True, for the most part. But when you are slowing down going down hill with you foot off the gas. There is something wrong......

 

It never goes to zero.It returns to idle. The feling you feel is the engine speed starting to overcome the speed of the trans mission. But, you are dead money on the problem. An here, jk's loose speed even on a 10% grade. The JK's are engine breaking in over drive.

 

I'm telling you, the pulse width goes to zero. I can see it on the AeroForce display. And what I feel at the bottom of the hill is the Jeep leaping forward a little when the injectors turn on, and the pulse with display shows they are functioning again.

Idle shows a pulse width greater than zero.

 

It's a fooking jeep! Current gas mileage on my jku is great compared to my old jeep, you guys bitching about mileage may be driving the wrong vehicle.

 

Wow you noticed that, What gave you the clue it was a Jeep. The big chrome letters. Or was it the letters on the steering wheel? or maybe did yours come with the tire cover that says JEEP? I really dont know how you could have found out it's a jeep.

We all know we own a JEEP. We know gas mileage is not a strong point. But one reason for this board is for people to make more out of there's. So you say we might be driving the wrong vehicle. I say being a TOOL is a strong suit for you. An you need to not butt in. Your comment was un-welcome.

Grow up! An stay off the forum unless your here to help.

 

I didnt know they totally shut them off. Hum, that adds new data for my research. Thank you.

I was hinting at needing to get 4th out of lock up. so that the idle would not slow it down. Let the tranny free spool like in Neutral. That is how the trans behaves in a camry for those years in the 4cyl. They seem to shift in and out smooth and will unlock when there is no peadle preasure and will lock up when you press down on the gas.

 

CLose. Smaller tires will reduce the aerodynamic drag, but you also need to reduce the vehicles rolling resistence to increase mileage.

Has anyone had exerience with that Fitch fuel thing? I've heard it can add 2+ mpg. I figured that if I added that plus the air intake and exhaust, and then reprogram it I could get 13 mpg! I think it would cost me about $1000 to get an extra 2+ mpg.

 

Seriously? You see the PW go to zero? I can't say I've ever seen that on any car and have never tried it on the jeep. I'm not familiar with the AeroForce display, hmmmm. You have an auto, right? How does the Aeroforce display that?
Hear me out, and I'm not doubting you, just curious if the jeep is somehow different than what I've seen. I've never scoped an injector on a downhill, but on a throttle snap, I've seen PW drop to .3 or .4 MS on the decel. At zero, and staying at zero for an extended time, I would think the engine would shut off, I mean there's no fuel to run. Maybe the Aeroforce can't display small PW's? Even a professional scanner isn't the best thing to watch PW's, they're too slow and not all that accurate. I wish I had one of the aeroforces to play with and see how it works.

But, really, the concept the OP is talking about isn't new, that's been talked about in multiple articles. Some go further to discuss other things, like shutting off the engine at red lights, even shutting off the engine on straight down hills,( not advisable because you lose power steering). I even read an article where a guy says when he's on the tollway, he gets behind a truck into the draft and shuts the engine off. Again, not advisable. He says he actually gets pulled along by the trucks draft, but that in order to get into it, he has to be literally like a foot off the rear bumper. Any time I've tried to replicate this I've been unsuccessful. The wind coming from under the trailer usually doesn't keep me in the slip stream for long. Plus, it's very unsafe. Don't try it.

 

Most newer vehicles do shut off the injectors during coast. But the perimeters of the shut down are set by the engine tuners. The jeep might be set for shut down from 99-50 mph and below that it's possibly at an idle pulsewidth. Maybe ronjx can chime in on what he is seeing. So with the injectors off the TCC has to be locked or rpms will be zero and the power steering, brakes, alternator and AC won't work. So alot of the drag on coast is the accessories as well as compressing air in the cylinders. My wifes 2010 Equinox uses a very aggressive fuel shut off, I think it's used all the way down to 15-20 mph. Also the TCC remains locked much longer than most and the the trans will actually downshift several times to keep the engine spinning in the 1500-2000 rpm range as you coast to a stop. I believe in older setups like the JK, the shut off only occurs in OD. I think my Rainier is like the JK in that if I coast all the way down an onramp there is a slight shudder as the TCC unlocks, shifts out of OD, and the engine fires.

My own way of improving mpgs is put syns in diffs, trans, and axles. And coast as much as possible. It shocks me how people getting off the highway don't slow down until they hit their brakes on the off ramp. They aren't doing their brakes or mpgs any favors.

 

Now I'm curious enough to go see this on my jeep. Interesting concept.

So Just so I have this straight, 50 MPH, slight downhill, TCC locked, I let my foot off the gas, the TCC stays locked, the PW drops to 0.0, and the trans will downshift. What about the ignition, I'd imagine it stays alive, just to avoid a build up of fuel if there is a leaky injector.

I can't say I've ever paid that much attention on newer cars, they're usually not in for a driveability complaint that would warrant such an investigation.

How did you find out about this, flip?
Now I really want to go watch this.

And what if you tap the brakes, does the TCC unlock and the fuel come back to life?
And what if you do like the OP says and slip it into neutral? Does it come back on then?