What is this called? Re: Coasting down a hill
What is this called? Re: Coasting down a hill I asked this question a long time ago, maybe a year, and can't seem to find the thread about it. So I'll ask again.
Everyday I drive down a hill when coming home. While going down the hill, I have the car in 4th gear and I'm just coating. As the car speeds up, so do the RPM's obviously, but when the RPM's reach around 1900, the car ever so slightly jolts, the exhaust tone slightly changes, and the car no longer speeds up but rather stays right at 1900 RPM. Now I was told that this is normal and is a system that the car uses to save fuel. It senses that the car is coasting w/o load and it shuts off the fuel to save gas, which would explain why the A/F doesn't read squat. Does this sound familiar to anyone? Does this "feature" have a name?
Following my cam swap, I noticed that my car won't do this anymore, which dissapoints me because anything to save gas is worth having, and it's a long hill to go down. If anyone knows what happened that would be great. I am getting the car tuned this Saturday and would like to have the tuner re-activate this feature if possible. It helps a ton for my everyday driving. This feature would be in use about 10 miles on my daily commute, which is money in the bank. Thanks a lot guys!
Everyday I drive down a hill when coming home. While going down the hill, I have the car in 4th gear and I'm just coating. As the car speeds up, so do the RPM's obviously, but when the RPM's reach around 1900, the car ever so slightly jolts, the exhaust tone slightly changes, and the car no longer speeds up but rather stays right at 1900 RPM. Now I was told that this is normal and is a system that the car uses to save fuel. It senses that the car is coasting w/o load and it shuts off the fuel to save gas, which would explain why the A/F doesn't read squat. Does this sound familiar to anyone? Does this "feature" have a name?
Following my cam swap, I noticed that my car won't do this anymore, which dissapoints me because anything to save gas is worth having, and it's a long hill to go down. If anyone knows what happened that would be great. I am getting the car tuned this Saturday and would like to have the tuner re-activate this feature if possible. It helps a ton for my everyday driving. This feature would be in use about 10 miles on my daily commute, which is money in the bank. Thanks a lot guys!
TECH Addict
Joined: Jul 2002
Posts: 2,261
Likes: 0
DFCO - Deceleration Fuel Cut Off - There is an RPM to enable by Gear and an RPM to disable by Gear within the PCM. There are also Minimum Speed ( mph vs kPa) to enable and Delay ( COT on/off vs millsecs). Hope this helps some.
joel
joel
TECH Addict
Joined: Nov 2001
Posts: 2,662
Likes: 1
From: LaConner WA
I'm not finding this DFCO in my HPtuner ? Is this an adjustable parameter ? I've always wondered what this affect was also because our LS1's don't have alot of compression braking and when this DFCO kicks in it increases compression braking by alot. The trouble is that it doesn't kick in early enough or in a predictable enough manner to depend on it and I'd like to change that if I can.
On another note what does COT have to do with DFCO ? COT just adds fuel to cool off the cats based on a time/TPS % factor correct ? Sorry to ask so many questions, but I'm very new to this, I just got my HPtuner a few weeks ago.
On another note what does COT have to do with DFCO ? COT just adds fuel to cool off the cats based on a time/TPS % factor correct ? Sorry to ask so many questions, but I'm very new to this, I just got my HPtuner a few weeks ago.
FormerVendor
Joined: Jan 2003
Posts: 525
Likes: 0
From: Melbourne, Australia
Originally Posted by Ferocity02
Thanks, I dont know what any of that stuff means, after the DFCO part. Why do you think changing the cam would deactivate this system?
