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Author Topic: Load & Boost  (Read 6249 times)
Rick
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« on: February 22, 2011, 07:18:49 AM »

Was looking at some logs earlier.  I'm requesting 190 load across the entire rpm range.  After about 5700 the actual load drops off.  I assume this is because the VE of the engine is ropping off at high rpm and the cylunders aren't being filled.

Boost is staying flat around 1.1-1.2 bar from 3000-7200rpm, which is perfect.

I can't remember how the load calculation works.  My first thought would be that the ECU would try and increase boost to maintain load, but it obviously isn't?  Requested and actual boost stay at around 1.1-1.2 bar.

Maximum pressure ratio is set to around 3, which is out of range of the MAP sensor so this shouldn't be stopping it.  What am i missing?

Also, are the main timing tables based on requested load or actual load?  At 7000rpm I only have around 140 load, so should I be tuning that load site or the requested of 190?

Rick
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elRey
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« Reply #1 on: February 22, 2011, 08:01:52 AM »

If boost actual is keeping up with boost requested then all is good. If boost is held constant thru upper RPM range, load will always decrease. If you want a constant load, then you have to increase boost as you climb thru RPMs.

20psi @ 6000 RPM is less VE than 20psi @ 5000 RPM.

I prefer an ever climbing boost curve because a flat curve feels like a plateau in power to me. Even tho the flat curve = more area under the torque curve (more over all power, faster car).
That's assuming peak boost is the same.
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Tony@NefMoto
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2001.5 Audi S4 Stage 3


« Reply #2 on: February 22, 2011, 12:06:14 PM »

The main timing tables are based on actual load, not on requested load.
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