An end to BTL?
03-09-2007, 08:52 PM
#1
AudiWorld Super User
Thread Starter
An end to BTL?
As a result of the responses to my earlier post (a few below) which implied that Left foot braking can minimize BTL, I opened up the faithful 2.7T Study guide PDF, now at home on www.allroadfaq.com.(thank you Uber.)
I did a simple search for 'brake' and up came the text that says the Brake Light switch and brake pedal switch is an integrated switch. One sends signals to the lights; then to the other which sends a signal to the ECU. The pedal switch is used to deactivate the cruise AND (here it comes) to help stabilize the idle, telling the ECU that the brake is depressed so the ECU needs to go into it idle program. These details are mentioned in some fail safe emergency text on page 38.
The pathways of the two switch functions are noted on page 55.
++++++++++
The text:
"Brake light switch F and brake pedal switch F47 are combined as a unit. Both serve as information senders for "brake operated", which means they are redundant (for safety reasons).
Brake light switch F is open in the "off" position and is supplied with voltage from terminal 30. It serves as an additional information input for the Motronic.
Brake pedal switch F47 is closed in the "off" position closed and is supplied with voltage from terminal 15. It serves exclusively as an information input for the Motronic."
+++++++++++
It is possible that the signal that is generated by this switch and travels on terminal 15 can be prevented from going to the ECU.
IMO, the diagram on Page 62 shows the paths and also would indicate that the signal that goes to the ECU can be stopped.
Other text does indicate that the throttle angle sensor also controls idle so this function should not be affected.
I have a strong feeling that this may just end the BTL.
On a second note, the clutch pedal also has a similar switch to induce idle during shifts and rest. This switch msy have been the one to cause my "safe mode" attacks. Because one of the specific areas this switch effects is the torque increase of the engine...ie Turbo Pressure. Now I'll get unde the dash and take a look.
I did a simple search for 'brake' and up came the text that says the Brake Light switch and brake pedal switch is an integrated switch. One sends signals to the lights; then to the other which sends a signal to the ECU. The pedal switch is used to deactivate the cruise AND (here it comes) to help stabilize the idle, telling the ECU that the brake is depressed so the ECU needs to go into it idle program. These details are mentioned in some fail safe emergency text on page 38.
The pathways of the two switch functions are noted on page 55.
++++++++++
The text:
"Brake light switch F and brake pedal switch F47 are combined as a unit. Both serve as information senders for "brake operated", which means they are redundant (for safety reasons).
Brake light switch F is open in the "off" position and is supplied with voltage from terminal 30. It serves as an additional information input for the Motronic.
Brake pedal switch F47 is closed in the "off" position closed and is supplied with voltage from terminal 15. It serves exclusively as an information input for the Motronic."
+++++++++++
It is possible that the signal that is generated by this switch and travels on terminal 15 can be prevented from going to the ECU.
IMO, the diagram on Page 62 shows the paths and also would indicate that the signal that goes to the ECU can be stopped.
Other text does indicate that the throttle angle sensor also controls idle so this function should not be affected.
I have a strong feeling that this may just end the BTL.
On a second note, the clutch pedal also has a similar switch to induce idle during shifts and rest. This switch msy have been the one to cause my "safe mode" attacks. Because one of the specific areas this switch effects is the torque increase of the engine...ie Turbo Pressure. Now I'll get unde the dash and take a look.
03-09-2007, 11:25 PM
#2
end BTL? possibly. sound dangerous? yes.
i have not read the 2.7t study guide yet, so this is an uninformed opinion. but just from your post where you said "they are redundant (for safety reasons)". hmmm... sounds like a good idea to me.
i really don't mind btl. btl might have changed the way i drive the ar, but that is fine with me
i really don't mind btl. btl might have changed the way i drive the ar, but that is fine with me
03-10-2007, 01:49 AM
#3
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I have a bad clutch switch, and it doesn't effect turbo pressure(I think), but if you want to try an
experiment drive in 2nd gear without using throttle while rolling, and push clutch in repeatedly. On my allroad when you push in clutch sometimes the engine releases smoothly, and sometimes it bucks/surges. I think the torque the switch adjusts is the "torque idle offset" which is one of the things that can be adjusted using lemmiwinks, and don't think it will have any effect on your "safe mode" problems.
03-10-2007, 05:51 AM
#6
Interesting....
Probably an easier thing to do is just adjust the plunger on the brake light switch. Adjust it so it has no extra travel to activate the brake system. If this switch is the cause then this would reduce BTL to an absolute minimum.
Just need an auto owner to be the guinea pig.
Just need an auto owner to be the guinea pig.
03-10-2007, 06:07 AM
#7
AudiWorld Super User
Thread Starter
Exactly....New Observation read on.
I just did my own test of sorts.
Accellerating in an easy way, and Gently with the left foot applying the brake pedal. Now I know the difference between brake drag and loss of power:
I stepped on the brake and felt a touch of drag, but as i applied a little more pressure, I suddenly felt the engine "switch off" Exactly is it would have felt had I let up on the gas.
I repeated it a few times at different speed and under varrying load.
Every single time, I would get to a certain point on the brake pedal's travel, the power would switch off. I'm not talking safe mode or turbos, simply a loss of power being delivered to the engine.
According to the text in the Study Guid, the brake switch is sending a signal that trigers the ECU to go to idle.
So QCRAZY, my have stumbled on the easy solution, adjust the switch so it does not acctivate as early. You may find your brake light won't come on as soon too.
Accellerating in an easy way, and Gently with the left foot applying the brake pedal. Now I know the difference between brake drag and loss of power:
I stepped on the brake and felt a touch of drag, but as i applied a little more pressure, I suddenly felt the engine "switch off" Exactly is it would have felt had I let up on the gas.
I repeated it a few times at different speed and under varrying load.
Every single time, I would get to a certain point on the brake pedal's travel, the power would switch off. I'm not talking safe mode or turbos, simply a loss of power being delivered to the engine.
According to the text in the Study Guid, the brake switch is sending a signal that trigers the ECU to go to idle.
So QCRAZY, my have stumbled on the easy solution, adjust the switch so it does not acctivate as early. You may find your brake light won't come on as soon too.
