(no wheel dyno)
NEW INFO sent in from a cool long time reader and an engineer:
I've enjoyed your web page for a few years now. Good work! I've never written before but I just saw something on your page that I simply must comment on. It is the non-roller chassis dyno, the Dynopack 3000. Though it is odd and not very well known, I'm actually very familiar with it. The place where I had my engineering intern last summer bought one, the first in North America as I was told. (They had some Dynopack 2000's here, but ours was the first 3000, a higher capacity unit.) It is an absorbtion dyno like a regular engine-only dyno. It pumps hydraulic fluid and calculates horsepower based on pressure and flowrate. That means you can run it steady state - no large roller to simply accelerate for a few seconds and then that's it. It is VERY accurate, as it can pick up a 1 hp difference consistently.
It is made by a company in New Zealand. (The guys came over to help us get it going.) It is quite impressive. Since it is an absorption dyno, it absorbs the horsepower, which eventually turns into heat. A large cooling unit must be set up to dissipate the heat, hence the two hoses you see going into the side of the unit. It can handle about 800 horsepower. They are mobile, much more so than roller dyno's, although they are quite heavy. One draw back is price, about double what a DynoJet roller dyno is, but it's capabilities are obvious and impressive. (The price may come down, too, if popularity increases, of course.) The unit is hooked up to a Windows based program on the computer, and you can monitor many parameters. Instead of revving up on a roller, the driver gets in the car, puts it in gear, and floors it. The unit holds the RPM at a determined amount by loading the engine with the hydraulic pumps, then steps it up in certain RPM increments and gets the horsepower curve. This loads the engine more than just accelerating a large drum. At my internship, it worked very well (once we got it ironed out) with the cars we put on it, and you could watch the suspension react and raise the car as it was loaded. Just thought I'd pitch in my experience since most know little about it. It is a fantastic unit and we may see more of these in the future.
Thanks Greg F. for the extra info - MW
<end new info>
You've probably seen Mike's cobra here on Mustangworld, recently he went in for a dyno and they used a "no wheel" dyno. This unit attaches directly to the axles (where the tires normally go) vs using a rolling drum to measure rear axle movement and get your numbers.
Notice the 2 units that basically replace the rear tires. This could be nice if you don't want to break ground in your shop to install a dyno, or get the car lifted to accommodate rolling drums under each tire. Just jack up the rear end, remove your rear tires, attach these units and go.
We were thinking, this opens up the possibility of putting these on all 4 wheels and running tests on 4wheel drive cars as well... mabye? interesting.
When we get more info on it, we'll post it up. Thanks to Mike for the pics.