Pedal Commander

lharrell79 said:

I'm trying to understand how the throttle by wire works. On my old Jeep, it was throttle by cable. If I mashed the throttle, it was instant response. With my truck, it is not. If I mash the throttle, there is a delay, and a slow ramp up in throttle. Why does this happen on my truck, and not on my old Jeep?

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lharrell79 said:

Also, on page 1, you said the same effect can be had from tipping in more? What does that mean? How do I tip in more?

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jaflowers said:

There is no "seems" or "perception" when it comes to what this little device is doing, period. I push the gas normally from a stop and the truck perks right up almost instantly and accelerates up to speed better. I understand it doesn't increase HP/TQ but it radically changes the throttle response to the computer, depending on how you set it. That's not perceived, that's what it does.
When I turn the PC off, the throttle response goes back to the same old way that it's been since I bought it.
I'm not an easy sell on gadgets. As an engineer I'm always skeptical. This thing actually makes the truck respond better and perform to my liking. If it was bogus, or if I thought the performance was just between my ears, it would go back immediately. I've had a tuner before on my last truck and it was great and made a noticeable difference in drivability. Since I didn't want to spend the extra money buying a new computer for this truck as you can't reprogram a 2015, I thought this device might work. I must say all the reviews I read before buying it proved true and I'm happy with the relatively little money that this cost for the better drivability.

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Moab_Rockstar said:

It's pretty much all perception.

In a cable throttle, your pedal is directly connected to the throttle. When you open it, air goes in instantaneously. In a carburetor fueling happens at the same time. With fuel injection, the computer is using TPS and MAP or MAF to calculate airflow and decide the necessary ignition timing.

In drive by wire, the pedal signal goes to the PCM as a voltage signal, and has to calculated to a torque request. There are a couple calculations it has to go through to become a torque request. The PCM then runs that request through an arbitration where other torque requests are compared. Generally, whatever request is "safest" becomes the actual request. With the actual request determined, the PCM then commands the fueling and timing for that loop.

The additional calculations all add up eventually, but for the most part the lag is more perception than fact. In the cable throttle, you open the throttle immediately and you can hear the change in the sound of the engine but it's not really making more power yet. Fuel/air is still on it's way to the cylinders. In a drive by wire, you hit the pedal, and the engine runs some calculations, then the throttle opens and the engine makes more power. In reality the difference in actual engine response between the two is actually fairly minimal, probably on the order or 40-50ms. The difference in an electronic throttle is that that throttle opens when the engine is ready, whereas in a cable throttle, it opens first, and everything else is reactionary.

Every muscle car I've ever driven, whether it's carbureted or electronically controlled, there's always been a lag between pedal to the floor, and being pushed back in the seat. The lag is due to the time it takes fuel and air getting to the cylinders. It seems faster in the carbureted car, because I get a more direct feedback in my perception as things change with the vehicle. The electronically controlled throttle does it more efficiently, so it doesn't seem as responsive.

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lharrell79 said:

When you say that the throttle by wire lag is a perception, I'm going to have to disagree with you 100%. There is more to it than that.

My Jeep, 98 TJ 4.0, throttle by cable. If I cruise along at 10 mph and nail the gas, I get instant full thottle, and it smokes the tires off. Immediately.

My Ram, 08 1500 4.7, throttle by wire. If I cruise along at 10 mph and nail the gas, I get a delay, and then full power. It is about a 1 second delay. It is not a perceived delay, it is an actual delay.

With the throttle by wire, there has to be a slow down in the process somewhere.

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lharrell79 said:

Okay, so essentially, if I cut the length of the pedal shorter, it would do the same thing? A shorter pedal would make the TPS respond quicker? The pedal commander amplifies the TPS signal?

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