It is very in depth. I'm looking at it right now.

 

OK, Pimpin'- I know you're dyin' for examples. Here goes.
Engine Torque=Roller RPMs divided by engine RPMs x roller torque
Then apply a drive line component "loss" factor of 30% or x .7

OK, 4153 roller RPMs divided by 5200 engine RPMs x roller torque of 313 ft/lb = 250 ft/lb of engine torque divided by a .7 loss factor = 357 ft/lb.

Now to check with "measured" example numbers: 4153 roller RPMs x 313 Lb/Ft. roller torque divided by 5252 = 247.5 H/P

Don't believe it? Well then, with a rollerspeed of 4153 RPMs divided by 5252 x roller torque of 313= 247.5 H/P.

Remember, power in equals power out divided by the efficiency factor. That's why Mustangs are so accurate in "actual" H/P nubers at the road. They do not use hypothetical numbers based upon a "no load" hypothetical equasion.

I hope this has helped.
BR
Michael

 

Thank you guysssssssssssss! I knew i was full of it when i typed that crap! I thought i had some kinda of an idea, but man i was way off target! Welp thanks for clearing that up! Sorry for stating non-researched facts and being such a retard!

 

Umm the equation that you used was basically...

HP= RPM x Torque / 5252

That is a "no load" hypothetical equation. The torque that was used in what you listed was the roller torque. So its the same generally used formula. How is that any different from any other dyno? I'm not trying to knock you. I really want to know how a Mustang dyno is different.

 

You are incorrect. DynoJet does use an engineering matmatical equasion to calculate the estimated torque from the acceleration of a weighted drum in a measured period of time. It must be a measurement made under acceleration. This is the main difference between the measurments taken with an inertia dynos and an eddy-current or other "loading"-type dynos. Remember: power in must = power out . Loading-type dynos can only give you a measured torque at the point where the rubber meets the road, at a predetermined speed based upon your test parameters. The load is based upon, in Mustangs case, the size and weight of the vehicle. The secondary roller is hydraulically pressed against the tires as the vehicle runs within the test- speed parameters and the eddy-current motor applies a breaking force on the secondary roller. A strain guage measures the load on the roller and that is utilized by the computer to caculate the shaft or roller torque. so while the equasion is technically the same, the data input is completely different. One is an unloaded or free measurement without regard to vehicle weight or resistance, while the load cell dyno makes the calculation under real world driving condidtions and will very the outcome based upon trans ratuios, fear end ratios, tire diameters, etc. In other words, what your entire power train exhibits. If you need only comparative "before and after" numbers there is nothing wrong with an inertia dyno. In fact DynoJet is probably the World leader in motorcycle jetting improvment kits, hence the name. Development of these kits, in partnership with K&N air filters, came through thousands of hours of inertia dyno testing and retesting. That is the reason NASCAR uses one to periodically test certain competitors for "comparative" horsepower. Penski, Roush, Childress and others all have eddy-current dynos to test their "packages" and engine dynos to test engines.

In the past some Mustang dyno operators were lax in not ensuring the RPM sensor was available to test with. No RPMs, NO torque. No torque, no accurate H/P. Since the load cell-type dyno can simulate drag racing and other acceleration tests, it can use acceleration data to arrive at h/p numbers during these tests, but not torque, unless the RPM sensor is attached. By the way, Mustangs are also capable of inertia-only testing by turning off the eddy-current motors. But, as they say, why bring a knife to a gun fight?

There have been reports of highly questionable numbers from a certain Mustang Dyno and if they were generated without a RPM sensor attached, due to operater inexperience, shame on them. If they were quoted from Dyno Drag events, which do not need to use them, and were quoted by people who will not take the time to listen to the operaters explanation of what is accurately tested during drag-only runs, shame on them. The point is a 3-axis CNC mill CAN be a lot more useful and accurate than a manually operated Bridgeport-style knee mill. Both are capeable of giving good results, but the enhanced capabilities of the CNC-type will offer you so many more capabilities.

The Dyno Shop's mobile eddy-current dyno can be used as a a concession, just like any other portable dyno, when it is taken to an outdoor event or a Dyno Drag event at their shop. If you expect to pay peanuts, don't ask for peanut butter. Normal going rates, for dyno tests, nationally, are $100-$125 for three H/P pulls or per hour. At $25, you should be enjoying the bragging rights with your friends during a fun-filled experience. Only an eddy-current dyno lets you generate drag race numbers AND usable H/P and torque numbers. Rain or shine day or night. You can test your improvments, on or b(u)y-one, for the entire six months of the "off season".

Let's loose the "flaming". It benifits no one except those who have nothing to loose. For those who are really interested in improving their performance, there are benifits to either type system. Tell us what you want to know and I am sure that owners of both type systems will be happy to serve you.
BR
Michael

 

That is the equation that you just used in the above Mustang dyno example. So no I am not incorrect. I looked at the math you did and it used the basic formula that I listed. Albeit it gets the data in a different way. Your post that you just made honestly made ALOT of sense. FINALLY someone has explained what a Mustang dyno does. THANK YOU! I heard somewhere that a Mustang dyno could do "inertia only" it was from a Supra guy. Since you explained how a Mustang dyno works so well can you explain the torque numbers a Mustang dyno puts out. It really has alot of people (including myself) confused. I'm not flaming you, I'm honestly looking to learn something new.

 

Thanks you very much michael. You have helped me a lot. I would love to know the equations for the torque conversion or how it measures torgue. Michael, do you work at the dyno shop??

 

yes it can it has a program called dynotrack where you can load the rollers with the brake for different engine loads/ while viewing the a/f livetime/ it can stop a 1200 hp car at wide open throttle if needed. if you are tuning a car a dynojet is one of the best we have ran 3 different widebands at the same time and the one on the dyno was the fastest to respond to changes. they all read within .4of each other [/B][/QUOTE]

Perhaps the DynoJet people say it best-

"A standard Dynojet 248H has no capability to load the vehicle with more than the drums' mass equivalent, however, an option called "Dynotrac," which adds computer control to the dyno's air brake, can load the vehicle to any wheel speed, engine rpm or percentage of braking force. While Dynotrac enables loading, currently, the dyno cannot measure torque output in real time because Dynotrac is simply a proportional air brake controller. At this writing, Dynojet Research has a strain gauge, necessary to measure torque in real time, under development. When it becomes available, the 248H will be able to function as a load cell dyno."

BR
Michael