Question regarding engine load.

[canuguzzi]

When an engine load is 100 percent is it true that applying the accelerator more is just a waste of fuel or does the fueling system account for the load and ignore the additional application of the accelerator?

This would be an engine equipped with modern ECU , fuel injection etc.

[lucky phil]

When an engine load is 100 percent is it true that applying the accelerator more is just a waste of fuel or does the fueling system account for the load and ignore the additional application of the accelerator?

This would be an engine equipped with modern ECU , fuel injection etc.

The typical Guzzi fueling system doesn't take engine load into account. Its looking at RPM and throttle angle off a set of tables and applying the injector duration and ignition advance called for in that table. It is then modified or trimmed within certain limits from input of the various sensors, OAT, pressure, etc.  If you are at a load point where more throttle opening doesn't result in more speed/acceleration ( I am making the assumption that you are not referring to an engine delivering peak torque as that happens at a load with wide open throttle, and you cant get any more) then yes you are just wasting fuel because the system will be trying to apply it. 
Ciao

[rodekyll]

Engine load is most easily sensed by vacuum.  The lower the "boost" the greater the load.  For example, a 4-cyl car might idle unloaded at 22" vacuum and cruise at 14" vacuum, but when you dump the throttle it drops to 0 - 4".  That's what those old 'econometers' were on the gass guzzlers -- a simple vacuum gauge with a green and red zone to help you keep your foot out of it.

But our bikes aren't 4-cyl cars.  So our vacuum properties are different.  The lag time between changing throttle/load and the ecu compensating for the vacuum change makes it an iffy way to go.  Other load sensors are expensive and also not real practical on a 2-pot engine.  And so we infer load from the throttle position, rpm, and (in some closed loop system) road speed and emissions.

[canuguzzi]

Sorry for the confusion, my fault. In used the NGC to indicate it wasn't related, its a car question.

My observation: once the load graph reaches 100%, additional accelerator doesn't seem to do anything until the speed catches up to load. It seems that I can keep the load at 100% with plenty of throttle left and just moderate it to stay at 100% load.

Does that mean the acceleration is also maximum and more throttle beyond that wastes fuel?

I realize that 100% might seem like wasting fuel but consider towing where you might be at maximum load for acceleration but with plenty of throttle remaining. You could chose a lower gear but that gets beyond my question.

Again, sorry for not being clear.

[rodekyll]

The way to sort it out is to compare the efi to carb.  There are engine properties that exist independent of the aspiration or fueling, and some that depend on the delivery method.  Some of what you're asking sorts along the lines of basic engine theory, and some sorts as the differences between injection and carburation.  So it's not a clear question.

The easy and not real good answer is yes, there comes a point that vacuum has dropped to zero and the engine has stalled.  In a car it gets sorted out by a crapload of sensors, the throttle position, mass air flow, emissions, etc.  The car is big and expensive enough to accommodate all that stuff.  Bikes not so much.

[Idontwantapickle]

Engine load is most easily sensed by vacuum.  The lower the "boost" the greater the load.  For example, a 4-cyl car might idle unloaded at 22" vacuum and cruise at 14" vacuum, but when you dump the throttle it drops to 0 - 4".  That's what those old 'econometers' were on the gass guzzlers -- a simple vacuum gauge with a green and red zone to help you keep your foot out of it.

But our bikes aren't 4-cyl cars.  So our vacuum properties are different.  The lag time between changing throttle/load and the ecu compensating for the vacuum change makes it an iffy way to go.  Other load sensors are expensive and also not real practical on a 2-pot engine.  And so we infer load from the throttle position, rpm, and (in some closed loop system) road speed and emissions.

I don't think I can agree with your lag time statement. The ECU runs at a clock speed far in excess of the motion of any part or process of the engine. The time that the ECU needs to process and react to a change in throttle position by looking at the map, adjust the ign timing and being ready to trigger the injector is far less than the time the engine can rotate through a stroke. For example a 2 cylinder 4 stroke running at 10000 rpm needs to fire 167 (rounded) times a second. In the world of computers that is ssssllllllllooooooo oowwwwwww. Now I realize there is not a direct correlation between the engine needing 167 ignition events a second and the ECU being able to process in the range of GHz. The ECU must handle all the inputs and variables individually and that takes a lot of ticks. But the ECU is still way faster than the engine could ever go. By comparison, the carb doesn't "know" a greater demand exists until the intake valve opens and the air starts moving.
Another thought I had, and I don't know if this is true, is if the reaction of the mass of the fuel in a carburetor is slower than the reaction of a fairly modern EFI. I would think so since the EFI has the ability to not only know how much fuel is needed but also has it under pressure for quick delivery.
Just my .02 
Hunter

[Waltr]

  I may be missing something here but what is 100 per cent load?  A brick wall could represent a 100 per cent load. A braking force enought to stall an engine is a 100 per cent load.
  If designed properly full throttle will provide more torque than half throttle but 100 percent load is not integral to the process of measuring.

  Now if were talking about steam engines of better yet diesel electric engines we can talk closer to 100 per cent load. 

[Idontwantapickle]

  I may be missing something here but what is 100 per cent load?  A brick wall could represent a 100 per cent load. A braking force enought to stall an engine is a 100 per cent load.
  If designed properly full throttle will provide more torque than half throttle but 100 percent load is not integral to the process of measuring.

  Now if were talking about steam engines of better yet diesel electric engines we can talk closer to 100 per cent load.

I think the OP is wondering what goes on when the engine is doing all it can and you open the throttle more. IE climbing Black Mountain to Boone NC is a very long grade. Say I'm in 4th gear with the Ol' Lady    on the back and I'm at half throttle to keep it at 55mph. Now at this point the engine, at that speed, can't make any more power at a higher throttle setting. If I open up I get no acceleration, I have to downshift to pick the revs up to get more power. So in that circumstance what happens?
I'm sure that varies by engine management type but as far as any practical situation goes, not much happens. Just uses a bit more fuel.
Hunter

[canuguzzi]

I think the OP is wondering what goes on when the engine is doing all it can and you open the throttle more. IE climbing Black Mountain to Boone NC is a very long grade. Say I'm in 4th gear with the Ol' Lady    on the back and I'm at half throttle to keep it at 55mph. Now at this point the engine, at that speed, can't make any more power at a higher throttle setting. If I open up I get no acceleration, I have to downshift to pick the revs up to get more power. So in that circumstance what happens?
I'm sure that varies by engine management type but as far as any practical situation goes, not much happens. Just uses a bit more fuel.
Hunter

Yes and thanks for that. I can get the engine load from the engine OD2 connection.

In the lower gears the acceleration is fast enough (for lack of a better term) that there really is no throttle position left when load measurement gets to 100%, time to upshift. On a long grade for example in the higher gear it is easy enough to see 100% engine load yet still have throttle left.

So the answer then if I read this all right is that there is waste of fuel if the throttle is opened greater when load is 100%?

If there is fuel waste, then using that indicator could reduce fuel consumption by running up to 100% load but not additional throttle after that?

[Idontwantapickle]

Yes and thanks for that. I can get the engine load from the engine OD2 connection.

In the lower gears the acceleration is fast enough (for lack of a better term) that there really is no throttle position left when load measurement gets to 100%, time to upshift. On a long grade for example in the higher gear it is easy enough to see 100% engine load yet still have throttle left.

So the answer then if I read this all right is that there is waste of fuel if the throttle is opened greater when load is 100%?

If there is fuel waste, then using that indicator could reduce fuel consumption by running up to 100% load but not additional throttle after that?

IDK for sure what EFI does in that situation. I would suppose that the mapping would be trimmed for the situation and that would minimize fuel waste. Maybe someone here familiar with the intricacies of EFI maps would know? Carbs run rich in that situation, that much I do know.

[QuattroValvole]

Some pretty carefully thought out and somewhat complicated answers here. An old trucker (my dad) once told me that if you give it more throttle and don't get more RPM's, you're probably hurting it. Downshift.

[Arizona Wayne]

With  closed loop EFI, what makes you think giving it more throttle when it's already maxed out uphill is going to use more fuel?   If you keep on doing that you are lugging the motor but I doubt it's getting any more fuel than if you weren't doing that.   In all these cases you should be trying to keep the motor in highest part of the torque curve for efficiency.  Only there will you use the least amount of fuel to accomplish the best mpg.

[Rough Edge racing]

 Several years ago a leading automotive magazine did gas consumption during acceleration testing on manual shift cars .It was found that for best fuel mileage to use heavy throttle and short shift the engine until you get up to speed. My 5 speed Jeep Cherokee has a MPG readout based on engine electronic  management fuel flow. Driving at a steady speed of let's say 50 mph, the lowest rpm results in the best fuel mileage even when the engine is being lugged up a slight grade. I'm not suggesting to lug a bike engine ...

[charlie b]

First, with an EFI, I don't know.  It depends on the system and the map.  If running open loop then it is all on the map.  If closed loop then the O2 sensor will probably rule and the fuel will be held to reasonable levels.

Second, carbs.  Carbs (butterfly style) deliver fuel through the venturi for the most part.  Lower the air flow and the fueling is reduced.  Even if you open the throttle more there is no more airflow so the fueling will not increase.  This does not take into account other fuel circuits, like accelerator pumps, coming into play.  Eg, if you open the throttle the accel pump will shoot extra fuel into the system, but, only as the throttle is opened.  Once opened it goes back to just the venturi. 

BUT....for those carbs with jets and needles opening the throttle enlarges the jet so more fuel will be sent to the venturi.  In those cases you will run richer if the throttle is opened more under load.  In an extreme case (high load, low RPM) you may even lose power as you open the throttle as it runs too rich.  This is a situation with some auto carbs.

And...some carbs use the slide as the venturi, so opening up the throttle will increase the size of the venturi reduce the vacuum and reduce the fuel delivered (again, like the delortos).  So, in these cases the jets are enlarged to deliver more fuel as the venturi is enlarged to reduce the amount delivered.  In these cases you might have too little airflow and starve the engine.

See....simple answer.  :)

[flangeman_70]

In all this really is a massively complex question as there are so many variables.
From what I've read from the posts so far I know it is an injected engine but are we talking about a petrol or diesel engine? Does it have a supercharger or turbo? Does it have direct injection? Does it use a rising rate fuel pressure regulator? Does it use a MAP as well as MAF?

I would suggest you look at the injector dwell time vs. RPM with your OBDII setup as this will give a definitive answer. Regardless you will use more fuel if only periodically as you open the throttle and pass through the 100% load mark without change in RPM. Why? All modern car EFI has a pseudo fuel pump component which increases the injector dwell as a rate of change of the throttle. How this happens is controlled by multiple inputs from the MAF, Air temp., MAP, Lambda, Fuel Pressure, timing, EGT and even selected gear.

EFI is not a simple thing and as someone mentioned the clocking speeds of the processing today is happening multiple times within one injector cycle.

Lookup some info on Ford's Econo Boost vehicles. By understanding wetting they completely changed EFI some years back and today protocols are extremely sophisticated in making vehicles burn fuel efficiently for both exhaust emissions and engine life.

Good luck with your quest.

Adam.

[Waltr]

First, with an EFI, I don't know.  It depends on the system and the map.  If running open loop then it is all on the map.  If closed loop then the O2 sensor will probably rule and the fuel will be held to reasonable levels.

Second, carbs.  Carbs (butterfly style) deliver fuel through the venturi for the most part.  Lower the air flow and the fueling is reduced.  Even if you open the throttle more there is no more airflow so the fueling will not increase.  This does not take into account other fuel circuits, like accelerator pumps, coming into play.  Eg, if you open the throttle the accel pump will shoot extra fuel into the system, but, only as the throttle is opened.  Once opened it goes back to just the venturi. 

BUT....for those carbs with jets and needles opening the throttle enlarges the jet so more fuel will be sent to the venturi.  In those cases you will run richer if the throttle is opened more under load.  In an extreme case (high load, low RPM) you may even lose power as you open the throttle as it runs too rich.  This is a situation with some auto carbs.

And...some carbs use the slide as the venturi, so opening up the throttle will increase the size of the venturi reduce the vacuum and reduce the fuel delivered (again, like the delortos).  So, in these cases the jets are enlarged to deliver more fuel as the venturi is enlarged to reduce the amount delivered.  In these cases you might have too little airflow and starve the engine.

See....simple answer.  :)

Your Norge goes out of closed loop when a preset load is exceeded.  Even then the LOAD is only based on the sum of a number of factors. Throttle position, RPM, speed and most importantly manifold vacuum is used to judge load.  So 100% load is only a planned for theoretical maximum.  All this becomes reality for those that challenge the record books at Bonneville vs even the best dyno jockeys.