SoundBoi

SoundBoi is the codename for a porject which is intended to use with the BLAT! module for the holden commodored OEM bimodel exhaust. However, it can be extended for use with other cars and valved mufflers. This project originally started when I still had my Holden Barina and wanted an automatic exhaust valve. Over time from trying to write my own CAN transceiver using the teensy line of transceivers and using dodgy rip-off ELM327s with ESP32s, I finally bit the bullet and invested in a few actual ELM327 chips... This is where SoundBoi comes in. SoundBoi is a complete custom solution using the ELM327 chip and an atTiny1614 to communicate with BLAT!. BLAT! is the module the creates the specific PWM and voltages needed to control the OEM Holden mufflers... And yes, all this could be built into one board, but BLAT! came before SoundBoi...

The board follow's a specific set of rules which can be found in the source code.

Rules

The SoundBoi uses 4 states and a set of rules it follows to determine if the valves should be oppened or closed. The valve will be open for the first 5 seconds since the car's startup.

Rules 1 (Default state)

The valve will open if:

• Speed < 90 AND:
  • RPM > 3000
  • Load > 50%
  • Throttle > 50%
• Speed > 90 AND:
  • RPM > 4000
  • Load > 70%
  • Throttle > 80%
• Speed < 5 AND engine is up to temperature.

Rules 2

The valve will open if:

• Speed < 90 AND:
  • RPM > 1900
  • Load > 30%
  • Throttle > 30%
• Speed > 90:
  • Revert back to Rules set 1.
• Speed < 15 AND engine is up to temperature.

Rules 3

The valve is always open.

Rules 4

The valve is always closed.

PCB

The PCB is meant to be attached to the BLAT! module back-to-back. This is to keep the boards small and modular. The SoundBoi PCB takes it's 5V from the Pololu regulator and reads the battery voltage from the 12v coming from the relay on the BLAT! module. Because of the ignition relay, there is no need for low power cutoff on the SoundBoi module, but it might come in future revisions....

Schematic

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3D Models

BOM

Description	Designator	Value	Manufacturer Part Number 1	Footprint	Quantity
Female Header, Pitch 5 mm, 1 x 2 Position, Height 10 mm, Tail Length 3.5 mm, Rohs, Bulk	BUTTON, LED		282836-2	TECO-282836-2_V	2
CAP CER 560PF 50V X7R 0603	C1, C2	560 pF	C0603C561K5RACTU	FP-C0603C-CF-MFG	2
CAP CER 0.1UF 50V X7R 0603	C3, C4	0.10 uF	C0603C104K5RACTU	FP-C0603C-CF-MFG	2
Multilayer Ceramic Capacitors 27pF 5% 50V NP0 SMD 0603	C5, C6		C1608NP01H270J080AA	FP-C1608-080-0_1-IPC_A	2
Typical RED, GREEN, YELLOW, AMBER GaAs LED	CON, IND, L1, L2, L3, L4, PWR			3.2X1.6X1.1	7
DIODE GEN PURP 100V 150MA SOD123	D1, D2	2pF	1N4148W-13-F	FP-SOD123-MFG	2
Header, 3-Pin	DEBUG, UPDI			HDR1X3	2
Male PCB Connector with Hex Screw WR-DSUB, 10.30 mm, Angled, 9 pins	J1		618009231421	618009231421	1
Header, 5-Pin	P2			HDR1X5	1
NPN General Purpose Amplifier, 40 V, 0.2 A, -55 to 150 degC, 3-Pin SOT23, RoHS, Tape and Reel	Q1, Q3, Q5, Q6, Q7		MMBT3904	FAIR-SOT23-3_V	5
General Purpose Transistor, PNP Silicon, 3-Pin SOT-23, Pb-Free, Tape and Reel	Q2, Q4		MMBT3906LT1G	ONSC-SOT-23-3-318-08_V	2
Resistor	R1, R4, R27, R28, R29, R35	4.7K		J1-0603	6
Resistor	R2, R3	100		J1-0603	2
Resistor	R5, R16, R24, R30, R32, R34	10K		J1-0603	6
Resistor	R6, R7, R8, R9, R10, R11, R12, R19, R22	470		J1-0603	9
Resistor	R13, R20, R33	47K		J1-0603	3
510O 5% 0.5W 1210 Thick Film Chip Resistor AEC-Q200 compliant	R14, R15		RMCF1210JT510R	FP-RMCF1210-MFG	2
Resistor	R17, R18, R23	2.2K		J1-0603	3
Resistor	R21	1.8K		J1-0603	1
Resistor	R25, R31	22K		J1-0603	2
Resistor	R26	33K		J1-0603	1
IC TRANSCEIVER HALF 1/1 8SOIC	U1		MCP2551T-I/SN	FP-C04-057-SN-IPC_B	1
IC MCU 8BIT 16KB FLASH 14SOIC	U2		ATTINY1614-SSFR	FP-C04-065-D3X-MFG	1
3-Terminal Adjustable Regulator, 3-pin TO-92	U3		LM317LZG	Z03A	1
	U4			SOIC28	1
CERAMIC RES 4.0000MHZ 15PF SMD	Y1		CSTCR4M00G53-R0	FP-CSTCR4M00G53-R0-MFG	1