This is intended to be a relatively simple explanation of some of the elements of a Dyno Chart.

I may present something rather simplisticly for the purpose of making a point and maybe you think I  present

some ideas incorrectly.... in either case I welcome feedback and will gladly update the page to aid understanding.

 

This page came about after a certain lack of understanding on the Fazer Site www.foc-u.co.uk and

I thank Hamos for his (albeit unwitting) contribution of the measured charts.

 

More specifically, in a discussion of the Dyno Curve of the FZ6 people seemed to have the mis-understanding that the charts

presented did not show the notorious "mid-range power gap". I think a deeper understanding of the charts will

show that the charts do indeed show a hole in the power delivery.

 

The chart below was published by Hamos as a stock, unmodified FZ6.

 

 

 

 

I have seen other charts from the FZ6 that are similar to this and believe that it is a good representation on the unmodified bike.

 

I have also heard various people say that this shows there is no loss of power in the mid-range.

 

But I'm afraid there is a loss... it is just that a curve of the horsepower is hard to translate into how the bike feels on the road.

 

And the reason is... when riding a bike you do not feel horsepower; you feel ACCELERATION and acceleration comes from the PUSH that is given by the TORQUE that the engine is giving.

 

 

 

 

 

This is an important bit to understand.... you only feel the PUSH that comes from TORQUE... you do not feel anything related to HORSEPOWER.

Lets just think about this a bit more.... if this statement was not true and you did feel horsepower then the curve above would be saying that your bike felt more and more powerful as the revs got higher.... look at the curve; at 3k revs it says you have 26bhp (about the same as the 125cc bike you learnt on) and at 7k revs it says you have 48bph (almost double and something like a 250cc hack) and at 10k revs it says you have 75bhp (three times more power).

 

 

 

If you feel that the question 1 is true then you may as well ride a 125cc bike most of the time because unless you rev over 7k you are only getting 125cc performance. You can test this question by sitting at traffic lights on your 600c bike next to a 125cc bike and race each other away... but you cannot go over 6k revs.... who will win? You or the "similarly powered" 125cc bike?

 

If you feel that question 2 is true then you are on the path to understanding Dyno Curves.... you only feel TORQUE not horsepower.

 

 

 

 

OK, so you now are beginning to realise that maybe horsepower is not what you feel on the bike but since torque and horsepower are related what's the problem?

A quick glance at the above Dyno Curve appears to show that horsepower is continually increasing and the un-tutored person may well conclude that this means torque is also continuously increasing... BUT THIS IS NOT THE CASE!!

 

 

 

 

 

 

 

 

There are two particular bits of the curve that cause concern and these are highlighted here... there are two bits of the curve that are flat (highlighted in red) and some bits of the curve where the slope of the line changes (two changes are highlighted in blue).

 

 

 

 

 

 

 


So why should a flat bit or a change in slope matter?

 

ALL THE FOLLOWING GRAPHS HAVE BEEN PRODUCED FROM REAL TORQUE TO HORSEPOWER CALCULATIONS PERFORMED IN EXCEL.

 

Let's have a look at TORQUE.

 

 

 

This is a simple Dyno Chart showing horsepower only.

 

What torque produced this steadily increasing curve?

 

Look at the next graph...

 

 


 

 

 

 

 

This is the TORQUE... a nice constant torque over the entire rev range.

 

Let's look at three curves showing the TORQUE and the Horsepower together...

 

 

 



 

 

 

 

 

 

 

 

 

 

 


 

 

 

Look carefully and you can see that a constant Torque produces an evenly rising Horsepower and that more Torque means the Slope is greater.

 

 

 

 

 

 

 


Well real Dyno curves have more "lumps and bumps" than this so let's now introduce some features to the curve... let's have the Horsepower tail off at the top end....

 

 

 

Notice how when the Torque curve starts to drop down the Horsepower slope only starts to even out... the PEAK HORSEPOWER happens after the TORQUE starts to drop down.

 

 

 

 

Let me highlight this change of slope effect with another graph....

 


 

 

 

 

Notice that the HORSEPOWER SLOPE changes and this is due to a DECREASE in TORQUE.

 

IE the Horsepower is still rising after the Torque start falling.

 

The rider feels this "horsepower slope change" as a DECREASE in PUSH.

 

 

 

 


 

 

So we can now relate the drop at the top of a Dyno curve to that "running out of steam" feeling that we are all familiar with.

 

And we can also relate a gentler slope on a Dyno Curve as a ALSO a "running out of steam" feeling.

 

 

 

What about the FLAT bits of the curve I mentioned at the top? Let's look at them....

 

This is a Horsepower curve with a flat bit and the Torque that produced it....

 

Notice that the Flat Horsepower Curve comes from a DECREASE in TORQUE. This is just like the graph above where the slope decreased but here the Torque goes down much quicker so the Horsepower slope decreases to a FLAT.

 

This is important because a rider FEELS TORQUE and if the TORQUE DECREASES the PUSH DECREASES and the rider feels this loss of PUSH.

 

Therefore, a rider will feel a FLAT Horsepower curve as a LOSS OF PUSH.

 


 

Study the above graph carefully... if you don't understand it then you won't understand why the FZ6 has a hole in it's power band.

 

Let me put up another graph of Horsepower....

 

 

This is similar to the previous graph with a flat bit in the middle.... but it has steeper slope after the flat bit....

 

 

Can you predict what the TORQUE will look like?

 

And, more importantly, can you imagine what the rider will feel?

 

 


 

 

The answer is here....

 

The flat portion of the Horsepower curve comes from a decrease in Torque and the steeply rising horsepower after the flat bit gives a rising Torque.

 

Remember the RIDER FEELS TORQUE so the rider feels PUSH drop off around 4k revs and then at 8k revs feels the PUSH come back rapidly.

 

This is a HOLE IN THE POWER CURVE !!!!!!

 

The "HOLE" is not seen in the Horsepower Curve but is very evident in the TORQUE Curve.

 


 

Let me repeat that last staement: The "HOLE" is not seen in the Horsepower Curve but is very evident in the TORQUE Curve.

 

 

 

Right, let's move onto the real curve given at the top of the page for the un-modified FZ6. Here it is transferred to my graphs.

 

 

Look at the curve carefully and there are flat spots and changes of slope....

 

 

So what does the rider feel?

 

 

To know that we must convert this to TORQUE...

 


 

This is the TORQUE curve...

 

 

Now the effects are not as large as those in my graphs above (because I was using large changes to make the points clear) but you can see the TORQUE falls off and then rises.

 

After 8k rpm the torque is running at around 38 to 40 foot-pounds. BUT before that the torque had dropped down to almost 30 foot-pounds.

 

This is felt by the rider as a LOSS of PUSH of around 20 to 25%

 

 


 

This is the FZ6's HOLE IN THE POWER BAND that is mentioned so often in the biking press.

 

 

 

If Hamos doesn't mind me reproducing his chart for his modified bike, you can see that he has made significant improvemnts.....

 

All these curves are after modifications to the bike.

Notice how the curves for horsepower and therefore torque are higher than the stock bike so the rider feels MORE PUSH over the whole range.

 

Notice how the Horsepower curves do NOT have the same FLAT bits so the TORQUE doesn't decrease like the stock bike so the rider DOESN'T feel a LOSS OF PUSH.

 

Notice how the Horsepower curve is a much straighter line so the TORQUE curve is much more constant.

 

 

 


 

 

 

All in all a dramatic improvement over the stock figures. Well Done!!!