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Old 08-08-2001, 11:49 AM   #1
fastang
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Post DQ, Whats the difference between a Mustang dyno and a dynojet?

Anyone?
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Old 08-08-2001, 07:46 PM   #2
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Umm...please
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Old 08-08-2001, 08:00 PM   #3
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A "Mustang Dyno" takes into account the cars weight and other factors from what I was led to understand. A Dynojet just measures the hp.

On deciding between the two, there is no question. The Dynojet IMHO. The Mustang Dyno allows it's operator to refigure the parameters around the cars output. What you get if the guy just wants to show you hp is a grossly inaccurante number. He simply edits the input "corrects it" lol, so it shows a much higher number. The Dynojets that I have seen don't allow for all that BS, and what you wind up with is an accurate power production chart.
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Old 08-09-2001, 12:34 PM   #4
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Like said above, the Mustang dyno takes into account the weight of the car (This is often also reffered to real-world load because on the track or the street...your car has to pull it's own weight).

Now, the fact is that the dynojet dyno has become more the standard than the mustang dyno. For this reason, if you just want to know your power...go with a dynojet and in a matter of saying speak the same "language" that everyone else is speaking.

But, if you want to properly "tune" your car...I would go with a Mustang dyno...because any tuning you do in the dynojet dyno will not be the right tuning for when you are hauling 1.5+ tons of steel on the street at 3g's.

Mike

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Old 08-09-2001, 01:46 PM   #5
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If mustang dyno's take the weight into the equasion shouldnt they bring lower hp numbers than a dynojet? How did it get the name "Mustang" dyno anyway?
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Old 08-09-2001, 02:41 PM   #6
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They do produce lower numbers than Dynojets...typically 10-15% I've seen. Where the name came from? Probably just chosen by the company who makes them. No idea.

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Old 08-09-2001, 03:08 PM   #7
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The Mustang Dyno is better for tuning. The dynojet has not "become" the standard, it set the standard by being the earliest of chassis dynos. But, they are old tech. The Mustang Dyno will set a testing window (say 65-115 mph, or whatever your rpm range works out to in a 1 to 1 drive gear.) It adds resistance to the rollers to simulate wind resistance, and vehicle weight as stated earlier.

Here is why a Mustang dyno is better. Tune a car on the ragged edge on a Dynojet. Then take it to the track and subject it to more of a strain than it ever saw on the dyno. What could happen?


Kaboom.

If you just want to whip it out and measure it with the boys, get on a Dynojet. The number will be higher.

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Old 08-11-2001, 01:54 AM   #8
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I have to disagree with the idea simulating load is better than simply getting raw horsepower. Horsepower is horsepower. How can you factor in wind resistance but not factor in ram air effect? Which car's downforce and drag coefficient do they use? Is the dyno actually in a wind tunnel? It's not scientific and it's adding variables that aren't necessary. The fact that they would report less horsepower than a DynoJet proves that they aren't good. These "features" just seem like sales hype.

It's like standing on a bathroom scale and having it factor in how much you would weigh if you were doing 60mph.

Am I opinionated or what?

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Old 08-11-2001, 09:55 PM   #9
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I'm right there with jimberg. A chassis dyno is meant to measure engine HP pure and simple as it gets to the rear wheels. If one needs a 1/4 mile simulation, then that's something else altogether. Programs are available that do just that. Not that that's not valuable info as well. Just not really dyno horse power. As jimberg said, too many other variables.

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Old 08-11-2001, 11:29 PM   #10
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Isnt it that the mustang dyno can hold a car at a certain rpm so you can tune the car at a certain rpm underload and the dynojet is just a redline run in a certain gear to get raw numbers?

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Old 08-15-2001, 03:30 PM   #11
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A dynojet does measure raw hp, and nothing else. A Mustang Dyno is much more valuable for tuning.

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Old 08-15-2001, 05:32 PM   #12
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LOL. This is rather interesting. In a perfect world, a "Mustang Dyno" would be better for tuning, maybe. But how do you figure it would be? I mean, think about it. How can having the max hp/torque availible under controlled conditions hurt you? The Mustang Dyno can pull in all the numbers it wants, it still can't change real hp production. If it doesn't read exactly the same as a dynojet for peak power/torque, it's messed up.

If you think somehow a "Mustang Dyno" gives the car a bigger workout I'd like to know how. The Dynojet will not cause "Kaboom." Otherwise they would be out of business.

Here is what my friend has seen with the "Superflo" dyno's for bikes, which offer changable parameters, unlike the Dynojets. The operator likes having customers, so he does a little tweak here, a little tweak there and wow, a stock bike is making 10hp more than it's supposed to. Add a pipe and a jet kit and it's performance really soars. The reason people go back is because they want to see the high numbers. Even if they aren't real.

I hate to bring up a fellow member here, but take a look at Skyman's car. He's trapping 106-107 with what a Mustang Dyno says is 330rwhp. That's over 400hp at the crank. With which, his car should trap more like 115 (which is what we think his car really should be trapping with his combo). Last time I talked to Skyler, he agree's that the Mustang Dyno was spoutin' bullshit.

Here's how I feel on the subject. If you want real numbers, run it on the Dynojet. If you want fake, made up numbers go for the Mustang Dyno.

As far as being out dated, maybe you should take a look at some of Dynojets new computers/software.
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Old 08-16-2001, 03:15 PM   #13
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Mustang Dyno's add resistance to the rollers simulating your 1 to 1 gear of a 1/4 mile run. so say my Mustang runs 4th gear from 75-115 mph (about 2000-5800 rpm) I believe that there is a wind resistance figure added in the dyno pull.

Your car may put down 300 rwhp sitting still on a Dynojet, but it is not putting that same number to the wheels at 100 mph. The demands on the engine are different, therefore most likely requiring different tuning. That is how a Mustang Dyno gives a car a harder workout.

I'm sure you could take the wind/weight factor out and get Dynojet numbers. As well as you could fudge the numbers to make customers happy. I was a bit disappointed with my 270 rwhp, but I can't argue with 111 mph traps. Does not look like any fudging on this particular MD.

Mustang Dynos can also hold a car at a given rpm at WOT. I know there is much more to this and I don't know it all. Turbolx has a Mustang dyno and maybe he will chime in with some details.
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Old 08-16-2001, 03:57 PM   #14
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www.mustangdyne.com

will explain the difference between a mustang dyno and a dynojet.



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Old 08-16-2001, 06:29 PM   #15
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Wind resistance and weight have absolutely nothing do to with engine performance.

You could have a Jeep with a 5.0HO drivetrain, then take a Mustang with the same drivetrain and they will dyno exactly the same. If they don't, your dyno is a pile of junk.

As far as tuning, a dynojet can tune just fine. When a dyno "tune" is made on a dynojet it's simple. You make runs in different gears. Say 3rd, and 4th gear. By looking at the performance the car is making over both runs, you can determine whether or not the engine is running rich/lean, and an exhuast gas analyzer will do the rest. Holding a car at a certain rpm at WOT will HURT your true tuning. That will NEVER happen in a real race situation and it will skew the numbers. Having the most safely available hp at any given rpm is what you're trying to get, regardless of the dyno you are using.
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Old 08-16-2001, 08:17 PM   #16
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You guys don't seem to understand what horsepower really is. It's just a way of measuring how much work is done in a specified amount of time. You can take horsepower from the engine (bhp) and that can be directly compared with other engines because it's like apples and apples. But take that same engine and put it on two different cars, say a Semi and a Mustang, you are going to get very very different rear wheel horsepower numbers. The semi is going to go way slower down the 1/4 mile than the mustang can, therefore less work done in a specified time, therefore less horsepower. A dynojet however will dyno the Semi as having the same rwhp as the Mustang because to it, the wheels spin without any resistance. This obviously is innacurate as compared with the 1/4 mile run! From what I have read, the Mustangdyno attempts to factor in these problems such as wind resistance and vehicle weight to give you an accurate hp rating down the 1/4 mile track. Which is what you want!!

Summed up, if your friends car gets the same rwhp as your car, don't expect the performance to be the same in the 1/4 mile. Weight, wind, it all matters. That's why the ET calculator has A WEIGHT FACTOR duh!

Trust me, you want the HP rating of your car as it goes down the 1/4 mile, not the HP rating of your car as it spins up the dyno.
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Old 08-16-2001, 10:32 PM   #17
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Vector, if horsepower at the drive wheels remains constant, the time it takes to cover a distance will increase as the weight of the vehicle increases. It's true that you could calculate a total amount of horsepower performed during a run if the only work you were concerned with was moving the weight of the vehicle. Say you have two track surfaces. One is absolutely slip proof, the other is an oily surface. You run the same exact car on each track. It may take you 10 seconds to cover the distance on the first track, and it may take you 20 seconds to cover the distance on the second track. If you were simply concerned with the power actually used to perform the task of moving the weight of the vehicle from the start to the end of the track, you used 1/2 the amount horsepower on the oily track.

In reality, though, the engine was still capable of putting out the same amount of power on each track. Power was just wasted spinning the weight of the wheels and generating heat on the oily track.

It may be that the Mustang Dyno is geared toward diagnosing drivetrain vibrations or other issues that you may have a need to crawl around the vehicle while it's running at highway speed under load. If that's the case, that's fine, but if technicians are trying to convince people that it gives you a better way to tune your car for horsepower, it's hogwash.

The horsepower we are most interested in is what is available at the rear wheels under a standard condition. This is what a DynoJet will give us.

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Old 08-17-2001, 12:36 AM   #18
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Quote:
Originally posted by Vector:
You guys don't seem to understand what horsepower really is. It's just a way of measuring how much work is done in a specified amount of time. You can take horsepower from the engine (bhp) and that can be directly compared with other engines because it's like apples and apples. But take that same engine and put it on two different cars, say a Semi and a Mustang, you are going to get very very different rear wheel horsepower numbers. The semi is going to go way slower down the 1/4 mile than the mustang can, therefore less work done in a specified time, therefore less horsepower. A dynojet however will dyno the Semi as having the same rwhp as the Mustang because to it, the wheels spin without any resistance. This obviously is innacurate as compared with the 1/4 mile run! From what I have read, the Mustangdyno attempts to factor in these problems such as wind resistance and vehicle weight to give you an accurate hp rating down the 1/4 mile track. Which is what you want!!

Summed up, if your friends car gets the same rwhp as your car, don't expect the performance to be the same in the 1/4 mile. Weight, wind, it all matters. That's why the ET calculator has A WEIGHT FACTOR duh!

Trust me, you want the HP rating of your car as it goes down the 1/4 mile, not the HP rating of your car as it spins up the dyno.
Stick to what you know. This argument is so flawed I'm not even sure I want to get into it.

Horsepower is ((Torque x RPM) / 5250) Please, tell me where weight enters into that equation? As far as bhp vs whp you're way off base. HP at the wheels measures power at the wheels, instead of the crank. All it's doing is showing you the frictional losses in the driveline, nothing else. A semi with an HO "engine" in it, and a Mustang with an HO "engine" in it WILL give different whp numbers. Only because the Semi has a less efficient transmission and driveline. If you were to put the engine 5.0 driveline into a semi you'd get the same whp numbers. As far as your comment about the Dynojet having no resistance? LOL. Yeah, right. Have you ever tried rolling one of the 1000lb+ drums on a dyno? That's the resistance. As far as drag, that's what the driveline is. Tranny, driveshaft, axle. It's all drag and friction.

Again weight has absolutely NOTHING to do with engine performance. Aerodynamic drag has absolutely NOTHING to do with engine performance.

I would like somebody to explain to me how a car that makes maximum peak, and average hp will be slower than it's twin, which was tuned using weight and drag in the equation (which is totally worthless)? If the engine is producing 300hp, it's making 300hp. If it's making 295, again, it's making 295. There is no way to tune an engine with better results at the track than giving it maximum power at all times. I'd hate to see the worthless numbers a Mustang Dyno would come up with if you added a ground effects package, or wing, or ram air hood. What Cd do they use then? I doubt most shops have a wind tunnel for testing on hand. What about weight? Do they have an accurate scale sitting right there for you to use as well? Or are they using book numbers, which can vary from car to car by several hundred pounds?

If they believe the hype the are spreading, people at Mustang Dyno are about as stupid as the link I saw not too long ago asking for a cars weight and hp to determine top speed.
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Old 08-17-2001, 01:58 AM   #19
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Quote:
Horsepower is ((Torque x RPM) / 5250) Please, tell me where weight enters into that equation?
Torque is measured in foot-pounds. A pound is a unit of force. A foot-pound is a unit of work (force over distance). Horsepower is a unit of work over time. 1 HP = 550 ft-lbs/sec.

The information you want to get from a dyno run is what your maximum power on tap is and at what RPM. Then you want to make sure that your 2nd through 4th shifts will be at the points where you have the most average HP between the low and high rpm.

You also want the least number of variables inserted into the equation.

I'm sure the Mustang Dyno serves a valid purpose, but the way it's been described on here, I'd be wary of a technician who claims they can tune for you better with one.

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Old 08-17-2001, 11:11 AM   #20
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Quote:
Originally posted by Unit 5302:
Again weight has absolutely NOTHING to do with engine performance. Aerodynamic drag has absolutely NOTHING to do with engine performance.
Not to start a flame war here, but please don't throw out misinformation like this. We use chassis dynos to tune the whole car, not just the engine. (that's what engine dynos are for!) The primary purpose of any chassis dyno is to try to accurately simulate what's happening on the road or at the drag strip, which should include wind drag, especially with trap speeds in the 1/4 over 100mph.

Please do a quick search on the terms "Proving Ground Equation" and "Tractive Effort" and you will quickly see how the same exact engine in a Corvette sees a different load than it does in a truck. This change in loading to the motor dictates how much spark lead the engine will tolerate for a given a/f ratio.

I have seen the difference first hand many times. I did my homework as an engineer before buying any dyno and am confident in my choice. Unscrupulous dyno operators aside, the MD tends to read lower than a Dynojet because the engine is actually seeing the correct load for the street. I have seen the difference where changing the load (NOT the roller weight parameter in the software) allows the car to pull quicker on the dyne and tends to mask some tuning issues such as detonation. An unknowing tuner could easily call this a "safe" tune and let the car go to the track where it can potentially gaskets or worse.

As for the numbers, I will gladly put a car that makes 400rwhp on my MD1750 up against any car that makes 400rwhp Dynojet in a race. I think my customers' trap speeds speak for themselves, and have yet to see anyone blow gaskets at the track after being "OK on the dyno" here.

Bottom line: Dynos are tuning tools just like the wideband and the timing light. You want to know who's really faster, go to the track!

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