Adding an high altitude switch to an european K75?

[frodef]

So as I've mentioned elsewhere my K75 trekked south across the alps to spend the winter where the sun does shine, while I'm now sitting here waiting for the snow and ice that is imminent, thinking about the not-so-imminent trek back north. Across those same alps, I suppose.

Going above 2000 meters altitude or so, the engine was noticeably less responsive, and at 2500 meters going up the steepest and twistiest hills it was like driving a heavy moped, frankly. Reading the lieberry etc. I understand the US bikes has a "high-altitude plug".

Would it be feasible to add this to my european K75C? Is it just a matter of finding the right electrical terminals and short them? Has anyone done this, or can point me to the relevant information?

Thanks

[Inge K.]

Is it just a matter of finding the right electrical terminals and short them?

Yes, two different metods is used on the L-jetronic equipped models.

1. Bridge #9 (green/red) & #11 (black) at the jetronic connector, ie. add 12V+ to #11
(wiring and female connector for #11 isn't present on European models).

2. Bridge #9 (green/red) & #3 (white/brown) at the jetronic connector, ie. add 12V+ to #3
(this is similar to TPS in WOT position, ie enrichment).

[frodef]

Thanks Inge. Are these two methods identical from the jetronics viewpoint? Seems to me the easiest would be to hook into the TPS connector.

[Inge K.]

Are these two methods identical from the jetronics viewpoint?

I would guess whatever metod you use, you would achieve the same result.....a richer mix.
Both metods is used forth and back........Early K100's using metod 1, late metod 2.
On the K75's it's the other way around  :dunno2:
All 75's respectively K100's using the same L-jetronic ECU both early and late models.

[kioolt]

Aren't you already running a richer mixture at high altitude because of the thinner air?

[Inge K.]

Aren't you already running a richer mixture at high altitude because of the thinner air?

Yes, you're correct about that.....But on the other hand, when the TPS is in WOT position 12V+ is added to
contact #3 at the jetronic connector and the fuel mix is enriched.
When the high altitude plug is connected it just add 12V+ to contact #3 at the jetronic connector (metod 2).
So it doesn't quite make sense..... :dunno2: .

[wmax351]

It's richer relative to the opening of the airflow meter flap. So basically, at the lower air densities, the flap is pushed less given the amount of air that makes it into the cylinder. At higher altitudes, the volumetric efficiency of an engine increases: The exhaust is more fully evacuated by the lower air pressure.


Part of the issue is you will just lose power based on altitude (without either a turbocharger or a multi stage supercharger). I had my K75 at 14,300 feet (4300 meters) and it ran fine. I had to crank the fast idle (choke) to the second notch to keep it idling, but it was fine otherwise. At 14,000 feet, the air is about half the pressure: so there is about 50 percent of the available power at WOT. This is also the amount of power before any internal losses in the engine: these remain the same regardless of the altitude.

Switching the altitude plug on and off in this case, I didn't notice any real changes. This was a tired engine already, so might have masked the changes.


http://wahiduddin.net/calc/calc_hp_dp.htm