thermal efficiency - that statement is true... But engines are over sized for that sort of driving. If I operated my engine at peak load all the time, two things would happen

1. I'd get a helluva lot of speeding tickets
2. I'd drastically reduce the operating hours of my engine

It is because the drive train is so big that lower thermal efficiency (lower brake specific fuel consumption) can lead to lower specific fuel consumption.

If I had a 20hp engine in there - it'd be much easier to operate at peak load all the time and maintain a legal speed But, operating a 20hp engine near 20hp for it's entire life will reduce it's service life. The gentleman from wrightspeed motors claimed that your typical car has about a 5,000 engine life. But, that's because these engine live at lower rpm and at low loads for most of their lives....
Very true points. I was thinking about doing the opposite of driving at the engine's peak efficiency...lower the peak efficiency to suit a particular driving style. I think that is the idea of the WAI, lean burn, EGR, etc. and definately applicable by more mechanically inclined members of this forum. Just another (tough) potential avenue for fuel economy...

As far as engine longevity, I would think some technology could help. SiC ceramic coatings on F1 engines are used to lower friction, increase cylinder wall hardness, and increase engine longevity. Supposedly, honing the bores is nearly as tough as cutting diamonds... Ofcourse, this is getting a bit fanciful...but not impossible.

Quote:
Hypermilers like abbreviations I don't know why - but it has allowed the term CODFISH to exist Goofy
Reminds me of the military.

Hmm, maybe we should name this the S.W.O.R.D.F.I.S.H. - the Super Wombat ORgan Dynamo for InFormatIon Subsystem's Headquarters.

Nothing like a good backronym...I wonder if the military has a whole department dedicated to that field.

- LostCause
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Old 04-03-2008, 10:32 PM   #16 (permalink)
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by watching my vac guage a little more and keeping it in the economy range or higher I just nailed my best mpg.. 31.15

Its definatly helping..

we need a sticky that defines abbreviations and explains what it is, how to do it and describes how it helps FE..

way too many abbreviations, definatly not new guy friendly..
Mite actually hurt more than help to keep people in the green if ya know what I mean..
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Old 08-03-2008, 12:16 PM   #17 (permalink)
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I may be wrong but I think diesel cars cruise control works so much better than gassers. (More torque) Uphill at highway speeds the RPM does not change much from flat road.

Last edited by SickMPGs; 09-25-2008 at 11:43 PM..
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Old 08-03-2008, 07:40 PM   #18 (permalink)
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Here is an example of where you want that gauge to read during a regular cruise..........



I do not use my gauge during accel only when at cruising speed. From there, I use the gauge to maintain 10-15 on the gauge. If I see the needle dropping below 10, then I am going up a hill or giving too much throttle. The readings from a manual vacuum gauge are instant and will help you control throttle output and save gas just like a Scangauge would.
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Old 09-26-2008, 12:12 AM   #19 (permalink)
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Quote:
Originally Posted by marthyj View Post
Can it really monitor the total vacuum pressure excerpted on your vehicle- more vacuum pressure = more pull? It's sounds ridiculous & confusing...
Fargo..

the more vacuum, the less throttle position = less energy being used..

with my autometer 2337 guage, it has parameters noted around the outter edge..

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Old 10-20-2008, 08:57 PM   #20 (permalink)
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A vacuum gauge along with actual fuel consumption rate would be the best tool for EACH application.

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