Manual transmission drivers
Thread Starter
Le Mans Master
Joined: Sep 2003
Posts: 8,847
Likes: 795
From: Longview Texas
Manual transmission drivers
Has anyone observed that under "braking only" in 3rd or 4th, that the engine RPM stays high and then drops, almost like an automatic transmission downshifting?
(This is before pushing in the clutch or taking shifter out of gear)
(This is before pushing in the clutch or taking shifter out of gear)
Safety Car
Joined: Sep 2000
Posts: 3,604
Likes: 396
From: Austin, TX
Only had my car one week but I've noticed some odd behavior like that. I think it is only when rev matching is on but I haven't really paid enough attention to it to tie it down to specific conditions.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
I believe that's the Active Rev matching as well---Even the autos do the same thing--They blip the throttle at downshifts---Until you get used to it ---it seems strange---but it is actually a good thing and easier on your drivetrain---It really depends on you speed how severe the rev matching RPM change is---
While you are braking--the TCM is "anticipating" a downshift-so it hold the RPM--If you decide NOT to downshift--it will briefly hold the RPM--Nature of the beast of ARM---Why some people don't like it-----On my auto C7---I love it !!!!!---Even when paddle shifting in manual mode--Just took me awhile to get used to it---
While you are braking--the TCM is "anticipating" a downshift-so it hold the RPM--If you decide NOT to downshift--it will briefly hold the RPM--Nature of the beast of ARM---Why some people don't like it-----On my auto C7---I love it !!!!!---Even when paddle shifting in manual mode--Just took me awhile to get used to it---
Pro
Joined: May 2000
Posts: 739
Likes: 67
From: Wichita Kansas
FedEx Bowl 4 St. Jude '09
St. Jude Donor '09-'10-'11-'12-'13-'14
Not to hi-jack, but I think this is on the same lines with my 7 speed.
I'm doing around 60 on the highway and come to road construction zone, instead of braking I just let off the gas and coast. For the first 5 seconds the car decelerates normally then all of a sudden something else kicks in like the computer is taking over and it starts to slow down a lot more rapidly, almost like another clutch kicks in or something, doesn't feel like brakes.
Someone try this on theirs and see if I am dreaming this up.
Edit - I was thinking it could be eco mode kicking in, but I run in sport mode all the time, exhaust open all the time. So it shouldn't be kicking into eco unless the manual is not correct.
I'm doing around 60 on the highway and come to road construction zone, instead of braking I just let off the gas and coast. For the first 5 seconds the car decelerates normally then all of a sudden something else kicks in like the computer is taking over and it starts to slow down a lot more rapidly, almost like another clutch kicks in or something, doesn't feel like brakes.
Someone try this on theirs and see if I am dreaming this up.
Edit - I was thinking it could be eco mode kicking in, but I run in sport mode all the time, exhaust open all the time. So it shouldn't be kicking into eco unless the manual is not correct.
Last edited by Jstockton; May 22, 2014 at 08:46 AM.
Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
if you have not pressed in the clutch then it is not rev matching.
what you are experiencing is the ECM modulating the throttle blade (remember these are not cable driven, they are computer controlled). the ECM can control engine braking and deceleration rates independently of the throttle position. this is not new, it's been this way since around 2001, I believe.
in the old ECMs we called it Throttle Cracker and Throttle Follower. the new ECMs have gone away from this form of management (airflow) and now use Torque Based models to control the airflow and spark, etc.
these items are fully adjustable with a tune. however, I haven't seen much yet for the C7 in the way of idle tables (where these adjustments typically take place). it's still fairly basic, more to crack and decode I suppose.
what you are experiencing is the ECM modulating the throttle blade (remember these are not cable driven, they are computer controlled). the ECM can control engine braking and deceleration rates independently of the throttle position. this is not new, it's been this way since around 2001, I believe.
in the old ECMs we called it Throttle Cracker and Throttle Follower. the new ECMs have gone away from this form of management (airflow) and now use Torque Based models to control the airflow and spark, etc.
these items are fully adjustable with a tune. however, I haven't seen much yet for the C7 in the way of idle tables (where these adjustments typically take place). it's still fairly basic, more to crack and decode I suppose.
Thread Starter
Le Mans Master
Joined: Sep 2003
Posts: 8,847
Likes: 795
From: Longview Texas
Not to hi-jack, but I think this is on the same lines with my 7 speed.
I'm doing around 60 on the highway and come to road construction zone, instead of braking I just let off the gas and coast. For the first 5 seconds the car decelerates normally then all of a sudden something else kicks in like the computer is taking over and it starts to slow down a lot more rapidly, almost like another clutch kicks in or something, doesn't feel like brakes.
Someone try this on theirs and see if I am dreaming this up.
Edit - I was thinking it could be eco mode kicking in, but I run in sport mode all the time, exhaust open all the time. So it shouldn't be kicking into eco unless the manual is not correct.
I'm doing around 60 on the highway and come to road construction zone, instead of braking I just let off the gas and coast. For the first 5 seconds the car decelerates normally then all of a sudden something else kicks in like the computer is taking over and it starts to slow down a lot more rapidly, almost like another clutch kicks in or something, doesn't feel like brakes.
Someone try this on theirs and see if I am dreaming this up.
Edit - I was thinking it could be eco mode kicking in, but I run in sport mode all the time, exhaust open all the time. So it shouldn't be kicking into eco unless the manual is not correct.
What you describe is the same thing I am observing. It is almost like the car tries to maintain the speed until it realizes you are trying to slow down, then the engine RPM drops and it changes its rate of deceleration. To me, it was almost like you are not getting any engine braking, and then you do.
At least we are not all dreaming...
Drifting
Joined: Jul 2007
Posts: 1,454
Likes: 4
From: Massapequa NY
NOTE: Rev matching is definitely off.
What you describe is the same thing I am observing. It is almost like the car tries to maintain the speed until it realizes you are trying to slow down, then the engine RPM drops and it changes its rate of deceleration. To me, it was almost like you are not getting any engine braking, and then you do.
At least we are not all dreaming...
What you describe is the same thing I am observing. It is almost like the car tries to maintain the speed until it realizes you are trying to slow down, then the engine RPM drops and it changes its rate of deceleration. To me, it was almost like you are not getting any engine braking, and then you do.
At least we are not all dreaming...
Last edited by vetehead; May 22, 2014 at 07:16 PM.
I'm Batman..
Joined: Apr 2014
Posts: 6,142
Likes: 921
From: Lehigh Acres FL
Tech Contributor
Mine does this too and I have a base so no eLSD. I noticed also when downshifting, ARH on or off, that after putting it in gear and starting to let off the clutch, the gear grabs when the pedal is closer to the bottom, and then when still bringing the pedal up it seems to grab again at the top of the pedal travel. It noticeable jerks the car. Acts like there are two clutches engaging.. Weird..
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Le Mans Master
Joined: Sep 2003
Posts: 8,847
Likes: 795
From: Longview Texas
Former Vendor
Joined: Oct 2007
Posts: 2,032
Likes: 6
From: longview tx
Guess ill have to go and drive my car when i get a free min and see if i can get it to do this and scan it and see if i can see what is making it do it. I bet it is in the tune and could be adjusted