Am I the only one that thinks this, *especially* noticeable and lower speeds < 10 mph for example?

Even in traffic I see brake lights and just let up on the pedal and never have to hit the brakes, feeling the rather quick slowdown, betting the guy behind me his hitting his brakes to slow down.

It's a Rubi, perhaps tires are contributing?

My e-brake lever is all the way down

 

I've noticed this also. I kind of like it.

 

Yep some engine breaking with the 2012. I like it. Should contribute to longer brake life.

 

Yep, new for the 2012's. My 2011 Rubi automatic just coasted when you let off the gas.

 

happened with my 2010 until I disabled the ESP - it doesn't do it as much but can still feel it.

 

Yeah, there is a reason for this. To squeeze extra mileage out of the JK, the injectors are programmed to completely shut off gas to the cylinders when you take your foot off the gas.

Previously when you coasted, the injectors would still be supplying some gas to the cylinders (enough to facilitate low-load combustion to keep the cylinders firing) wheras now it shuts off completely (if you have a scangauge connected you can actually see the injector pulse-width drop to zero when you coast). They introduced this feature on late build 3.8L-equipped JKs so I'm assuming the new 3.6L Pentastar-equipped JKs utilize this feature as well. It operates along the same principals as the cylinder deactivation system fitted to the V8 Hemis (and also some GM motors for that matter) that allows four cylinders to shut down and turn them into V4s when they're just cruising under light load in order to get better mileage.

 

Define late build 3.8L - because I had a mid-year 2011 Rubicon that didn't do that.

Curious because everything else I've heard/read is that it's transmisson specific (the non-coasting and slap stick features). Shutting off the fuel and changing the torque convertor/tranny workings are two separate worlds.

Actually, if you wanted to squeeze extra mileage out of the JK you'd shut off the fuel and let it coast at the same time, not brake it.

 

A couple of the regular posters and long-term members on this forum (chime in if you're reading this; can't remember exactly who you were) noted this with their '11s, and confirmed via their scangauges that the injector pulse-width readings dropped to zero (indicating fuel shut-off)when coasting; they mentioned that they had never seen this on the various '07-'10 JKs they had previously owned. I can't remember if they had autos or 6-speeds though.

I'm sure with the new 5spd auto transmission that there is probably some additional braking feature such as it pre-emptively shifting down gears as speed decreases when coasting (similar to the way you change down in a manual to slow down while using no brakes), though I am not knowledgable about this transmission.

 

I have the Bully Dog tuner and one of the things I monitor is the IPW.

My 2007 does not shut it down completely on short stretches but if I am going downhill for a while and do not touch the gas pedal it goes to zero.

Now, I do not know if this feature was already there or was introduced by the tuner.

 

I've already read those posts. That's done for a returnless fuel system.