Long canyon drive, loss of power, high elevations

[Jaybird09]

I have a awesome little scoot (Honda pcx 150) that I drive every where. And I mean I drive this thing all over the place. I live in utah and we have some big, long and high elevated drives. I went up a smaller canyons all summer and it has always handled great, last night I decided I would take it up a Ogden canyon and hit powder mountain. It was doing awesome till I got bout half way (45 miles) up the canyon (this is a steep and big mountain drive) and as the air got much much cooler and as I got higher up the canyon the power just seem to go away. I was cruising up the bottom of the canyon at a cozy 50-55 but the higher I got the slower the scoot went. At one time I was only pushing 32-33 mph and I had to pull over and let traffic go around. Frustrated and confused of never having this problem before I turned around and head back, I gained power as I came down witch made me start to think... Is the thinner, cooler air at high elevations causing my scoot to loose so much power to cruise at 50 all the way down to 30? I'd like to hear what y'all think would have caused this.... I have drove it all morning into the afternoon and she has all the power she has ever had and runs perfect. :hmm:

[finaljudgement]

Altitude definitely affects a motor's performance. You don't say whether your scoot is fuel injected or has a carburetor. If it fuel injected the computer should correct for the change in altitude. With most cars, the altitude reading is taken when the vehicle is first turned on. If you gain a lot of elevation, you need to stop and start again for the computer to measure outside air pressure. With carbs, you don't get as much vacuum since the outside air pressure has dropped. The cold temps actually help by making the air more dense. If you lived in Taos, elevation around 9000 feet, you would have to reject the carb because of the elevation change.

Finaljudgement

[Jaybird09]

My scoot is fuel injected. And I am suppose to go again this weekend. I hope can figure out the problem

[inuyasha]

Hi
Your fuel injection will maintain the correct fuel/air ratio at the new higher altitude. But at the same time the reduced amount of air available at this altitude will require a reduction in the amount of fuel to maintain the correct ratio.
This will produce a reduced power output.
Take care and ride safely my friend
Yours Hank

[skuttadawg]

Yes higher altitude has thinner air . EFI should should make some adjustments but they may not have it rich enough .

My scooter dealer has a scooter with the same EFI engine as mine but on a diff body , he installed an injector for a 250cc ( we both have 150ccs ) and had to get a plug for a 32I BMW since the wire was diff than that of the 150 wire . With a modded airbox and Cherrybomb muffler it was running at 13 to 1 fuel spectrum on a dyno that rated it at 12.5 HP at the rear wheel .

Most have a closed system to where only a dealer could mod the CPU instead of anyone with a home computer . I would check out www.ecotrons.com and see if they have a larger injector or if their CPU with software will work on your Honda . If you buy their EFI kit you can set up the timing curve and option to have a RPM limit or not ETC .

I have seen 2 programmable modules that piggyback to a stock CPU in order to make it richer and remove RPM limit , but could not find a simple person or report on of using it on an Echarm like mine so I did not want to spend 200 on junk or fry anything

[Bob Shaw]

Ok, I'll take a different take on this (nothing unusual). Reading your post about the long elevated drives (this is a steep and big mountain drive), is it possible that your scoot was starting to overheat, and bog down? Is it possible that your valves are getting a little tight, maybe contributing to the problem? I kinda figure, a 150cc scoot, and 45 miles up a steep canyon road, I think that's a tall order for a 150.

[inuyasha]

Ok, I'll take a different take on this (nothing unusual). Reading your post about the long elevated drives (this is a steep and big mountain drive), is it possible that your scoot was starting to overheat, and bog down? Is it possible that your valves are getting a little tight, maybe contributing to the problem? I kinda figure, a 150cc scoot, and 45 miles up a steep canyon road, I think that's a tall order for a 150.
Hi Bob
The Honda PCX 150 is liquid cooled so i dont think hes over heating and the engine puts out 13BHP so should have no problems with that kind of distance
Its most likely the efi and higher altitudes
Take care and ride safely
Yours Hank

[qwertydude]

It's simply the uphill. The altitude of even 10,000 foot high mountains would only be 10.1 PSI vs sea level which is 14.7. This means on a fuel injected scooter you lose 31% power.

Combine that with the fact that you can't downshift to put more power to the ground and on a CVT it's a combination for sluggishness. Less power output overall combined with a CVT that may have heavy weights in it to provide lower RPM's for MPG. Adds up to a loss in speed on uphills.

But on long uphill rides you never seem to notice the inclination which is why you feel like you have no power. You literally don't. The solution would obviously be lighter roller weights or sliders to keep the engine in its powerband but then you'll lose mpg and your engine will be revvy all the time. That's kinda the downside with roller weight CVT automatic transmissions.

[cheapeto]

some reading for you.
http://www.thunderproducts.com/dial_a_jet.htm

BRed over at totalruckus has installed one of these on his BR.

Maybe it's something that could help you. Looks pretty straight forward to install.

After rejetting (not Dial-a-jet) mine, and swapping out roller weights, resetting idle, mine has a lot more power. I still need to drill out my exhaust and and do a hot engine valve adjustment, to squeek a bit more.

[gitsum]

The Honda fuel injection should do a good job of keeping the fuel mixture correct at higher elevations. It sounds like less available oxygen in the thin air in conjunction with a steep grade is just too much for the stock PCX 150's capabilities.

The stock airbox will probably have a small snorkel hose inside that you could either remove or replace with something larger. The EFI should be able to compensate for the extra air flow at lower elevations and it should give you a little more air and power at higher elevation.

You could also tune the variator with some lighter Dr. Pulley slider weighs that should allow the engine to run higher rpm's during WOT throttle acceleration, which could be a big help when bogging down on inclines.