LOL, why don't you explain how it measures HP?? You know, a real technical explanation with the basic physics and math used to do so.

Oh wait, you can't because it's impossible to directly measure HP.

 

It would mean you didn't get a measurement of your torque peak.

Is your car an auto? I do find it hard to believe your torque peak occurs below 2k rpm. I would expect something else caused that.

 

Yes I have a 700R4 automatic Tranny.

I contacted Ed the man who ran the Dyno when my Car was on it.
It will be interesting to hear what he has to say.

I for one appreciate every one's input on this subject.
I do have a better understanding of what's really going on.
At least I think I do.

Ralph

 

That early torque peak might be caused by the torque converter.

 

This is not the first time this horse has been beat.

 

I do have a 2400 rpm Converter.
The cam is a Lunati RV cam.
It is the hottest cam I could run with a stock converter.

R~

 

I don't think that your peaked below 2000 rpm either. Don't know why it shows that, but with a 2400 rpm converter I don't beleave that it possible. What rpm did they have you pull from? it looks like 2400 rpm.

 

The chart shows it started at 2000 rpm, other than that I don't know.

Ralph

 

FYI u can measure your own horsepower using the actual weight of your can and measuring the acceleration through rpm minus the drag while coasting using a stop watch. This is described in Dr. Jacobs book: "The Doctor's Step by Step Guide to Optimizing Your Ignition". BTW i have not tried this but it sounds much more acurate using road tests to measure the car performance rather than a set of rollers.

cardo0

 

I've had my car dynoed several times, and I have a 2900/4300 flash stall TQ converter. It was also dynoed with a 2400 rpm converter. Both gave the same results - you must start your full throttle runs above the footbrake RPM of the converter or it will flash or you will possibly downshift on the dyno, causing a high peak reading when it happens. My dyno operator always accelerates me slow to reach high gear and begin full throttle at 3500 RPM to remedy this and begin measurements to get an accurate peak reading.

 

As an engineer I have really enjoyed this discussion. But It reminds me of a story I heard in engineering school.

A young man and a young woman are standing some distance apart, every few minutes they get half the distance closer to each other. The physicist claims that they will never touch,and the engineer replies "we will get close enough"

My point? After I baseline the car at some constant distance, say a quarter mile, I change something on the car and it goes faster, that is good. If it goes slower, undo that change and try something else. Hp and torque numbers only have meaning if you have a beer in your hand. If making a change makes the number go up, that is good and will most likely make you motor through the distance faster. I am not changing stuff to make the number change, but to make the car go faster through the distance. What a rush. The true measure is the who crosses the line first.

 

Yes, you use the dyno to test things to get more power with the goal to make the car faster. In other words, the dyno is a tuning tool. I believe this has already been mentioned a few times in this thread.

 

This is exactly what I am doing, I had the car on the dyno 2 Wednesdays ago and have spent the time since figuring out what to do next (with a lot of help from people right on this thread) before going back to the dyno in the next week or 2.

 

Ahhh, the difference between engineers and scientists!

As a scientist, rather than an engineer, I recognize that this won't happen. You will only asymptotically approach twice the distance of the first step.

So if she is standing 12 feet away, and he can't make a distance in excess of 6 feet for the first step, he won't reach her.

On the other hand, if he can step more than half the distance on the first step, there is no reason that he can't reach her exactly.

It's really just a simple equation. The total distance he can attain is: (x + 1/2x + 1/4x + 1/8x, etc.) which approaches, but never reaches 2x.

 

Anyone going to Reno for Hot August Nights?

There is a Company going to be there MCE Racing.
He'll be at JA Nugget, in the parking lot, offering Dyno pulls for $20.00 a pull.

I checked out Kevin's web site and sent him an email.
He answered first thing this morning, said he'd look over this thread and get back to me.

He looks very creditable, his shop is at Thunderhill Raceway in Willows, California.
I'm anxious to hear what he has to say.

Ralph

http://www.mcedyno.com/MCE%20RACING%...0Services.html

 

The physicist is not taking into account both have mass. At a certain point gravitational attraction will take over and they will touch. Physics.

 

Okay this is what Mark had to say.
"Ralph,I did look over the Dyno Results,I did not see that any of those Dyno results were Dynojet,That makes a Big difference,only Dynojet uses a calibrated mass to determine true power,the others are dependent on Eddy current,which varies due to input voltage, calibrated (Dynojet)mass stays constant,Thank you,Kevin."

 

I don't buy that explanation. I believe most brake type dynos use load cells for the force measurement and then calculates torque and power using that force. In other words, the hydraulic or eddy current brake is there to provide load and the amount of twisting the brake does in the dyno chassis is directly measured by a load cell to give the "lbs" and the distance of the load cell from the dyno axle gives the "ft" to get torque in ft-lbs. Of course, it's more complex than this, because the dyno also has to calculate the torque that accelerated the dyno inertia and then sum the torques to get the total torque.

Besides, if a dyno does measure the power in the eddy current brake it wouldn't be too difficult to compensate for the voltage.

Also, DynoJet isn't the only manufacturer of inertia wheel dynos and a DynoJet isn't any more capable of measuring "true power" than any other wheel dyno.

You would likely find inconsistancies in the data entered by the operator causes more error than the ability of the dyno to measure and calculate the "raw" data.

 

There isn't a dyno on the planet that can measure HP, no matter what any dyno company glossy literature says or what "Joe Blow" who runs a dyno shop has posted on the internet. I'm not sure why I have to explain this to you. If you don't understand the basic physics involved then how can you argue that someone is wrong?

The dyno can measure certain things during the test, such as the force using a strain guage or the pulses from metal teeth passing a hall effect sensor or the acceleration of the drum using an accelerometer or the pulses from the ignition system using a pickup on a plug wire.

The dyno can not measure the HP. It is calculated.

 

What is your issue with my use of calculated vs measured? I have always clearly stated that HP is never measured, but always calculated. If you could use a sensor to directly measure hp (you can't because a hp sensor doesn't exist) then the measurement would be as accurate as the sensor. Using other measurements and then calculating hp means the answer will depend on the errors of each sensor used (and the errors can be cumulative), as well as any effect due to correction factors added into the calculation. Even if you consider the dyno to be the sensor, you have to look at what it does internally to get a better understanding of the possible errors involved. And internally, it measures other things and takes operator data and then calculates the hp curve.


So, what exactly do you want to be proved wrong about? I'm not even sure where you stand or what your point is. Early in post #41 you describe the dyno as measuring the rate of change of rotation of the drum and "knowing" the power necessary to do so? That sure sounds like the dyno is measuring the acceleration of the drum (with an accelerometer) and then calculating the power. Later in post #41, you then go on about how your dyno measures HP and again in post #49 you're back to it measuring power. So, do you believe the dyno measures the acceleration of the drum or that it directly measures hp?

On another note, if I do go to Wasaga, I won't be wasting my time giving you a free physics lessons.