Now that I'm currently unemployed and have lots of time on my hands I figured I'd post some pictures of the dyno I built for myself with the help of some friends a couple of years ago. Cross posting to Speedtalk as well.
I picked up an ancient Superflow water brake on eBay late 2012 from a marine engine builder in New York. Then I started gathering some more parts I needed, such as load cell and speed sensor. Initially I was going to get my hands on a Superflow water servo but the wallet didn't allow that at the time so I built my own servo valve using a 1.5" ball valve and a stepper motor and some parts I had machined for me on a water jet.
For data acquisition and control I decided to use an ARM+FPGA based ECU I had designed earlier, just with firmware changes to run a dyno, the ECU had all the IO I needed, 24x 12 bit ADC channels, 2 programmable level speed inputs, 6 logic level inputs, 26 low side switch outputs, 8 logic level outputs, 100Mb ethernet, 2x CAN, 2x rs232. I desoldered some parts and repurposed 8 of the low side switch outputs for logic IO to interface with the water servo and future expansion boards. I also made EGT boards that take 8 thermocouples each and output the data over rs232 into the main control board. It interfaces over UDP/IP to a Windows application I wrote for tuning ECUs but made some extensions to for dyno operation.
The chassis is made of 6" U section and I opted to rigid mount the brake and use a U joint driveshaft instead of going the Superflow route of having a short splined shaft and requiring a bellhousing that bolts to the brake. Reason is I wanted to be able to test snowmobile and motorcycle engines as well.
For the first year the dyno was operational it was hired by a local company who were developing diesel additives and needed accurate fuel consumption tests. This was accomplished by putting the fuel tank on a scale which was interfaced with the dyno controller as we had no luck getting repeatable numbers with flow turbines due to foaming of the fuel returned from the engine back to the tank. They ran three engines during this time, first was an International 6.9, next was a Mercedes OM662 and the last an Isuzu 3.0 common rail. In none of those cases did we do any acceleration tests and hardly any application of full throttle except to figure out the parameters to use for the fuel economy tests. The fuel economy tests were done steady state with double control loops. Dyno controlled brake load to set constant RPM and engine throttle to set a constant power output.
Brake as it arrived, I believe it comes off a SF801 but to my surprise most parts sold by Superflow today for the current generation SF833 actually fit this one.
Water outlet servo
48V DC Power supply for servo
Testing the drive code for the servo, as it's a stepper the code must take care to not accelerate or decelerate too hard or steps will be missed and accuracy is compromised.https://www.youtube.com/watch?v=7BZTkccdjTo
Extra 1.2V feed because when I did the layout I failed to note that different variants of this Cyclone 3 in the same 144 pin package have different pin-outs.
Fitting out the data/control box with 8 external logic inputs for frequency or duty cycle sensing (flow turbines, injector pulse width sensing, turbo speed sensing, etc), 16 external analog inputs for pressure sensors, wide band lambda and such and 16 K type thermocouples. I'm using XLR connectors for the sensors. 3 pin for the logic level sensors and 4 pins for the analog. The analogs get an extra 12V feed along with the 5V reference.
Logic level input buffer expansion board on the right, instrumentation amplifier for the torque sensing load cell on the left
Nearly finished control box
First test with 6.9, august 2013
Calibration, the eye at the end of the arm is at a 1000mm radius to the centreline of the brake. Local value for g is 9.82 and so hanging 30kg weights off it nets a reading of 294.6Nm.
First petrol engine tested, an ancient Ford 302 with TBI and a turbo
Live trace of one of the tests done on the 302, it didn't perform well, fell flat on its face and started to detonate at 4300RPM, probably overheating the plugs. But seeing as this is the only petrol engine that has been dyno tested in this country (I am the only one with an engine dyno) it is still holds a national record for measured horsepower.
One of the early tests on the 6.9https://www.youtube.com/watch?v=KIGKFZD8NBA
The Isuzu being testedhttps://www.youtube.com/watch?v=yb15HcSz2ig
Acceleration test of the 302, aborted due to knocking at over 4000RPMhttps://www.youtube.com/watch?v=TkJqy_fIfJY