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Drive By Wire (DBW) throttle
Drive By Wire (DBW) throttle
electronic throttle control basics and pics
Published by Chris H
15th February 2010
Drive By Wire (DBW) throttle

Drive by wire throttle is actually very old, anything 'by wire' is very old, aeroplanes, forklifts, heavy equipment etc have been using electronic control for decades.

However integration on a massive scale has only really happened in the auto industry in the last 10 or so years.

What does DBW mean? It means there's no mechanical connection, its controlled completely by electronics.

There are several advantages of FBW from reduced drive line shock to integration within the passenger compartment.

The pedal assembly is a conventional pedal attached to a spring loaded box (for pedal return), within the box the pedals spindle is attached to a conventional TPS.

At the throttle plate end its a bit busier. Theres the usual throttle plate which restricts airflow into the engine (this is Si engines). On the end of the spindle there's instead of a TPS and a cable onto an arm there's a box of tricks, within this box of tricks there's is a TPS and there is a motor.

The pedals TPS informs the control ecu of the pedal position and this is then replicated at the throttle body. Thats it. The throttle plate on these engines also regulates the idle speed, there's no separate idle control mechanism.

Anyway onto the pictures, this is off a Laguna 2 1.8 16V, as always oil contamination is an issue within any inlet tract (except those of course with a vent to atmosphere set up but they don't include us), oil contamination coats the TB and can cause issues.

This picture shows the TB and plate from the air filter side, as you can see there is contamination



this is the inlet manifold side after a wipe down



The black cover removed from the electrics

you can see the coil and the spindle, note the crack on the spindle, nothing to worry about but it shouldn't be there



Coil removed and the TPS tracks are revealed. These are matched to the pedals TPS and the ecu also uses them to regulate the idle control. Its hard to see but if you look closely you can see the wiper contacts, these are actually several small wires that rub against the track,



clean the tracks of dust with an air can or some carb cleaner and a cotton bud, be careful and don't use a rag or paper towel as they will catch the wiper arm wires and pull them away.

A blurry pic from further away, the spindle turns easily, theres a small return spring on the other side of the TB to keep the plate closed



The coil, this is what actually operates the spindle, a conventional coil setup, so this throttle is activated through electro magnetism



The other side showing the contacts for the coil feed, if the wires are melted or cut/shorted this will cause problems and the coil assembly is useless



So after a thorough clean up I checked the live data to see if it had improved anything, rpm held a steadier speed and slightly lower as well, in this frame the rpm's are holding 773 they were over 800 before cleaning in the same conditions



in this frame the throttle position is 11% which is better as before the lowest it ever went was 11.5%, most likely this came about as the contamination build up affected airflow past the throttle plate



this shows the engine load at 20.8% thats heater on, door open (theres several interior lights), radio etc etc. The STF is cycling nicely, in the first image the LTF was 4.7% this is down from 24% when I first got the car, various drive cycles have cleaned it up a lot clearly!



The other issues with DBW are the very thin wires used, these break and corrode easily as they are very small, they can also get quite warm which means they are to thin for the job! Cost cutting by the manufacturers as usual.

Interference can occur with these throttles if the spark plug gap is to large I have found this on a few vehicles now. If you have a decent scope like a Picoscope you can actually see the spikes to the TB and the resultant impact it has on it.

And thats it really.
  #1  
By bncrew on 16th February 2010, 07:17 AM
Outstanding article Chris, i remember this came up on here about a year ago, I didnt really understand the whole thing to any great extent but didnt want to ask either in case it seemed like a stupid question, now I wont have to ask.
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