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Old 10-07-2011, 10:29 PM   #1 (permalink)
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What is Engine Load % - UG Question

What is engine load %. What does it measure?

I'm guessing this is related to DWL, and I would think this is important to monitor for fuel efficiency.

If so, what % should I be aiming for?

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Old 10-08-2011, 02:17 PM   #2 (permalink)
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...that's probably going to be an "...ask the UG manufacturer..." question, because it's a derived parameter and probably all done in software and using assumptions about engine performance. What algorithm and assumptions they use is anybody's guess.
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Old 10-08-2011, 03:52 PM   #3 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
...that's probably going to be an "...ask the UG manufacturer..." question, because it's a derived parameter and probably all done in software and using assumptions about engine performance. What algorithm and assumptions they use is anybody's guess.
Ah, just thought maybe someone had already found out the info, considering the popularity of the UG and the inquiring minds of those on this forum.
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Old 10-08-2011, 09:12 PM   #4 (permalink)
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Load is a function of measured manifold vacuum. When there is no restriction meaning 0 manifold vacuum then you have 100% load without enrichment. As you increase the throttle position to 100% you reach a point where the ECU will provide enrichment for additional power.

If you do not consider full load enrichment, then load is directly proportional to manifold vacuum. MAP (manifold absolute pressure) is the measurement of pressure actually delivered to the combustion chamber. Manifold vacuum is the remaining atmospheric pressure not allowed in to the combustion chamber.

Atmospheric pressure varies with climate, altitude, and density. MAP readings cover this, while manifold vacuum does not tell you what the atmospheric pressure reading is, just the difference between atmospheric pressure and the remaining atmospheric pressure delivered to the cylinders for compression.

Make any sense?

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Old 10-08-2011, 10:43 PM   #5 (permalink)
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When I saw a fairly large %LOD on my Scangauge at idle, I lost interest in using LOD for driving. I now use MAP, Manifold Absolute Pressure.

The exact numbers are not as important as minimizing variation. I use it as a steady foot indicator.
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Old 10-10-2011, 12:20 AM   #6 (permalink)
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I have been aiming for 80% engine load during acceleration for no reason other than I heard engines are generally most efficient (most unit power per unit fuel) at 80% of full capacity. I don't know if 80% engine load equates to 80% capacity, or the basis of the 80% claim in general. Any info on this appreciated.

Thank you Old Mech for the detailed explanation of manifold vacuum and MAP.

FYI, my UG shows something like 25% Engine Load at idle, and falls several points below 100% at WOT.
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Old 11-08-2011, 12:43 PM   #7 (permalink)
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The explanation of how it is calculated is interesting to me... since my engine generates zero vacuum...

I'm sure it's true, many of the derived gauges do not apply directly or necessarily accurately to diesel owners.

I have seen engine load % reported by some obd2 diagnostic tools, as some ecm's actually report this themselves. I don't know if this is necessarily the case for your vehicle or mine, or if the number represented by UG is reading from this or calculating its own. In my case, I'm noticing that I rarely show it over 25-30% during acceleration so far, which seems fairly accurate... 25-30% of 500 HP is 125-150 HP or 250-300 ft-lbs if based of my torque number. It's a heavy truck, it takes a lot or power to ramp up to speed even when gentle with it. Even still, this seems a little crazy, because even at stock power the way I accelerate for economy, I'd expect the actual HP/tq numbers for acceleration to be much lower, probably even half of above.

This brings me to other gauges that I believe to be derived from other sensors, such as the HP/Torque gauges (I think that's an EM-only feature, some of you may not have it). The setup asked me for my peak torque and RPM numbers, which is roughly 1000 @ 1800 RPM... at the wheel. As such, UG tells me that I'm idling at 505.6 ft-lbs, which is absurd. It also tells me I'm idling at 75+ HP, which is equally as absurd. It knows my boost is at 0 (approx) at idle, and I know the engine doesn't produce that power except under 100% load with 35+ psi boost...

I don't know if these and others are "off" though, due to the fact my UG has never seen this engine opened up (maybe it rethinks things when it sees what power it really has, otherwise just assumes it's a 3 cylinder eco box?) or if it's somehow related to the "Power on Demand" setting of my tuner. This setting is a scalar value of apparent arbitrary effect on the power output of the actual tuning program itself. That is to say, the engine + tuner will put about 500 HP / 1000 ft-lbs to pavement, but when I set PoD to "30", I get some amount of power below that of the stock program but with enhanced drive-ability- with higher rail pressures and more advanced timing for better fuel economy.
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Old 11-08-2011, 12:49 PM   #8 (permalink)
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I would like to know more as well. Relative simplicity. The "idea" of what load percentage the engine is working would be informative.

In the meantime, the old rule of 600-60-6 for steady state optimal FE offers some illumination:

Pyrometer at 600-F, or less

Road Speed at 60-mph, or less

Manifold Pressure Gauge at 6-psi, or less

It just isn't enough, though, for transitional states. At what rhythm to use the controls.

.
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Old 11-08-2011, 01:33 PM   #9 (permalink)
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calculated load - load - engine load

calculated load is an OBD2 PID , Parameter id
it is not unique to UG or SG or any other scan tool

it is a measurement of
calculated load -

the values used to measure load include MAP , MAF , Temp , RPM , throttle position and timing , there can be others

KISS
at cruise
lower calculated load translates to
improved fuel economy

at WOT increased calculated load translates better flow and to more power
expect around 90 to 95% calculated load at WOT at 4k rpm on a NA car
WITH real time fuel trim at +/- 5% FROM ZERO FUEL TRIM ADJUSTMENT -
if not
there are problems , depends which PID does not meet what is expected .
expect 150% calculated load at WOT over 4k rpm on a boosted system , same fuel trim conditions.

you can watch load change at idle
switch AC and Hi beams on while monitoring calculated load

Last edited by mwebb; 11-08-2011 at 01:43 PM..
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Old 11-08-2011, 04:20 PM   #10 (permalink)
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I'm not really familiar with the Ultragauge, but I believe %Load is an estimate of the amount of torque your engine is producing, divided by the max torque at that rpm. Torque is basicaly propostional to fueling. On a gas engine fueling is proportial to air flow and air flow is proportional to intake presssure. On a diesel, the ECM commands the fueling directly.

As far as the usefulness goes, %Load will basically tell you where you are vertically on a BSFC map (0% is at the bottom, 50% is halfway up, etc).

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