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Old 01-18-2014, 08:54 AM   #61 (permalink)
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Most of the main points have already been addressed by others ... just my own 2 bits on the topic.

There are different pros and cons... stemming from the combination of two things:
#A> What method uses the least total joules of energy needed to travel a given route, under given conditions ( average speed , weather, traffic , etc. )

#B> What method maximizes the highest average ICE conversion / operating efficiency to convert fuel energy to travel energy in order to provide the energy needed for #A above.

You can 2x the #A travel joules , and 2x the #B average efficiency ... and would still result in the same FE or MPG.

Does speed variation increase #A ... yes, absolutely.
But if that speed variation allows for a higher #B ... than a non-varying speed would have ... it can potentially produce a net benefit... despite the increase in #A.

If you can get any amount of increase in #B without a increase in #A you are net better off... or any amount of decrease in #A with no change in #B.

Quote:
Originally Posted by niky View Post
I'm pretty sure that's just about everything with computerized fuel injection. There are those that still inject a miniscule amount during engine braking, but it's a tiny percentage of what you use while idling.
For my 2 bits.
Engine braking is best used as just that braking ... otherwise ... it isn't as much about the potential for tiny amounts of fuel ... some cars do due fuel cut during engine braking ( and consume nothing ) ... but the engine braking losses from air pumping and friction of just rotating the ICE add up... that is loss that often has to be paid back latter... if you want to brake anyway that's fine ... but if you don't want to brake , then don't.

For example of the engine braking air pumping , friction losses , etc.
I see about
~2.67 kw @ ~1,365 RPMs
~2.98 kw @ ~1,682 RPMs
~3.41 kw @ ~2,107 RPMs
~4.67 kw @ ~3,364 RPMs

That is lost power any time the ICE is turning ... and one of the potential benefits of P&G techniques... if used under the right conditions.

Quote:
Originally Posted by Arragonis View Post
The instrumentation available - built in or add in - isn't accurate enough to determine which is better in one run or a collection of runs really but they give a guide, better than nothing.
If one is motivated it can be measured and determined in as little as one run of each method.

Once you know the ICE's BSFC warmed up ... and once the ICE is warmed up ... you only need a few pieces of real time data.

#1> ICE Load
#2> ICE RPM
#3> Vehicle Speed
#4> Weather Conditions

With #1 and #2 and a BSFC you know the real time operating efficiency of that warmed up ICE ... over the run you can average it out to measure the average % ICE Effiiency for that method.

With #3 and #4 you can quantify and determine any travel joule differences between the runs.

A real time operating % efficiency meter is one of my dream Mods ... I may never get it ... but definitely on my wish list.

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Old 01-18-2014, 10:23 AM   #62 (permalink)
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Quote:
Originally Posted by IamIan View Post
...If one is motivated it can be measured and determined in as little as one run of each method.

Once you know the ICE's BSFC warmed up ... and once the ICE is warmed up ... you only need a few pieces of real time data.

#1> ICE Load
#2> ICE RPM
#3> Vehicle Speed
#4> Weather Conditions

With #1 and #2 and a BSFC you know the real time operating efficiency of that warmed up ICE ... over the run you can average it out to measure the average % ICE Effiiency for that method.

With #3 and #4 you can quantify and determine any travel joule differences between the runs.

A real time operating % efficiency meter is one of my dream Mods ... I may never get it ... but definitely on my wish list.
How do you get ICE Load ?
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Old 01-18-2014, 05:23 PM   #63 (permalink)
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Quote:
Originally Posted by Arragonis View Post
How do you get ICE Load ?
There are a few different ways depending on preferences.

There are torque sensors that can be installed in the shaft itself as it comes out of the ICE ... or in the transmission ... or at the wheel .... any of which would give the equivalent kind of load information needed to reference back on one's known ICE BSFC.

Some Cars have some type of OEM torque sensors already for the car to be able to determine when to shift to different gear ratios, and such.

My Gen-1 Insight OEM gives me a crude % based load signal 0 to 100 ... it's not ideal ... but , until I upgrade to a better sensor ... I can use that and the RPM signal to determine ... or data log ... an idea of where I am on the BSFC for real time operating efficiency ... if data logged I can go back latter to crunch the numbers over a given route and given driving method / technique.

- - - - - -

For my dream efficiency meter mod ... I have been leaning more to an at the wheel type of sensor... By knowing the torque and RPM at the wheel ... I can account for all kinds of vehicle losses and loads more easily.

Last edited by IamIan; 01-18-2014 at 05:29 PM..
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Old 01-18-2014, 06:09 PM   #64 (permalink)
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How do you measure torque, how does a torque sensor work and how does it work in an engine ?

(P.S. I'm not trolling, I really want to know)
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Last edited by Arragonis; 01-18-2014 at 06:10 PM.. Reason: Added a space
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Old 01-18-2014, 08:04 PM   #65 (permalink)
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Quote:
Originally Posted by Arragonis View Post
How do you measure torque, how does a torque sensor work and how does it work in an engine ?

(P.S. I'm not trolling, I really want to know)
There are different mechanisms that can be used to achieve the result of torque measurement.

Just there are different mechanisms that allow you to measure temperature... or light... or weight ... etc.

- - - - - -
Without getting too crazy about it.
- - - - - -

#1> One type of common torque mechanism exploited in many sensors is the spring rate of a specific material.

If you know that a specific calibrated device will 'deflect' a specific known amount under a specific amount of torque ... than you can later use that deflection in order to deduce the torque.

For example a section of the metal drive shaft. When you put the metal under a load it will flex. This happens weather the load is at any right angle to the shaft or if the load is in a rotational direction about the shaft.

Many metals have a point of bending that does not deform the metal, it bends under the load but down not retain that bend when the load is removed. This effect is used by all metal springs. The load compresses the spring, but it does not permanently deform the spring. ... your non-digital bathroom scale uses this to measure the load you apply to it... so does some torque wrenches.

~2 years ago I was quoted $9,000 to measure the rotational torque deflection of the OEM drive shaft ... which could then be used as a basis to make a sensor to real time measure the torque for anyone's Gen-1 Insight OEM drive shaft.

~2 years ago I was also quoted $12,000 to alter an existing drive shaft to include a pre-made and calibrated sensor to do that shaft torque measurement function.

I'm hoping the price will come down, by the time I finish other projects.

- - - - - - - - - - - -

#2> Although less common ... When the deflection is too small to get meaningful measurements from directly ... Other means can be used to measure the other effects ... be they pizeo-electric effects ... changes in resistance ... changes in magnetic flux , and fields .... etc.

Those other mechanisms exploit the fact that material under load have slightly different properties then when not under a load.

As long as the effects on the material under load can be quantified you can then make a sensor to measure it... some digital scales make use of this kind of mechanism for their sensors.

- -- - - - -

Forgot to include before:
If you have a more common type of car ... there are lower cost ... at least less than the $9k options than what I previously wrote about above.

Shaft

Wheel

Last edited by IamIan; 02-11-2014 at 07:34 PM.. Reason: Other more common cars
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Old 01-18-2014, 11:54 PM   #66 (permalink)
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My old truck driving experience explains it easily. Try driving a 175hp, 18 speed, 60,000 truck through the mountains, much like you are around. My experience was around Durango and Farmington NM. I named it " Conversation of momentum " back in the day, late 70's. It led to trucks which were geared to a 60 mph limit, being taken out of gear so "Glide" could be optimized to the point of 80+ mph, just to get up the next hill without having to downshift 10 or 12 times and end up full throttle at 10 mph cresting the peaks. Not safe or recommended, but talk to "any old" trucker, and you'll get the idea. I'm surprised anyone with the name of " bikenfool ", if it relates to bicycles, does not understand the process.
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Old 02-11-2014, 01:34 PM   #67 (permalink)
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Your truck example makes perfect sense for a heavy truck. I'm not sure that is DWL tho, since the driver probably has is foot on the floor. On a bike, if you can go fast coasting, of course you go as fast as sanely possible on the downhill. It's actually more efficient to increase power on the climb since the 'extra' energy output is not wasted as much as it is on the flats where the the extra energy would have more loss due to the v^2 aero losses.

I think DWL is applicable to a powertrain/hill combo where you need to do this to keep it in high gear, and many modern automatics require a very light foot to keep it from shifting down.
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Old 02-11-2014, 02:37 PM   #68 (permalink)
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Quote:
Originally Posted by Arragonis View Post
How do you get ICE Load ?
Vacuum gauge can also give you load. And on my bsfc chart I give approximate vacuum readings that correspond to the load for magenta Optimum efficiency line. Useful for acceleration and P&G.
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Old 02-11-2014, 02:37 PM   #69 (permalink)
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It was a diesel so there was no intake obstruction to create manifold vacuum, which P&G gets around. Or " driving with load" as I see it.
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Old 02-11-2014, 06:33 PM   #70 (permalink)
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Even diesels have efficiency islands at higher loads and benefit from p&g, but can't measure intake vac to determine load.

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