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Old 01-14-2016, 05:14 PM
olddog olddog is offline
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Quote:
Originally Posted by Phill Pollard View Post
Olddog,

Your statement isn't entirely true. You were good up until you gave the 4000 feet comment.

Speed Density systems actually DO compensate for altitude on the fly without having to turn the key on/engine off (KOEO). They do it by sensing the manifold pressure (via the MAP) every time it sees WOT (via the TPS or Full Throttle switch on a minimum function system).

So on your way up that 4000' mountain, every time you push the throttle to the floor the ECM sees atmospheric pressure (since man vac drops to 0"Hg) and notes it as BARO.

I have seen ONE instance where a customer drove his car over a very long distance with a *gradual* rise in elevation without ever having to floor the gas pedal and he got a CEL out of it. That's one instance in over 25 years of EEC work so it is rare.


Hope That Helps,

Phill Pollard
Phill,

Thanks for the correction (I don't want to put bad info out). I never studied Speed Density in great detail, but read a bit. I do not recall anyone ever pointing out that it will correct the Baro at WOT (not doubting you). That is not intuitive that they could do that because vacuum would not necessarily drop to zero at WOT. At high rpm WOT, I would expect there to still be a bit of vacuum. Otherwise the claims of a bigger TB increasing power is BS.

Rick
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