CornBurner Beta

Flexfuel adapter for 4 cylinder gasoline engine with indirect injection.

Instructions

Only to change GPIO and peripheral parameters, open stm_config.ioc using STM32CubeMX.

You need stm32pio:

pip install stm32pio

For more details about stm32pio follow: https://github.com/ussserrr/stm32pio

In PlatformIO CLI run:

./update_config.sh

Calculation of extra injection time

Ethanol AFR

Combustion equation is:

$$C_2H_6O + 3 O_2 \rightarrow 3 H_2O + 2 CO_2$$

Molar mass are:

$M_{C_2H_6O} = 46.07g.mol^{-1}$
$M_{O_2} = 32g.mol^{-1}$

Then for 1kg of $C_2H_6O$ $$m_{O_2} = \frac{3 * M_{O_2}}{M_{C_2H_6O}} = 2.08kg$$

Therefore for 1kg of ethanol we need 2.08kg of O₂
Ambient air composition is 21% of O₂ then

$$AFR_{eth} = \frac{1}{0.21} * 2.08 = 9.90$$

Gasoline AFR

Avearage value for gasoline is 14.7

$$AFR_{gas} = 14.7$$

Mix AFR

$P_{eth}$ is ethanol proportion in fuel from 0 to 1

Then

$$AFR_{mix} = AFR_{eth}*P_{eth} + AFR_{gas}*P_{gas}$$

Assuming ethanol and gasoline have the same density

$$P_{gas} = 1 - P_{eth}$$

Extra time coefficient is:

$${\alpha} = \frac{AFR_{gas}}{AFR_{mix}}$$

$T_{ECU}$ is injection time calculated by car ECU and $T_{applied}$ is real injection time provided by the adapter.
Finaly injection time is: $$T_{applied} = T_{ECU} *{\alpha}$$

Example values

Fuel	Ethanol Proportion	AFR	Extra time
SP95	0%	14.7	0
E10	10%	14.22	+3.4%
E100	100%	9.9	+48%
E85	85%	10.62	+38%
E65	65%	11.58	+27%
50/50	47.5%	12.42	+18%

50/50 is a mix than contain 50% of SP95E10 and 50% of E85

Environmental aspect

Let the following gasoline reaction equation be: $$2 C_8H_{18} + 25 O_2 \rightarrow 18 H_2O + 16 CO_2$$

Molar mass are:

$M_{C_8H_{18}} = 114g.mol^{-1}$
$M_{CO_2} = 44g.mol^{-1}$

Then for 1kg of $C_8H_{18}$

$$m_{CO_2} = \frac{8 * M_{CO_2}}{M_{C_8H_{18}}} = 3.09kg$$

And for 1kg of $C_2H_6O$

$$m_{CO_2} = \frac{2 * M_{CO_2}}{M_{C_2H_6O}} = 1.91kg$$

Gasoline consumption: 8L/100km
Assuming ethanol and gasoline have the same density $\rho = 0.75$

E85	Extra Consumption	C02/km	Fossil CO2/km	CO2 Reduction
100%	38%	173g	38g	-79%
80%	29%	176g	76g	-59%
60%	20%	178g	109g	-41%
40%	12%	181g	137g	-26%
20%	6%	183g	162	-12%
0%	0%	185g	185g	0%

(Many approximations were made during these calculations. They are presented for indicative purposes only and are quite optimistic)

Economic aspect

Avearage price per liter for fuel in France are 1.75€ for E10, 0.92€ for E85 and Gasole (B7) cost 1.73€
For comparison purposes we will consider also a Diesel car.
Gasoline consumption: 8L/100km
Diesel consumption: 6L/100km

E85	Extra Consumption	Gas Equivalent Price	Saving	Diesel
100%	38%	1.27€	0.48€	-1.7%
80%	29%	1.40€	0.35€	+11%
60%	20%	1.50€	0.25€	+21%
40%	12%	1.60€	0.15€	+30%
20%	6%	1.68€	0.07€	+39%
0%	0%	1.75€	0.00€	+46%

AntoninPvr/CornBurnerBeta