One reason that RPMs hang is due to the engine design, or more specifically the ratio of intake manifold size (cc's after TB) to engine displacement. This can vary quite a bit engine to engine. Plus even if you slam the throttle shut, it takes some time to pull the intake down to a vacuume. Plus the challanges of being just right (not to rich nor lean) on each combustion event even though you aren't reading the specific airflow for each combustion event might drive the tuning to be more 'gentle'.
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RogerBvonCEG on that forum explained it almost exactly like I've heard Bob Lutz himself explain it:
Quote:
"Throttle Hang" is an emissions reduction technique, and it's controlled by the IAC valve.
...
Something about unburned hydrocarbons when rapidly closing the throttle, so to make sure they undergo full combustion and don't mess up emissions, the drop in RPMs is slowed to make sure there is enough air running through the engine.
He (Lutz) also used the term "dash-pot", which I assume means a kind of sticky feel in the throttle not unlike a very heavy flywheel or this 'throttle hang' thingy.
RogerBvonCEG on that forum explained it almost exactly like I've heard Bob Lutz himself explain it:
Something about unburned hydrocarbons when rapidly closing the throttle, so to make sure they undergo full combustion and don't mess up emissions, the drop in RPMs is slowed to make sure there is enough air running through the engine.
He (Lutz) also used the term "dash-pot", which I assume means a kind of sticky feel in the throttle not unlike a very heavy flywheel or this 'throttle hang' thingy.
Thanks, now how do we override it....
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Thats where GTPprix tune comes in to take care of those kind of things, but GTPprix is the better person to answer your question.
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Guys guys... this is a feature. Think about it, when you shift quickly the rpm is held for the next gear, you basically dont have to blip the throttle to rev match
It does make it a bit easier to drive for people who arent used to manual cars though.
Guys guys... this is a feature. Think about it, when you shift quickly the rpm is held for the next gear, you basically dont have to blip the throttle to rev match
It does make it a bit easier to drive for people who arent used to manual cars though.
true, and good point. I think I'm still getting used to this engine after 3 months, it's diff than I'm used to.
I can also see LVs point, get it tuned
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All of the animals except for man know that the principle business of life is to enjoy it.-- Samuel Butler
You can find me at the lake -- RODEOSOLSTICE @ YAHOO.COM
Us'ns who don't need to please the EPA Natzi can maybe have Chris take a look at getting rid of this nonsence. We didn't need it in the good old days and transmissions have come a long way since then. Learn to RPM match with your right foot and slam her home shabby.
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"An armed populace is a polite populace".
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Ponder that awhile.
Heh I have no problem with rpm matching, the clutch in my current car is like an on/off switch. Either you stall it, match it perfectly or bog it with too much rpm... theres no slipping. I simply wasnt used to the very light clutch in the solstice so thats why the rpm hang helped during shifts.
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