Would double battery = double mileage?

[dcb]

certainly a modder can atkinsinize his/her engine as well.

[IamIan]

Originally Posted by jamesqf

But again, my question wasn't about overall passenger mpg efficiency, it was about the relative mechanical/electrical efficiency of the mechanism(s) between the engine and the wheels of the Prius and Insight.

Or even between the gas pump and the wheels: is the Prius Atcheson-cycle engine more or less efficient than the Insight's lean burn?

I think the design goals of the two are very different... it will depend on the context.

We can look at some of the components ... OEM ... as of the tests I've seen... here would be my summery.

ICE: Efficiency
The Gen-1 Insight Lean Burn ICE has higher peak efficiencies than the Prius ICE... more than ~12% higher peak efficiency fuel chemical energy to mechanical energy.

The Prius ICE has wider bands of high efficiency than the Lean Burn Gen-1 Insight... more operating condition / easier to stay in high efficiency bands.

ICE: Pollution:
The Prius ICE produces less smog contributing emissions than the Lean Burn Gen-1 Insight.

The Gen-1 Insight ICE produces less green house gasses than the Prius ICE.

Transmission:
The Gen-1 Insight MT is more efficient transmission than the Prius.

The Prius transmission has a better ability to autonomously keep the ICE in higher states of efficiency than the Gen-1 Insight MT.

Electric Motor + Inverter Combined:
Prius system is ~15% less efficient at low RPM & High Torque than Honda's IMA ... but up to ~8% better efficiency at high RPM low Torque.

- - - - - - - - - - -

The Prius design does not seem to be about having the highest peak efficiency ... instead it seems to be about avoiding the low efficiency points as much as possible ... and as a secondary objective to increasing the % of the time in relatively higher states of average efficiency.

The Gen-1 Honda Insight Lean Burn + IMA system in contrast seems to focus on Highest peak efficiencies first ... and as a secondary objective to avoid low efficiency points as much as possible.

Which design compromises result in the best efficiency ... will depend on the specifics of a specific context.

The nut behind the wheel being a massive part of that equation.

And of course either can be tweaked and modified in a variety of ways.

- - - - - - - - - - -

Originally Posted by bwilson4web

Hi folks,
If you agree with those citations, so too do I. <GRINS>

I agree that the context matters... that there is no one design compromise that is the best most efficient design for every possible context ... There are several contexts in which the Prius does not have 'unmatched efficiency'... such an open ended statement is incorrect... which is why I asked about the context from the beginning.

As for the citations you made ... it is open source ... as such it is one of the weakest types of references ... I think it can be useful in some limited contexts ... but Wikipedia as an open source that anyone can edit , is not nearly as robust as other sources ... so there is some significant limits to how much credibility or trust I would put in such references.

Originally Posted by bwilson4web

You might not like how we got here but I'm very happy with it . . .

The only thing that comes to mind that I dislike about it is how incredibly slow it took ...

It seemed so painfully obvious from the beginning that there had to be qualifiers and limitations put in place for a specific context in which the Prius had 'unmatched efficiency'.

Originally Posted by bwilson4web

BTW, I'm only 'pro' engineering and accuracy. If it happens to be the Prius, good. But I also like the latest Honda Insight and Ford is doing some notable work. Heck, even GM s*ck's less. What I'm seeing in the 2011 and 2012 models is radically different from what we saw before. By no means perfect, it raises the bar.

Nice to read ... but I have my doubts.

So far you have bent over backwards to be almost exclusively pro-Prius ... even making some very silly comments about inflatable mannequins making the Prius more efficient... hardly pro-engineering... or pro-accuracy.

Nice to read statement ... but I'll wait to read evidence of your being more pro-engineering than your already demonstrated pro-Prius.

[bwilson4web]

Originally Posted by bwilson4web

. . .
Also today, I reinstalled the Graham miniscanner and programmed it to record:

• MG1 torque - that is 28% of the ICE torque and used to calculate energy flow
• MG2 torque - used to calculate MG2 energy flow
• ICE MAF flow - used to calculate fuel flow to calculate BSFC in operation and indicated and true MPG
• MG1 rpm - used to calculate MG1 power
• MG2 rpm - used to calculate MG2 power and in combination with MG1 rpm, the ICE rpm and power
• traction battery current - used to calculate traction battery energy flow
• parallel GPS tracking - recording true velocity and altitude, total mechanical energy

I was thinking about this and decided to modify the test configuration:

• MG1 torque - is 28% of the ICE torque
• MG2 torque - energy flow via electrical paths from MG1 and traction battery
• MG1 rpm - used for MG1 power
• MG2 rpm - gives indicated speed and with MG1 rpm, gives ICE rpm
• traction battery volt - provides part of power measure
• traction battery current - with voltage, provides exact energy flow
• GPS - provides true velocity and altitude, the kinetic energy state

This drops the ICE fuel consumption for a more accurate traction battery power measurement. In the past, I've used the rated traction battery voltage for energy flow which was close enough but not exact. The new data will be as accurate as possible.

With this new setup, I'll be able to record and calculate:

• ICE power
• MG1 power
• MG2 power
• traction battery power
• vehicle kinetic energy
• vehicle potential energy

I just don't have enough fields to include fuel-flow but the operational BSFC can be done in a separate study.

I can replace the traction battery metrics with ICE metrics to remap the BSFC 'in operation.' This will also improve the accuracy of my mph vs MPG charts based upon an NHW11 with 138,000 miles. In particular, using GPS true velocity will be a great improvement as past measurements used just the indicated mph.

So I'll return to the lab, the experimental method, and measure with more accuracy what is going on in the Prius drive-train. Found my serial cable so should start data collecting early in the morning to get the lowest possible temperature. Will also add a short post-test set to measure traction battery electrical consumption with engine off and engine on. We'll average these short tests and take them out of the energy flow.

Bob Wilson

[IamIan]

Originally Posted by bwilson4web

In particular, using GPS true velocity will be a great improvement as past measurements used just the indicated mph.

Have you quantified the error rate of the GPS?
How many measured miles can you travel before the GPS calculated distance develops a discrepancy?

[bwilson4web]

<SIGH>

Bob Wilson

[dcb]

But Bob, Bumblebees CAN fly though, despite all your precious science! did you consider THAT?!?