Applying brake = loss of throttle response!!
12-18-2002, 06:52 PM
#1
Guest
Posts: n/a
Applying brake = loss of throttle response!!
So I'm browsing forums and come across a piece of information that says: when the brake pedal is pressed the engine throttle response drops to only around 20%. This can apparently have an adverse affect on heel/tow downshifting. However, I feel 'only 20%' throttle response sounds way low from my experience in the car when I have heel/toe shifted.
The post also stated all that needs to be done to defeat this safety feature is to pull a fuse.
I confirmed this information in the service manual, but it did not state the actual percentage of throttle response decrease.
Apparently the Brake Switch sends a on/off signal to the ECM via the stop lamp switch which in turn decreases the engine speed.
I, for one, am then aggrivated at Nissan for using the throttle-by-wire as a selling point to the car. Quick and linear throttle response is a good thing.
The question I have is: Why increase the cost of the car to incorporate this technology then disable it's full potential in the name of apparent safety??? Beats the **** outta me.
So... from what I got out of the manual, this feature can be disabled by unplugging the brake switch (different than the stop lamp switch) or pulling a fuse. Fair enough. Now the ECM does not know to dial down throttle response. But..... the ECM is smarter than that.
Apparently the ECM monitors the frequency of the Brake Switch input. If no signal is received for an "extremely long time" then the ECM enters fail-safe mode. Now the throttle response is poor ALL the time.
This information is a little bumming.
Then I thought... It may be possible to unplug the Brake Switch, then plug it back into a cut-and-snipped modified replacement OEM part that can then send a short activation signal in a preset 'not quite so extremely long' interval.
I have no freak'n clue how to go about that myself though.
If any of you guys think this is an important issue and have the know-how to do this, please post instructions.
Look at the EC-538 section of the service manual to see what I am talking about.
The post also stated all that needs to be done to defeat this safety feature is to pull a fuse.
I confirmed this information in the service manual, but it did not state the actual percentage of throttle response decrease.
Apparently the Brake Switch sends a on/off signal to the ECM via the stop lamp switch which in turn decreases the engine speed.
I, for one, am then aggrivated at Nissan for using the throttle-by-wire as a selling point to the car. Quick and linear throttle response is a good thing.
The question I have is: Why increase the cost of the car to incorporate this technology then disable it's full potential in the name of apparent safety??? Beats the **** outta me.
So... from what I got out of the manual, this feature can be disabled by unplugging the brake switch (different than the stop lamp switch) or pulling a fuse. Fair enough. Now the ECM does not know to dial down throttle response. But..... the ECM is smarter than that.
Apparently the ECM monitors the frequency of the Brake Switch input. If no signal is received for an "extremely long time" then the ECM enters fail-safe mode. Now the throttle response is poor ALL the time.
This information is a little bumming.
Then I thought... It may be possible to unplug the Brake Switch, then plug it back into a cut-and-snipped modified replacement OEM part that can then send a short activation signal in a preset 'not quite so extremely long' interval.
I have no freak'n clue how to go about that myself though.
If any of you guys think this is an important issue and have the know-how to do this, please post instructions.
Look at the EC-538 section of the service manual to see what I am talking about.
12-18-2002, 07:48 PM
#2
New Member
Join Date: May 2002
Location: Atlanta
Posts: 1,026
Likes: 0
Received 0 Likes
on
0 Posts
I've read the same comments that you have. I think the general cause for concern all started when SCC printed their first article about the production 350Z. Basically, they were not able to do a burnout for their cover shot. I believe they disconnected the brake switch to rectify the problem.
As for heel/toe, I have just recently begun practicing heel/toe myself on my Z. So far I've only gained the dexterity to do it at a slow/moderate pace. Basically I'm undergoing light braking while blipping the throttle. I've probably blipped to no higher than 4000rpm as of yet.
In any case, I haven't felt any noticable cut in power. In a couple weeks maybe I'll be able to report on more aggressive braking and downshifting.
Anyone with more heel/toe experience than me care to report?
Keep in mind that when heel/toeing, you only need enough gas to get the engine to rev in neutral. And once you let the clutch out--during heel/toe--you want the engine to slow down anyways. At least until you reach corner entry speeds, but then you take your foot off the brakes and there should no longer be a problem with cut power.
Where there might be a more serious problem is if you want to do some left foot braking.
--
Jeff
As for heel/toe, I have just recently begun practicing heel/toe myself on my Z. So far I've only gained the dexterity to do it at a slow/moderate pace. Basically I'm undergoing light braking while blipping the throttle. I've probably blipped to no higher than 4000rpm as of yet.
In any case, I haven't felt any noticable cut in power. In a couple weeks maybe I'll be able to report on more aggressive braking and downshifting.
Anyone with more heel/toe experience than me care to report?
Keep in mind that when heel/toeing, you only need enough gas to get the engine to rev in neutral. And once you let the clutch out--during heel/toe--you want the engine to slow down anyways. At least until you reach corner entry speeds, but then you take your foot off the brakes and there should no longer be a problem with cut power.
Where there might be a more serious problem is if you want to do some left foot braking.
--
Jeff
12-18-2002, 07:53 PM
#3
it was an article in SCC that I got the information from, they werent real happy about it either. after reading their story, it did seem like they fixed something that wasnt broken by creating driveby wire. I understand drive by wire steering, cause then the steering wheel can move, but the pedals arent ajustable...
owell. you could maybe use something that builds up a charge then releases it, but I donno... maybe an ECU upgrade will rectify this problem? or is the drive by wire computer seperate?
owell. you could maybe use something that builds up a charge then releases it, but I donno... maybe an ECU upgrade will rectify this problem? or is the drive by wire computer seperate?
12-18-2002, 08:22 PM
#5
Charter Member #34
Join Date: May 2002
Location: -
Posts: 1,228
Likes: 0
Received 0 Likes
on
0 Posts
actually, i just read the passage in the service manual...
the brake switch is the same as the stop lamp switch. the ASCD switch is the cruise control "Stop" switch...
see below.. the stop lamp switch sends battery voltage to the ecu when the brake is pressed...
on 2nd thought about my clutch recommendation...
i wouldnt do it there, since the ecu will lower the RPM when the clutch would be pressed.. not good for matching revs..
here is a better idea... hook a switch next to the vdc button which can cut the signal going to the ecu.
this makes it easy to do everything before "spirited" driving. you would leave the switch normally on, so the ecu doesnt get mad... then when its fun time, you hit VDC off and "brake" off...
get it?
i will do this on the weekend and let you all know how it goes.. also, i will find out how long before the ECU throws the MIL for not seeing the brake input. (i guess this has to be really long, since i can cruise control for an hour without braking will on the highway....)
m
the brake switch is the same as the stop lamp switch. the ASCD switch is the cruise control "Stop" switch...
see below.. the stop lamp switch sends battery voltage to the ecu when the brake is pressed...
on 2nd thought about my clutch recommendation...
i wouldnt do it there, since the ecu will lower the RPM when the clutch would be pressed.. not good for matching revs..
here is a better idea... hook a switch next to the vdc button which can cut the signal going to the ecu.
this makes it easy to do everything before "spirited" driving. you would leave the switch normally on, so the ecu doesnt get mad... then when its fun time, you hit VDC off and "brake" off...
get it?
i will do this on the weekend and let you all know how it goes.. also, i will find out how long before the ECU throws the MIL for not seeing the brake input. (i guess this has to be really long, since i can cruise control for an hour without braking will on the highway....)
m
12-18-2002, 08:23 PM
#6
Registered User
To me, the throttle response (maybe I'm using the wrong term, but I'm talking about the time delay between the moment you blip the throttle and when the engine revs) on the Z seems pretty poor all the time. Do you really notice a difference when the brake is on? I haven't, but I'll pay attention tomorrow and see if I can even tell. It seems like we may be worried about something that we won't really notice anyway.
Although it does bug me a bit that it is there.
-D'oh!
Although it does bug me a bit that it is there.
-D'oh!
12-18-2002, 08:43 PM
#7
Charter Member #34
Join Date: May 2002
Location: -
Posts: 1,228
Likes: 0
Received 0 Likes
on
0 Posts
some more information...
you can read most below, but here are some highlights:
1) the dtc (P1805) is stored when the brake signal is not detected by the ecu for "an extremely long time..." whatever that is.
2) the check engine will NOT turn on if there is an error, but the car will not let you accelerate properly until it sees the signal again.
i am glad i have an obd2 scanner, since it can show dtc even when there is no CE light...
here is the official word:
you can read most below, but here are some highlights:
1) the dtc (P1805) is stored when the brake signal is not detected by the ecu for "an extremely long time..." whatever that is.
2) the check engine will NOT turn on if there is an error, but the car will not let you accelerate properly until it sees the signal again.
i am glad i have an obd2 scanner, since it can show dtc even when there is no CE light...
here is the official word:
Trending Topics
12-18-2002, 08:52 PM
#8
good luck, I think many of us will be needing a "VDC replacement switch" soon. just scratch off the letters and a perfectly sized switch for burns on demand.
as for throttle response, I have not noticed this problem...
tho really, anyone that wants to go play with their car, do a test, hold the brake and nail the throttle, see how high the revs go, now of course out of gear, on flat surface, hit the throttle the same way without the brake on. the outcome should be a higher max rev acheived with the brake off.
as for its implications on the track, they dont apply to me just yet. but hopefully Ill get to do a driving school at road atlanta one day. then Ill need it.
as for throttle response, I have not noticed this problem...
tho really, anyone that wants to go play with their car, do a test, hold the brake and nail the throttle, see how high the revs go, now of course out of gear, on flat surface, hit the throttle the same way without the brake on. the outcome should be a higher max rev acheived with the brake off.
as for its implications on the track, they dont apply to me just yet. but hopefully Ill get to do a driving school at road atlanta one day. then Ill need it.
12-19-2002, 06:48 AM
#9
Originally posted by SKiDaZZLe
actually, i just read the passage in the service manual...
the brake switch is the same as the stop lamp switch. the ASCD switch is the cruise control "Stop" switch...
see below.. the stop lamp switch sends battery voltage to the ecu when the brake is pressed...
on 2nd thought about my clutch recommendation...
i wouldnt do it there, since the ecu will lower the RPM when the clutch would be pressed.. not good for matching revs..
here is a better idea... hook a switch next to the vdc button which can cut the signal going to the ecu.
this makes it easy to do everything before "spirited" driving. you would leave the switch normally on, so the ecu doesnt get mad... then when its fun time, you hit VDC off and "brake" off...
get it?
i will do this on the weekend and let you all know how it goes.. also, i will find out how long before the ECU throws the MIL for not seeing the brake input. (i guess this has to be really long, since i can cruise control for an hour without braking will on the highway....)
m
actually, i just read the passage in the service manual...
the brake switch is the same as the stop lamp switch. the ASCD switch is the cruise control "Stop" switch...
see below.. the stop lamp switch sends battery voltage to the ecu when the brake is pressed...
on 2nd thought about my clutch recommendation...
i wouldnt do it there, since the ecu will lower the RPM when the clutch would be pressed.. not good for matching revs..
here is a better idea... hook a switch next to the vdc button which can cut the signal going to the ecu.
this makes it easy to do everything before "spirited" driving. you would leave the switch normally on, so the ecu doesnt get mad... then when its fun time, you hit VDC off and "brake" off...
get it?
i will do this on the weekend and let you all know how it goes.. also, i will find out how long before the ECU throws the MIL for not seeing the brake input. (i guess this has to be really long, since i can cruise control for an hour without braking will on the highway....)
m
12-19-2002, 08:11 AM
#11
Charter Member #34
Join Date: May 2002
Location: -
Posts: 1,228
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by ares
just for the record I sat in my car, in nuetral, clutch out. reved the car with brake down, and not. there was no difference in the Max RPMs acheived....
just for the record I sat in my car, in nuetral, clutch out. reved the car with brake down, and not. there was no difference in the Max RPMs acheived....
m
12-19-2002, 10:31 AM
#12
Charter Member #55
Join Date: May 2002
Location: Austin, TX
Posts: 890
Likes: 0
Received 0 Likes
on
0 Posts
In my experiences, the only time the throttle response is reduced is while in gear, clutch pedal out, brake applied, and throttle applied.
I will try again, but IIRC, the throttle response with the clutch in, brake applied, during a downshift seems to be the same as normal driving. But accelerating, if you left foot brake and floor the accelerator with your right, you will not accelerate at all. As soon as you lift off the brake, you will get full acceleration.
JD
I will try again, but IIRC, the throttle response with the clutch in, brake applied, during a downshift seems to be the same as normal driving. But accelerating, if you left foot brake and floor the accelerator with your right, you will not accelerate at all. As soon as you lift off the brake, you will get full acceleration.
JD
12-19-2002, 10:42 AM
#13
Registered User
Join Date: Oct 2002
Location: Montana
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
I have experienced no engine peculiarities while performing heel toe downshifts. However, the article in SSC bothered me, and while it's not really necessary trail brake that aggressively, I don't appreciate the over protective, Nissan mother either.
To execute a simple throttle response while braking test, i found a nice slick surface. I tried various combinations of simultaneous brake and throttle with VDC off.
When the rear slips it acts just like it does in the dry. When the front slips, things get messy. When both the front and rear are attempting to slip, the car becomes confused and befuddled. The ABS will fart, shudder, and pop while the engine will drop RPM with no clear connection to the accelerator pedal. I then tried the same test on dry pavement. I did not push it to the point of making the front or rear wheels slip but the engine was more than willing to provide thrust.
My decision was that unless it becomes confused on the track I won't need to modify the VDC operation.
However, If I get the chance, I will modify whatever system/mechanics that causes the RPM's to linger before dropping. It acts as though the flywheel is overly massive, but then again, it could be the flyby wire electronics.
koryo
To execute a simple throttle response while braking test, i found a nice slick surface. I tried various combinations of simultaneous brake and throttle with VDC off.
When the rear slips it acts just like it does in the dry. When the front slips, things get messy. When both the front and rear are attempting to slip, the car becomes confused and befuddled. The ABS will fart, shudder, and pop while the engine will drop RPM with no clear connection to the accelerator pedal. I then tried the same test on dry pavement. I did not push it to the point of making the front or rear wheels slip but the engine was more than willing to provide thrust.
My decision was that unless it becomes confused on the track I won't need to modify the VDC operation.
However, If I get the chance, I will modify whatever system/mechanics that causes the RPM's to linger before dropping. It acts as though the flywheel is overly massive, but then again, it could be the flyby wire electronics.
koryo
12-20-2002, 09:12 AM
#17
Registered User
Join Date: Sep 2002
Location: Canada
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
It may engage only when the wheels slip. It kills all throttle input from the driver and TCS takes over to controll the situation, once traction is restored she's back to normal.
12-20-2002, 12:16 PM
#18
Registered User
Join Date: Oct 2002
Location: Montana
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
>This discussion has nothing to do with VDC.
true, my mistake.
It should have read "My decision was that unless it becomes confused on the track I won't need to modify the ECM operation."
koryo
true, my mistake.
It should have read "My decision was that unless it becomes confused on the track I won't need to modify the ECM operation."
koryo
12-20-2002, 05:23 PM
#19
Registered User
Join Date: Oct 2002
Location: AZ
Posts: 359
Likes: 0
Received 0 Likes
on
0 Posts
Can you switch the TCS off in th Enthusiast model? I understand that the VDC and TCS are the same switch in Performance up, just wondering about the Enth. and TCS.
Not sure if I want Enth. or Perf.
Not sure if I want Enth. or Perf.
12-20-2002, 07:23 PM
#20
iTrader: (1)
Join Date: May 2002
Location: Plano (Dallas), TX
Posts: 671
Likes: 0
Received 0 Likes
on
0 Posts
The enth. has only the TCS switch, all models are drive by wire, including base.... All have this "problem." There is a good article in the most recent Sport Compact Car that talks about.
One thing I will say (from reading the article), I am glad that the Z has "good" throttle response, they make it sound like the IS300 has some serious lag (If my memory serves)....
One thing I will say (from reading the article), I am glad that the Z has "good" throttle response, they make it sound like the IS300 has some serious lag (If my memory serves)....
Thread
Thread Starter
Forum
Replies
Last Post
Colombo
Forced Induction
35
11-09-2020 10:27 AM
