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Old 12-10-2008, 12:36 PM   #11 (permalink)
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Diesel values added to the select list.

In searching around, I've noticed there are varying values posted in various places for both diesel and gasoline energy content. Not sure how to decide which to rely on.

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Old 12-10-2008, 03:00 PM   #12 (permalink)
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same thinking

Quote:
Originally Posted by MetroMPG View Post
Do you know if the same thinking applies to losses in the CV/universal joints, potential brake drag, and differential/transaxle resistance - strictly for the purposes of calculating RR?



Good idea. Currently you can lump that into the "engine efficiency" figure in the calculator, if you're working backward from a known MPG at a certain speed.

Still some refinement to be done, for sure. Thanks for the feedback Phil.
Darin,the SAE likes to limit RR to the tires only,as an independent variable. When official testing is done,brake drag is checked for,and eliminated before the testing cycle(so it isn't included in the methodology,although we definitely need to be aware of it). With respect to bearings,ring and pinion,C-V joints,split-driveshaft center support bearing perch,pin-bearings in U-joints,dust seals,transmission/transaxle/transfer-case,oil,grease hydrodynamic losses,these are all contained within Mu,the mechanical -efficiency value of the driveline.

Hoerner uses 90%(1950),CAR and DRIVER have used as low as 80% when discussing their Maxda RX-7 at Bonneville.SAE says 95% for 1/2-ton pickup.

We could use some current good numbers for these values.CVTs are supposed to have horrible efficiencies which cancel out much of their benefit.

Perhaps GOOGLE can provide some up-to-date and accurate quanta for us to use.Anyone lurking could jump on this one and help out.

I'll check back should I have any revelations.Thanks for all you do,Phil.
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Old 12-10-2008, 06:59 PM   #13 (permalink)
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Great tool!

does it make since to add a parasitic load input?
alternator, A/C and other loads would be relatively flat compared to speed
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Old 12-10-2008, 08:59 PM   #14 (permalink)
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That's an interesting idea. Most people probably don't know how much power watts their power steering pump, for example, requires from the engine though. But for people who experimentally determine their electrical overhead, it could prove useful...

Anyway, I've added the drivetrain efficiency field.

And I prettied up the entry form a little bit and have started adding notes/explanations for the various fields/values.
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Old 12-11-2008, 12:10 AM   #15 (permalink)
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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
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Old 12-11-2008, 03:28 PM   #16 (permalink)
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Any suggestions on specifically how you'd like to see that variable worked in to the existing tool? What units?
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Old 12-12-2008, 05:59 PM   #17 (permalink)
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I'm up for anything as long as there is a field for a flat load fudge factor
GPH, like I used is probably not appropriate

watts or Horsepower is probably more acceptable
- what do you think?
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Old 12-13-2008, 12:58 PM   #18 (permalink)
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misc. data for spreadsheet

Darin,I know you'd probably like to finalize your estimator so I'll throw this last stuff at you,then leave you alone.When concrete brought up the mention of accessories,I thought I'd posted some things for that on the general ecomodding sticky,but I didn't,and was probably thinking of maxmpg. Anyway,I have a few things from SAE,they are dated now,however they may be considered a worst-case scenario.Also,they're for a "medium-size" car,about 3,500-lbs:

- Air conditioning 1.5mpg loss urban,1.0 mpg loss at constant 70 mph.
- Alternator 0.9 mpg loss urban, 0.5 mpg loss at 70 mph.
- Fan (cooling) 0.1 mpg loss urban,0.5 mpg loss at 70.
- Power steering 0.1 mpg urban, 0.4 loss at 70.
- Automatic transmission 5-15.5% loss urban.

++++++++++++++++++++++++++++

From a CAR and DRIVER experiment at 60-mph with a Ford Escort:

- 3rd instead of 4th-gear cruising 9.0 mpg loss.
- Rooftop carrier 6.0 mpg loss.
- Air conditioning 3.0 mpg loss.
- Windows down 1.0 mpg loss.
- Heavy load 1.0 mpg.
- Underinflated tires 0.5 mpg loss.
- Overinflated tires (no change).

***************************

From Road and Track: Geo Metro:

- calm wind 56.6 mpg
- 25-mph headwind 44 mpg
- 20 mph in 3rd gear 84.1 mpg
- Burn/glide/bumpstart-repeat,from 20 mph down to 8 mph = 116.6 mpg.
- Honda VX doing hyper-miling= 104.8mpg.(tests were conducted at U.C.Davis,with Professor Dr.Andrew Frank).
- The little university research car with 3.8-ft-sq frontal area and Cd 0.14 got 3,300-mpg doing hyper-mileing.

Last thought,and this is about Diesels.A diesel Rabbit had a 35mpg advantage over a gasoline Chevette at 30-mph.At 80-mph,that advantage had shrunk to 9mpg.At 80 mph(legal in West Texas and elsewhere now) my T-100 gets 3-mpg better than the Rabbit diesel.It looks like the high inertia loads of the early diesels really cost them at elevated velocities.Like to think modern TDis are much more efficient!
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Old 12-13-2008, 08:29 PM   #19 (permalink)
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Quote:
~.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)
What is your base idle gph BTW?
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Old 12-13-2008, 11:22 PM   #20 (permalink)
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about .46 GPH during testing
fully warm it would be a little less
but I did not want a hot engine while I was removing the belt on the water pump

the test was just rough order of magnitude work
I was discussing steering losses with a friend at work and he suggested a quick test
it was actually one of the easier and most fun tests I have run

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