Drive By Wire

[petert 549]

I'm going to use a GTi6 inlet manifold on my turbo 16V project. Does anyone know of a DBW throttle that will adapt easily?

[Andy 105 1 Cars]

Wow. Interesting project. The Peugeot 308 used a DBW arrangement and replacement throttle bodies are not much money. How easily one could be adapted to fit the gti6 inlet is another matter. 

[opticaltrigger 52]

Like the sound of that Pete.

 

O.T.

 

[wicked 103 3 Cars]

Maybe you've already seen these:

https://www.efisolutions.com.au/bosch-68mm-electronic-throttle-body

 

Doesn't fit, but they also have adapters and flanges...

[petert 549]

That looks the goods. I can make an adapter. Can you run any pedal? The plan is to limit boost so it doesn't light the tyres up exiting tight corners.

[Andy 105 1 Cars]

Might be a stab in the dark here Peter but I think that the pedal will be nothing more than a potential divider that gives a voltage to your ECU which in turn then controls the stepper motor on the throttle. That is how my current ECU wants to control a dbw anyway. Not that I have done it although at a price a motor and adaptor are available for my bodies. DBW is not something for me to consider at the moment as the ‘driving’ bit is the challenge! 

[welshpug 1,621]

a 206/berlingo pedal sensor might be useful for a 205, they retain the original cable placing the sensor wherever you want it in the engine bay.

[SRDT 146]

You can also find this kind of cable sensor on the 306 HDI or the diesel 605/XM.

[wicked 103 3 Cars]

You need indeed something in between the pedal that translates the amount of pedal in control of the throttle. Can be the ecu if it supports it it.

 

But don't you think you'll take off the sharp edge of your engine if you want hold it back with the throttle? 

Did you consider traction control with wheel sensors and ignition retard? 

 

In terms of engineering dbw probably a fun thing to build and explore.

 

[SRDT 146]

Yes you drive the throttle with the engine ECU.

BMW had a standalone EML ECU and one engine ECU per bank on the early 750i V12 but at the time that was probably the only way.

[opticaltrigger 52]

14 hours ago, wicked said:

You need indeed something in between the pedal that translates the amount of pedal in control of the throttle. Can be the ecu if it supports it it.

  

But don't you think you'll take off the sharp edge of your engine if you want hold it back with the throttle? 

Did you consider traction control with wheel sensors and ignition retard? 

 

In terms of engineering dbw probably a fun thing to build and explore.

Hey Wicked,

Just to throw a thought in here,

When OEM's do DBW throttles, quite a lot of effort goes into making sure that in the event of a failure of the motor drive circuitry. The throttle only fails to safe...

I'm not entirely certain of the exact methodology that they normally use to achieve this, or what the feedback structure is though. That kind of stuff is more your thing than me,,, have you got any ideas on how they ensure the DBW "fail to safe" protocol runs.

 

All the best,

O.T.

 

Edited April 19, 2020 by opticaltrigger

[petert 549]

I suspect I'm over thinking it, making it harder than it needs to be. The idea was to have a boost table something like below, for 2nd gear. I'll probably just start limiting boost via gear ratio and see how it goes. Getting rid of the throttle cable is a bonus.

[Tom Fenton 1,524]

I would and have done it using boost by gear ratio. Trying to also compensate using TPS position seems a good idea, but in practise the boost control doesn't react quickly enough. The lift of the throttle by the driver has already done the job.

[wicked 103 3 Cars]

10 hours ago, opticaltrigger said:

That kind of stuff is more your thing than me,,, have you got any ideas on how they ensure the DBW "fail to safe" protocol runs.

 

Making the electronics of lesser quality than the mechanical spring to close the valve...  

(And limited dutycycle on the control signal when in limp home mode)

 

Quote

I would and have done it using boost by gear ratio. Trying to also compensate using TPS position seems a good idea, but in practise the boost control doesn't react quickly enough. The lift of the throttle by the driver has already done the job.

Agree with that plus the remark of peter; limit the boost in lower gears where it kicks in hard, to have predictable power and that your right foot/boost control does not have to fix spinning wheels, which will always take time.

 

But DBW on 205 is next level....

Edited April 20, 2020 by wicked

[petert 549]

The other benefit of DBW is being able to limit the throttle opening under a certain circumstance. ie at 2000RPM in 2nd gear, the full pedal travel may only give 40% of opening. Thus a lot more controllable coming on boost.

Edited April 20, 2020 by petert

[wicked 103 3 Cars]

If you also adapt the rate of opening the throtte in that gear, it would be a nice feature and give you indeed another knob to turn on.

Doubt if you really need it to avoid spinning sticky tires on a track, but don't think you need that justification if you just want it. If you want it, just build it!  
Looking forward to the results.

[opticaltrigger 52]

7 hours ago, wicked said:

Making the electronics of lesser quality than the mechanical spring to close the valve...  

(And limited dutycycle on the control signal when in limp home mode)

h

Sure, it's just that I seem to remember that with the OEM ME7.5's, there's some certain parameters in the control loop to ensure WOT can't happen unless certain criteria are met no matter what happens to the PWM signal or the output stage. I will have to try and go and look it all back up,

 

2 hours ago, petert said:

The other benefit of DBW is being able to limit the throttle opening under a certain circumstance. ie at 2000RPM in 2nd gear, the full pedal travel may only give 40% of opening. Thus a lot more controllable coming on boost.

Yes, this sounds absolutely great Pete. As Wicked says above, you really should go build that for yourself...

Just the amount of data you could gather in setting up the parameters for that make it worth the effort, let alone the fun.......

Keep us posted on this one,

 

All the best,

O.T.