home made water brake

[bruce]

That Innovate SSI-4 setup looks like a good deal! I'm gonna have to do more reading on it.

The DI-194 reads -10 to +10 volt signals. I purchased amps that output 0-10 volt signals off ebay for my rpm and torque my egt temp gage already has 0-10 volt output signal built into it. I just have to come up with a cal factor for volts versus dyno reading. So far total cost has been under $100 not counting the digital meters I had to purchase for my console. I would have liked to find gages that all had 0-10 volt output but was unable so I settled for the amps instead. The data from the DI-194 can be dumped to Excel or a program can be written in VB (which I have no clue of but willing to learn someday)

Sorry I have to do this on the cheap, I'd love to purchase a real A/D unit it's just not going to happen anytime soon. So this is my attempt at coming up with something that will work for my purpose. The next step after getting the DAQ working would be to automate the dyno load. Thats another bridge I have to cross someday.

My load cell is calibrated using weights since it is not on a 1' arm. The digital console gage allows an input for each weight I add to create a calibration chart. I'm not working with 500lbs so it works for me. At most I'm looking at 100lb-ft at max rpm on my engines. I have not taken into consideration at this time the inertia of my dyno and how that effects my torque readings. I have not really preformed any real testing to date yet, I'm just glad I got this far with the dyno project.



Edited By bruce on 1164335167

[86rocco]

Bruce, I hope to have my system up and running sometime within the next month or two so if you're not in a hurry, I can let you know how it works before you make any decisions.

[Tony]

There are really two quite different aspects to this problem.

Monitoring the output of any type of dyno, only really requires speed and torque readings, and there are many readily available off the shelf solutions to building a successful home dyno monitoring system.

A much bigger problem is controlling the dyno speed and load. Because there are so many different types and sizes of power absorber, and different applications, you will be pretty much on your own designing the dyno control system.

In many ways this is a much more complex problem, because safety comes into it as well. An unexpected sudden loss of load, causing violent overspeed can be very serious.

So working up a good dyno monitoring system is only half the problem, arguably the easy half.

Controlling water flow and temperature is a whole different problem to tackle. Especially if you wish to do acceleration sweep testing. The dyno controller will need some fast acting safety systems to instantly and automatically shut down the engine should something go wrong.

[86rocco]

Agreed, data aquisition is only half the job and by far the easier half, nevertheless, it's a VAST improvement over no data aquisition at all.

[JDM Dyno]

absorber inside L&S

My home made Rolling Road

[DaveMcLain]

Yes, that's exactly what my absorber looks like inside thanks for posting a photo for whatever reason I don't seem to have one of the inside of the brake. As far as control systems go, it's more simple than you think. Controlling the load is as easy as having a water valve that can be hand opperated and controlling an over speed condition can be done with the ignition. On my dyno I have an MSD 6AL box with a selector box where I can pick the limit rpm in 200 rpm increments. If something would happen the max rpm is thus safely limited. Engine temp is easily regulated by using a thermostaticly controlled valve to let in fresh cool water whenever the coolant temp in the cooling tower exceeds a certain level.

You can run your pulls with manual control of the enigne, I did that for at least a year or two before I bought the servo load control.

For DA, I wonder how a racing system like those sold by Edelbrock and others would work, I think pretty slick actually.

[Tony]

One possibility not to be overlooked for an engine monitoring system on a dyno, would be to use one of the top shelf ECUs such as Autronic or Motec.

The ECU may or may not be used to run the actual engine, but these systems already have inputs for all the various types of engine sensors, and an on screen display of all engine operating parameters, very comprehensive data logging, and alarms and limits that can be set for fast engine shutdown.

While by no means a low cost solution, it would have everything already there without having to build a rats nest of amplifiers and interfaces, and having to play around writing custom software.

[86rocco]

[Mattz Larsson]

JDM Dyno hawe you more photo on the Dyno (inside)

[DaveMcLain]

That picture is worth a 1000 words believe it or not. The absorber is made just like that on both sides. See how the fins are made by milling pockets out of the endplate? Boths sections are made this way, near the center in the picture you see the back of a pipe plug that's where the water enters the brake on the other section(they are identical pieces). See the fittings that exit at a angle? Those are the drains and they work the same way, there are four of them but only one is used in one section or the other flowing in the direction of rotation so that if you have a reverse rotation engine situation you can use one or the other. The drain fittings are tapped pipe thread on their ID so that a restrictor orifice can be screwed in to control the drain rate of the absorber if needed for a marginal water supply. My drain is fully open for max flow/power dissipation with minimum heat buildup.

Also at about the 11:00 position in the picture right near the center of the absorber, closer in than the fill hole you see one more hole. This is where the magnetic rpm pickup can be screwed in if needed to get a universal rpm signal. There is a little magnet staked into a hole near the center of the rotor that passes by the pickup giving one pulse per revolution. This works out really well because it gives a nice clean signal free from ignition noise etc.

[Tony]

I have been giving some thought on how the water flow to the dyno load could be controlled fairly rapidly with a computer, without having to buy a horribly large and expensive stepper motor driven control valve and it's power interface.

While I have not tried this idea myself, I believe a turbo external wastegate would make a fine water control valve, if the control diaphragm could be modulated with suitably high pressure compressed air. The spring in the wastegate would probably need to be made a bit stiffer to work at higher pressure, but that is easy.

The compressed air supply could be pulse width modulated with a small and inexpensive control solenoid that would require far less drive power, and be much faster to respond, than a large stepper motor.

The air control pressure to the wastegate could be varied up and down very rapidly by computer control if the air volumes are kept small, and with great sensitivity. The wastegate would respond almost instantly, and have a huge water flow capacity when fully open.

Just an idea, but it could be a budget solution to a rather interesting problem. Suitably low cost Chinese wastegates are now widely available. Even the crappy zinc diecast bodied ones should be well up to the job.

[86rocco]

Would a VFD on the pump be a viable option? Open the manual control valve all the way and let the computer contol the pump speed through the VFD. I'm not sure but judging by the schematic I found , I think Stuska's automatic load controller works on a similar principle.

[DaveMcLain]

I think the idea is that when the engine speed increases so does the non engine driven pump speed thus water volume. I think that Superflow's absorber works on that principle, there is an engine driven supply pump section that feeds the water brake. What happens is that if the engine rpm rises the volume of water supplied to the brake increases thus slowing the engine and if the rpm falls the supply is reduced thus speeding up the engine, sort of a negative feedback loop idea.

Personally, I don't think it needs to be all that complicated. I've often wondered if my setup would be better if I moved the servo load valve to the rear of the stand, right next to the absorber instead of on the other side of 8ft of hose at the control panel. Seriously, I've never had many problems with getting a nice smooth pull out of my dyno setup as it is. I have had it give me trouble at the hold rpm with an engine that has a very steep torque curve, it would tend to occilate more than 2 or 3 cycles before settling down, a setup like Superflow's might be better in that situation than my simple setup. My cure was to see what the torque curve was doing and raise my hold rpm 500rpm and into an area where the torque rise/rpm wasn't as great.