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I will be having my bike/new engine ('05 EFI) build dyno tuned this month in Phoenix. I'll be riding it in AZ until spring when I return to Colorado (I spend winters only in Tucson). I've assumed that the EFI will "automatically" compensate for altitude changes between AZ and CO. Is this correct? Will a good tuning job done in Phoenix still be a good tune at CO altitude? Thanks.
 

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I had my SERT installed and the bike dyno tuned (T. Bagger) at Frederich Co. which I believe is about 6,000 ft in elevation. Rid it back to Michigan which is about 200 ft in elevation and it still runs perfect. No coughs, backfires, and the engine runs about 20* cooler than before the SERT install. That wuz about 4,000 miles ago.
 

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I was "told" that the tune would be good regardless of altitude (by a power commander tuning center), but I am not an expert and do not know for sure. Hopefully someone with knowledge will let us all know for sure.
 

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My bike has a PC111r and has been dynoed at about 4000ft.
It runs fine but completely different at higher and lower
altitudes. It becomes a bit sluggish at around 7000+ and runs
like a rocket ship at sea level.
 

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nvsteve said:
My bike has a PC111r and has been dynoed at about 4000ft.
It runs fine but completely different at higher and lower
altitudes. It becomes a bit sluggish at around 7000+ and runs
like a rocket ship at sea level.
The closer to sea level the better the air....the better the air the more compression....the more compression the better the power.
To answer your question, even though the HP is down at 7000 feet the AFR is adjusted to the thinner air through the ECU giving you a good AFR.
Not to worry...computers will take the readings of the air and compensate with the correct amount of fuel.
 

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kjtrot said:
Doc
I thought that happened only with closed EFI systems not the Harley open ones?
The ECM takes readings from 5 sensors such as absolute barometric pressure, air intake temp, engine temp, throttle position, etc. from these signals the ecm selects a map from the programed look up tables. If the barometric pressure changes the ECM will change the fuel delivery to match the engines needs.
Its not like a closed loop system where if I changed the pipes the ECM will learn how much fuel to add to the new volume of air flowing through.....open loop will however measure the amount of oxygen in the air and compensate for it.
 

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hdmd88 said:
T.....open loop will however measure the amount of oxygen in the air and compensate for it.
Indirectly, I think. Rather than "measure", Open Loop systems make assumptions about oxygen content based in part on atmospheric pressure. They are designed to compensate within the expected range of pressures (altitudes).

Just as an interesting tidbit: They would also compensate for thunderstorms, since any change in pressure is interpreted as a need to adjust the mixture appropriately.

Sorry if I seem to be nit-picking, Doc. No disrespect intended.
 
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