Joined: 11 Sep 2006 Posts: 648 Location: London, England
Posted: Tue Feb 09, 2010 2:28 am Post subject: Lets have a chat about drive by wire
I think it's a given that drive by wire is with us going forward whether we personally favor it right now or not, and getting our heads around it asap is probably sensible if you value your future prospects as a tuner.
So with that in mind what are peoples thoughts regarding drive by wire?
Does it offer any significant performance benefits?
Does it simplify some aspects of engine control or just further complicate the issue?
Joined: 21 Mar 2008 Posts: 352 Location: Pretoria, South Africa
Posted: Tue Feb 09, 2010 9:03 am Post subject:
I Like DBW,
Performance benefits are in Anti-Lag, downshift assistance, throttle limiting at low RPM on individual throttle engines all increase overall performance.
It maybe be complex to get to work 100%, but once its working well I prefer mapping an engine with DBW. If you ramp it you can control throttle opening. With response times sorted out, not OEM, it doesnt interfere with driver control, it could just enhance it with all the setting at your disposal.
i see it as something that can go wrong and loose a race !
but it does have some benefits
i'd like to try and see how it can be used to tame an engine that struggles to get the power down - against say traction control
I will reserve my judgement till i have mapped a car that has it
I guess until every aftermarket ecu can work with it, it will always be a nuisance _________________ Dyno Developments
2WD and 4WD Chassis Dynamometers
Joined: 30 Aug 2006 Posts: 500 Location: Cruisin for a bruisin
Posted: Tue Feb 09, 2010 11:06 am Post subject:
It is what it is,
A driver request system that is manageable. The driver requests maximum forward motion, that doesn´t have to be maximum intake pressure,
So traction control, jerk elimination with touchy engines, all kinds of drivability enhancements are possible.
i haven´t done one yet, but I can see that some time is needed to iron out some aspects of driving controls so that things become smooth and faultless.
As an aspect , I can think of a throttle cable as 85% perfect control,
medium setup DBW can be 90% and much time spent to get the last 10%´s
Joined: 13 Nov 2004 Posts: 726 Location: Venice, CA
Posted: Tue Feb 09, 2010 12:29 pm Post subject: drive by wire
Quote:
do the race drivers prefer it ?
does it improve lap times or economy ?
100% of the time in every single professional racing series I've worked in. I'm at the point where I convert cable throttle cars TO FBW. _________________ Neel Vasavada
Apex Speed Technology
2947 S. Sepulveda Blvd
Los Angeles, CA 90064
310-314-2005
www.apexspeedtech.com
Joined: 11 Sep 2006 Posts: 648 Location: London, England
Posted: Tue Feb 09, 2010 2:47 pm Post subject:
I've found the exactly the same, that once the control systems are working fast and accurate drivers love it.
I found myself thrown in the deep end with this about 18mths ago and whilst it's been a very steep learning curve (I now know everything there is to know about H'bridges ) I'm now getting to the point where we are beginning to be able to do some fantastic stuff with the pedal position vs throttle position cartography and yes it's really showing up in the lap times.
I guess the thing that has struck me most is just how much my knowledge of pure electronics and PID calculus has had to expand in order for me to design and work with these systems, I mean in terms of making them work properly and efficiently.
From a simplicity stand point I'm loving DBW control with regards engine start up and closed loop idle control whilst being able to delete external control stepper motors and solenoids. _________________ Sam Borgman
www.facebook.com/torquedevelopments www.tdi-plc.com www.rototest.com
We have just convert a cable driven s2000 to drive by wire throttle by using motec mx00.
It is an daily street driven vehicle. It drive alot smoother, easiler to clutch in on 1st gear.
But main reason for conversion are traction control, anti-lag and DBW downshift rev match.
Posted: Wed Feb 10, 2010 4:29 am Post subject: Re: drive by wire
APEX Speed Technology wrote:
Quote:
do the race drivers prefer it ?
does it improve lap times or economy ?
100% of the time in every single professional racing series I've worked in. I'm at the point where I convert cable throttle cars TO FBW.
Im trying to figure a way to do this myself. But are mainly looking for something that will be pulling on the cable rather than working directly on the throttle body. Can i ask for some pic`s or any other info on your setup?
Lets assume throttle open @ 80% on a standard throttle turbo engine ...
With a DBW you can open your throttle @ 100% when you are at 80% of the pedal , and simply reduce the boost to reduce the load : less pressure drop means better fuel economy ...
I don't know if pressure drop is the correct terme , in fact i want to mean how much work need the engine to pump the air into cylinders ...
Also about performance during shifting , with a normal throttle your cable is unbending ... With DBW he isn't ...
And also for traction control , as you say ...
But normal throttle are far more fun , easier and cheaper to repair , and you better " feel " your engine ...
Joined: 21 Mar 2008 Posts: 352 Location: Pretoria, South Africa
Posted: Wed Feb 10, 2010 12:18 pm Post subject:
Ive done Downshift blip in track cars with H pattern boxes.
simple test that you can do is look at what a driver does with brake pressure when he blips the throttle with his heel and again where he can fully concentrate on the brake force and the ECU takes care of the blip.
In sequentail gearboxes with voltage gear pos measurement you can set the Mx00 to match the lower gears rpm limit for the speed you are doing, This way if you downshift blip it will blip up to the limiter where the lower gear`s rpm is at the particular tail shaft rpm. (tail shaft rpm either red from tailshaft or calculated from drive speed)
You can also set the air bypass throttle position while anti lag is active, so you can have a daily drive with half throtte air bypass for anti lag is you wished to have it.
One could also increase power on large butterfly engines at low RPM where its frequently the case where it makes more power at smaller throttle openings.
Modified (cams) BMW S54`s in particular will make more power very low down with less throttle.
Joined: 29 Aug 2006 Posts: 846 Location: Northern Ireland
Posted: Wed Feb 10, 2010 4:29 pm Post subject:
Gadgeroonie wrote:
what is the biggest advantage the DBW gives the driver to improve lap times ?
is it reducing power to tame the car ?
I'd imagine better control over the actual power delivery. And possibly better ( or more controlled ) engine response to foot movements. ( cant really say throttle response )
You could probably program in more resolution over power under foot, than you could with a conventional throttle. Even more so when bigger power engines start using very large TB's _________________ LS1, V7 YSi
Joined: 11 Sep 2006 Posts: 648 Location: London, England
Posted: Thu Feb 11, 2010 3:48 am Post subject:
I'd be interested in seeing which triggering system works well for an auto throttle blip with an H' pattern? I'd like ot try to implement it on a GT car I'm working with. _________________ Sam Borgman
www.facebook.com/torquedevelopments www.tdi-plc.com www.rototest.com
Joined: 11 Sep 2006 Posts: 648 Location: London, England
Posted: Thu Feb 11, 2010 4:00 am Post subject:
Gadgeroonie wrote:
what is the biggest advantage the DBW gives the driver to improve lap times ?
is it reducing power to tame the car ?
In a word "ergonomics".... it helps us move closer to a "do what I mean" control system rather than the historically typical "do what I say" style system
The drivers brain stem automatically controls huge chunks of the driving task and as long as everything goes as expected the control functions stay closed looping in the brain stem and never have to be flagged up to the higher level areas of the brain, which leaves these higher levels free to do other complex functions better.
The driver doesn't care about throttle position, the driver cares about torque applied to the contact patch. So my target is to program the throttle translation tables so that the throttle pedal (or torque demander) grants contact patch torque progression in a linear fashion, for the sake of this discussion we can say 1:1. That is to say 25% pedal position should result in 25% of available torque being applied to the contact patches of the tyres, 50% pedal then equals 50% output and so on.
Keeping the ratio linear and predictable keeps the throttle control function in the drivers brain stem, that effectively increases the drivers ability to deal with other control tasks and deal with emerging conditions.
Joined: 30 Aug 2006 Posts: 500 Location: Cruisin for a bruisin
Posted: Thu Feb 11, 2010 6:34 am Post subject:
DBW on bikes is also linked to their incline in bends.
I.e they can have it fully open but when they lean into the bend the ecu lowers the plate opening so they don´t loose traction or try to lift the bike from the gearing change because of the tire circumference changes as the bike leans.
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) I'm now getting to the point where we are beginning to be able to do some fantastic stuff with the pedal position vs throttle position cartography and 
