Car takes awhile to rev down
04-28-2010, 11:48 AM
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Car takes awhile to rev down Driving around, when i go to shift it stays revd. It goes down but seems to go down to 2k, then 1.5k then to 1k in a 3 step increment. This has happened since I had a pcm4less tune. Any ideas what It is? I i figure its some sensor.. i have LT1 Edit now so if i need to change something.. TPS maybe?
04-28-2010, 11:50 AM
#2
Driving around, when i go to shift it stays revd. It goes down but seems to go down to 2k, then 1.5k then to 1k in a 3 step increment. This has happened since I had a pcm4less tune. Any ideas what It is? I i figure its some sensor.. i have LT1 Edit now so if i need to change something.. TPS maybe?
05-13-2010, 03:06 PM
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That same thing happened to me on my 97 camaro. I got a PCMforless tune and it did the exact same thing after the tune. It ended up being his issue and he fixed it free.
05-13-2010, 09:13 PM
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wonder if this is part of it? I was just reading about lt1 tuning on this website today, and remembered this..........
DFCO
This leads us to DFCO, deceleration fuel cut off. This controls fuel cutoff when the throttle is closed and the car is moving, to enable engine braking. So, as mentioned above, when your RPMs are up and you let off the gas pedal, this table will enter play.
The way to tune these values is to log your car and determine a few things:
•What is the highest MAP value reached when coasting begins? This can vary depending on your RPM and speed, so look for the highest value whenever coasting starts. Use that value, or 1 less, for your "DFCO MAP Enable" value.
•What is the highest MAP value reached when you'd like engine braking to stop? It will usually be at least 3-5kPa higher than the above value. You will use this value for your "DFCO MAP Disable" value; but, be careful you don't set it too high, or you will run into engine stalling when coming to a stop.
•In what RPM range would you like engine braking to occur? Set the "Enable" value to the RPM above which the engine must be for DFCO start, and the "Disable" value to the RPM when you want DFCO to stop.
•Lastly, how "hard" do you want the engine braking to be? By increasing "DFCO Spark Retard," you will be increasing the rate of deceleration; lowering the retard value will make engine braking slower/smoother. There may be times when your total timing will be 0°, if you set this value high enough and your "Closed TPS Timing" values low enough. That will make for pretty fast engine deceleration.
DFCO
This leads us to DFCO, deceleration fuel cut off. This controls fuel cutoff when the throttle is closed and the car is moving, to enable engine braking. So, as mentioned above, when your RPMs are up and you let off the gas pedal, this table will enter play.
The way to tune these values is to log your car and determine a few things:
•What is the highest MAP value reached when coasting begins? This can vary depending on your RPM and speed, so look for the highest value whenever coasting starts. Use that value, or 1 less, for your "DFCO MAP Enable" value.
•What is the highest MAP value reached when you'd like engine braking to stop? It will usually be at least 3-5kPa higher than the above value. You will use this value for your "DFCO MAP Disable" value; but, be careful you don't set it too high, or you will run into engine stalling when coming to a stop.
•In what RPM range would you like engine braking to occur? Set the "Enable" value to the RPM above which the engine must be for DFCO start, and the "Disable" value to the RPM when you want DFCO to stop.
•Lastly, how "hard" do you want the engine braking to be? By increasing "DFCO Spark Retard," you will be increasing the rate of deceleration; lowering the retard value will make engine braking slower/smoother. There may be times when your total timing will be 0°, if you set this value high enough and your "Closed TPS Timing" values low enough. That will make for pretty fast engine deceleration.
