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BHarvey 04-30-2012 05:04 PM

Acceleration load
I have seen it posted many times that the 70-80% range is most often used, but I have a question. My UG classic only showed load, while the EM model shows load, and absolute load and they are very different.

So, do I accelerate with 80% load, or 80% absolute load?

Daox 04-30-2012 05:18 PM

80% load. Its not possible to accelerate at 80% abolute load at low rpms since you don't have anywhere near 80% of the maximum power available. :)

user removed 04-30-2012 05:58 PM

About 1-2 inches of manifold vacuum should be close to your 80% load, regardless of the engines RPM as long as it is above about 1000. As I understand it 80% load should be possible at any RPM from just above idle speed to redline.


BHarvey 04-30-2012 08:18 PM


Originally Posted by Daox (Post 304213)
80% load. Its not possible to accelerate at 80% abolute load at low rpms since you don't have anywhere near 80% of the maximum power available. :)

With the (load) at 80, the absolute load is at 55 or so.

Will play more with it and see, but 80% absolute load is MUCH more acceleration!

mwebb 04-30-2012 11:38 PM

Ford Paul Baltusis
there is a very good explanation from a Ford engineer regarding the use of absolute load

in IATN it may be available elsewhere on the net

the bottom line is
do not use absolute load for testing as the upper limit will always be 100%
even if the system is under performing by a huge amount

many / all systems (un boosted) can never get to 100% load even under optimum conditions , it is normal to see peak load values between 90 and 95% under WOT in 2nd at 4k rpm
a system with restriction to flow will report much less , it is how we determine
(when combined with fuel trim values)
when systems have restriction to flow or fuel delivery problems or under reporting MAF sensors

Load in green peaks at 80% , real time fuel trim in red is heavy ADD over 15% at WOT
new MAF sensor is UNder reporting

NEW means

user removed 05-01-2012 09:41 AM

80% load means the engine is producing 80% of the potential 100% which is maximum load in an engine in perfect operating condition. If atmospheric pressure is 30 inches of mercury, then the calculated 80% load would be 30X80% or 24 inches. A vacuum gauge would read 6 inches of manifold vacuum.
I think in reality it is closer to 2-3 inches depending on the engine and the RPM at which you are applying the load.
Take any engine, put it on a dyno and pick any RPM. Increase the load until you have 2-3 inches of manifold vacuum measured and you would be near 80% load, regardless of the RPM. 100% would be the maximum power that engine could produce and that specific RPM reading.
You also have to choose whether you are measuring horsepower or torque which would be at different RPM for the maximum the engine is capable of producing. Peak torque is efficient, while peak horsepower is not generally nearly as efficient.


renault_megane_dci 05-04-2012 09:22 AM

No straight relation with the throttle position then ?

(i was thinking of marking my throttle with a dot at 75% opening, maybe not a good idea then)

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