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On recent highway trips I found it difficult to trigger lean burn on my Insight 1 under all conditions. I seem to be able to trigger lean burn after shifting to 5th by easing up on the accelerator, allowing the FCD to rise quite high, and then gently squeezing on the accelerator, making sure to keep the FCD at around 100MPG or more.

On downshifts to 4th, I can't quite get the hang of retriggering lean burn. I try the same technique, but it doesn't seem to work as well. I've tried shifting early, say near the end of downhills well before the uphill, and applying the same technique, but it seems more difficult.

What is the best technique to retrigger on the 5th/4th downshift? BTW, I'm detecting lean burn with an X-guage programming of my SGII.

Hi, Jim -- what is the instantaneous readout when you are doing this? I don't have a SG II in my Insight so I can't see what you are seeing but I can generally keep mine above 75mpg on a downshift. On a level (low load) I can usually keep it over 90mpg.

Hi, Jim -- what is the instantaneous readout when you are doing this? I don't have a SG II in my Insight so I can't see what you are seeing but I can generally keep mine above 75mpg on a downshift. On a level (low load) I can usually keep it over 90mpg.

Well, obviously the SGII makes it a lot easier because the x-gauge "snaps" directly to zero when lean burn is activated. After lots of practice and lots of your coaching, I am acheiving about the same results you outline above, except for the wasteful 5th/4th downshift.

On the FCD, I get the correct indication pretty rapidly in fifth. I shift up, give it a second or so, and then squeeze on gently. The FCD may drop to 80-100 MPG and stay there if I'm smooth on the accelerator. The FCD is showing lean burn and I can confirm it with the SGII.

I have more problems with the 5th/4th downshift which I frequently do when on a downhill approaching an uphill. During the downshift, I'm obviously off the accelerator entirely. When I try to get back on the accelerator, however gently, I have very errating lean burn initiation. The FCD just plunges to values like 50-55 MPG. (I confirm that I'm not in lean burn by a quick glance at the SGII.) As you mentioned earlier, I usually try to snag the downshift early, so that I have a low load situation in which to get lean burn back, but the delays frequently get me into the uphill portion, and then it is impossible to get lean burn. Sometimes I get it into lean burn by lifting very slightly, and then pressing down again, and the FCD just shows the usual - rises very high on lifting and drops to 75 MPG plus on squeezing back on, when successful.

I suspect my accelerator technique may be the problem, but I thought I was being pretty smooth.

Jim, what speed are you doing this? At highway speeds I can keep the instantaneous at 70+mpg as long as I downshift before hitting 50mph (on the deceleration caused by incline). At lower speeds it generally drops from the 75mpg range when I cross through 26mph. There is a jump in the instantaneous when accelerating through that speed as well.

Cold weather has a big impact as well (in spite of a full grill block with good air intake temps). In this weather I often have to settle for 50mpg on the instantaneous for hills and accelerations. :(

[QUOTE=Right Lane Cruiser;252237]Jim, what speed are you doing this? At highway speeds I can keep the instantaneous at 70+mpg as long as I downshift before hitting 50mph (on the deceleration caused by incline). At lower speeds it generally drops from the 75mpg range when I cross through 26mph. There is a jump in the instantaneous when accelerating through that speed as well.QUOTE]

For highway driving I usually execute this 5th/4th downshift in anticipation while still on the downhill, and yes above 50 mph. Perhaps that is the problem. I will experiment with letting the car decelerate a bit on the up incline before trying to downshift and reactive lean burn. I think I understand that I should avoid dropping below 50 mph, for highway. I had thought that my best performance would be achieved by snagging the downshift early, but maybe I was wrong.

Though the car is has better FE at lower speeds, I figure I'm pretty well stuck in the 50-55 range, with some flasher use, for highway travel. Otherwise, the irritation factor for other drivers is too high, and one never gets anywhere.

Jim, you've got the right idea. Gain what speed you can in 5th on the downhill, then if the uphill is really steep downshift around 55mph. Otherwise, around 52mph should be good enough. A fast downshift without dead "off the pedal" time seems to work best for me.

I agree on the speed ranges. I generally will venture over 55 on downhills to whatever speed 100mpg instantaneous will allow while staying within the legal limits.

Jim, you've got the right idea. Gain what speed you can in 5th on the downhill, then if the uphill is really steep downshift around 55mph. Otherwise, around 52mph should be good enough. A fast downshift without dead "off the pedal" time seems to work best for me.

I agree on the speed ranges. I generally will venture over 55 on downhills to whatever speed 100mpg instantaneous will allow while staying within the legal limits.
My target is 50mph on the highway, but sometimes it drops into the 40's, especially if the road behind me is clear. I avoid going >55mph on downhills to avoid discarding energy to aero drag. Even if an uphill is coming up, because I find that its speed bleeds off really quickly on uphills. I'll feed in regen on a downhill if the SOC is not maxed. If the SOC is maxed, I do an FAS and let the speed build up. If the speed will build up >the PSL, I don't FAS and instead leave it in gear with fuel cut engaged, so the ICE acts as a brake.

I found that my FE is noticeably better at 50mph than at 55mph.

Oh, on hills I use MIMA to shut off assist and just accept whatever mpg I get, figuring that FAS on the downhill might make up for the losses. At least at wider throttle openings I'm burning gas more efficiently than I would at smaller openings. On steeper hills I downshift if I must, but 4th seems like an overdrive gear and doesn't get me much more power and I just continue losing speed. So when I have to downshift on a hill 3rd seems to yield better results.

Oh, on hills I use MIMA to shut off assist and just accept whatever mpg I get, figuring that FAS on the downhill might make up for the losses. At least at wider throttle openings I'm burning gas more efficiently than I would at smaller openings. On steeper hills I downshift if I must, but 4th seems like an overdrive gear and doesn't get me much more power and I just continue losing speed. So when I have to downshift on a hill 3rd seems to yield better results.

Wish I had MIMA, but don't think that's in my future.

I too have noticed that 4th doesn't really seem to add much torque when shifting down from 5th. Sometimes, if the hill doesn't look too steep or long, I just "nurse" 5th lean burn as long as I possibly can. That seems to provide results just as good as downshifting. Obviously I'm still experimenting and learning the car. After a year I still find it a mystery in many ways - but an interesting mystery :Banane59:

Obviously I'm still experimenting and learning the car. After a year I still find it a mystery in many ways - but an interesting mystery :Banane59:
I've had mine 3 1/3 years and I'm still learning it. Maybe I'm just a slow learner. Just last year I learned from Sean to shut off assist on hills to avoid draining the battery. That alone was worth 5-10mpg.

Hey Sean, I think I may have discovered my problem with the downshift. I may be letting the clutch out too abruptly. That seems to cause a torque tansient which seems to kill the lean burn state. I'll let you know if that turns out to be the problem.

Ah... I have noticed that for some transitions I get better results if I "finesse" the clutch modulation. Perhaps this is what you are seeing? It is really hard to describe but yes, it does feel like I'm holding onto the clutch pedal a bit longer.