My K1500 DD Tow Pig

[L31MaxExpress]

@Supercharged111 I forgot to ask you if this was for the 1500 or the Dually?

 

[Supercharged111]

Those are in the left top corner of the first picture. Enable Time 180 seconds, Moving Delay is 15 seconds. Enable Speed 55 mph. Disable Speed 52 mph. Lean Out rate is 2x the factory PE entrance rate.

Ahh, didn't even catch that. Wasn't looking for it in that screen, gotta love HPT vs EFILive differences like that and the axis being flipped. This is on the 1500, I figure it stands a better chance of benefitting vs the dually but if it has an appreciable effect I'll try it on the dually too. I'm about to drive this thing 1300 miles back to MI so if I can pick up 1-2 mpg I'd like to. I dropped the off idle enable timer to 30 seconds. With it having the ECT multiplier and VSS enable/disable I don't see much point in the timers other than to prevent excess cycling in transient conditions.

 

[L31MaxExpress]

Ahh, didn't even catch that. Wasn't looking for it in that screen, gotta love HPT vs EFILive differences like that and the axis being flipped. This is on the 1500, I figure it stands a better chance of benefitting vs the dually but if it has an appreciable effect I'll try it on the dually too. I'm about to drive this thing 1300 miles back to MI so if I can pick up 1-2 mpg I'd like to. I dropped the off idle enable timer to 30 seconds. With it having the ECT multiplier and VSS enable/disable I don't see much point in the timers other than to prevent excess cycling in transient conditions.

One thing the enable delay allows is for the long fuel trims to adjust for shifts in fuel delivery over time like a fuel pump that is getting weak or a vacuum leak. Another reason for the enable time could be for a stop with the engine hot. Such as stopping for fuel at a station just off the highway. It lets the engine cool off from the heat soak of being stopped before it enters lean cruise again. There are a lot of Texas backroads that I drive that have towns with one blinking red light or stop sign on the square. Coast into town, stop and then go again. Speed limit picks back up nearly immediately after getting off the square. I do not see a reason to wait 2-3 minutes to re-enter lean cruise in that situation so my off-idle or rolling enable delay is only 15 seconds.

 

[L31MaxExpress]

Figured I might throw this out there as well while we are talking about tuning. I finally became tired of the rough, shuddering idle that my cam was creating in closed loop. I went to open loop idle. The engine starts using the standard enrichment and cold start routine. The closed loop table is set for 131*F. The HOT PE table is set to enable at 131*F. So during warmup at idle the PCM basically switches from Open Loop - Not Ready to Open Loop - WOT Enrichement. The wideband tapers down from 0.80 or so to 0.95 during warmup and holds around there when the engine is hot. I am now idling at ~13.4:1 with 10* of timing in Park/Neutral and 16* of timing in Drive. I had previously varied the timing between 20* and 30* when playing with the idle timing and settled on 25* because it felt the same and that was the point where the MAP stopped decreasing. I went to open loop idle and it was still idling rough with what I can best describe as a skip or almost misfire feeling to it. I was talking with a friend that is a big carburetor fan. He reminded me of the fact that some hot rod engines like ported vacuum rather than manifold vacuum on the vacuum advance canister. I decided to duplicate that in my PCM tuning. Glad I actually tried it. Not only is the idle smoother, but it has mellowed out the tip-in throttle response and then smoothed out the transition from coasting to idle. The chop of the cam sounds more natural as well. Once I did that I played with the idle under/overspeed until I decided to start over. I ended up using slightly tweaked values from a GM LS3 6.2L 525 HP crate engine file. With the displacement, compression, and cylinder head flow I have, I figure its a GEN1 version of a LS anyway, LOL. Underspeed adder stops at 200 RPM because that is where the stall saver is mostly set to activate. Definately do not want to add a big bump of timing while the IAC is being aggressively opened.

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[Supercharged111]

I left the run time timer alone, assuming there was a good reason and I think that hot restart is a really good reason. Heat soaked fuel in the rails will also make the thing run lean and it takes a minute or 2 to purge that out. I remember that from a 4 cylinder build of years gone by, it had a standalone and was not fond of hot restarts. It also lacked the ability to interpolate cells, so hot restarts would drag it out of its little happy spot in the tune and make it hunt for idle for the first minute or 2. I think I'll just press with the new off idle timer, lean the low load out a little more, and consider dropping or tapering at the .56 cell. I need to see how big my window is between lean cruise and PE, don't want to just jump right from one to the other.

 

[Supercharged111]

So today I mostly copied you L31, 15 seconds off idle but left the stock 150 second vehicle run timer. I also noticed last night that my coolant was dropping down around 170 which is less than the 176 bottom end of where it was kicking in. That explains why it seemed like it was only partially kicking in and not as frequently as I thought it should. I dropped it down one more, but will likely be getting a new thermostat here sooner than later to keep it 180. I then revised the fueling, again largely copying L31's theme which is the one that made more sense in my head as it progresses from leaner under less load transitioning more toward stoich as load increases.

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The first round I tried earlier had it still in the .56 gm/s cells, but after rechecking yesterday's datalogs I decided 82kpa is too much air to be in lean burn mode, it's the beginning of boost here at 6500' so no bueno. On the test drive though, it would roll right into and out of lean cruise every time without hesitation so now it's pared back to above. Around town 45-55 mph it holds lean cruise nicely, not too sure what the demands will be like on the highway at 80 pushing wind and 33s. I blended the stolen Holden timing values too.

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I'd like to get some more data tomorrow, the laptop locked up after flashing the truck earlier so I just went for a drive and watched the wideband gauge to get a feel for what the truck was doing. The lean bit feels pretty seamless so far, but I do need to live with it more because I'm sure I'll start to notice something about it.

Oh, and lamda vs AFR is nothing. The fact that lamda and EQ exist simultaneously is what's evil.

 

[L31MaxExpress]

So today I mostly copied you L31, 15 seconds off idle but left the stock 150 second vehicle run timer. I also noticed last night that my coolant was dropping down around 170 which is less than the 176 bottom end of where it was kicking in. That explains why it seemed like it was only partially kicking in and not as frequently as I thought it should. I dropped it down one more, but will likely be getting a new thermostat here sooner than later to keep it 180. I then revised the fueling, again largely copying L31's theme which is the one that made more sense in my head as it progresses from leaner under less load transitioning more toward stoich as load increases.

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The first round I tried earlier had it still in the .56 gm/s cells, but after rechecking yesterday's datalogs I decided 82kpa is too much air to be in lean burn mode, it's the beginning of boost here at 6500' so no bueno. On the test drive though, it would roll right into and out of lean cruise every time without hesitation so now it's pared back to above. Around town 45-55 mph it holds lean cruise nicely, not too sure what the demands will be like on the highway at 80 pushing wind and 33s. I blended the stolen Holden timing values too.

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I'd like to get some more data tomorrow, the laptop locked up after flashing the truck earlier so I just went for a drive and watched the wideband gauge to get a feel for what the truck was doing. The lean bit feels pretty seamless so far, but I do need to live with it more because I'm sure I'll start to notice something about it.

Oh, and lamda vs AFR is nothing. The fact that lamda and EQ exist simultaneously is what's evil.

I actually just crunched your overall gearing. With 33s and 4.10s you are very similarly geared to my 30.5 and 3.73s. On paper, 2,200 rpm is 70 mph for you and 71 mph for me.

My living room on wheels does not seem to mind running anywhere between 55 and 80 mph in lean cruise. At 65+ mph, it will even lug itself up a 1-2% grade without coming out of lean cruise.

That being said a big chunk of the gains will come from the downhill side of things, like when you ease up on the throttle to maintain speed going down a slight grade. The gains especially there are bigger than one would think.

Lets say for example on flat road you are getting an instant 16 mpg at stoich. 10% gain would be 17.6 mpg. However run down a 2-3% downgrade with less throttle. Running at stoich that might show 30 mpg. In lean cruise that 30 mpg jumps to 33 mpg. Now point the nose up a 2-3% grade. The lean cruise will fade away as the load increases and at some point the air/fuel will be the same as stoich and then into PE. That 2% uphill grade may drop the thing to 10 mpg and air/fuel in lean cruise is now commanded at 15:1 where it is only helping squeeze another 1/2 mpg out of it.

I guess that is a really long winded way of saying that trying to run lean at higher loading is not where you benifit heavily from using it, so don't stress over allowing it to exit as the gm/cyl readings rise.

I just looked over some datalogs both with and without lean cruise functional. I never really analyzed the how and why mechanics of it. I looked at points where the MPH, RPM and Delivered Torque were all roughly equal. I actually found it odd that the throttle opening to maintain speed on level sections of the same road actually decreased in lean cruise. The engine was running the same MAP reading with less throttle. The TPS, MAP, and MAF are exactly backwards from how I had always assumed lean cruise gained mileage. I always assumed you put your foot into it more which reduced the vacuum. Looking at the data it seems the engine is making power more efficently from the reduced pumping losses and less throttle is being used. I guess it could make perfect sense because the engine is being throttled by the leaner mixture and it is not fighting the intake manifold vacuum as much to run itself and that shows up as less throttle to run a given speed. I will say it was a pretty drastic difference.

Stoich
65 mph
1,988 rpm
16.9% TPS
62.0 KPA
0.39 gm/cyl
120 ft/lbs
14.12:1 AFR
32* Timing
15.88 mpg calc

Lean Cruise
65 mph
1,984 rpm
14.5% TPS
61.8 KPA
0.38 gm/cyl
122 ft/lbs
15.77:1 Afr
39* Timing
17.42 calc mpg

 

[Supercharged111]

I got to reading and saw the same thing with the MAP readings, so to get any better I'd need to log for that in and out of lean cruise on the same stretch of road to find out what makes it happiest. Looking at where it's 17:1 and leaner it's where I barely have the throttle cracked going downhill, so very low threat there. Flat roads are scarce near the house to get a feel for 70-80 mph, but I figured if I dragged it out at too high a load I'd just be shooting myself in the foot. I have a 1300mi one way/2600mi round trip road trip coming up next Saturday. If the wind isn't blowing like a sunofabitch I'll be able to get a good idea for the change in highway economy. Makes me want to try it on the Z06, but I think it'll kill cruise control if I do it. Worth a shot though as it's totally reversible. That gets 25+ mpg highway, 30 would be pretty sweet. I saw 31 on a trip to Denver and back. I don't know what it is about that stretch of interstate, everything I own gets freakishly good mpg on it.

 

[89RCLB]

There's a pretty flat stretch of road between Garrett Rd and Peyton that might work for your test?

 

[Supercharged111]

There's a pretty flat stretch of road between Garrett Rd and Peyton that might work for your test?

Kinda short, out past Stapleton Rd would be better but I'd need to do it both ways as there is a fairly constant, lazy elevation change.