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engine starts in 4low?

1275 Views 2 Replies 2 Participants Last post by  Nathan
Hmm, I've noticed the engine always seems to run in 4low in hybrid mode (and 4low+eSave, of course!). Electric works like you'd think, engine stays off. I wonder why they chose to do that?

Looking at the power flow page, it appears the battery is charging at a few kW if I just sit there in 4low, even when not in eSave mode. Once I move, the engine seems to clutch in immediately and power the Jeep, same behavior as eSave in 2WD with a low battery. It actually feels all smooth and normal automatic-like, which might be part of the reason it's handled this way. It still strikes me as odd that the engine starts the moment you go in to 4low in hybrid mode though...
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Yeah, I noted that as well at the beach the other day. I'd =guess= because Hybrid is designed to manage the ICE and EV in the most optimal way, and that's based on the (assumed) use case. So if you're in 4L, you must be getting ready for some serious s***, so it puts all 470 ft/lbs of torque on deck.

And like you said, you can still hit the Electric [only] mode and tool around in silence while still being in Low.
I think I read somewhere that you can't use full power (all 470 ft-lbs) in 4Low. But having the engine ready still kinda makes sense from a consistency-of-power standpoint, that does mean nothing will change with battery % or coolant temp while you try to crawl over whatever crazy obstacle you found.

Another theory - battery use is pretty high when bouncing around rocky trails in 4Low, I've noticed, so maybe the engineers felt it's more efficient to just use gas in that situation unless you ask for electric only. I noticed the engine started doing 75MPH in hybrid mode on the highway the other day, probably for the same reason - they know you'd just kill the battery in short order doing that, might as well just start the engine.

Man, I wish either FCA would release detailed info on all this (maybe in a repair manual?) or some tuning company would reverse engineer the powertrain control software. Mainly just to satisfy my curiousity, the 4xE works great as-is.
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