I want to build an engine dyno

JRV had one in his shop equipment....search out Jeremey Lawrence and ask where it is located now......HTH

 

If you are going to use it to test an air-cooled engine, perhaps it would be best to not vent the cooling air exhaust output to the outside. I heard that Ford/Gulf sucked the walls and ceiling down around one of their dyno cells with a Porsche 917 motor back in the old days.

 

Isn't this a bit like reinventing the wheel? There are used dynos out there to be had. Shops close down and sell them off all the time. I knew of two of them here in NJ not long ago (both sold now), and one of them they were basically giving away if someone would just come and take it out, computer and all.

 

Buy a single stage centrifugal (or centripetal) water pump,,,
1000HP capacity.
Hook up your motor,
Measure pressure.....Ta Da…!

you have a Dyno....!

 

http://ferrarichat.com/forum/showthread.php?t=25446&highlight=redneck+dyno

I think it was a truck rear axle with wheels and tires, than they drove the driven wheels of the car to be measured on the wheels of the truck axle and put it on to a chain and a load cell to the chain, the truck axle drum brakes were activated and the force in the chain is a measure for torque...crude. To bad the pictures are gone.

 

You're out of control man......


If you can find a used one it will be much cheaper than building your own. You can add any updates/improvements you want, but you'll get the mechanical bits at under scap prices on an old machine if you search a bit.

 

I can't think of any reason a water-break can't do what you are talking about but....I don't know how useful it would really be.

Any dyno is way better than during all your tuning at the track. A dyno that controls the engine's acceleration rate tells you more than a plain acceleration type dyno (dynojet). Being able to them run a simulated lap on the dyno is kind of cool, but if you have the dyno graphs for the acceleration rates in the various gears, you can run the laps in excel, add time for gear changes, mess with shift points and probably learn more.

 

I watched a real old manual machine run and you had to mess with brake valve and throttle....very hard to use that way. Really what you did was turn the load and throttle up until the throttle was 100%, then control rpm with the load and record the data points.

The computer machines do all that for you and sure you could put a controller on the water valve to make it work, I think the automotive dynos are all electric these day bacause it's easier to build and calibrate. With a water brake dyno, just knowing the water pressure doesn't do it, you need the pump efficency curves too. Or you mount the pump with torque arm contected to a force gage and get your reading there.

 

A quick search says the bigger dynos are all still water brake machines, her's an example

http://www.land-and-sea.com/dyno/dyno.htm

 

Ive looked at a few commercial dynos, there was even an article a while back on Speed I believe where they were running an engine at a factory. In those systems, they were using an electric generator, and measuring both torque as well as electrical output. Torque and rpm can easily be calculated into HP. But when you are simultaneously generating electrical power, you can cross check KW's into HP. I would imagine the same is possible with a water brake as was pointed out above using pressure/flow rates.

I found an interesting book years ago, the Iowa farm test. Apparently in the early part of the 20th century so many tractors were being manufactured with wild performance claims and yet no real testing was being done that could verify anything. Some Iowa farmers got together and started figuring out ways to test them. Some of the stuff they did was so simple it was actually hillarious. In one test they chained a tractor to the floor of a barn, wound rope around the bull wheel, ran it out through a hole they cut in the wall, and hooked it to a sled. Then they altered the weight of the sled, and measured its speed etc., and started calculating the actual PTO HP against the claims of the manufacture. They even did traction tests with tracked machines like Caterpillars and measured draw bar pull at the point it lost traction on different soils, which could also be converted to HP. But to go up to the level of testing engine and gearbox assemblies under mimiced race track trials would be pretty impressive. Better not miss a shift at redline or have a water line blow.

 

Paul, I mentioned to LuckyD today just that, why not build a rig using electrical resistance? my thought was along the lines of the way trains slowdown and brake on grades using resistance. simple math would convert the KW's to HP and you could hold any rpm you want. downside is the cost apparently, however I know some people in the train buiss so I'll see what I can dig up for 'spare parts'

 

http://wwwlegacy.cranfield.ac.uk/soe/departments/auto/powertrain_dynamometer.htm

been done, apparently an expensive getup but accurate.

 

That math is simple as is the flow@pressure, the hard part is knowing the motor/pump curves so you can add back in what was lost getting to KW or flow@pressure.

 

Only to the point of specing parts to handle the flows and pressures you except to see, but will have nothing to do with torque of hp measurement. You could use the info as a rough double check, the actual hp/torque should 10-15% higher (pump losses) than the pump power calc for the flow/pressure you have. You mease presuure with a $10 gauge that you probably want anyway and the flow with a stopwatch and bucket, compare the results and you can be pretty sure your insturmentation is correct.