My assumption was wrong, sorry about that.

Ken@Japan

 

I've been out of town, but had a chance to experiment with this somemore. My original observations were accurate but incomplete. On a long downgrade, when in fuel-cut mode, I stay closed-loop while in D. However, shifting to L and getting engine run-up will cause open-loop until I shift back to D and the rpm's drop. But in both D and L I see what is apparently zero fuel flow as indicated on the dash econ gauge.

I think we would all have consistent results if we all understood and agreed on what we mean by the terms "fuel-cut mode", and "engine run-up" and how to tell when those conditions are occurring. Although I maybe the only one not fully understanding.

 

Mine still sounds different.

'Fuel Cut' to me means 0.0L / 100km on the stock system, with ICE spinning.

'Run Up' is whenever the engine RPM races solely for engine braking.

Going down I70 from 11,000 feet to 6,000 feet elevation change, at highway speeds ( 55-65 mph ) I would shift to L to get engine run-up. This would make it go open loop on the SG after a couple of seconds, and also show 0.0L/100km on the stock display. But this would also cause lots of regen slowing, and engine brake slowing. SG = about 60 MPG.

AFTER the open-loop *(and 4000 RPM ) I can shift to D, Lower regen amount and RPM to 1800, and still keep 0.0L/100km. SG now = 120 to 200 MPG.

 

My definition of "fuel-cut" is zero fuel usage while the ICE is spinning — the same as gpsman1's. Provided that the FEH's FE gauge reads correctly in these cases, you are able to reliably determine when the FEH is in fuel-cut (otherwise it might explain some of these inconsistencies). The FE gauge in my metric (Canadian) TCH seems to give completely consistent readings of 0 L/100 km whenever fuel-cut is in effect. (ScanGauge incorrectly reports fuel usage.) I regularly see fuel-cut when coasting at speeds above ~64 km/h (~40 mph) in both 'D' and 'B.' In 'D' no run-up occurs — the ICE continues to spin at idle speed (~1000 rpm). In 'B' run-up does occur (to ~3000 rpm or greater). Your definition of "run-up" does not require fuel-cut to be in effect during run-up. I assume that you chose this deliberately. Does the FEH ever run-up without fuel-cut? In my TCH, I've never observed run-up in 'B' without fuel-cut (I'm not asserting that it cannot occur without fuel-cut, but I doubt it).

Stan

 

Yes. I just found out when the engine is cold ( below normal temp ) after a cold start, the ICE will run-up to slow you, but fuel was ~1.0L / 100km.

 

gpsman1 and econoline — So, what's your considered final opinion on the matter? Are your two different models of the FEH behaving differently as regards saying open- or closed-loop when in fuel-cut mode, or are you still unsure? I'd like to let Ron DeLong know the answer.

Stan

 

I do not think the 2005 and 2007 behave differently.
I think there are just many permutations and combinations on this subject.

I think open loop, on a hot engine, means either WOT or fuel cut.

I think engine run-up ( engine brake ) on a hot engine = fuel cut.
I think engine run-up on a cold engine does not = fuel cut.

I know I can get fuel cut when coasting in D or L. Never in N.

I do not think there are absolute conditions you can count on.
It would take weeks, many hours, and many gallons of gas to find out all the conditions.

Simply put, you cannot rely on "open loop" to always mean fuel cut.
Sometimes it does, but not always.

Open loop only meansAn operating condition based on instructions not modified by PCM feedback.

 

SPL: I agree with John on this. I don't have enough technical knowledge of the hybrid drive to do other than make the simplistic observations I have reported in this thread. I believe the 2005 and 2007 behaviors are probably identical, but we are trying to reverse engineer both hardware and software that probably has many different modes/states. Given that, our observations will likely differ on occasion.

 

gpsman1 and econoline — The only question I'm hoping to get settled here is whether either of you (or anybody else) indeed gets both fuel-cut and closed-loop indications at the same time. Of course, open-loop operation does not imply fuel-cut operation. I never said that it did. However, Ron DeLong's experience is that conversely fuel-cut operation invariably does imply open-loop operation. (That is, open-loop is necessary, but not sufficient, for fuel-cut operation.) If this is universally true, then an open-loop indication, together with additional checks, could constitute a sufficient condition to detect fuel-cut operation. That's what he's planning to implement. But this will fail if the FEH violates this "rule." We want to detect fuel-cut operation, so that ScanGauge's fuel consumption calculations can be made correct even when fuel-cut occurs — currently (at least in the Toyota hybrids) ScanGauge reads incorrectly during fuel-cut. So, what I'm trying to determine from you is whether either of your FEHs actually contradicts this "rule" — i.e., performs fuel-cut while indicating closed-loop operation.

Stan

 

Okay, but what is the indication that the FEH is in "fuel-cut" mode? Tell me precisely what to look for.