engine rev after shifting
03-27-2007, 02:54 PM
#13
4th Gear Member
Join Date: Feb 2007
Location: Green Mt State
Posts: 1,028
RE: engine rev after shifting
ORIGINAL: Racefiend
I've owned quite a few cars and never had one that did this. I datalogged the car to see what was happening, and what I found is that whenever you let off the throttle, the throttle plate does not close all the way. Itcloses to 7-9%, and has about a 7+ seconddecay time (it will slowly continue to close all the way during those7 seconds). This is for emissions reasons, as it is simulating a mechanical dashpot. It also does not shut off the injectors. It does it while shifting also, and is what must be causing the engine to continue revving. It's also the reason the mustang has horrible engine braking.
I've owned quite a few cars and never had one that did this. I datalogged the car to see what was happening, and what I found is that whenever you let off the throttle, the throttle plate does not close all the way. Itcloses to 7-9%, and has about a 7+ seconddecay time (it will slowly continue to close all the way during those7 seconds). This is for emissions reasons, as it is simulating a mechanical dashpot. It also does not shut off the injectors. It does it while shifting also, and is what must be causing the engine to continue revving. It's also the reason the mustang has horrible engine braking.
I have a V6 and it drives me nuts.
No longer is it possible to take your foot off the gas and "coast" downhill...
As you say, 7 seconds after you take your foot off the gas the engine speed drops 200-400 RPM and decelerates the car rather abruptly. What'sworse is if you manually downshift, it will do the same thing 7 seconds later in each lower gear.
Hopefully a tuner will work for us V6 guys as well.
Nice ride, BTW.
YouV8 guys are OK,got passed by an 07ROUSH last week and he gave ME a thumbs up!
SOHC
03-27-2007, 06:09 PM
#14
2nd Gear Member
Join Date: Nov 2005
Location:
Posts: 176
RE: engine rev after shifting
ORIGINAL: SOHCman
Is this more pronounced with automatic transmissions?
I have a V6 and it drives me nuts.
No longer is it possible to take your foot off the gas and "coast" downhill...
As you say, 7 seconds after you take your foot off the gas the engine speed drops 200-400 RPM and decelerates the car rather abruptly. What'sworse is if you manually downshift, it will do the same thing 7 seconds later in each lower gear.
Hopefully a tuner will work for us V6 guys as well.
Nice ride, BTW.
YouV8 guys are OK,got passed by an 07ROUSH last week and he gave ME a thumbs up!
SOHC
Is this more pronounced with automatic transmissions?
I have a V6 and it drives me nuts.
No longer is it possible to take your foot off the gas and "coast" downhill...
As you say, 7 seconds after you take your foot off the gas the engine speed drops 200-400 RPM and decelerates the car rather abruptly. What'sworse is if you manually downshift, it will do the same thing 7 seconds later in each lower gear.
Hopefully a tuner will work for us V6 guys as well.
Nice ride, BTW.
YouV8 guys are OK,got passed by an 07ROUSH last week and he gave ME a thumbs up!
SOHC
04-08-2007, 02:57 PM
#15
Join Date: Apr 2007
Posts: 6
RE: engine rev after shifting
I've noticed that it doesn't seem to do it all the time, though I haven't really noticed a pattern to it. But, it can also be used to your advantage when downshifting. If I'm just shifting from, say, 5th to 4th on a steep hill, when I depress the clutch, it will usually rev the engine up just enough to make it a smooth shift.
But besides that, engine braking usually isn't beneficial anyway. What engine braking is really doing is a just adjusting the brake bias (in the case of any RWD car, adding more rear-brake bias).
But besides that, engine braking usually isn't beneficial anyway. What engine braking is really doing is a just adjusting the brake bias (in the case of any RWD car, adding more rear-brake bias).
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