Hey guys, I swapped a motor in a 2001 A4 (B5 right?) 1.8T a while ago and managed to keep the throttle body from the bad motor.

I'm trying to get involved with the Formula SAE team at my school. They were talking about coming up with a new throttle body system, so I took this thing apart, diagrammed it, and measured resistances of what looks like a control system.

The idea is to develop a throttle system that open viariably in relation to pedal position. For example, at 50% pedal, the throttle pos. would open slowly to 25%. Then from 50% to 100% pedal, the throttle would accelerate toward 100%. If you were to plot a graph x=pedal pos., y=throttle pos. the graph would be a curve concave upward. The slope would be less than 1 until x=50%, at which it would be 1 and rise from there until 100%. The idea is to give a more linear throttle response from a butterfly style throttle body.

I've spent a good 3 hours searching through forums (here, audiworld, VAG-COM yahoo group, google, etc.) looking for some technical data on the system and perhaps a wiring diagram. There are 6 pins on the throttle body. I found that 2 (pins 3 and 5) are + and - for the servo motor, and 4 (pins 1, 2, 4, and 6) lead to the variable resistor array which follows the butterfly. It looks like pin 6 is reference voltage and the other 3 will show voltage with relation to throttle position. The resistance ranges vary, and some are curved. What I am trying to figure out is what info this array is giving the ecu about the throttle's position, and how it interprets that information and drives the motor in the throttle body, of course with dependency on throttle pos. input.

Does anyone have a service manual with this kind of info, or anyone/anywere to go for info on this system?

TIA

 

any ideas?

 

I'm sorry, I have no idea. But I am curious, what good would this do. It sounds like you are going to try to take away all responsiveness from the car. And make it take forever to speed up. This might be good for grandma, but I don't think it would be good for us 'race inspired' daily drivers...

 

The idea is to give a more linear throttle response. For example, a butterfly will give you less difference in engine power output from say 30% to 100% than it will from 0-30%. So if the throttle is one-to-one with the pedal, the throttle could be too sensitive at partial.. especially in a sub 500lb cycle engine powered car. That's the idea anyway. This could be achieved with a cam throttle sprocket, but hey, just trying to see if this would work.

 

well, I see where you are coming from. Sounds like it could be a good idea. Stick with it and let us know how it turns out. Good luck!

 

You should be aware that both control signal and feedback can be a changing signal (frequency or PWM signal) and not necessarily a voltage.

 

if I ever come across another running Audi, I'm gonna probe it I found out today what the real problem is. The rule book (80 freakin pages) requires a 20mm restrictor on the 600cc GSX-R motor we're using. The throttle body is about 3 times that size, I'd say 60 maybe 70mm. SO the throttle body flows waaay too much air and it's useful working range is from like 0-15% throttle. The restrictor caps the motor at about 10,500rpm. I also believe that DBW is prohibited in the rules, but hey, I'm gonna hold on to this thing for whenever I get a cycle-powered road rocket of my own.