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[Immortality]

Isn't it interesting that the factory shift maps and throttle positions for the cruise control function are quiet aggressive. Holden/GM had specialist test equipment fitted in cars and covered millions of K's datalogging all of this to optimize this stuff.

 

[VS 5.0]

I to like to drive with economically (efficiently ) as possible when cruising which to be honest is most of the time , but not always and enjoy the power when I want it but not always . Just because I try to get reasonable ltr/100 ks does not mean I don't deserve a v8 ! I have 3 v8s at the moment my hq gets 1 petrol station per 100 ks when cruising at 100 kph (3000 rpm) 2 ps /100ks if having fun and I don't have a problem with that, my Cadillac is reasonably economic for a 429 cubic inch carbureted tank . What i trying to say is just because I try and cruise without braking and gentle as can be on the go pedal I still enjoy putting my foot hard into it ,the push back into the seat, the sound of the v8 and the thrill but I must admit I don't like going to the petrol station at all and this has very little to do with money

Petrol station per 100kms......Lol.

 

[J_D 2.0]

Use cruise control as much as possible(when safe), that tells the smarts that you want to cruise, and puts the ECM in lean cruise mode.

Lean cruise mode doesn’t have anything to do with cruise control (ie: the system isn’t activated by cruise control). It just reduces the air fuel ratio progressively when the car is running on light throttle inputs. Unless its a flat highway cruise control actually uses more fuel as the computer can’t see the road ahead and floors it when you go up an incline to maintain the set speed.

If it’s an even slightly hilly road or highway you are far better off controlling the throttle yourself and slightly increasing speed before you get to the hill and letting the speed slightly decrease on the uphill run (say gain 5 or 10, lose 5 or 10).

 

[J_D 2.0]

I'm interested to hear about what is happening with lean cruise mode. Kind of makes you wonder, why they don't have some sort of button where the car computer adjusts everything so its in economy mode. Even older cars used to do it although from what I understood, that was mainly playing around with the transmission and how aggressively it would change.

The testing I have been doing as far as I could see, I was leaning towards the opposite. With manual control of the throttle, I can better foresee upcoming conditions ahead of me and act accordingly. Whereas, I found cruise control more aggressive in maintaining the set speed. When I'm driving for efficiency, I look as far ahead as I can possibly can and drive accordingly. If I see a set of lights a long way in the distance, I either put it in neutral or aim for DFCO if I need to slow down. If I'm heading for a head especially after being on a hill, I'll let it gather speed for the uphill so that I don't have to accelerate as much as cruise control would on that same hill. Accelerating on the downhill and lifting off as much as possible saves a fair bit in my experience.

I'm going on a long cruise in a few hours and should have a lot more distance to do some more testing.

What I do with my manual SSV when coming to a stop is run the revs down as low as possible in the gear that I’m already in and then flick to neutral. Trying to switch down gears to keep the decel fuel shutoff going is going to burn more energy anyway as you’ve got to match revs for the downshift, not to mention the extra clutch wear which would easily outweigh any potential fuel saving you may get from the decel cut off.

My trip computer says I average 12.3l/100kms in my SSV. That’s with a mix of probably 80% highway and 20% city. I don’t try to be economical (I like the shove back into the seat on acceleration) but I don’t flog it either. Normally never get over 3000rpm as there’s no need to.

 

[Immortality]

Lean cruise mode doesn’t have anything to do with cruise control (ie: the system isn’t activated by cruise control). It just reduces the air fuel ratio progressively when the car is running on light throttle inputs. Unless its a flat highway cruise control actually uses more fuel as the computer can’t see the road ahead and floors it when you go up an incline to maintain the set speed.

If it’s an even slightly hilly road or highway you are far better off controlling the throttle yourself and slightly increasing speed before you get to the hill and letting the speed slightly decrease on the uphill run (say gain 5 or 10, lose 5 or 10).

You can still do that with cruise on, just apply a little throttle coming up to the hill to accelerate and then gently lift off the throttle and let cruise take control again as the speed drops back to the original set speed.

 

[J_D 2.0]

You can still do that with cruise on, just apply a little throttle coming up to the hill to accelerate and then gently lift off the throttle and let cruise take control again as the speed drops back to the original set speed.

Yes, I suppose you could do it that way as well but it won’t run under your set speed. If the speed limit is 100 and you go plus 5 before the hill and minus 5 on the run up the hill you’ve done a difference of ten for a cost of 5 acceleration. If you do it on cruise you have to gain the full 10 to lose 10 on the uphill so it’s less efficient.

 

[Immortality]

I'm not that concerned with penny pinching. It's only a worthwhile effort on small hills, when it's a big climb just let cruise do it's thing.

 

[07GTS]

lean cruise was tried in the early commodores and LS1 but not in any current e38+ ecu as they brought in DOD, also just leaning out AFR dosnt save fuel its a game u have to get right, leaner AFR also looses torque so the throttle has to be increased to hold set speed which offsets the leaner mix, so u can add timing and lean out to try keep torque but dosnt always work without alot of testing, petrol i had best results from staying CL and dial in spark timing and injection timing, on ethanol as its much richer and safer (knock wise) fuel it can be leaned out as it also makes alot more torque then petrol so if i done some proper testing i could prob get that to around the same usage as petrol for long hwy trips

 

[J_D 2.0]

I'm not that concerned with penny pinching. It's only a worthwhile effort on small hills, when it's a big climb just let cruise do it's thing.

Well yes, I’m not that concerned either tbh (I didn’t buy a V8 for the frugal fuel consumption!), just pointing out that manual control is more efficient than cruise control if it’s done correctly.

The cruise does **** me on hills with its heavy throttle application and kicking back gears (on an auto) when its unnecessary. My SV6 can do most moderate hills without losing speed or kicking back gears if the throttle pedal is used judiciously but the cruise control just smashes the throttle and kicks it back to fourth every time.

 

[Immortality]

lean cruise was tried in the early commodores and LS1 but not in any current e38+ ecu as they brought in DOD, also just leaning out AFR dosnt save fuel its a game u have to get right, leaner AFR also looses torque so the throttle has to be increased to hold set speed which offsets the leaner mix, so u can add timing and lean out to try keep torque but dosnt always work without alot of testing, petrol i had best results from staying CL and dial in spark timing and injection timing, on ethanol as its much richer and safer (knock wise) fuel it can be leaned out as it also makes alot more torque then petrol so if i done some proper testing i could prob get that to around the same usage as petrol for long hwy trips

Yup. The lean cruise on the earlier engines would lean out the AFR's by up to 3 ratio's so going from 14.7:1 out to 18:1 and added a couple of degrees of timing. What the boys on the PCM hacking forum found was that you got the most complete burn at 15.4:1 on lean cruise and my findings are much the same. On my most recent trip where lean cruise went from .75 to 1.35 as speed increased from 100 to 110km/h economy went out the window and the throttle felt crap. Unfortunately I didn't have any tuning gear with me so I couldn't adjust to suit on the return trip but have adjusted the rest of the lean cruise on the L67 to 15.4:1 and pegged back the timing a touch to suit. Need to go on another long cruise to test now....