Hi,
As follow-up to the bump:
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Originally Posted by bwilson4web
Works for me. BTW, I've found it possible to parse the detailed records from the GH database. I did this with my Prius data to load it into Excel and do some correlation studies. One of my 'get around to it' tasks is to use a Perl script to do web data harvesting: (1) Ebay for 'fair market value' and (2) GH for other correlation studies.
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I still need to 'get around to it' but that effort is taking a backseat to collecting oil samples. Although not completed, I've got a first cut at a web form to capture hybrid vehicle oil samples:
http://hiwaay.net/~bzwilson/hybrid_fleet/oil.html
I've got to complete the e-mail confirmation page and backend database. Then I'll add all of the known samples. At that point, we can start taking new reports. The goal is to provide simular oil analysis like this for all of our hybrids:
http://hiwaay.net/~bzwilson/prius/pri_toil.html
This can lead to smarter, more efficienct oil changing strategies based upon oil testing, not marketing hype.
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Originally Posted by bwilson4web
The Ebay script will automate looking for 'new listings' as well as provide 'fair market value' data for the price of hybrids. From what I'm learning about our Prius, there appears to be some 'price-performance' sweet spots. Tracking may lead to a second hybrid electric for our family which would be a Prius.
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Doug's Ebay tracking will have to do for now but I've not forgotten the need. This is especially important since "CNW Marketing" is describing the eventual softening of the 'white hot' demand as nobody likes hybrids any more.
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Originally Posted by bwilson4web
The correlation studies I'm interested in are 'trip duration' and 'temperature'. I have noticed in my data extracted from GH database a step function between 45(F) and 50(F) for 20 minute duration commutes. I suspect the warm-up fuel penalty has two componets, initial temperature and trip duration. Simular warm-up functions should exist for each make and model of hybrid-electric and the parameters are embedded in the GH database.
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This summer, I'm adding an engine block heater and transaxle pre-heater with thermostat control. This will allow controlled experiments when the cold weather returns to quantify the effects. The database records still exist but I prefer analysis of more controlled tests.
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Originally Posted by bwilson4web
One item I forgot to mention is a curious 'aging' effect the Prius fleet data shows in the first year. Within the first year, the Prius fleet data shows the initial high MPG seems to decrease by 5-10% and stays constant thereafter. My Prius cold weather experiments suggest this may be due to Prius transaxle oil fatigue from over-stress and an unfiltered breather tube. |
This should be visible in the existing mileage database after factoring out weather
effects. However, it remains a lower priority after getting the oil testing program working.
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Originally Posted by bwilson4web
I found the viscosity of my Prius transaxle fluid was significantly lower than the virgin Type T oil. Although a lower viscosity oil would reduce internal resistance and energy loss, if it also came with a lower 'film strength' (unmeasured), the higher friction would eat up any viscosity savings. Oil can be stressed by mechanical and/or heat and this is something I'm looking into.
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I was especially impressed by the difference between the Type T, NHW11 Prius oil, and the Type W, NHW20 Prius oil. The virgin Type W oil has simular viscosity to the worn-out Type T. I'm thinking about going with Type W in a controlled test in my NHW11 this fall after I complete my current vent and Amsoil ATF oil testing. Toyota had mentioned a change in transaxle oil along with adding a roller bearing for a bushing.
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Originally Posted by bwilson4web
The second problem, possibly unique to my Prius that came from Ft. Worth Texas, is silicon contamination. I'm still working on this problem and plan to install a filtered air breather tube. However, it is likly to be a problem other Prius owners are unaware of. Certainly those still under the spell of 'warrantee' are not likly to even ask much less investigate.
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This experiment is at 6,000 miles, about half-way:
http://hiwaay.net/~bzwilson/prius/pri_vent.html
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Originally Posted by bwilson4web
Now if we compare the size and architecture of an ordinary manual transmission versus the Prius CVT, several differences stand out:
- Prius transaxle has both an 18 kW and 40 kW motor generators (Prius I)
- Prius transaxle has two distinct gear assemblies and chain transfer
The higher powered Prius motor generators means there is a significantly larger heat load than in an ordinary manual transmission. This provides more opportunity for heat stressing the transaxle oil.
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So far, I can not find evidence of oil overheating:
http://hiwaay.net/~bzwilson/prius/pri_tt.html
The hottest I've seen is ~70C, about 10C cooler than the ICE coolant temperature. There may be local hot-spots and some have reported MG temperatures above 100C.
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Originally Posted by bwilson4web
The larger Prius transaxle galleries for the motor generators means that thermal cycles can ingest more dirt laden air than the smaller galleries of an ordinary manual transmission. The Prius planetary and normal gear assemblies are linked via a chain which again increases the internal air gallery space that thermal cycles can fill with dirt laden air. Contaminated transaxle oil would significantly increase energy loss.
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As pointed out earlier, this is something that has my interest. Curiously, the used NHW20 sample had half of the particulate matter of my NHW11 and better viscosity wear patterns. It looks like NHW20, Prius II, transaxle oil is good for a 60,000 mi. change interval. The wear materials appeared to be higher but the contaminates were half of the NHW11.
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Originally Posted by bwilson4web
Although possible, I don't think the Prius helical gears are likly to mechanically stress the oil. Helical gears that make a 90 degree power transfer are more likly to cause mechanical stress than those that don't make the bend. But I would note the Prius differential is embedded in the transaxle. Ordinary differentials have a heavier grade of lubricant than typical transaxle oil.
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I'm begining to suspect that the higher viscosity of the Type T oil leads to mechanical stress wear. A thinner oil would not suffer the shear stress and would be less likly to lose viscosity. This is consistent with the different results between the NHW11-TypeT and NHW20-TypeW results that we have today.
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Originally Posted by bwilson4web
This is probably more information than you were interested in but we are comparing two dissemular transmission technologies. A simple, manual transmission and a constant velocity transmission. My wife has forbidden us from ever having a manual transmission again.
IMHO, I suspect changing the Prius transaxle oil annually would make a significant improvement in Prius fleet performance. But it will take a Toyota technical change notice to make that happen for warrantee vehicles.
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These results beg the question of what happens if Type W is used instead of Type T in an NHW11 transaxle. I expected to perform that experiment this winter.
Bob Wilson