LT-4 Cold Weather Performance
Thread Starter
Instructor
Joined: Jun 2016
Posts: 191
Likes: 12
From: Kennesaw GA
LT-4 Cold Weather Performance
Do LT-4s rested timing when they're cold?
I don't beat my car when it's cold for obvious reasons but I do notice above 2,500RPM it seems like the car is holding itself back.
It may just be because I'm being a little less aggressive, though.
Any authorities on this kind of stuff?
I don't beat my car when it's cold for obvious reasons but I do notice above 2,500RPM it seems like the car is holding itself back.
It may just be because I'm being a little less aggressive, though.
Any authorities on this kind of stuff?
Race Director
Joined: May 2006
Posts: 10,691
Likes: 71
From: Phoenix Arizona
When the C4 is cold, it is running in "open loop". That means the car computer is relying on preset assumptions to run the car. When it warms up it goes into "closed loop" meaning it uses sensors to run.
Thread Starter
Instructor
Joined: Jun 2016
Posts: 191
Likes: 12
From: Kennesaw GA
Originally Posted by zr1fred
When the C4 is cold, it is running in "open loop". That means the car computer is relying on preset assumptions to run the car. When it warms up it goes into "closed loop" meaning it uses sensors to run.
I could feel something holding the car back and that makes complete sense.
Thanks for the info
Race Director
Joined: Oct 2005
Posts: 11,772
Likes: 177
From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
And just to be clear, it has nothing to do with it being an LT4
All computer controlled cars operate the zr1fred described.
All computer controlled cars operate the zr1fred described.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Air flow through the MAF
Calc'ed air flow with a MAP
Coolant temp
Inlet air temp
crank and cam speed position
..and more. So the assumptions are very limited and the information is very complete. The O2 is feed back; confirmation of A/f ratio for minor corrections primarily for emissions -not performance.
Performance should be as good as any time -though I'm not recommending that one should test that until the oil has warmed sufficiently.
Thread Starter
Instructor
Joined: Jun 2016
Posts: 191
Likes: 12
From: Kennesaw GA
Originally Posted by Tom400CFI
Whoa, whoa whoa...the LT4 (and all computer controlled cars) still use a plethora of sensors when cold, and assumes very little. In fact, it uses every sensor that it has, except for the O2 sensors (which are heated and should come online fairly quickly). So in open loop, it's still measuring:
Air flow through the MAF
Calc'ed air flow with a MAP
Coolant temp
Inlet air temp
crank and cam speed position
..and more. So the assumptions are very limited and the information is very complete. The O2 is feed back; confirmation of A/f ratio for minor corrections primarily for emissions -not performance.
Performance should be as good as any time -though I'm not recommending that one should test that until the oil has warmed sufficiently.
Air flow through the MAF
Calc'ed air flow with a MAP
Coolant temp
Inlet air temp
crank and cam speed position
..and more. So the assumptions are very limited and the information is very complete. The O2 is feed back; confirmation of A/f ratio for minor corrections primarily for emissions -not performance.
Performance should be as good as any time -though I'm not recommending that one should test that until the oil has warmed sufficiently.
