• GY6 Engine Dyno - Built, not bought! (with custom dyno computer)

  • Can you tell good performance advice (from snake oil advertising) when you see it? There are many GY6 performance myths (and outright lies) pushed by sellers, meant to part you from your hard earned money. It may sound good, but is it tested?

    Ask your engine upgrade questions here. We'll provide tested answers.

    We're building our own GY6 DYNO (dynamometer) from scratch. Subscribe to the dyno build thread to stay updated!
Can you tell good performance advice (from snake oil advertising) when you see it? There are many GY6 performance myths (and outright lies) pushed by sellers, meant to part you from your hard earned money. It may sound good, but is it tested?

Ask your engine upgrade questions here. We'll provide tested answers.

We're building our own GY6 DYNO (dynamometer) from scratch. Subscribe to the dyno build thread to stay updated!
 #10636  by Travis @ Buggy Depot
 Sun Jul 16, 2017 7:28 pm
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You're looking at the dyno's progress as of July 2017

I started building this dyno in the summer of 2012, before I knew anything about hydraulics, electronics, or circuit board design. In the beginning, my motivation for building a dyno wasn't really connected to the business. I wanted to do it because I wanted to push the GY6 engine to its limits, find its breaking points, and make improvements based on real test data (not superstitions).

It's been a long project, and a very deep learning experience. If you'd asked me in 2012 how long it would take to build the dyno, I would have told you "2 months tops". That was somewhat true, as the physical frame and hydraulics were all functional at that point, but capturing good data out of the machine (with no computer) was too difficult. Now here we are in the 5th year. Dev time is extremely limited. On average, I've only been able to dedicate a couple days per month to developing the dyno. Life and building a company tends to get in the way of non-critical things.

As of July 2017, I have every detail worked out. All of the components on hand. All of the plans and diagrams laid out on the table. At this point the only issue is getting the time. Time to put it all together physically, electronically, and bring it to life by coding the software.

The 2012 "two month" version of the dyno (no computer)
At this point, I could simulate a load for up to 28hp. But I couldn't easily capture good data. This wasn't cutting it, as a dyno isn't a dyno without rock solid data. Just a fancy test stand.

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Making it a true dyno with reliable data capture and automation control
Professional dyno suppliers wanted $3,000 for JUST the dedicated dyno computer alone, so developing one myself for my exact needs was the obvious decision.

Here is my custom Dyno Computer. On the left is my dyno computer fitted into an off-the-shelf panel box enclosure. On the right are the stepper motors, driver, and power supply. All of the computer-related hardware was less than $300, sourced from Amazon, eBay, and standard CNC online parts stores. It's up to me make everything work together, and write the software.

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I found that the most advanced commercially available dyno computers (for small engines) are built with yesterday's technology and are lackluster on features unless you want to spend upwards of $40,000 on a turn-key machine! This may have changed in the last few years. I haven't checked.

Q: What will you do with the dyno when it's finished?
A: Test performance parts, publish the data here, do shootout tests, and piss off a lot of snake oil sellers!

Q: How much has it all cost, up to this point?
A: I'll tally up everything and edit this post later. A decent estimate would be $2,500 (stretched out over 5 years).

Q: Where do you source your parts?
A: Everywhere.
  • The frame was an old $35 piece of junk I picked up at an estate auction.
  • The engine cradle is a Yerf Dog GX150 swingarm.
  • The rest came from Amazon and eBay mostly.
  • The mechanical parts were fabricated here in the BD machine shop on the mill, lathe and plasma table.

This project is entirely funded by your orders!
YOU make this possible. Thanks for your support!

Progress in chronological order:
  • Features Overview
  • The 2012 build - Frame fabrication, and the Hydraulic system
  • Lessons learned
  • Developing a rock solid dyno computer system
    • First failed attempt
    • Final computer setup
    • Modifying the enclosure
    • The last bit of hardware (custom input converter board)
  • Stripping, painting, and rebuilding
  • Hydraulic "working fluid" temperature control
  • Automation and remote control (with stepper motors)
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 #10678  by Travis @ Buggy Depot
 Mon Jul 24, 2017 9:24 pm
Dyno Features (as of July 2017)

Non-techie Feature Overview:
  • Made mostly of off-the-shelf parts.
  • Up to 28 horsepower maximum.
  • Fly-by-wire remote wireless control via laptop. Safety first!
  • Now extremely reliable data capture and storage.
  • WiFi connectivity. No wires!
  • Can test any GY6 engine variant (125cc to 235cc).
  • Can be easily moved and trailer mounted for dyno sessions anywhere.
(Slightly more) Technical Overview:
  • Capable of a blazing fast 500 data sample captures per second!
  • WiFi 802.11b/g/n WPA2 Encryption.
  • Dedicated Linux-based capture server for extremely reliable data storage, logging, and other data intensive operations.
  • Hydraulic load cell rated up to 3000psi.
  • Fully automated hydraulic fluid temperature monitoring and regulation.
  • Heavy Duty Oil-to-Water Heat Exchanger.
The full blown Linux data capture server may have been a bit overkill. But as a web programmer, it's one of the most familiar and "no research needed" parts of this build for me. The server approach opens many opportunities for future features, like really outstanding graphs and real time webcasts later.

Benchmark testing of the current design shows that we're able to capture over 500 samples per second. Earlier "no server" designs could only capture 50 samples per second, and had very limited storage. That would have worked, but again, setting up the server comes at very little actual cost.

More current pictures (July 2017)

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 #11063  by Travis @ Buggy Depot
 Sat Oct 14, 2017 6:50 pm
The 2012 build - Frame fabrication, and the Hydraulic system

- The frame was some type of ancient junk table I picked up for $35 at an estate auction
- Yerf Dog GX150 swingarm
- Hydraulic tank was made from an old water heater
- The rest is just bar stock, bearings, flanges, etc

Making the hydraulic pump flange.

I have no idea where this piece of scrap came from, but it worked. I used the rotary table and a 5/8" end mill. You'll probably recognize the spindle bolt in the center that I used as an arbor.

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Looking back, I wish I had taken more pictures of the process of welding the swingarm to the frame.

The very first "working" version of the dyno. It was rough for sure, but it worked!

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 #11067  by Travis @ Buggy Depot
 Sun Oct 15, 2017 10:36 am
Why a Hydraulic Brake dyno? Why not inertia?

Well in a nutshell, inertia dynos are good if you only want to test the power of an engine as a "snapshot". A brake dyno is able to test power output over long duration of time. And perhaps more importantly, a brake dyno can help test reliability and longevity as well.

After all, what good is making great peak horsepower, if your hopped up engine won't last more than a few rides? With the brake dyno, we can stress test engines for hours at a time instead of seconds.

I'll explain more, but keep in mind that this is all oversimplified for the sake of brevity.

Most times when we think of a dyno, an inertia type comes to mind. You roll your vehicle up onto a machine (or mount your engine) in such a way that spins and accelerates a weighted drum as quickly as possible. As soon as you hit redline, the test is over. This only lasts between 20 to 30 seconds. That's good for measuring power if you only plan to ride in bursts of acceleration on flat ground, but doesn't quite allow us to test engines the real way we ride all ride the 150's. There are all sorts of terrain scenarios to measure that an inertia dyno isn't capable of reproducing.

That's why a hydraulic brake dyno is great for testing the GY6 and developing upgrades. Since it acts as a very powerful brake, we can simulate all sorts of terrain and scenarios, even hill climbing. We can test the engine and transmission's responses to varying loads, and even hold a steady RPM under high load for long duration to test for specific problems. This is awesome for reliability and longevity testing especially for developing new and exciting big bore, stroker, high-compression, and/or turbocharged configurations.

How does it run?
On a dyno run with a hydraulic brake, the engine is locked in at WOT first under just enough load to keep the engine under red line. Then the hydraulic valve is closed progressively, to force the engine to lower and lower RPM while still held at 100% throttle if you want max HP/TQ readings. If you're testing for something other than maximum power, you have infinite control over the load and throttle being applied, so extremely fine tuning is possible any particular RPM, throttle position, and amount of load.

How is HP/TQ determined?
You (generally speaking) need three things on a hydraulic brake dyno.

1. RPM of the engine
2. RPM (and fluid displacement per RPM) of the pump
3. PSI of the hydraulic fluid.

The PSI gauge, RPM of the engine, and RPM of the pump are used to calculate the torque and horsepower produced by the engine at that moment.

Early lessons learned

1. Writing is slow!
Who would have thought? As it turns out, reading 3 separate gauges and writing them down to calculate later isn't a very effective data capture method.

2. Lack of resolution with a mechanical dial gauge
The resolution of mechanical dial gauges isn't a good fit for this application. 3,000PSI dial gauge are typically marked in 50PSI intervals. Just one tick means a big difference in HP/TQ numbers and can throw everything off. Standalone digital pressure gauges are very expensive and cost prohibitive.

The solution for us is a fully digital 0 - 5000psi Industrial Hydraulic Pressure Transducer sensor. The sensor has 2ms response time (1/50th of a second), and delivers ±0.25% full scale accuracy up to 5000PSI.

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3. Without a good way to control Hydraulic fluid temperature, repeatability goes out the window
In my opinion, the true measure of any dyno is it's repeatability. Even with great sensors, the numbers can get thrown off on a hydraulic dyno by uncontrolled temperatures of the fluid. To correct this, I've added a oil-to-water heat exchange, and a microprocessor-controlled radiator system to reject heat and maintain hydraulic temperature withing a very narrow range even during extended runs.

4. Safety.
Even with shielding, I don't want to be facing an engine running 10,000RPM under maximum load. Some sort of remote control was necessary in my opinion.
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 #11068  by Travis @ Buggy Depot
 Sun Oct 15, 2017 12:24 pm
Building the dyno computer

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Main Processor: Microchip 64Mhz PIC18F45K22

Responsible for Automation and Data Acquisition

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Microchip PIC18F45K22 Quick specs:
  • 64Mhz Processor (16MIPS)
  • 44-pin (36 Input/Output Pins)
  • 10-bit Analog-to-Digital Converter
  • 5-bit DAC (unused, but reserved for later)
  • 1024 bytes EEPROM for settings
  • 64kB Instruction Space
  • 3x External Interrupts
  • 4x Interrupt-on-change

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Co-processor: Particle WiFi Module (120Mhz ARM Cortex M3 processor)

Responsible for wireless communications between the main processor and the server:

Task 1. Live streaming data to the server
Task 2. Receiving and relaying operator commands from the server

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Particle PØ Wi-Fi module Quick specs:
  • STM32F205RGY6 120Mhz ARM Cortex M3 Processor
  • Broadcom BCM43362 Wi-Fi chip
  • 802.11b/g/n capable
  • 1MB flash, 128KB RAM
  • 18 Mixed-signal GPIO and advanced peripherals
  • Open source design
  • Real-time operating system (FreeRTOS)
  • Soft AP setup
  • FCC, CE and IC certified

Serial Peripheral Interface: Getting the processors talking over the SPI protocol

Getting the processors communicating with each other required a bit of hookup wire to the correct pins, and a voltage level translator in the middle. The processors communicate over a protocol called SPI.

SPI is a serial data protocol that allows the chips to share information at high speed, millions of bits per second. This is more than fast enough for the streaming sensor data and commands in real time.

Although I like the "DIY" look of the hookup wire, this will all be replaced with a custom PCB motherboard that I'm developing now. The motherboard will contain circuitry for all of the voltage translation circuits, as well as all Input/Output conditioning, filtering, and protection for the overall computer system.

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SPI Signal Diagram
Here's a good diagram of what an SPI conversation "looks like" between processors. This the main processor transmits "S" and the co-processor transmits "F". This happens about 1 million times per second at speeds that I've tested so far.

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The enclosure

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Making a Wall Mount

Drawing up the wall mount

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I'm happy with how it turned out!
The unit you see on the left is the hydraulic fluid heater control circuitry and solid state relays. I'll cover details about that side of the system in a later update.

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