TZRIDER

Ok, I was not going to get involved in this post but I feel I can offer some information that you all may find helpfull. Let me preface this by saying that all of us at Razors Edge strive to give you the best advice,tuning and information we can. We do not always agree with the practices of others but feel if they "our competitors" are being mistakenly "trashed" and we can offer some kind of explaination, we will.
Based on the dyne numbers I'm seeing I'll assume they were taken from a Dyno Jet Accelerometer.( Because a dyno jet measures how fast a given mass ie: the drive roller is accelerated and converts that to Trq\HP) it is really not a dyne.To keep this post short and less boring I'll try to keep this explaination simple.The inertia value of a Dyno jet is much less than that of the Lightning, therefore the load applied during a run is not equivelant to that which is applied on the street or track.This causes cylinder temp to be somewhere between 300-400 degrees cooler and fuel needs to be much less.What does all this garble mean? What appears rich on an inertia dyne is usually very close on the street and what appers just right is usually too lean. To make good hp numbers on a dyno jet you must accelerate the drum as quickly as possible, the real fuel curve for a 4900lb vehicle is too rich for a 1600lb drive roller so tuners lean the curve down. This makes it accelerate the drum quickly but once on the street this fuel curve is much too lean for our trucks. Ever wonder why the inertia dyne 12.5 fuel curves are rumored to blow motors?
Hopefully this offers some insight, if anyone would like a more detailed and technical explaination please feel free to call the shop at 954-917-9200 or post it here
Paul

There are a few things a Dynojet can't do. Most importantly, it can't duplicate a drag strip, thus it cannot directly predict a car's ET and speed in a quarter mile pass, however, it can predict trends in a car's performance. That is, if the car runs well on an inertia dyno, it's most likely going to run well on the race track.

There are exceptions to this and they come with vehicles that use load tables in their engine control calibrations to set the air/fuel ratio It has been difficult to get specific information on which cars have this and which don't, however, our limited research indicates this is more typical of Ford and Diamler-Chrysler products than it is of GM vehicles. It is also a problem most likely to occur if the mass of the vehicle (or combination of vehicles, if the vehicle in question is towing) is significantly more than the mass equivalent of the dyno drum.

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.

Several years ago NASCAR's Winston Cup Technical Director, Gary Nelson, discovered the Dynojet 248H as a tool to help him keep all the teams competing equally. It's now the officially licensed chassis dynamometer of NASCAR. Also, most major teams in Winston Cup Racing have their own units. With most of them, no car goes on the truck for a race if it hasn't run on the dyno before it leaves the shop.

K&N Engineering, Lingenfelter Performance Engineering, B&B Fabrication, Doug Rippie Motorsports, Dutweiller Performance, Kenne-Bell, Flowmaster, Second Street Speed, Motorsport Technologies and Borla Performance Industries...(unquote: all use DynoJet)

Originally posted by NCETRY
JDM put in a new Dyno Jet I would like to see what he has to say. ...

Do your customers always drive their cars at wide open throttle?

No, of course not. So why would you tune their vehicles on a dynamometer that tests that way? AutoDyn, with its optional computer-controlled power absorber, allows you to test vehicles under real-world driving conditions. AutoDyn lets you test under load at part-throttle settings, in different gears, steady RPMs… almost any test you can imagine. Now you can properly jet carburetors, and adjust fuel injection for driveability. You can troubleshoot timing, clutches and surging problems.

“Dynojet" has become something of a generic term when referring to chassis dynos - quite amazing when you consider it is actually a relative newcomer to the world of dynamometers, which go back in one form or another nearly 100 years. Dynojet's prolific line of chassis dynos includes models for motorcycles, ATVs, karts, and even snowmobiles. The model we're most likely to run into is the ubiquitous Model 248, in either in-ground or raised-platform configuration, and in basic form is an example of the inertia-only type of operation. Dynojet also offers an optional load-control system called DynoTrac that utilizes the air-actuated friction brake normally used to slow the drum after a run.

The 248s 48-inch diameter drums can handle up to 1,200 hp and 200 mph, making it more than a match for any conceivably streetable Mustang. The248 is often optioned with the company's wide-band 02 sensor, so that A/F ratios can be recorded and displayed against rpm.

As an aside, we've also seen savvy Dynojet operators such as Paul Svinicki at Paul's High Performance plug Ford's NGS (New Generation STAR) diagnostic tester/data-logger into the car's EEC dataport while running a power sweep on the dyno. This is done in order to monitor things such as total timing and injector-pulse width. This is especially useful when chip tuning a vehicle.

While the NGS is totally unrelated to, and does not communicate with, the dyno itself, it's much easier and safer to use it with the car on a chassis dyno than ripping around on the street at sustained full throttle. Though it likely has little relevance to those of us with street 'Stangs, Dynojet's hardware and software are specifically compatible with sophisticated, race-oriented, data-acquisition systems from CDS and Pi Research.

Dynojet's current operating software is called WinPEP (Windows-based Performance Evaluation Program), which allows display and comparison of up to12 dyno runs simultaneously. The runs can be printed as either a data table or a color graph.

For repeatable measurement of full-throttle power, the Dynojet is hard to fault. The availability of the DynoTrac loading option expands its versatility.

Of the various models manufactured by Mustang Dynamometer (MD), the ones we're most likely to see are the paired-roller MD-250 and the single-roller MD-1750. Though either may be found in inertia-only form, they are most commonly optioned with eddy-current power absorbers. For the benefit of those who, like the author, consider anything to do with the flow of electrons as incomprehensible black magic, an eddy current is defined as one induced in a conductor by changes in the magnetic field. In an eddy-current power absorption unit, application of current causes this magnetic field to oppose rotation of a cast-iron rotor on a shaft spun by the dyno's drum.

In function, then, an eddy-current PAU is an electromagnetic brake that can be applied to the dyno's rotating drum shaft, absorbing some of the kinetic energy being transferred from the test vehicle and converting it into heat energy, which is then dissipated to atmosphere. As with your car's brakes, the degree of braking can be controlled (in this case, precisely so by the dyno's computer), but unlike your car's brakes, an eddy-current PAUs electromagnet operation is frictionless. A strain gauge measures how much torque is being absorbed. This data is looped back to the computer, which is also simultaneously monitoring the usual factors, including drum rotation speed and engine rpm.

Within its operating range, the eddy-current PAU is basically infinitely, adjustable for load. This and the system's closed-loop operation mean an operator can perform a wide array of tests, for either performance measurement or diagnostic purposes, beyond basic full-throttle acceleration.

Likewise, the system's processor and MD-7000 Windows-based software is able to compute and display a wide array of results, including diagnostic and elapsed-time tests.