Hi,
For the completion I added the original curves from Honda (from the shop manual, printed 1965).
I will compare this curve with the other curves, but it is already clear to see that Honda also
worked with a brake "dyno" setup, hence the lack of data bellow the 3500 rpm.
I scanned the original, and stretched it a bit to the ratio I prefer so that I can compare the curves.
Jensen
CB450 K0 dynojet and why it doesn't need a five speed trans
Hi,
I tried to make an overlay of the three curves, but I decided it was easier to extract the data from each curve and transport it to an Excel sheet. I have three different curves, my own dyno runs, the curve shown in the manual, and the curve shown in the article of a Dutch motorcycle magazine. From this point I call my dyno curve “curve dyno”, the curve in the manual “curve manual”, and last but not least the curve shown in the article “curve article”. There are two CB450 K0 curves (dyno curve and manual curve) and one CB450 K1 curve (curve article). Is it fair to compare all three curves ?, I think it is, because it also shows the differences between the engines. The dyno curve shows a rear wheel measurement curve, the manual curve shows a shaft output curve, and the article curve shows both. I like to compare only one type of curve, rear wheel curves or shaft output curves. Earlier I explained that a shaft output power curve is mathematical extracted from a rear wheel power curve, I choose for rear wheel power curve, because that’s the curve which is directly measured. The problem is that the manual doesn’t give the rear wheel power curve, but when I can extract that curve from the shaft output power curve I can compare all three curves. But how can I extract this curve from the shaft output curve ? The difference between both curves is the transmission loses, and for simplicity, the loss is a factor from the shaft output power curve. But how big is this factor ? A simple way to find out is to extract that factor from the article curves, because that’s the only diagram with both curves. I calculated that the factor between those curves is 1,426, so “rear wheel power curve * 1,426 = shaft output power curve” I took the same factor the calculate the rear wheel power curve from the shaft output curve shown in the manual. I know it is from a scientific approach not correct, but gives enough information to compare the curves. The curves are shown in the below illustration. Jensen
assembly of Japanese motorcycles requires great peace of mind (Pirsig)
Hi,
Now we can compare the curves more closely, so what can we say about it ? Remember that this is only a theoretical comparison, and one cannot say much about the absolute numbers. Then we have SAE, DIN and many other differences between dyno’s and the way it is measured. I also used the factor extracted from the article curves to calculate the manual curve, but who says that this factor is correct for the K0, and is this factor correctly determined at Delft ? Honda claimed 43 Hp @ 9000 rpm shaft output power from a CB450 K0 and 44 HP @ 8000 rpm for the CB450 K1. In the curves I extracted, the manual curve gives indeed the highest power @ 9000 rpm, but my own bike reaches that point at 8000 rpm (hence the red curve). The K1 curve reaches that point indeed at 8000 rpm, but the output is a few HP lower then my K0. But, despite all the differences, the curves are remarkably similar, especially the shapes of the curves. We see that the red curve (my CB450 K0 dyno curve) represents the strongest engine, it is even stronger than then the K1 and the K0 in the manual, so do I have a very strong engine ? Maybe yes, maybe no, remember this is no absolute comparison. However I do think that my engine is a good example how good a “real” engine can be, compared to the manual curve, but like I stated earlier, it’s not scientific correct. The only thing I can say that the engine in my bomber delivers an output of 32 Hp, and that is a good figure. On the street, a few months ago in Germany, lying flat, no wind, it did 170 km/hr (105,63 mph) @ 10 something rpm (GPS Garmin Zumo 550, see track information). In the morning, the same day, in Germany, a little foggy, it was hitting 171 km/hr (106,25 mph), but I'm sure I saw a top speed of 177 km/hr (109,98 mph) on the screen of my GPS (a very short period). The given 171 km/hr is the average over 427 meters. So, on the road it does reach an astonishing 177 km / hour at 10.000 rpm, and that isn’t bad at all (hence the blue colored pipes, this bike is hot). But are the maximum ratings really that interesting ? No, it’s fun to compare (and to ride it legal at those speeds), but the real interesting information is hidden in the shape of the curves. It shows that only the dyno curve gives information from the lower regions, I explained earlier why. The manual curve has more or less the same shape as the dyno curve until 6000 rpm, It is hard to say the same about the CB450 K1 curve, because there is not enough information, especially below 4000 rpm. Next to that the curve is steeper then both other curves. It seems not very important, but later we will see (when I extracted the torque curves) why it is important and how it translated to a certain behavior on the road. In the next update I will show the torque curves, and that is far more interesting then the power curves, it will reveal why people experienced the K1 as a much better bike (according to many people) then the K0. But in my opinion the K1 is an easier bike (to ride) than the K0, and that makes it seem a better bike, hence the title of this thread, Jensen
assembly of Japanese motorcycles requires great peace of mind (Pirsig)
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