Online tool: shows aerodynamic drag, rolling resistance, power required & est. MPG

[TestDrive]

Originally Posted by Blue Bomber Man

I thought I should point you towards an existing spreadsheet that is the culmination of years of research (I believe it is someones PhD thesis) that is availible on the web.

Just search for Pamvec on google, it should turn up an excel file. It is extremely customizeable for many things that you have already included but also for things like: various drivetrains (hybrids, electric etc), driving models, can specify design goals, or just input known variants. When I used it to model my current car it nailed its MPG rating and I used it to model hypothetical cars.

FWIW here are links to:

the actual spread sheet in xls format
an html view of the spread sheet.
a pdf of the actual thesis (281 pages)

Abstract

This thesis presents a novel approach to modelling energy consumption in road vehicles – the Parametric Analytical Model of Vehicle Energy Consumption (PAMVEC).

The technique is offered as a complement to existing vehicle modelling tools, the majority of which are dynamic vehicle simulators such as ADVISOR. Dynamic vehicle simulators are powerful modelling tools with high precision and accuracy (error typically <5%), and this makes them ideally suited to detailed simulation, testing and refinement of vehicle designs as part of a design process. However, they can be disadvantaged by their complexity, their need for detailed powertrain component models (which often are not publicly available), and excessive computational requirements due to their inherently iterative nature. In the context of vehicle technology assessment where many vehicles or technologies may need to be compared, these attributes can make dynamic simulators quite costly and time-consuming to use. Furthermore, dynamic vehicle simulators rely upon deterministic driving cycles to represent the driving pattern. Existing cycles have been shown in the literature to be quite unrepresentative of real-world driving patterns, and this deterministic approach is particularly unsuited to the modelling of uncertainty. Again, these attributes are not desirable for the purposes of vehicle technology assessment.

In contrast, the PAMVEC tool is designed to be particularly well-suited to vehicle technology assessment. Relative to dynamic simulators, the PAMVEC lumped-parameter models are easier to analyse and interpret, requiring only minimal input data to produce a result, and the calculations are performed nearly instantaneously. Furthermore, with its parametric construction, PAMVEC is ideally-suited to performing sensitivity analyses and modelling of uncertainty. Its features include:

• Parametric analytical expressions for predicting vehicle energy consumption that are derived from the well-known road load equation
• Parametric analytical expressions to size powertrain components implicitly in terms of specified performance targets that include driving range
• A novel parametric driving pattern description that encompasses the multiple
• dimensions of real-world driving patterns, but is also well-suited to the modelling of uncertainty
• Simple component models based on parametric inputs for efficiency and specific power/energy
• Transparent implementation in a Microsoft Excel spreadsheet with calculations that occur almost instantaneously.

[MetroMPG]

Originally Posted by Funny

Perhaps you could also utilize this online tool for gear calculations and adjustments. That is for those of us who are interested in swapping transmissions and gears.

That's coming too.

Blue Bomber: that's the mother of all spreadsheets!

[aerohead]

Originally Posted by TestDrive

FWIW here are links to:

the actual spread sheet in xls format
an html view of the spread sheet.
a pdf of the actual thesis (281 pages)

When things slow down,and I can "camp-out" on the computer,I'd like to take a long look at this program.It looks like a terrific prediction tool and could save countless man-lives of computational time.An advanced thank you,and big thumbs-up for sharing this!

[TestDrive]

Originally Posted by aerohead

When things slow down,and I can "camp-out" on the computer,I'd like to take a long look at this program.It looks like a terrific prediction tool and could save countless man-lives of computational time.An advanced thank you,and big thumbs-up for sharing this!

It does look very impressive.

Blue Bomber Man is the one to be thanked, hadn't heard of it until I read his post. Simply googling Pamvec (as he suggested) produces the first two links on the very first hit.

The thesis was harder to find.

[aerohead]

Originally Posted by Blue Bomber Man

I thought I should point you towards an existing spreadsheet that is the culmination of years of research (I believe it is someones PhD thesis) that is availible on the web.

Just search for Pamvec on google, it should turn up an excel file. It is extremely customizeable for many things that you have already included but also for things like: various drivetrains (hybrids, electric etc), driving models, can specify design goals, or just input known variants. When I used it to model my current car it nailed its MPG rating and I used it to model hypothetical cars.

Blue Bomber Man,TestDrive straightened me out on the "source" of the spreadsheet post and I wanted to throw a two-fisted thumbs-up your way.I'll have to park my regular life and spend some time with it.'looks like a awesome prediction tool.Thank you big-time!

[daklein]

Originally Posted by Concrete

determining ball park parasitic loads is not too hard with instrumentation

I just pulled the serpentine and watched the scan gauge
(I really love that thing)

~.1 GPH difference without any belt (from 900-3000 RPM pretty flat)
~.1 GPH difference A/C on and off (idle)
~.12 GPH difference steering wheel still to loaded against the stops (idle)
~.01 GPH difference head lights on and off (maybe)

I think the power steering pump should watch it's back
it is not worth .12 gph to me

for the hyper-miler with manual everything & EOC this may be insignificant
for my truck (and probably the average vehicle) this is significant
during the test my unloaded consumption was ~.46 GPH
parasitic load can be 70% of my idle load and 10-20% of my cruise load

a parasitic input might help folks determine what their "conveniences" cost

just a thought

concrete,
I have a '98 s10 4cyl manual (without factory A/C), and the power steering and the mechanical fan were not watching their backs. Not sure if this has been discussed here yet, It is pretty simple to use a short belt to run just the alternator and waterpump. Not sure how this would work with A/C, you'd probably have to quit that bad habit at the same time too...

Remove the fan, but put the fan pulley back on for use as an idler pulley. grind away a little bit under the thermostat housing for clearance to the belt. In the direction of belt travel: Belt comes off the crank, around the idler and alternator as before. then over the top of the fan pulley (this is where you needed the clearance), originally went under the fan pulley. And back down to the crank, the water pump is driven from the back side of the belt between the fan pulley and the crank. The water pump is still driven in the normal rotation, the fan pulley turns opposite so you probably want the mech fan removed.

What's it worth, I don't know, it's directionally correct, I've moved on...

I did put an electric fan on, but have never used it because I didn't finish wiring in a thermostatic switch, and it is not required the way I drive. With normal practices discussed here, (turn off engine while coasting or stopped). I should have not bothered putting in the fan. Anyone want an elec fan from a v6 camaro, with a couple aluminum angle pieces to fit in a 4cyl s10? 20$ ?

The steering is obviously not great for parking lots, but really it's much better otherwise, the steering does not change assist as you start & stop the engine.
Dale

[Blue Bomber Man]

Thanks for finding the links, interestingly enough I tried that day and for some reason was getting blocked by the host website and could not access them to verify that I had the right links. When I started to design a car a few months I came across that and it allowed me to start specing out what I thought I would need for batteries and motor. It is very useful if you want to estimate the effects of like removing mirrors, low rr tires, etc .

[bwilson4web]

Excellent calculator that returns values close to my own:
The blue line is what the calculator appears to be generating. My gray line includes the fixed vehicle overhead, the 'heart beat' cost of having the vehicle on. Thus at 0 mph the vehicle achieves 0 MPG.

The only element missing from the calculator is vehicle overhead, what it costs if the vehicle is turned on and not moving (aka., idling overhead.) What this does is identify the maximum range speed and expected MPG. The calculator is fairly accurate at speed ranges where the vehicle overhead is much less than the rolling and aerodynamic drag.

Performance models are great because they give an idea of what the vehicle should achieve. To a greater or lessor extent, I can evaluate changes with the model and verify them on the road. But it is very important to go on the road and plot the mph vs MPG. The gaps between the model and field measurements can identify "sweet spots" as well as 'black holes' and leads to insights about our vehicle systems.

Bob Wilson

[MetroMPG]

Thanks for reminding me, Bob. Concrete had asked for this a while back and I just added a field for "Parasitic overhead" which you can optionally fill in with a value in Watts.

[MetroMPG]

Oh, and another drawback to the tool (maybe obvious, but worth saying) is that it doesn't account for gearing changes affecting engine load/efficiency.

Obviously it was meant more for looking at the "top gear" speed range.