Mustang dyno?

[KNSX]

This past weekend I took my car to a new shop with a Mustang syno. They (the shop owners) claim that it is more accurate than the more common dynojet on account. They said that it's more accurate because they dynojet is a simple inertia drum which, once it's spinning, actually reduces the transmission load leading to slightly inflated hp & torque numbers. The mustang, however, uses some sort of braking in a second drum and thereby simulates the aerodynamic drag on the car producing more accurate metrics. In addition, it does allow for quarter mile testing but again it's numbers were low. In fact, I ran 14.2 at the track vs its 14.7 (yes, I know conditions, etc were different)

Is anyone familiar with this mustang dyno? Is it really more accurate or does it just produce more depressing numbers?

my dynojet #s: 237 hp & 185 lbs/ft
my mustang #s: 208 hp & 165 lbs/ft

mustang
dynojet

 

[milz50]

For tuning purposes I'd value percision over accuracy.

 

[PHOEN$X]

For tuning purposes I'd value percision over accuracy.

Huh? What's the diff?

 

[Ojas]

I think milz50 is refering something analogous to the last 2 diagrams below.

 

[Accord-R]

You'd probably prefer accuracy then, being precisely wrong about something gets you nothing! (I feel like I'm back in Managerial Statistics!)

 

[true]

A braking type or "Eddy Current" dynamometer is more accurate and precision. One of the main advantages is that you can load the engine -- for example, hold the car at 4k RPM for a period of time. Also, I've never seen a 4 gas exhaust analyzer used on any inertial dyno....which is what you need to see if your timing is on point. Dynojet is pretty nice for bragging rights, and for getting a good idea of where you are at with your tune using a wideband a/f, but the load type dyno is where the real racers are.

I think there was another thread with a lot of good Dyno info somewhere, but I couldn't find it with a search.

 

[1BADNSX]

They said that it's more accurate because they dynojet is a simple inertia drum which, once it's spinning, actually reduces the transmission load leading to slightly inflated hp & torque numbers. The mustang, however, uses some sort of braking in a second drum and thereby simulates the aerodynamic drag on the car producing more accurate metrics.

I have never used a Mustang Dyno, but the statement about it simulating aerodynamic load is rubbish. Why would you want the dyno simulating aerodynamic load? Aero forces vary drastically between different vehicles and speed.

All dynos vary from one to another, even within the same brand type. The drum type dyno is a very simple instrument that is based on pure physics (harder to mess up in my opinion). Brake type dynos must use fluid measurement or electric absoption to determine horsepower. I don't know why your Mustang Dynos numbers are so low, but do they pass the logic test? Drum type dynos seem to also vary and that is why comparing measurements on different machines can not be done very accurately.

Bob

 

[Carguy!]

Re: Re: Mustang dyno?

I have never used a Mustang Dyno, but the statement about it simulating aerodynamic load is rubbish. Why would you want the dyno simulating aerodynamic load? Aero forces vary drastically between different vehicles and speed.

All dynos vary from one to another, even within the same brand type. The drum type dyno is a very simple instrument that is based on pure physics (harder to mess up in my opinion). Brake type dynos must use fluid measurement or electric absoption to determine horsepower. I don't know why your Mustang Dynos numbers are so low, but do they pass the logic test? Drum type dynos seem to also vary and that is why comparing measurements on different machines can not be done very accurately.

Bob

It is not rubbish about simulating aerodynamic load on the Mustang dyno. The computer that runs the dyno has a list of most cars available and if it doesn't have your car you are able to input the frontal area of the car and the CD and it will generate the appropriate resistance.

This type of dyno is better for tuning because in the real world you have resistance and if you tune using a dyno that doesn't provide this resistance when you take the car out on the road it can run too lean. This is the reason that a lot of tuners will build in a large comfort margin on the air/fuel ratio. You are able to set the car up much more accurately if it represents the kind of resistance you will have when driving.

 

[Number9]

I agree with Carguy! about the Mustang being better for realtime dyno tuning, but I would argue that the Dynojet is better for comparing the relative improvement of added go-fast parts.

Assuming for the sake of argument that the Mustang is capable of more accurate measurement in the objective sense, it nonetheless does require regular calibration whereas the Dynojet has a fixed mass roller that doesn't suffer from calibration drift (short of some catastrophic bearing issue or something like that).

 

[PHOEN$X]

I think milz50 is refering something analogous to the last 2 diagrams below.

LOL, thanks for the pictorial illustration, Ojas! Took me a while to figure out those were darts.

 

[ak]

I had my car dyno on a mustang dyno and it put down 250hp and 183ft-lb torque with header/exhaust. My car put down 230hp and 186ft-lb torque on dynojet with just exhaust.
Do you have auto?

 

[1BADNSX]

Re: Re: Re: Mustang dyno?

It is not rubbish about simulating aerodynamic load on the Mustang dyno. The computer that runs the dyno has a list of most cars available and if it doesn't have your car you are able to input the frontal area of the car and the CD and it will generate the appropriate resistance.

I stand corrected. I agree it isn't difficult to input a desired aerodynamic load, but I still state, why would you want it to? Are the horsepower numbers quoted above for 1st, 2nd, 3rd, 4th, or 5th gear. The difference in aerodynamic power loss between just 3rd and 5th gears in the NSX at any given RPM is greater than 400%. The error in this inputed load could be very large and as you said the operator has the ability to change it! This gives me less confidence in any posted numbers.

In my mind, you want to know the available power from the wheels to do work. What the work is doing (ie. accelerating the car, over-coming rolling friction, aerodynamic losses, wind direction, or climbing a hill) is a second order effect and has the potential of polluting the result for the average user.

Bob

 

[KNSX]

I agree that it's accuracy for which I'm looking when baselining my car on the dynos .... I'm just not quite convinced that it really is more accurate. They're just claiming that it's more accurate. I would think that there would have to be an awful lot of measurements taken into account in order to simulate air resistance & drag.

And while they seemed to know what they were doing, in retrospect, I'm not sure that they did. The shop is brand new which leads me to think that the dyno is as well.

Anybody hang out on the S2k boards? Apparently there was a group of them in CLT which had planned the dyno day (only one of them showed up)

ak - nope, I have a '96 with manual transmission.

 

[Edgemts]

Eddy Current/Mustang Dyno

A eddy current/mustang dyno is a tuning tool used to accurately tune and test performance changes etc. anywhere in the country or out of the country a mustang dyno will perform and give you accurate #'s to less than 1hp, and it is true rwhp not an inflated # from dynojet.
As far as a dyno jet dyno being simple, yes it is, its a heavy concrete drum that is accelerated, the computer measures how fast it accelerates and then uses a "approximated #" to get to a HP #. Hp is derived from torque not acceleration without accurate #s.
??for everyone?? Do wheels make HP?
I think not. So why when you change to lighter wheels does a Dynojet dyno say that you have more HP.???
Because the measurement is not under load and is BS.
Just my .$.02
Yes I do own a mustang dyno, I had a Dynojet in the past. I will will leave it at that.
Mike F

 

[1BADNSX]

Re: Eddy Current/Mustang Dyno

a mustang dyno will perform and give you accurate #'s to less than 1hp

As I admitted above, I have never used a Mustang Dyno. Can you check your Mustang literature and see if it really states it is 1% accurate? This seems impossible to me and their web page doesn’t make such claims. It may have 1% repeatability or some other wording, but probably not 1% accurate in horsepower.

Mass accelerating dynos do not approximate horsepower any more than a Mustang dyno. They both use physical laws that directly relate horsepower to the measure and calculate the value.

As far as the wheel creating horsepower, of course it doesn’t. The wheel does require horsepower to spin it, therefore less is available to accelerate the car or do some other useful work. Making a statement like the Dynojet result “is BS” shows a lack of understanding. If the Mustang dyno didn’t measure a difference with different wheels/tires under unsteady testing, I would question its measurement. The Mustang does have the advantage of doing steady-state testing where there wouldn’t be a difference in available power due to heavier wheels/tires.

Bob

 

[Edgemts]

Dyno-

As far as understanding goes, I understand a dynojet is an ok dyno, Is it accurate, that depends on what you are looking at.
You talk about it taking HP to deal with heavier wheels, that is correct, but a dyno should measure hp not the inertial weight of your drivetrain etc. Dynojet uses one constant for all vehicles, so if you put a race car with all lightweight components on it, it reads artificially high, if you put a truck with heavy wheels it reads low. SO how is that accurate.
A eddy current dyno uses both steady state and acceleration to get you accurate hp #s not an estimate.
Forget all the other stuff, ask a dynojet person to give you a hp reading at 50% throttle at 6000rpm!!
Mike F
I just prefer accuracy, So we chose an accurate dyno that is a valuable tuning tool.

 

[Edgemts]

??1%??

As far as 1% accurate on hp #s, yes I can honestly say they are at least that accurate, On the other hand depending on who is operating it, ??. We calibrate ours every day we use it.