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Discussion Starter · #1 ·
Alright, I was reading around on all kinds of stuff and fell over a post about gear ratios and how the horse power was distributed through out the gears.

The article was about bikes with a maximum power output that wasn't near the red line of the rev limiter and the importance of shifting at the right time instead of just letting it go all the way on the RPM each gear.
I found a such example here. Max power is at ~13.000 rpm. Article stated it would be far better to calculate your point of rpm that gave the least difference in HP per gear you're changing out of and in to. So, for example, you would shift up at 14.700 rpm where you have around 100hp to next gear where you would hit 11.800 rpm and still have 100hp at your disposal.


I sat down and did all the numbers just because I was curious about to see what RPM you're landing on when shifting gears and how much power you got.
Of course having max power at the red line means if you want max power you should go to the red line in all gears.

So it makes no sense to do the calculation. Anyway... if someone finds it interesting:

(Stock) Gear ratio
1 2.467
2 1.765
3 1.400
4 1.182
5 1.043
6 0.958

I found a Ducati 848 Evo dyno chart and made assumptions from that


Formula:
RPM when shifting * next gear ratio / current gear ratio = RPM in next gear

The charts should be read like, Shifting gear from 1st to 2nd at 10800 RPM would mean you land on 7727 RPM in second gear with 100.99 horse power at your disposal.
Calculations goes as following:

 

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A slightly curious approach. This probably only really applies to flat-out race-track riding.

The equally (or more) important part of this story is that slightly different type of power output referred to as torque.

Although pamphlets and sales-people obsess about horsepower, torque is the engine character more relevant to most road-riding.

If you worked it out, you would probably find that the rev at which you change up gears relates more to the torque delivery curve than the horsepower output. At least on the road.

And torque delivery in the middle revs is Ducati's 'strong suit', as I have discussed previously. I just had a bit of a ride on mine, and rarely exceeded 5,000 RPM.

I probably only exceed 8,000 briefly, and occasionally, on the road. It gets revved 'til the lights blink on the track, but not often on the road.

The fact that the torque starts to be delivered at much lower RPM than the peak horsepower is the characteristic that makes the Ducati engine so effective in variable conditions.

We can let the revs drop as we negotiate difficult or unexpected conditions, and get immediate response again when we need it. Without the wait for revs to build or changing down two or three gears, like on an in-line four..

:p
 

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A couple of different considerations here.

First, red line is primarily a factor of engine durability. The manufacturer says don't rev higher than this or you'll wear your engine prematurely and sets either a hard or soft limiter there. This does not necessarily (and usually doesn't) correspond with peak horsepower. For the Evo, max horsepower is at 10,000rpm with the soft limiter at 10,750 (per Ducati). And just like the dyno graphs show, you will get several hundred rpm extra beyond peak horsepower. So it's not necessarily a good idea to run it to the limit - I would argue it's a terrible idea because the more you bounce off the limiter the greater your chance of torpedoing the motor IMO.

As for the shift lights, these are usually adjustable and should be referenced either to max hp or just after in an attempt to maximize hp for the next gear ratio. Of course they can be set simply to redline. I couldn't tell you where they're usually set stock, but I set mine to max hp because I feel getting into the next gear and riding the higher torque and rising hp are more important than holding the gear for an extra 1000 rpm. And as you get into the latter gears where the ratios are closer to 1, there's a smaller hp gap between gears so it doesn't really matter much, just shift at the peak.

I think the bottom line, specifically for racers trying to max-perform the bike, is know where your peak hp is and shift there. From experience I can tell you that you definitely can feel where the hp plateaus at its peak. The bike seems to "run out of breath." Some bikes are more pronounced here with wider plateaus than others.
 

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In the context of track riding/ racing this seems like what one would pursue as perfection. Although, in the real world, on a race track, at speed there exists many variables. Of the tracks i frequent there are many points where i let the motor over rev in order to carry the gear i want to use for the corner. And there's places where i lug it a bit to avoid spinning or wheelieing on a corner exit. That said, i use a programmable dashboard (Starlane Davinci) that allows the user to adjust the tacho and shift light. And mine is set to come on at the maximum horse power point, not maximum revs. So, on the stretches i try to time upshifts to keep the blue "shift" light lit up. Thereby basicly achieving what your chart is saying.
If one were drag racing this would be what everything was about.
 

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Exactly. It struck me as a drag racing approach.

And yes - of course on track we are often compromising our final gearing and choice of gear ratio to suit various corners and straights between them, and to allow us to use lower revs over bumpy patches etc..

But the virtue of the Ducati is that its torque is delivered well before it makes a lot of horsepower. (Torque, in simple terms, tends to drive the bike forward, whereas horsepower can tend to spin the rear and lift the front, as well as, obviously, move things along..).

And higher revs tend to make rear suspensions work harder, so there are many virtues to having torque delivered thousands of revs before there is a lot of horsepower available.

Makes them easier to ride under all conditions. The IL4s I mentioned tend to get those high horsepower symptoms whatever you do as the torque is delivered only slightly before the horsepower, and accessing it can give those 'hard to ride' issues.

So Ducati riders are all just pussies really.. :flash:

But a lot of IL4 guys get into Ducatis and really love the difference. Once they get out of the habit of revving it unnecessarily..

:eek:
 

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Discussion Starter · #6 ·
A couple of different considerations here.

First, red line is primarily a factor of engine durability. The manufacturer says don't rev higher than this or you'll wear your engine prematurely and sets either a hard or soft limiter there. This does not necessarily (and usually doesn't) correspond with peak horsepower. For the Evo, max horsepower is at 10,000rpm with the soft limiter at 10,750 (per Ducati). And just like the dyno graphs show, you will get several hundred rpm extra beyond peak horsepower. So it's not necessarily a good idea to run it to the limit - I would argue it's a terrible idea because the more you bounce off the limiter the greater your chance of torpedoing the motor IMO.

As for the shift lights, these are usually adjustable and should be referenced either to max hp or just after in an attempt to maximize hp for the next gear ratio. Of course they can be set simply to redline. I couldn't tell you where they're usually set stock, but I set mine to max hp because I feel getting into the next gear and riding the higher torque and rising hp are more important than holding the gear for an extra 1000 rpm. And as you get into the latter gears where the ratios are closer to 1, there's a smaller hp gap between gears so it doesn't really matter much, just shift at the peak.

I think the bottom line, specifically for racers trying to max-perform the bike, is know where your peak hp is and shift there. From experience I can tell you that you definitely can feel where the hp plateaus at its peak. The bike seems to "run out of breath." Some bikes are more pronounced here with wider plateaus than others.
the red line was more a term of end-of-the-rpm-spectrum, if you compare with the Gixxer on top there's clearly a difference in when the curve peaks.
 

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Discussion Starter · #7 ·
You can make the same charts with torque if you want.

As stated in the first post, it makes no sense to do this calculation for HP on the this bike as the peak is so near the end of the scale. The reason why I posted was just for the sake of it, maybe someone was as unknown as me and didn't get how it was working :blah:
 

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Exactly. It struck me as a drag racing approach.

And yes - of course on track we are often compromising our final gearing and choice of gear ratio to suit various corners and straights between them, and to allow us to use lower revs over bumpy patches etc..

But the virtue of the Ducati is that its torque is delivered well before it makes a lot of horsepower. (Torque, in simple terms, tends to drive the bike forward, whereas horsepower can tend to spin the rear and lift the front, as well as, obviously, move things along..).

And higher revs tend to make rear suspensions work harder, so there are many virtues to having torque delivered thousands of revs before there is a lot of horsepower available.

Makes them easier to ride under all conditions. The IL4s I mentioned tend to get those high horsepower symptoms whatever you do as the torque is delivered only slightly before the horsepower, and accessing it can give those 'hard to ride' issues.

So Ducati riders are all just pussies really.. :flash:

But a lot of IL4 guys get into Ducatis and really love the difference. Once they get out of the habit of revving it unnecessarily..

:eek:

interesting point, I love my EVO, but I also still own my '94 CBR600F2, the 600 is so easy to ride in town, lug it down to 30mph in 6th gear and it still moves along smoothly, take the EVO on the highway and it will eat the miles smooth and easy. I love to ride the torque wave of my Ducati. 4000-7000rpm = same fun as 10,000-13,000rpm on my Honda.
 
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