Re-scaling gas pedal (for better resolution)?

[Piwoslaw]

My car has a fly-by-wire gas pedal, with a potentiometer mounted directly on the pedal. Some slightly older cars still have a cable going into the engine bay and turning a pot there. Either way, the pedal's position is translated into an electrical resistance which the ECU reads to know how much the driver wants to accelerate.

Since I keep an eye on the ScanGauge to adjust acceleration, I never floor the go pedal, in fact I hardly ever press it farther then 60-70% of its total travel distance.

On the other hand, the slightest, barely noticible microchange in the pedal's position can change engine load by a lot, for example barely increasing the pressure on the gas pedal can change engine load from 55% to 90%.

So this got me thinking if I could rescale the pedal's potentiometer so that the max value is the resistance when the pedal would normally be pressed 75% of the way. This would allow better resolution, making it easier to stay at the optimal load.

What do you think?

[redpoint5]

I like the thought, but would be unwilling to give up that other 25% just to gain the extra resolution. I see no reason this wouldn't work though. The bigger question is whether the effort will result in measurable fuel economy improvements. I'd like to see you test it.

In high school, I built an electric "car" that was a reverse trike design made of aluminum and custom built bicycle wheels. This was entered into the PGE (Portland General Electric) sponsored 1hr endurance races against other schools. I mention this because I thought about how difficult throttle control was on a bumpy road combined with the imprecision of a shoe-covered foot. I designed the throttle into the steering mechanism to help isolate bumps and increase precision. The design resembled the handle of a pull-starter and was operated by placing the wood-carved handle between the index and middle fingers and pulling towards the driver. This actuated the spring-loaded POT.

[some_other_dave]

There are electronic devices out there that will modify the signal of the throttle pedal for you. I think "Sprint Booster" is one? They are generally intended to give you a quicker response, which is the opposite of what you want, but you may be able to program them or find a way to modify them so that the top 20% of the signal happens only at the very end of travel. That would give you the option to use WOT in the rare instance you actually need to.

-soD

[baldlobo]

wouldn't putting a variable resistor in series (or parallel) help for fine tuning.

[Piwoslaw]

The thing is that I can live without the last 25% of travel without even noticing. I've noted (and Euromodder, who has the same engine) that in most situations max acceleration is within the first 30-50% of pressing the gas pedal, any more and at best more fuel is used, but without more acceleration.
A none-linear resistor would be great, but not in my case, as 80% engine load is sometimes seen with the pedal pressed halfway, and sometimes only 10-15%.

I have thought about a hand operated lever on the steering wheel (a few ecomodders have done this, but with a bicycle gear shifter operating the throttle cable), or at least a switch which would let me choose between stock and improved resolution, but I'm still wondering whether I'll do this mod. If I actually go into this, then I might just limit the max engine load to 80%, or to its best BSFC.

[serialk11r]

So I'm pretty sure the throttle maps are meant to imitate the more intuitive aspects of a cable throttle (on the highway for example I feel like cable throttle makes you step a lot more to get more speed, because you're "locally" directly controlling airflow and thus power, not torque. The one throttle map I've seen is for the BRZ/FRS and it basically almost all of the change in commanded torque happens in the middle third of pedal travel. Pushing the pedal to the metal doesn't add nearly as much power as pushing from fully lifted to halfwayish.

I think the e-throttle maps are one of the more easily modified things when reflashing an ECU, but not sure. Should be pretty easy to give it a gentler torque ramp up.

[ron]

I'll be interested to see how this works ,my daily driver is also hard to control for best FE I find that if I drive by ear (i can hear when the engine is loaded)and back off a bit I get to work just as fast and save fuel.