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Dyno operation- beginners tips?

(@gasssed)
Member

I've finally got to the point that the dyno is safe and operable. 

So now I'm faced with the concept of how to operate it "properly" to achieve the results I'm after. 

Steady state is simple enough, set the rpm and away you go. 

But the "power run" side of things, admittedly confuses me. 

 

So, questions. 

I've selected power sweep mode. 

Set the start rpm to 2000

Does the delay figure matter? 

I set the sweep rate to 500rpm per second? 

How do I determine a proper sweep rate- is 500 just a standard figure? 

I set the stop rpm above the redline of my engine? Or on the case of engine without redline- what do I set this to? 

I accelerate through the gears into fourth (1:1 ratio gear) 

I'm at a light throttle, maintaining 2000rpm. 

I hit start run/start brake control

Do I go wide open throttle before hitting start or directly after? 

If I back off before the rpm finish, I then need to hit stop manually to finish the run? 

 

Hoping that those who've been doing this far longer can help me out

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Topic starter Posted : 10/02/2021 11:24 am
(@admin)
Member Admin

Hi,

Delay in the power sweep means the delay from when you first reach the start RPM (2000 RPM in your case) and the time the sweep starts. 

There are two ways to do it. Either you ease into the start RPM, then once you reach start RPM you floor the throttle. Then in the "Delay" period the RPM will stabilize at 2000. Then the sweep starts. You keep full throttle all the way until your end RPM. A that point clutch goes in and you coast down to the start RPM to measure the drag. This drag is added to the wheel power to estimate Engine HP. 

The other way is to have 0 or very little Delay, but to add a reasonable figure in the "Ramp up brake to xx% before run starts". In that case you can just floor the throttle before the run starts and let it start with no delay. 

You don't need to select a 1:1 ratio gear ratio. The gear ratio is anyway different since you have a diff etc. Generally the highest gear is best, unless you hit the max speed of the dyno. 

Sweep rate is up to you. 500RPM/sec can be fine, but you should go lower if you have a small RPM window you want to test. Generally you want to test from the lowest RPM you are interested in (no-one cares what power you have just above idle...) and up to to the engine's RPM limit and the run should be slow enough that boost has built up etc. If in doubt, go slower. Sometimes if you have a very high strung engine you don't want to test the full RPM range every time. So this is all up to you. The dyno does not care what the RPM limit of your engine is. 

 

This post was modified 2 months ago by admin
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Posted : 10/02/2021 6:12 pm
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