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Colvin Automotive's DynoJet Dynamometer

The Dynojet model 248 Dynamometer provides a core advanced diagnostic and evaluation tool for Colvin Automotive.  Vehicle power from 20 to 1200 horsepower at speeds up to 200 mph can be tested safely, consistently and reliably in the shop under controlled loads realisticallly simulating street or track conditions.  The heart of a dynamometer consists of two rotating drums embedded into the floor.  Under test, the vehicle is anchored so that the vehicle wheels contact the pair of drums.  In operation, the vehicle transfers and stores energy from its wheels into the rotating masses of the dynamometer drums.  By measuring the acceleration of the drum, the dynamometer is in turn, able to compute and display the horsepower generated by the vehicle's engine and drive train.

It's All In The Drums

The DynoJet 248 Chassis Dynamometer design features 48" diameter, knurled, precision balanced drums which provide stable contact for the tires eliminating unnecessary slippage and tire deformation resulting in precise repeatable results every time.  More than simply measuring horsepower, the DynoJet 248 dynamic testing and graphing capability highlight problems in an easy to interpret manner.  Electrical, fuel, clutch or convertor slippage and drive train problems are determined quickly.  Dynamic dynamometer testing often highlights problems that only become visible under high speed conditions.  When the run is complete, the DynoJet 248's air braking system can be utilized to speed up the testing process by quickly slowing the rotating drums to a stop.

From the Control Deck...

The dynamometer interfaces with a standard PC computer through the DynoJet hardware and software package.  Under computer control, the mechanic can quickly set up a run, add specific notes or comments as desired and then execute the run and graphically display the results on screen or to a hardcopy.  All tests are stored for comparison and analysis.  The software enables one to not only develop new dyno runs, but view previously stored runs, and compare multiple runs.  In addition to horsepower, the PC can also display graphs of torque, engine RPM and speed in MPH.

Automatic measurement of the barometric pressure and ambient air temperature together with humidity measurements ensure repeatability between tests.  With both primary and secondary inductive tachometer pickup probes, the dynamometer can accomodate a wide variety of engine types, ignition sequences and vehicle characteristics.  The software package also includes the ability to select from any of the several industry standard correction factors to normalize a run's data to standard temperature and atmospheric pressure conditions.  With normalized data one can make meaningful comparisions, no matter what temperature or pressure existed when the dyno run was collected.  For most situations, the SAE correction factor is typically applied.

DynoJet Research offers free run viewer software that you can download from their website.  This software allows you to graphically view and print your own dyno runs.  Colvin Automotive will be happy to provide your dyno run data sets on floppy disk or email it to you.

Colvin Automotive's dynamometer is further equipped with the accessory equipment to measure fuel/air ratio and control the intake air temperature to the vehicle under test.  Here's what the end result of an air-fuel run looks like. As you can see, the red horsepower graph dips at 4000 rpm, which also corresponds with the lean air/fuel ratio on the lower graph.

Professional Perspective

For an in-depth analysis of the model 248, see what the professionals have to say about it.

Dynojet's Automotive Chassis Dynamometer has been recognized by the National Association for Stock Car Auto Racing as the benchmark in automotive dynamometers.  Dynojet Research recently announced that it has inked a three-year deal with NASCAR to provide dynamometer services for the organization's NASCAR Winston Cup Series, NASCAR Busch Grand National Series, and NASCAR Craftsman Truck Series events.  NASCAR uses Dynojet's dyno for race rule enforcement, and to determine power production of the competing cars in race trim.  DynoJet dynamometers are officially licensed with the following race organizations: Pace "Formula USA" National Road Race Series; AMA / ProStar National Drag Race Series; AMA ProRacing - The MBNA SuperBike Series;  and NASCAR - Nat'l Assoc. of Stock Car Auto Racing.

DynoJet Model 248 Specifications

DynoJet Model 248 Specifications:

Maximum Horsepower


Maximum Speed

200 MPH (322 km/hr)



Drum Diameter

48 inches

Drum Width

26 inches

Minimum AxleWidth

29.5 inches

Maximum Axle Width

81.5 inches

Maximum Axle Weight

3000 lbs

Timing Accurary

+/- 1.0 microsecond

Drum Speed Accurary

+/- 0.01 MPH

RPM Accuracy

+/- 0.1 RPM

Primary & Secondary Tachometer Pickup Leads

Drum Air Brakes

Air/Fuel Ratio Meter

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