SAE Papers Available
 

At $15/each, these were a little pricy. But papers can save a lot of 'lab time.' I'll be a little quiet thanks to the release of the SAE hybrid conference papers:

SAE 2009-01-1332 - "Development of New Hybrid System for Compact Class Vehicles"

This is the general systems approach to the new ZVH30 (2010) Prius. It is a recommended first read since it covers all systems.

SAE 2009-01-1048 - "Newly Developed Inline 4 AR Series SI Engine"

Here we get the details of the internal mechanics. One surprise, it uses variable oil pump to reduce internal losses.

NOTE: this is the Camry engine, not the 1.8L ZVH30 engine. Although not the same model, it introduces another energy saving device, a variable oil pump.

SAE 2009-01-0726 - "Development of New Hybrid Transmission for Compact-Class Vehicles"

It took me nearly a year and looking at Graham mini-scanner data to finally stop getting a headache. Time to bulk up on aspirin again. <GRINS>

SAE 2009-01-1322 - "Vehicle Inertia Impact on Fuel Consumption of Conventional and Hybrid Electric Vehicles Using Acceleration and Coast Driving Strategy"

I'm not a fan of "pulse and glide" and this paper requires close reading. A vehicle model was used along with some benchmarking so I'll be looking closely at the model and results. Looking at Table 4, "30-40 mph, 20 seconds of acceleration" shows their field test had a 25% performance improvement over the equivalent steady state, 35 mph cruise speed. My field testing of 25-40 mph, 33 mph cruise speed showed only an 11% improvement. We're off by a factor of two so the I'll be looking closely at their protocol.

SAE 2009-01-1321 - "An Analytic Foundataion for the Two-Mode Hybrid-Electric Powertrain with a Comparison to the Single-Mode Toyota Prius THS-II Powertrain"

Sad to say, this is an analysis of the soon to be replaced transaxle. Still, a quick scan suggests there may be some analytic techniques that may help us understand the ZVH30.

NOTE: This report is flawed because the author didn't realize MG1 is rated at 24 kW yet his model claims a loss of 15.6 kW at 80 mph. There is no way with any reasonable efficiency numbers that the MG1-to-MG2 power loss could exceed 3 kW. I'm also concerned about his use of "42 mph" as "its mechanical point," which is used in other parts of the same paper as a transition between a forward or reverse power flow.

BTW, I would recommend advocates of other hybrids search the SAE web page for released papers. The conference starts on Monday and releasing them before the conference gives folks a chance to read and review them. NOTE: there are some security features implemented in these SAE papers to limit making multiple copies. For example, there is a maximum limit of two print operations on a paper ... even if the software has a flaw that causes it to fail. I use a Mac and have two copies of paper that are lacking the first three pages and I can't print another copy. This leaves screen snapshots as the only way to get a hardcopy.

Bob Wilson

This is good info, Bob - thanks for posting...

Which vehicle/s was/were tested for this report?

Ben came home from the NY Auto Show with an interesting tidbit from the lead engineer on the Ford Fusion hybrid: he said the drivetrain was "optimized" for P&G. Not sure if he meant compared to non-hybrid drivetrains, or compared to other hybrids.

Ben's trying to track down his contact info. That's one bit of info I'd like clarified.

They used a 2007 Ford Focus and 2004 Prius (NHW20), which were tested on a dynamometer at the Argonne National Laboratory. It also includes a vehicle model. It is a good report although I still feel their model is not complete.

I have a design for that with my NHW11 (2003) Prius now that all warranties have expired. But we can chat about that after I build and test it. <grins>

Bob Wilson

"Development of New Hybrid System for Compact Class Vehicles"

I'd be interested in a pdf copy if anyone picks one up.

Hi,

I've started two threads about SAE 2009-01-1322 to discuss "Vehicle Inertia Impact on Fuel Consumption of Conventional and Hybrid Electric Vehicles Using Acceleration and Coast Driving Strategy" Lee, Nelson, and Lohse-Busch:

• "Prius Technical Stuff"
• MyHybridCar.com

I am not interested in 'trolling for members' to either site but there is a technical issue of trying to address discussions in multiple threads. It is my hope that someone here may also look at SAE 2009-01-1322 and if there is an interest in technical aspects of the paper, we may explore the paper.

The short form of my concern is I don't think the paper has properly factored in aerodynamic drag. If so, it may go a long way to explaining why their pulse and glide results, 25% better, or nearly twice the value I've found in my testing, 11%.

BTW, I think this paper makes a number of significant and important advances and in particular I appreciate:

• comparing P&G vs. equivalent constant speed
• modeling both

There is much more right with this paper and I believe it should be the starting point for follow-up papers that fully address what is going on.

Bob Wilson

Sae
 

Thanks for all the sleuthing Bob.This will be good science to chew on.

Based on what you've posted of the SAE paper, it appears they are at least including aerodynamic drag in the power approximation since it's the only term that could be associated with V^3, but whether or not they have the correct constant C wrt the vehicle in question depends, since I didn't notice them specifying what that was.