We're waiting for our third run. First run. 205, second 208. This is on an awd mustang dyno, figure 22-23 drivetrain loss. Airbox is being used and not the cai. I'll post charts and pics when I get back tonight.

 

You need to run a baseline on that dyno first. How can you know how much the mods make a difference if you're simply estimating the drivetrain loss?

 

^^^Thats why I and a couple of other guys are going there on Saturday to get dyno runs on our stock Xfire's as a baseline.

 

We ran a dyno with the CAI, Injectors, no tune and measured 179 RWHP. The new one averaged a best of 205 RWHP. Look at it as a gain of 26HP from just the tune then. We will be having stock Crossfires on the dyno soon enough, but for right now this is the best we can do. It shows a gain of about 40HP over stock.

Anyway here is the chart.

Ok I can't post the chart on here. Someone shoot me an email to send them to and maybe they can post them.

 

stevebarden1@hotmail.com

 

Ok, figrued it out as I was emailing it. They weren't JPG.

 

Just to clarify the differnce in numbers between a Mustang Dyno and a Dynapack, jet, or other similar machine. The conversion factor is about 10-12% to get at "typical" dyno numbers. Then calculating drive train loss at 15-18% you arrive at the crank HP.

Using our 205RWHP (mustang) you would arrive at 228-233 RWHP(dynojet). Then taking the 15-18% drivetrain loss you arrive at, using 230 RWHP, 261-270HP at the crank.

We stocked 176 HP on a dynojet, which would give the car an 18% DT loss from the factory.

The Mustang to Dynojet numbers I'm getting from the Dyno owner and tons of experience both with my cars and other people's cars on using a Mustang Dyno.

Just an example the car before us was an 02 Trans Am, heads, cam, full exhaust, 6 spd. Runs high 11's, layed down 372 RWHP.

 

I'm interested, but is there any way you can overlay the stock dyno with the mod dyno graph? I kind of want to see where power is gained and lost... If I were to get this stuff done, how long would it take? Its like a 2-3 hour drive and I would like to have it done in one day.

 

Why not use the same dyno every time then? This would greatly help your tunning, and critics confusion.

 

After our initial dyno, which we only made a 5000RPM run, we found an AWD Mustang dyno that allows for full pulls.

We've used the same dyno since.

This can be done within the day. Three to four hours tops.

 

Brief Explanation

Dynojet
The Dynojet chassis dyno is referred to as an inertia-type dynamometer, because large drums provide an inertial load to the drivetrain instead of a friction brake. The working end of the Dynojet includes two 48-inch diameter drums that are mostly below the surface and driven by the vehicle's drive wheels. In the photos of the Dynojet, notice how the rear wheels are centered on the drums and there is one drum per wheel. This will become important later.
The vehicle is typically run in the transmission gear closest to 1:1 (Forth gear for manuals and Third gear for automatics) to or a variable load that maintains a preset engine rpm or vehicle speed. This feature is ideal for forcing the vehicle to operate at certain loads for tuning. The Dynojet can also measure air/fuel ratio while testing.


Mustang
The Mustang chassis dyno uses an Inertia load as well as an eddycurrent brake load to simulate the "actual" load (combined aerodynamic plus rolling frictional load) that the vehicle would experience when in motion. Notice in the photos how the rear wheels sit between two smaller 10.7-inch diameter rollers. There has been some discussion about the tires getting "pinched" between the rollers and creating more rolling friction, but no substantial evidence of this could be found. However, Mustang has a dyno (MD-1750) with a single 50-inch diameter roller per wheel that alleviates the wheel-pinch concerns. The internals of the Mustang dyno are composed of an eddy current brake to provide a variable load and an inertial disc to provide a fixed load. Mustang claims because its dyno loads the vehicle as it would be on the road, you can perform 0-60 mph, 0-100 mph, and quarter-mile measurements on its chassis dyno. Speed Nation has obtained quarter mile times within 0.1 second of actual runs at the track. We're not sure how the launch dynamics are simulated on the Mustang dyno, which
includes weight transfer, acceleration, jerk (the derivative of acceleration - how fast the acceleration occurs) and some other variables. The Mustang dyno can also measure the air/fuel ratio while testing.


CorrectIon Factors
Correction factors are used by both dynos to account for varying atmospheric conditions such as temperature, pressure, and humidity. The measured horsepower and torque are multiplied by the correction factor to obtain the corrected values. This is similar to the corrected times and speeds provided by some quarter mile tracks. Theoretically, you can dyno on a hot day in the high altitude of Denver and on some other cool day at sea level and produce the same corrected horsepower even though the observed horsepower you are producing at each location is different. Both dynos calculate a correction factor based on a Society of Automotive Engineering document (SAE-J1349). When testing was performed on the Dynojet, the correction factor was 1.10, which means the observed numbers were multiplied by 1.10 (adding 10 percent) to get the corrected values. The correction factor for the day when testing was performed on the Mustang dyno was 0.9595 (removing 4.05 percent). The correction factor when road-testing at
Keystone Raceway was 0.962, a correction reduction of 3.8 percent.


Testing
Testing was performed on each dyno using a '00 six-speed Z28 Camaro. We measured the horsepower and torque versus engine rpm in Second, Third, and Fourth gear. The test data also included how fast the engine accelerated in Second and Third gear (in rpm versus time) to be compared with actual road tests to assess each dyno's loading of the drivetrain. After each individual test we let the engine coolant temperature as displayed by our AutoTap OBD-II scanner to read between 200 and 205 degrees F for consistency. Dynojet sent out a representative to Strope's Speed Shop to verify calibration and witness testing. Calibration for the Dynojet is just a matter of verifying that the computer's configure file has the proper load-roller inertia factor. There are no manual calibrations for the Dynojet.
The road tests were pertorrned at Keystone Raceway to provide a level surface to measure the vehicle's rpm versus time in Second and Third gear using AutoTap. Chad Fellabaum of C&C Racing in Pennsylvania weighed the car so the exact weight could be used for the Mustang dyno loading to be compared with the road tests.
The dyno curve charts show horsepower and torque versus rpm in Third gears for both chassis dynos. You can also see that the Dynojet dyno measures a higher rear-wheel horsepower than the Mustang dyno.
The Dynojet measured 5.1 percent higher horsepower in Fourth gear, 7 percent higher horsepower in Third gear, and 8.2 percent higher horsepower in Second gear. We will try and explain this difference a little later.
Graphs 8 and 9 show the engine rpm versus time when the vehicle was loaded by the Dynojet dyno, Mustang dyno, and the actual road loading at Keystone Raceway in Third gear. You can see that the Mustang dyno loaded the car much closer to the actual loading in Second and Third gears.
Why Is loading the Vehicle Important?
The answer to this Question is twofold. First, the engine produces horsepower at the flywheel (brake horsepower) that is reported by the automobile manufacturers. Engine power is coupled to the rear wheels by a transmission and a rearend. But this is no free ride - there are losses in both the trans and the rearend. Therefore, the power to the rear wheels is equal to the flywheel horsepower minus the drivetrain power loss. The drivetrain losses are
mainly composed of three loss areas: friction loss, inertia loss, and viscous loss. The friction loss is largely due to the surfaces of the gear teeth rubbing against each other. Gear friction is related to the torque being transmitted through the drivetrain. The gear power loss is related to the speed at which the torque is being transmitted. This is why it is recommended to have a transmission cooler for towing. The transmission must couple more torque to pull the boat resulting in more frictional power loss, which shows up as more heat in the transmission to be taken away by the transmission cooler.
Inertial loss is related to the rotational acceleration (i.e., angular acceleration) of the drivetrain components. The inertial loss does not result in a power loss (i.e., heat) but absorbs energy that can be coupled to the rear wheels. This energy actually gets stored in the drivetrain components. The stored inertial energy in the flywheel keeps the revs up while the clutch is pressed in during shifts. The inertia loss is more pronounced in lower gears (i.e., First or Second) when the acceleration is highest. The viscous loss is basically the pumping of lubrication fluid in the transmission and the rearend. This is one reason why you get better e.t's when the
drivetrain is warm, because the oil is thinner and provides less "pumping loss." Therefore, to measure the actual rear-wheel horsepower, the drivetrain must be properly loaded to obtain the correct drivetrain loss. If the dyno provides a lower drivetrain load, then the drivetrain losses will be lower and the resulting rear-wheel horsepower will be higher.
The second reason why vehicle loading is important is that the newer computer-controlled vehicles use engine load as a control parameter. For example, ignition timing is a function of engine load. You will see higher timing advance when revving the engine in Neutral than you will when the vehicle is fully loaded at wide-open throttle in Third gear. This engine loading factor (and airflow dynamics, which is beyond the scope of this article) can help explain why some people have dyno'd identical to a friend's engine on a Dynojet dyno but got different results on a Mustang dyno.
Which Dyno Measures the Actual Rear-Wheel Horsepower?
West Automotive Performance Engineering has developed a proprietary device that independently measures a vehicle's actual speed and acceleration. This device is similar in operation to a fifth wheel but doesn't use accelerometers that can be influenced by the vehicle's body tilt. Using the vehicle's speed, acceleration, and weight (mass) and the application of simple physics equations, the exact horsepower and torque can be calculated. The horsepower and torque measured by West Automotive Performance Engineering's dyno is actually the horsepower made-good, or the horsepower left over to accelerate the vehicle after all the aerodynamic and rolling-friction losses have been overcome. These losses were accounted for and included West Automotive Performance Engineering's dyno so that a comparison with a chassis dynamometer can be made. The Mustang dyno includes the aerodynamic load that it places on the drivetrain as part of its reported rear-wheel horsepower and torque. Stated another way, the Mustang dyno does not measure the horsepower made-good.
Graphs 7 and 10 show the horsepower and torque versus rpm in Second and Third gear, respectively, for the Dynojet dyno, the Mustang dyno, and from road testing with the dyno from West Automotive Performance Engineering. You can see that the horsepower and the torque, as measured on the road, are closer to the Mustang dyno measurements. Also from the acceleration tests you can see how the Mustang dyno loads the vehicle very closely to how it will be actually loaded on the road. Based on our test data, the Mustang dyno loaded our test vehicle and measured the rearwheel horsepower closer to what the vehicle experiences on the road.

 

How about a g-tec run using the same entrance and exit points on clean road, should give good numbers? for only $200 maybe a forum member can do some passes?

 

We'll be heading to the track on Friday before RI.

 

How did it go?