| [ Total Views: 1807 | Total Replies: 22 | Thread Id: 71507 ] |
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 General_Failure
A.k.a.: Tristan
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 posted on September 3rd, 2008 at 11:40 AM |
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Fly by wire. Something that could be very useful.
Having a fly by wire throttle is something that has rattled around in my head for years as a great mod to do to a VW. It's actually a little
difficult to even see a downside to it.
I know I would love to delete the massive accelerator cable from my van. Because of its length, it is temperature sensitive, both (I guess) through
expansion, and more realisticaly through the lubricant getting thicker at low temps. Also contamination inteferes with it. I noticed recently that the
difference between it working and not working with a pretty beefy return spring was lubricating the accelerator pedal shaft.
Also now that I have walked the path to the dark side and ventured from standard dual carbs to the single weber progressive, I can see even more
benefit to having fly by wire.
I could easily handle the electronics by myself, but the carburettor actuation and accelerator pedal position sensing are another matter. How would
people go about this.
Back to my point though. Through custom electronics, it would monitor accelerator position and manifold vacuum, to avoid stumbling when planting the
accelerator and also preventing lugging, which as we all know can barbecue a VW motor.
Ie. it wouldn't let the butterfly open too far, causing the vacuum to plummet. Instead it would regulate appropriately.
Now that I think of it, it would also avoid that annoying issue of stretch or slip causing full throttle to be inaccessible until the cable is
readjusted.
I'm not sure if it would need feedback on current RPM. Would it? Sure, that would allow for some other nifty features like electronically regulating
the idle speed, because we all know how finicky VWs can be about idling. But would it be necessary?
Another possible feature would be a brake detect. Easy to do. Just needs to connect to the brake light wiring really. Electrically isolated of
course. This could kill the throttle when braking. Although who can actually push both at the same time, except for the occasional accidental stumble
where the foot gets both.
What do people think of this idea. Is it worth pursuing? I believe it is. As a project at very least. Would anyone else like such a thing?
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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Camo
A.k.a.: Kev
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| posted on September 3rd, 2008 at 06:59 PM |
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I think I have seen on a Nissan ute before where the accelerator pedal has a cable only about 6 inches long that connects to an electronic component,
that then controls an electronic throttle body etc. This may be of no help, but thought I would let you know anyway.
Kev
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Tratty
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| posted on September 3rd, 2008 at 08:06 PM |
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I don't know about about having the brake inhibit throttle operation because that would stop you using heel and toe to double the clutch whilst
braking.
Tratty
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General_Failure
A.k.a.: Tristan
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| posted on September 3rd, 2008 at 09:29 PM |
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Thanks for the info Kev, That's exactly the sort of thing I want to hear.
Tratty, you make a good point. It was only a possibility anyway. I wasn't entirely sure it'd be a useful option.
I really do love the idea of lugging prevention though. It'd help prolong engine life and probably increase economy too.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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Grey 57
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| posted on September 3rd, 2008 at 10:35 PM |
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I would go for something like that. With 6 throttle body return springs, 1 injection pump return spring and 2 safety return springs, my throttle pedal
gets pretty heavy. Be nice to have some servo motor do all the work
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General_Failure
A.k.a.: Tristan
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| posted on September 4th, 2008 at 08:35 AM |
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I've been asking elsewhere and apparently what they normally use is just a servo controlled by PWM. Now I just have to find a servo. A while back I
stumbled across some nice strong ones somewhere at good price. Can't remember where though.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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Joel
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| posted on September 4th, 2008 at 09:08 PM |
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alot of the car manufacturers are making the switch to it now
ive heard only a couple of cases with ppl having dramas
main one being lag and one that was just going haywire on its own on a Yamaha
my only experience with it is the new Same Lamborgini tractor has it and ive noticed that it can be slow to return to idle sometimes which is
something u wouldnt want in a car
and the other feature which is great in a tractor is it has a memory button u can set so it always returns to those revs when u press the button
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Grey 57
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| posted on September 5th, 2008 at 12:51 PM |
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Yep the Holden Astra was really bad for throttle lag . Really annoying
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modulus
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| posted on September 6th, 2008 at 09:44 AM |
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Sounds interesting.
Make sure the design is fail-safe, i.e. whatever goes wrong or breaks (physically or electronically) should result in a closed throttle, not e.g.
wide-open throttle and the fail-safe should ideally be duplex (in case *it* fails, just like dual return springs). The other thing that comes to mind
is to incorporate some appropriate "feel" or feedback to the pedal, as we're all accustomed to having to press harder for more throttle opening.
It's quite a bigish project, and I wonder whether a good fuel injection project for Type IV engines might not yield better results.
Good luck with it.
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matara
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| posted on September 6th, 2008 at 10:19 AM |
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Here's a Honda one on a split bus motor
And at the pedal:-
Cheers
Steve
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VWCOOL
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| posted on September 6th, 2008 at 10:31 AM |
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all new cars have it as it allows easy, cheap and reliable interface to chassis stability electronics (ABS, Traction etc etc) and cruise control. When
Holden went to FBW on its V8s, it saved about 10kg and several hundred bucks in manufacturing costs and labour by deleting the throttle relaxer,
several cables and the cruise control actuator. It also makes the car easier to tune (by the manufacturer)for cold start emissions legislation etc
It can also be programmed for different throttle 'feel' for 'sport' modes in performance cars and less throttle surge in off-road vehicles. eg BMW
M series, VW Touarag
But as for fitment to a Kombi... without all those systems to support, FBW will not be 'very useful' and will be an expensive pain in the arse
project...
Pay your debts, CxxT
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General_Failure
A.k.a.: Tristan
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| posted on September 6th, 2008 at 09:24 PM |
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Yeah, possibly expensive and not worth it, but definitely interesting.
I am experienced with electronics, programming and microcontrollers, so the technical aspects are pretty straightforward. There are just the X factors
like a reliable method of reading the throttle position. Although I feel a decent potentiometer combined with a filtering algorithm to catch any
spikes from the pot.
I have vague memories of digital position sensors, but I don't really remember them too well.
The most widely used method for actuating seems like a servo. I was looking at some 15kg metal geared unit on eBay. I just have to wonder how long
they last. In the case of a servo, cut the power and they return to where their spring takes them.
Regarding accelerator response and needing to push harder for more throttle, that's what springs are best at!
It'd have no throttle and wide open sensors. The microcontroller would also have a calibration / test setting, where it checks that it still has the
right duty cycle for wide open and closed throttle still works.
Personally I'm sick of wide open throttle failures. A bit of grit or moisture gets in somewhere and the painfully delicate balance of strong spring
and long cable is upset.
As it is, when something adds that little bit extra drag into the setup either the throttle jams or the pedal collapses sideways. I was fighting with
the sideways collapse today. I really don't like the factory accelerator pedal on the autos.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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Brad
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| posted on September 6th, 2008 at 10:26 PM |
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I have fitted FBW to my Iguana Buggy, granted I also fitted an EJ 25T which comes factory fitted with FBW and used a late model falcon Accel pedal as
it matched up with the M800 ECU and FBW controller.
It is setup that any irregularity in signal or power failer causes the TB to shut so the engine returns to idle. The great thing about FBW was that it
got rid of the last cable in the system.
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General_Failure
A.k.a.: Tristan
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| posted on September 20th, 2008 at 09:57 AM |
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I haven't abandoned this idea. It's just been a bit more busy than I'd like recently.
Is there any more info on that splitty bus setup? I can't really understand what's going on there on the motor end of things.
There's a little bit more incentive now to figure this out. Now I have the Weber progressive on and the motor and throttle linkage happening, the
accelerator response is utterly berzerk! It's practically impossible just to give it a little bit. It'd be really nice to add a custom tuneable
response curve in there.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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 matberry
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| posted on September 20th, 2008 at 01:44 PM |
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Talk about reinventing the wheel.
I dont have a problem with Brad , where a system, computer etc is 90% already there, but mr general failure, the throttle problems in your bus are
exactly that, problems. Get it back into order, repair, clean out the tube, use oil not grease, etc etc and you will be on the road and a lot more
fixable if ever anything ever goes wrong.
IMO anyway.
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Euro_67
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| posted on September 20th, 2008 at 03:30 PM |
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I have a 2007 Alloytec Holden Commodore Ute with FBW. Give me back the cable actuated throttle any day. I am sure they arent all as bad as Holdens
version, but Id hope there are none worse !
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VWCOOL
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| posted on September 20th, 2008 at 07:44 PM |
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| Quote: | Originally
posted by General_Failure
I haven't abandoned this idea. It's just been a bit more busy than I'd like recently.
Is there any more info on that splitty bus setup? I can't really understand what's going on there on the motor end of things.
There's a little bit more incentive now to figure this out. Now I have the Weber progressive on and the motor and throttle linkage happening, the
accelerator response is utterly berzerk! It's practically impossible just to give it a little bit. It'd be really nice to add a custom tuneable
response curve in there.
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Find the problem(s) and fix it - frayed cable; grit in the system; lack of lube; poorly-designed linkages; etc - before you frig around with
electrickery
Pay your debts, CxxT
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VWCOOL
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| posted on September 20th, 2008 at 07:46 PM |
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| Quote: | Originally
posted by Euro_67
I have a 2007 Alloytec Holden Commodore Ute with FBW. Give me back the cable actuated throttle any day. I am sure they arent all as bad as Holdens
version, but Id hope there are none worse !
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What is the problem? I've never had any problem with the dozens of FBW Holdens I've driven...?
Pay your debts, CxxT
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Sides
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| posted on September 20th, 2008 at 07:51 PM |
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All the cars I've driven with FBW have been fine, with the only exception being a Corolla hire-car I had in South Africa - it had about half a second
lag, which since it was a manual made it VERY interesting to drive !!!
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Euro_67
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| posted on September 21st, 2008 at 07:02 AM |
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| Quote: | Originally
posted by VWCOOL
| Quote: | Originally
posted by Euro_67
I have a 2007 Alloytec Holden Commodore Ute with FBW. Give me back the cable actuated throttle any day. I am sure they arent all as bad as Holdens
version, but Id hope there are none worse !
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What is the problem? I've never had any problem with the dozens of FBW Holdens I've driven...?
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It is called torque management. I have the "alleged" 190kw high output V6, and the torque management is so bad my 1776 beetle is more responsive to
drive.
Really doughy off the line, and no torque. you have to rev the crap out of it, and it seems to run out of puff well before redline.The Holden dealer
assures me all is ok. There are a few threads about it on various holden forums and its responsiveness can be improved about 50% with a re map to rid
the torque management.
I guess my grievance with the FBW is how easily it is overridden (your throttle input) by the ECU. If I want WOT, damn it, thats what I want. Not what
the ECU thinks I should have !.
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VWCOOL
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| posted on September 21st, 2008 at 08:07 AM |
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...you shoulda got the V8!
yes, FBW throttle response can be tailored by manufacturer (or aftermarket) but the 'torque management' is an anti-abuse power-delivery strategy
(usually only at WOT) to prevent the gearbox being fried...
I reckon the High Output jobbie is okay - nicer/snappier than my old HSV 5.0 - but it IS a big car with only 3.6 litres so it needs revs. Nothing will
ever change that
Pay your debts, CxxT
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Euro_67
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| posted on September 26th, 2008 at 09:48 PM |
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Id prefer the 5.0L BT1 i had to the alloytec any day.
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General_Failure
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| posted on September 27th, 2008 at 08:47 AM |
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Sure I could just fix up the cable system, which I do plan on doing in the near future, somehow. If I could get hold of the pedal setup from a manual
I would be far, far happier.
My current linkage geometry isn't far off from the original really. The lever coming off the accelerator cable has the same length and is at roughly
the same starting angle and position.
The short cable going from the other side of that linkage to the carburettor utilised one of those constant angle, guide style throttle levers that I
took from a mikuni solex progressive. I adjusted the cable position on my linkage to accommodate for the longer cable travel required by that
design.
None of that is the point anyway. I just thought it would be an interesting project, especially since I also have a background in electronics. And I
think a _tunable_torque control would be a great thing to have. It's far too easy to keep pushing the motor on a van too hard without realising it.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.
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