[Drgnracin72]

Originally Posted by acmillr Originally Posted by JohnnyZ Originally Posted by Bob17830 400 at the wheels? i've never heard of a na 2v making 400 rwhp The class I race in, the 2V mustangs are making from 400-440 rwhp. They are going 11.30's ON MOTOR I'm not saying you're being dishonest here, but KB was running those numbers with under 400 HP if I'm not mistaken. For the record, you are not going to make 400+ on the stock bottom end- I have been chasing that number with the 2V for a while. However, I believe it is about to happen. Boomer and I have come to an agreement that may finally see the legendary 400+ in a N/A 2V street car.

just make sure those numbers are ona mustang dyno so we cna see what it makes in real life

[JohnnyZ]

Originally Posted by drgnracin72 Originally Posted by acmillr Originally Posted by JohnnyZ Originally Posted by Bob17830 400 at the wheels? i've never heard of a na 2v making 400 rwhp The class I race in, the 2V mustangs are making from 400-440 rwhp. They are going 11.30's ON MOTOR I'm not saying you're being dishonest here, but KB was running those numbers with under 400 HP if I'm not mistaken. For the record, you are not going to make 400+ on the stock bottom end- I have been chasing that number with the 2V for a while. However, I believe it is about to happen. Boomer and I have come to an agreement that may finally see the legendary 400+ in a N/A 2V street car. just make sure those numbers are ona mustang dyno so we cna see what it makes in real life

The new dynojets w/ load factoring are just as accurate. Regardless, it's being done in numerous cars. Just look at every single 2 valve mustang running in NMRA factory stock. They are all pushing roughly the same horsepower.

[B0B]

this is with high compression and not stock bottom ends right?

and heres a question, why are NA mustangs with say 400 rwhp so much faster than S/C mustangs with 400 rwhp?

i've heard of people breaking 11's with a little over 300 rwhp. most sc mustangs making 400+ at the wheels are running mid to high 12's right? correct me if i'm wrong

[SWEET2KSTANG]

it is on how the power pours on. the way the motors are set up have a lot better curve and less chance of little problems. belt slip, hot lap, lag, etc can vary and can make big differences with power output.

[acmillr]

Originally Posted by drgnracin72 Originally Posted by acmillr Originally Posted by JohnnyZ Originally Posted by Bob17830 400 at the wheels? i've never heard of a na 2v making 400 rwhp The class I race in, the 2V mustangs are making from 400-440 rwhp. They are going 11.30's ON MOTOR I'm not saying you're being dishonest here, but KB was running those numbers with under 400 HP if I'm not mistaken. For the record, you are not going to make 400+ on the stock bottom end- I have been chasing that number with the 2V for a while. However, I believe it is about to happen. Boomer and I have come to an agreement that may finally see the legendary 400+ in a N/A 2V street car. just make sure those numbers are ona mustang dyno so we cna see what it makes in real life

Why would I use a Mustang Dyno? It is one of the only currently marketed dynos that can have it's output numbers manipulated by the tuner. Do a little research on your legendary Mustang Dyno.

[acmillr]

Originally Posted by JohnnyZ Originally Posted by drgnracin72 just make sure those numbers are ona mustang dyno so we cna see what it makes in real life The new dynojets w/ load factoring are just as accurate. Regardless, it's being done in numerous cars. Just look at every single 2 valve mustang running in NMRA factory stock. They are all pushing roughly the same horsepower.

Dragn knows everything- He is in OK with all the companies that are on the cutting edge of performance- Not like FL where there are no dyno or software companies.

[acmillr]

OK, back to reality. That Dyno comparison is brought up alot, and I thought I would share something I found the other day while reading up on the subject. I DID NOT write this. This is the first in depth read I have found that gets to the real difference in the two dynos. However, I do not have access to a Mustang dyno within reasonable driving distance- so, the track numbers may have to be heavily relied on in my case. Thank God for good FL air.

BTW: This may be a good sticky.





"It's been said that a man with a watch always knows the correct time, but a man with two watches is never really sure. Unfortunately, there are no proverbs about a man with two knowing how much power his car really makes. In this article, we'll examine two popular chassis dynamometers and explain why each will give us a different rear-wheel horsepower for the same engine. We test both the Dynojet model 248 chassis dyno located at Strope's Speed Shop in Washington, Pennsylvania and the MD-250 Mustang chassis dyno located at Speed Nation in McDonald, Pennsylvania. We also performed testing at Keystone Raceway in New Alexandria, Pennsylvania, using a dyno system
from West Automotive Performance Engineering.


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.

Conclusions

The Test Results table summarizes the testing that we performed. Keep in mind that the peak numbers are influenced by the amount of smoothing or averaging done to the final data. For comparing dyno plots to determine losses or gains, don't focus on the peak values but take a visual average by comparing the before and after curves on the same graph. If you can't see a marked improvement on the dyno, you probably won't see a performance improvement on the street. Also, realize that both the Dynojet and Mustang chassis dynamometers are useful tools that have excellent repeatability. Both dynos measure the correct horsepower and torque for the load that they apply. Both dynos will show losses or gains from modifications. It is recommended that you pick a dyno for your baseline testing and stick with that dyno type and dyno location (and dyno operator) for subsequent testing. Always start at the same engine coolant temperatures before each run. Also, use an OBD-II diagnostic scanner like AutoTap (from B&B Electronics) to monitor your engine's operating parameters. This will provide the best indication of power improvements or losses. We like to monitor the engine-coolant temperature, timing advance, knock retard, pre-cat O2 voltage, and rpm. Monitoring the engine-coolant temperature lets you make sure your engine is at the same temperature before each run to produce the most consistent results. The timing advance and knock retard indicate if any detonation is occurring that results in reduced timing and lower horsepower. After doing some research, the pre-cat O2 voltage can provide a correlation to the air/fuel ratio even though the O2 sensors are not too reliable in this air/fuel ratio region.

The bottom line:

dyno numbers are for show, and track times are for the dough!

-author unknown

[Drgnracin72]

ok i should have said "use a loaded dyno so we can see a truer number"

[acmillr]

Originally Posted by drgnracin72 ok i should have said "use a loaded dyno so we can see a truer number"

I see your point and it is valid. However, when comparing Mustangs to Mustangs, I think it is safe to say that the Dynojet is the "accepted standard" among the majority of enthusiasts. It is really rare for me to see a Mustang Dyno around here.

[04GTAMPA]

I haven't seen one yet....

[Drgnracin72]

im just saying a loaded dyno will give more accurate numbers, but will also result in a better tune. and like you said dyno numbers mean nothing, numbers at the track mean everything

[acmillr]

Originally Posted by drgnracin72 im just saying a loaded dyno will give more accurate numbers, but will also result in a better tune. and like you said dyno numbers mean nothing, numbers at the track mean everything

Undeniable statement right there.

[Eagle2000GT]

Now you'all have gotten me confused.

Acmillr's post had a lot of conclusions but not a lot of data. Does a Mustang tuner rate horsepower the same as a Dynojet? That is my first question. Apparently from the data presented, the answer is "it depends."

General consensus is that a dyno is only good for comparative improvements and iit is the track that matters. While I agree in principal... I DISAGREE COMPLETELY.

Did I shout. Sorry. You guys tell me that I will max out at 420-450 on a stock block and that 450 is pushing it. Other than a dyno, how am I to know when I'm getting close. I've been trying to figure this out for months. IS THE 420-450 NUMBER BASED UPON A DYNOJET OR MUSTANG DYNO? And yes, I fully intended to shout that time. Because when you're pushing the limits its very important to know where the limits are.

This is importnat to me. You'all say you don't see Mustang Dynos. My car is tuned by one. Can I put headers on, or am I max'ed out?

I have found a tuner closer to home that has a Dynojet. He has told me that I cannot do both headers and a new 10 psi pulley. If they are the same and I'm at 385 them why not?

Inquiring minds want to know.