Dyno graph for Pcx 125, 125esp and 150esp

[wingz]

I'm going to use my ears and put the money towards a long ratio gear.

[wingz]

I would like full throttle to result in peak power (eg 8000rpm regardless of speed).

My USA 2013 PCX150 pretty much does that after just changing to 12 gram DrPulley sliders. full throttle pulls see the rpms climb quickly right up to 7.900 rpm where it stays until the gearing is maxed out around 50-55 mph.

On full throttle pulloff, at what speed do your rpms reach 7900?

Now I see what you are talking about re the drop in rpm's from the progressive torque slot. I will video my 150 with 12gm sliders to compare.

I would be very interested to see this video.

[sendler2112]

Here is another good dyno video posted by Pcxdeamon.
.
http://www.youtube.com/watch?v=wr_ftfA2Mtg
.
They have their weights set to pull at 8,200 rpm. You can see the rpm drop from the torque slot at 0:40 where it drops to 7,900. And redline is 9,200 on this bike as seen on the tach gauge on the. Also important to note when looking at dyno charts of scooters is that the power read out seems to be dependent on some arbitrary setting that the operator types in as a calibration. And appears to be influenced by the changing gearing of the CVT. Watching the second pull on the video, you can see the center gauge climb quickly to peak power by 0:36. The tach on the left is already at 8,200. Where it stays until the second profile of the torque slot pulls the belt more quickly down in the rear pulley to lose gearing multiplication, dropping the rpm to 7,900 at 0:40. And apparently dropping the power from 18.5 back to 16.
.
The problem I have with trying to glean any absolute power numbers from these dyno tests is that the indicated power never makes it back up to the same peak number even though the rpm climbs again after the weights lock out. At 0:45 the rpm is back to 8,200 but the power only reads 17.5. The indicated power should come back to be the same for any given rpm. The 16 that is pictured at 0:40 is really only dropping to 17 compared to the high of 18.5. So this tells me that rear wheel dyno tests are heavily influenced by an assumed or extrapolated gearing parameter that weighs on the final numbers in the chart.
.
The apparent power loss due the action of the two stage torque slot is not quite as large as these dynos seem to show. It is partially due to a quirk in the testing. How do we really know what the 18.5 is? Is it in horsepower or another similar unit. Is it really 18.5 as shown by the earlier peak or 17.5 at the same rpm later in the run
.
The power band of their 190cc PCX is a bit narrow, falling off again above 8,700 as shown on the right gauge at 0:46. 10% longer gearing with a bigger vario or longer final gears, or at least tuned sliders to let the stock variator of the PCX150 push the belt out all the way, would help high speed cruise performance quite a bit to get the cruise rpms back down to 8,200 at 65 mph.

[Mgalutia88]

What needs to be kept in mind is that crank hp and rwhp are different. As the ratio gets longer the gearing advantage drops and hp will drop.

[sendler2112]

As the ratio gets longer the gearing advantage drops and hp will drop.

The topic of torque versus horsepower spawned a weeks long discussion on several different threads that branched off in all directions including airplane props and rocket engines in space. It is a very common misconception but believe it or not, rear wheel power versus engine rpm on a dyno is exactly the same regardless of what gear you are in. Torque goes up with shorter gearing as the wheel speed goes down. But the power curve measures the same in any gear.
.
http://www.cbr250.net/forum/cbr250-perf ... -half.html
.

[Pcxdemon]

That power loss at 8400 is due to Takegawa camshaft. It's lift design is made to work with stock valve springs and obviously designed to work best in the inner city environment where engine speeds don't fully max out.
Yuminashi cam is better in that regard and they will supply harder progressive valve springs to avoid valve float at higher rpms and will actually make good power all the way to 9300rpm.
The reason Takegawa cam was used in this video was due to high comp set up of the engine and Takegawa cam comes with decomp feature for easier start, Yuminashi cam doesn't so they had trouble starting the engine without it.

[wingz]

The reason Takegawa cam was used in this video was due to high comp set up of the engine and Takegawa cam comes with decomp feature for easier start, Yuminashi cam doesn't so they had trouble starting the engine without it.

How does the decompression feature work?

[Mgalutia88]

Great question.

[Pcxdemon]

How it works..someone more technical may answer that question better. I know it has an removable attachment next to one of the lobes,i assume an intake one? Takegawa cam comes without it supplied but it has made provision for it that one can reuse from the stock cam. The only thing is you need a press to remove the bearing to get to it..

[sendler2112]

That power loss at 8400 is due to Takegawa camshaft.

Similar to the stock camshaft which we have been assuming peaks at 8,000 rpm.

[waspmike]

How it works..someone more technical may answer that question better. I know it has an removable attachment next to one of the lobes,i assume an intake one? Takegawa cam comes without it supplied but it has made provision for it that one can reuse from the stock cam. The only thing is you need a press to remove the bearing to get to it..

Keep the exhaust valve slightly open when the engine is stopped, works centrifugally. Above about 200 rpm it ceases to function.

[wingz]

How it works..someone more technical may answer that question better. I know it has an removable attachment next to one of the lobes,i assume an intake one? Takegawa cam comes without it supplied but it has made provision for it that one can reuse from the stock cam. The only thing is you need a press to remove the bearing to get to it..

Keep the exhaust valve slightly open when the engine is stopped, works centrifugally. Above about 200 rpm it ceases to function.

Conceptually I think I get what you are saying. Did you read that somewhere or figure it out?

I posted some nice links here: http://www.hondapcx.org/viewtopic.php?f=2&t=2011
But regarding decompression, they explain the result - not how it is achieved.

[waspmike]

How it works..someone more technical may answer that question better. I know it has an removable attachment next to one of the lobes,i assume an intake one? Takegawa cam comes without it supplied but it has made provision for it that one can reuse from the stock cam. The only thing is you need a press to remove the bearing to get to it..

Keep the exhaust valve slightly open when the engine is stopped, works centrifugally. Above about 200 rpm it ceases to function.

Conceptually I think I get what you are saying. Did you read that somewhere or figure it out?

I posted some nice links here: http://www.hondapcx.org/viewtopic.php?f=2&t=2011
But regarding decompression, they explain the result - not how it is achieved.

Sorry Wingz I missed this one.

Well I looked at the widget on a PCX camshaft and then did a bit of Googling. Same idea is used on Honda ATV's

Like this



Or



May not be exact but similar in principle.