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Old 8th November 2010, 01:59   #91
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Nice dyno you guys have there

Are you friends with RD Chinoy by any chance? I'd got word one of the dynos in CBE through him, not sure if it was yours.

Nonetheless, can you give details about the pricing scheme by PM? Very interested in tuning on a load-type dyno
The Land and Sea at KSM in Mumbai wouls cater for all your tuning needs. The load cells are only really of use when you do live mapping, which can't be done with most stock ECUs.
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Old 8th November 2010, 02:29   #92
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I want to do live mapping with my ECU which can do live mapping. With my NA build, street tuning is alright, but once I go FI, I don't wish to fool around with that kind of power on the street while having to pay attention to the data on the laptop. Right now, the only option is using the brakes to apply load while tuning but I'm sure you'd understand the pitfalls of doing something like this all the time.
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Old 9th November 2010, 20:46   #93
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Hi All

We have been hearing about dynos and dyno tuning.

I thought I would give a multi part series of posts about dynos and how they can be used for tuning.

......
to be continued......
Waiting.

Regards
Sutripta
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Old 9th November 2010, 22:16   #94
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Waiting.

Regards
Sutripta
Soon sir!! ... I have a livelihood to protect too !
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Old 10th November 2010, 08:36   #95
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Default Inertia Dyno run

In this instalment, I describe a typical interia dyno run. This description is indicative and is by no means exhaustive.

There will be many differences between dynos and others could add their points on this.

The dyno controller will be set up to start measuring at a particular rpm and stop measuring when the operator choses to.

The dyno will then be calibrated to correlate between the engine rpm and the roller rpm in the chosen gear. Some dynos have the ability to directly measure the engine rpm and this step may not be needed.

After this, the operator holds the throttle steady at full throttle. The car will accelerate the rollers from the starting rpm and keeps on doing so until the operator lifts off the throttle - this could be at the rev limiter or at any point the operator wants to stop.

The dyno controller continuously monitors the rpm of the roller and based on this, computes the instantaneous power/torque at various rpm points. The results are output in a graph and in tabular form. Some dynos give the output as a continuous graph of the instantaneous values, while some dynos select measurement points at pre-determined intervals and draw an interpolated graph.

The figures thus derived are the figures at the wheels.

Some dynos also have what is called the coast down mode. For this feature, the operator, after reaching the maximum desired rpm, lifts off the throttle and simultaneously depresses the clutch and keeps it depressed. The deceleration of the rollers will then depend on the drag created by the driveline (from the wheels to the clutch plate) and the dyno can compute the estimated drivetrain losses, thereby arriving at an estimated "at the crank" values rather than only the "at the wheel" values.

These figures reflect a fair estimate of the power at the flywheel.

to be continued .......
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Old 11th November 2010, 11:43   #96
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Default Inertia Dyno - principle of operation

The inertia dyno works by constantly monitoring the speed (rpm) of the roller(s).

The mass of the dyno roller(s) is a known constant. The frictional losses for a particular type of dyno are also known, because they can be accurately measured.

Since the rpm of the roller(s) is constantly monitored, the controller is easily able to derive the acceleration figures of the roller(s) at each rpm.

Since mass and acceleration are known, the force is calculated using the simple formula Force = Mass x Acceleration (thanks to our friend Mr. Newton and his second law of motion). The more sophisticated dynos will apply the corrections for frictional and other invisible losses.

Once the force is known, it is a simple matter to derive the power and the
torque at the wheels using other simple formulae (let's leave out the physics classes from here!).

With these figures computed, the dyno controller software can then present this data in various forms to the user.

Of course, from manufacturer to manufacturer, various bells and whistles will get added to the basic features for collating and presenting the data.

The advantages of the inertia dyno:
The figures are highly repeatable
Very simple to operate
Negligible maintenance
Lower initial investment
Negligible power consumption
No heat generation

The disadvantages:
Not possible to do live tuning
Nearly impossible to study part throttle and part load performance

to be continued......
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Old 26th October 2011, 16:02   #97
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Default The loading dyno

Back after a longish gap.... been a busy few months.

In this final instalment, I will give some details of a loading dyno.

The loading type dyno can either be a roller type dyno or a hub type.

The principle of operation is that a known load is precisely applied when the vehicle is run on the dyno. his load is precisely applied by means of a computerised controller.

This load can be applied in many ways - the earliest dynos always used some kind of frictional load and computed the torque by measuring the applied load. Once the torque is known, the power is easily calculated.

As dynos evolved, the loading methods became more and more sophisticated.

The device which absorbs the power is called the Power Absorption Unit (PAU)

The latest PAUs use a braking system called eddy current braking. This works by generating "eddy currents" in a rotating disc which is positioned close to one or two stationary discs. The stationary discs try to hold back the rotating disc and cause a braking action.

Some dynos also use a water brake system where the vehicle's wheels are opposed by water brake where water is circulated. The water needs to be constantly cooled to ensure that the operation is stable.

In its elementary form, the loading dyno applies a computer controlled braking force to the car to keep the wheels running at a constant rpm. Even if you apply more throttle, the controller will automatically increase the braking force so that the rpm remains constant. This correction is done very quickly. In many ways, the accuracy of the dyno depends on how accurately the system reacts to changing loads.

Once the speed is held constant, it is possible for the tuner to vary tuning parameters (e.g. fuelling, boost, ignition), while at the same time measuring various parameters to see the best operating point. This process is repeated at various rpm and load conditions until the operating regions of the engine are covered. This process is what is commonly known as "dyno tuning".

Along with the basic function of applying a load, modern dynamometers offer the ability to simultaneously monitor and record various other parameters to get a complete picture.

In the hands of a good tuner, the dyno is a potent tool for completely diagnosing a car's engine and unlocking the full potential of the vehicle.

I would be happy to answer any queries. I hope the series was useful.

Cheers
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Old 27th October 2011, 22:56   #98
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Default Re: The loading dyno

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Originally Posted by sapl View Post
Back after a longish gap.... been a busy few months.
11 months!

his load is precisely applied by means of a computerised controller.

In its elementary form, the loading dyno applies a computer controlled braking force to the car to keep the wheels running at a constant rpm. Even if you apply more throttle, the controller will automatically increase the braking force so that the rpm remains constant. This correction is done very quickly. In many ways, the accuracy of the dyno depends on how accurately the system reacts to changing loads.
Pre electronics/ computer days, any idea how was the rpm held constant, esp. on that part of the curve where torque increases with speed?

Regards
Sutripta
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Old 27th October 2011, 23:30   #99
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Default Re: The loading dyno

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Originally Posted by Sutripta View Post
Pre electronics/ computer days, any idea how was the rpm held constant, esp. on that part of the curve where torque increases with speed?

Regards
Sutripta
Yes, 11 months indeed !!

Very similar to the old age UTMs in the Civil engineering lab - you had a spring balance on the braking hub which would show the load. When you wanted more load, you would increase the force on the brake until the rpm stabilised.

Cheers.
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Old 27th October 2011, 23:38   #100
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Default Re: The loading dyno

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Originally Posted by sapl View Post
Yes, 11 months indeed !!

Very similar to the old age UTMs in the Civil engineering lab - you had a spring balance on the braking hub which would show the load. When you wanted more load, you would increase the force on the brake until the rpm stabilised.

Cheers.
Hi,

No, that is how the load was applied/ varied/ measured. How was the rpm held constant?

Regards
Sutripta
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Old 27th October 2011, 23:59   #101
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Default Re: The loading dyno

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Originally Posted by Sutripta View Post
Hi,

No, that is how the load was applied/ varied/ measured. How was the rpm held constant?

Regards
Sutripta
By varying the load on the brake ! Each time you changed the load, you varied the load on the brake to bring the rpm back on track and took a load reading !

Naturally you would have had a slide rule at hand to calculate the torque/power !

Cheers
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Old 28th October 2011, 14:44   #102
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Default Re: The loading dyno

^^^
Hi,
Was not talking of how load was varied, but by how rpm was controlled when load was varied. We are talking of tests at WOT.

Regards
Sutripta
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Old 28th October 2011, 15:37   #103
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Default Re: The loading dyno

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Originally Posted by Sutripta View Post
^^^
Hi,
Was not talking of how load was varied, but by how rpm was controlled when load was varied. We are talking of tests at WOT.

Regards
Sutripta
At WOT, the only way you control rpm is by increasing or reducing the load!

Once the rpm is reduced, automatically the engine breathing also reduces and the parameters for that rpm can be studied.

Sounds like brute force methods? - yes, but that's the only way it can be done.

Even in modern dynos, once under a particular throttle position (including WOT), we can adjust the rpm up or down by varying the load.

That is one of the reasons why a loading dyno rung should be done with great care, allowing plenty of cooling time between load points.

Regds
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Old 28th October 2011, 23:55   #104
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Default Re: The loading dyno

^^^
The nature of the torque - rpm characteristics of the engine and the load make for an inherently unstable system.

Frequent precise control of the load can obviously hold steady at any rpm. Easy to understand in the context of say computer controlled eddy current brakes. What about other cases? What about the pre electronic era? How was it done then?

Regards
Sutripta
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Old 30th October 2011, 17:56   #105
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Default Re: The loading dyno

Quote:
Originally Posted by Sutripta View Post
^^^
The nature of the torque - rpm characteristics of the engine and the load make for an inherently unstable system.

Frequent precise control of the load can obviously hold steady at any rpm. Easy to understand in the context of say computer controlled eddy current brakes. What about other cases? What about the pre electronic era? How was it done then?

Regards
Sutripta
The pre electronic era had manually adjusted dynos. No frequent preecise control ! So each speed point would probably take 2 minutes to settle.

So you repeated the test at various speed points with their attendant slow settling times.

Probably a significant portion of the engine life used to be consumed on the dyno itself !

Regds.
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