Engine mod (BJ 1991)

[Jack-Lee]

SI system
g/kWh !

[RustyLugNut]

Originally Posted by Jack-Lee

SI system
g/kWh !

The average gasoline engine has a thermal efficiency of about 25% and a BSFC of 325 g/kW*h ( just a rule of thumb for comparison ).

The Atkinson over-expansion engine found in the Prius has a given thermal efficiency of about 36% for a BSFC of 225 g/kw*h.

It would seem the 0.25 is in Kilograms? 0.25 g would be mind-boggling.

[Jack-Lee]

Hi,
maximal effciency of 36% cannot be possible.
The "VTEC" Engine from Honda reach 215g/kWh at the best point!
File:Honda Insight 5mt.jpg - EcoModder

Heat engine - Wikipedia, the free encyclopedia
Burning temperatures about 2500°C and exhaust temperatures about 1000°C equals a maximal efficency of 54%.
Theoretical efficency for gasoline engine -> 63%
http://einrichtungen.ph.tum.de/T37/S...SS07/page3.pdf

[RustyLugNut]

Originally Posted by Jack-Lee

Hi,
maximal effciency of 36% cannot be possible.
The "VTEC" Engine from Honda reach 215g/kWh at the best point!
File:Honda Insight 5mt.jpg - EcoModder

Heat engine - Wikipedia, the free encyclopedia
Burning temperatures about 2500°C and exhaust temperatures about 1000°C equals a maximal efficency of 54%.
Theoretical efficency for gasoline engine -> 63%
http://einrichtungen.ph.tum.de/T37/S...SS07/page3.pdf

Gasoline has a power density potential of 0.0122225 kW*h/g. Multiplying that power per gram potential by BSFC:

(0.0122225 kW*h/g)(215 g/ kW*h)=2.62784

Dividing into unity:

1/2.62784=0.381 or 38.1% thermal efficiency.

This is achieved via lean-burn combustion in the Honda Insight. Someone who is intimate with the engine will know more about this. Please make corrections as needed.

The 225 g/kW*h BSFC that has been published for the older Toyota Prius engines would yield:

1/(0.0122225 kW*h/g)(225 g/kW*h)=0.364 or 36.4% thermal efficiency.

This is achieved with over-expansion (Atkinson) cycles.

Both engines were state of the art at the time and were leaps and bounds better ( in thermal efficiency ) than gasoline engines of the time.

Modern engines hope to do better and are closing the gap between gasoline and diesel engines in the measure of thermal efficiency.

Green Car Congress: Toyota targeting thermal efficiency of more than 45% for next-generation gasoline engines for hybrids

[renault_megane_dci]

Thank you for your reply and technical details Jack-Lee.
Congratulations on actually doing stuff.

[oldtamiyaphile]

Originally Posted by Jack-Lee

-modified controlbox (no wide-open-throttle enrichment, deceleration fuel cutoff from 1200U/min [currently 2000U/min]

I would love a more effective DFCO in some of my cars. My Fiat will DFCO from only 1500rpm and go all the way down to idle - I'm quite happy with that. My MB100 and Jeep will DFCO from 2000 down to 1500, for the MB that often means a downshift, while on the Jeep it's almost useless as there's little need to ever exceed 1500rpm in normal driving.

Is this something any dyno tuner car do for me? Will it cause any drivability issues? Also, what RPM did you chose for the fuel to come back at?

[Jack-Lee]

hi,
i dont write a long time, but the work still in progress

News:
-Engine is back from restoring -> drill, honed, new pistons, new bearings, new hyd. valve lifter, new valve, new valve seats, DIY fan type exhaust, other CAM, DIY Intake System (single Plenum Racing EFI), short.. all new! 2200€ ..
-build a new engine in the ventilation System. Same airflow, but only 25Watts instead of 100W with the old thing.
-all screws new
-complete chassis restauration new Brakes, new Paint, and many more
-free programmable engine controll unit

[renault_megane_dci]

I happen to own an Audi A2 with the 1.4 liter gas engine.

Any quick and easy mod you'd had in mind to improve FE ?

I was thinking of knife edging the throttle body shaft but it's already quite involved ...

[Jack-Lee]

I build in another EFI, with longer tubes.

[elhigh]

We only hear from you about every six months or so, Jack, but you drop us these tantalizing photos and short, maddening descriptions.

"...with longer tubes." YES, we see that! Can we see it in the car, or hear about how it changes the car's performance?

You're waving the steak in front of our noses, please give us a taste!