6MT owners: have any of you tried light throttle app from idle to redline in first gear?
10-05-2004, 01:38 PM
#1
6MT owners: have any of you tried light throttle app from idle to redline in first gear?
While moving at idle speed in first gear, apply the throttle to about 15% and see what happens. The car will accelerate at the same leisurely pace from 800rpm all the way to 7,000rpm, all with 15% pedal application.
The reason I mention this is that it's not what engines normally do. The rpms should plateau at a certain rpm and in order to get more, you should have to apply more throttle. I think what the computer is doing is trying to artificially maintain the same "level" of acceleration all the way through the rev range by opening the throttle valve more and more as the revs increase, without the driver requesting it.
It's weird because by the time you're at, say, 6,000rpm, even though your foot is asking for 15% throttle the butterfly valve is really at 50%.
This would also explain why it's nearly impossible to hold the revs at a constant rpm in neutral.
Anyway, just a random observation.
The reason I mention this is that it's not what engines normally do. The rpms should plateau at a certain rpm and in order to get more, you should have to apply more throttle. I think what the computer is doing is trying to artificially maintain the same "level" of acceleration all the way through the rev range by opening the throttle valve more and more as the revs increase, without the driver requesting it.
It's weird because by the time you're at, say, 6,000rpm, even though your foot is asking for 15% throttle the butterfly valve is really at 50%.
This would also explain why it's nearly impossible to hold the revs at a constant rpm in neutral.
Anyway, just a random observation.
10-05-2004, 01:51 PM
#2
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Yeah, the wonderful world of drive by wire
Personally, I hate it. If I push the gas half way, I want 1/2 throtte. DBW sucks if you ask me. I don't get what the benefit is, must be emmision. Cause it sure isn't driveability, as least not the way I drive. Car is always trying to guess what I want it to do.
10-05-2004, 02:13 PM
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Re: Cost.
AHHH!! That explains everything. Why spend another $1 per car for a cable. Anything to save a buck. Never thought DBW would be cheaper than the old fashion way, even with cruise. Seems like a pretty expensive, complicated system to me.
10-05-2004, 02:40 PM
#5
Lol...I think when you throw in the cost of installing the throttle cable...
...it's just not worthwhile to them. Also, they can program in "drivetrain safety nets" that reduce the shock sent through the drivetrain and ultimately save Audi money in warranty work.
10-05-2004, 03:15 PM
#6
AudiWorld Senior Member
but all that programming doesn't come for free ...
It's got to be a lot more complicated to implement in code (I know something about that as I used to do control law design and development for military aircraft). Not to mention the added reliability issues that they have to deal with. I'm sure the benefit is in the engine management, at least theoretically anyway.
10-05-2004, 03:37 PM
#7
(I assume you meant to respond below)
Sure it's not free. But cars have had servos messing with their cable-actuated throttles for years--holding revs up on cold startup, preventing the revs from dropping too quickly on upshifts, idle speed adjustments due to varying load, cruise control, etc. I think the e-throttle was just the next logical step.
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10-05-2004, 05:53 PM
#10
AudiWorld Senior Member
Yes, I did ...
sometimes I really hate this bulletin board software ... too easy to lose track of just where you are. That said, the cable controlled throttle system was very simple and very reliable. I just can't see it being cheaper to drop something like that for a fully electronic system (more failure modes, critical faults, etc.). The systems in use up to now have not be full authority systems either. What happens with dbw if the throttle command sensor fails and demands full throttle? A cruise control system can much more easily be limited to not allow that since it's not necessary for it to be able to command full throttle. There's a great deal more involved in safely implementing dbw than may seem immediately apparent. dbw just can't be a cheaper solution than a cable actuated system.