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?

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

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

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.

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

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.

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

Yep the Holden Astra was really bad for throttle lag . Really annoying

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.

Here's a Honda one on a split bus motor



And at the pedal:-



Cheers

Steve

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...

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.

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.

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.

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.

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 !

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 !!!

...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

Id prefer the 5.0L BT1 i had to the alloytec any day.

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.