So I have a nifty scan tool that allows me to check parameters on the JK in real time. One of those being throttle position. Now as we all know, our Jeeps are controlled electronically. Riding down the highway, in 6th gear, I put it too the floor and only are given about 78% throttle. In 5th about 81. And 4th about 88. What gives? I feel the Jeep would be a lot less underpowered if it actually would give you all of the available range.

 

Mine does, on the highway its WOT, idle ,WOT, idle, WOT, idle.

 

no programmer, just a scan tool

 

Well, on an aircraft with a constant speed propeller, it would be because your manifold pressure is getting too high. Would a car sense that you are giving it too much throttle in too high of a gear (lugging the engine)?

 

At what RPM did you try this ?

 

yah, its not a pedal with a cable, so maybe what you ask for(foot to the floor) and what you get(not 100%) are two different things.

just guessing and still interested

 

This was all done rolling down the highway at 70ish mph. So i was not lugging the engine

 

I'll venture to say that this is normal. The 3.8 doesn't hit it's stride until 3000 rpm. Notice how the percentage rises with lower gears. This is because the motor just can't use the added air until the rpms rise so it knows not to open the throttle body more.

Sometimes the engine computer knows what's best.

 

70 ish isn't an rpm.

you can still lug an engine at 70

its all in the power curve and with the 3.8 any W.O.T under 2500rpm would be concidered lugging

 

To be honest WOT or not it does not change much, it your mixture that you need to tune properly. There is no point in getting WOT if you're running lean.