Effects of Elevation on Performance - Fifth Generation VFR's

I recently returned from a two-week trip on my 2000 VFR.  I was riding solo, carrying approx. 80 lbs. of gear.  While riding in the Durango, Colorado, area, I thought I felt reduced power from what I have gotten used to the in the last six months of owning this bike.  I then rode in sub 3000' elevations for the next ten days or so and the bike supplied all of the power I could have wanted.  As I was coming home through Albuquerque (approx. 6000'?), I thought I felt the bike was down on power again.  Returned home to the Phoenix area and been riding the bike unladen and it seems to have as much power as ever.

Just before leaving on my trip, I had performed all maintenance/tune-up tasks, including changing the plugs and checking valve clearances.  I was very careful in labeling and putting all hoses on the air box back where they came from.

I thought a fuel injection system made adjustments to altitude changes, minimizing changes in performance as altitude changes.

My question is, is it normal to experience a noticible loss in performance at higher altitude?  Am I imagining things?  Did I mess something up when peformaining maintenance?

Any thoughts on this would be much appreciated.

That was perfectly normal. Even most cars can't adjust enough for those high elevations and a 00's fuel computer is alot less refined compared to most cars. No worrys.

Oh and welcome to the forum!

[image: View Post]Napper, on 27 June 2012 - 01:18 PM, said:

I thought a fuel injection system made adjustments to altitude changes, minimizing changes in performance as altitude changes.


What it does is adjust the amount of fuel so that the mixture stays at an optimal ratio. At altitude there is less oxygen, so it feeds in less gas. Less oxygen + less gas = less power. The drop off here in Boulder, at about 5300', is about 15%.

As I was rideing in the Italian Alps last summer, the only thing I notised was that going uphill the engine temps were werry high, but performance, well, enough for me and the twisty hairpin alp roads :smile:
I think highest point was around 3000m, but mostly arounsd 2000m passes.

When I was out in the Colorado/Utah area few years ago on my '91, about 6k-7k feet is where I noticed a big change in power.

Every vehicle will suffer power loss at altitude Except Turbo charged ones! :tour:

Altitude is not the only thing that reduces power.  Humidity, temp., and barometric pressure all play a role.  Bonneville is only 4000 ft +/-, but density altitude during Speedweek can range anywhere between 6200 and 7500 on a given day.  This is one reason why record runs are in the morning.