specific power output chart from Autospeed

[moses]

There was an interesting article about specific power in Autospeed:
"Brake Specific Fuel Consumption, A really useful concept" -- http://autospeed.com/cms/A_110216/article.html
that has a graph of the Insight engine's specific power output.

I was thinking about making an indicator for my car that would help me stay in the "sweet spot" where the engine can be 50% more efficient than otherwise (this is related to "pulse and glide" hypermiling), but the chart in the article has something called IMPE measured in 1-12 bars on the vertical axis, and IMPE doesn't ring any bells with me. I might have thought that the IMP part meant Intake Manifold Pressure but the intake manifold is always below 1 atm (1 bar ~ 1 atm) in non-turbo cars so I'm not sure what is on the vertical axis.

I think the graph came from the sixth reference at the end of the autospeed article (Trigui, R, et al, (2003) Hybrid Light Duty Vehicles Evaluation Program, International Journal of Automotive Technology, Vol 4, No 2) but my university library doesn't subscribe to that journal so I can't get it (at least not for free).

Can anybody (like maybe Autospeed Editor ) sort this out for me?

[Insightful Trekker]

Originally Posted by moses

Can anybody (like maybe Autospeed Editor ) sort this out for me?

He only astroturfs here.

Maybe ask on his site?

[moses]

OK, right, what's his website?

[Insightful Trekker]

<shaking head in disbelief>
(don't read your own posts )

Your slipping Troy

[Dougie]

That is a very interesting article.

One problem is that for the vast majority of driving conditions, high rpm and full throttle aren't needed. The big black hump at 2500 rpm may be why the shift light goes on at 2000, telling you to stay in the red area.

It's only when going up steep, long hills that you get into a situation where you can make the most of the engine power. The last curve seems to suggest that the best strategy in that case is to ignore the shift lights that are telling you to stay in a high gear, and instead to shift down so you are running at 4000 rpm--which is a higher engine speed than I have used in the past--and keep the throttle open. Will have to try it!

[moses]

Dougie,

I completely agree with your observation. It's funny that the "problem" with our 3 cylinder 60hp cars is that they have "too much" power and we drive them at nearly closed throttle most of the time in city/commuting traffic. It drives me nuts sometimes to be driving just off idle stuck behind somebody in a V8 SUV 5 or 10 mph below a 35mph speed limit knowing that my economy would actually be better speeding up.

To be entirely honest, if I characterized the specific output well enough I was going to think about cylinder deactivation so I could run the engine at higher loads and rpms on 2 cylinders, planning to kick all 3 in when really needed, like on the highway.



So what is the self-endowed "Insightful" Trekker rattling on about? Who is Troy? (as if it could possibly matter)
(Mod Insert: It dosen't matter and more properly addressed in a PM if you must know)

thanks to "Editor at Autospeed" for replying to my PM, but he didn't have any more information.

[IamIan]

It makes more sense when you read the whole article that the graph of the Insight was taken from.

International Journal of Automotive Technology, Vol. 4, No. 2, pp. 65-75 (2003)
HYBRID LIGHT DUTY VEHICLES EVALUATION PROGRAM

The following Figures (9 and 10) show the engine mapping of ISFC (Indicated Specific Fuel Consumption) versus engine speed and IMEP for the two hybrid vehicles Toyota Prius 1 and Honda Insight.

The given graph for the Insight is Figure 10 on page 70.
The picutre also chopped the legend: the numbers on the graph are g/kWh of fuel for the ISFC.



IMPE is a typo... it is supposed to be as per the articles description of the graph IMEP.

IMEP: Indicated Mean Effective Pressure

imep = fmep + bmep ( where imep is the indicated mep equivalent to fuel mep* ? )

[Insightful Trekker]

Originally Posted by IamIan

It makes more sense when you read the whole article that the graph of the Insight was taken from.

International Journal of Automotive Technology, Vol. 4, No. 2, pp. 65-75 (2003)
HYBRID LIGHT DUTY VEHICLES EVALUATION PROGRAM

Link please

[Dougie]

http://society.kisti.re.kr/~Eksae/_note ... v4n2_2.pdf

[Insightful Trekker]

Any State side links?

(don't know why anybody would have to go to South Korea for such)
(and there are too many .pdf exploits for me to trust such)