Lean Cruise and Cruise Control

[neil]

I was just wondering if Lean Cruise works while Cruise Control is activated?
Also are there any adjustments that can be made for economy while in Cruise Control mode?

Regards,

Neil.

[Tordne]

I would imagine that Lean Cruise would function exactly the same In Cruise Control Mode. I haven't seen anything in the PCM calibration for Cruise Control, maybe it is a BCM function?

[gto_in_nc]

Lean cruise works very nicely with cruise control engaged on my GTO, including through minor speed corrections via the C/C stalk. I see 2 to 3 MPG increase with lean cruise enabled at "highway speeds". I have mapped RPM vs. DYNCYLAIR_DMA and created a less-smooth-than-I'd-like lump in {B3639}(the table is not granular enough), bringing AFR to just under 16 under Interstate cruise conditions. This makes the transition gentle and helps minimize the slightly annoying reluctance to disengage that lean cruise seems to exhibit (said reluctance being a double-edged sword.) Overall, I find lean cruise worthwhile and mildly entertaining...

[bifster]

lean cruise works without cruise control???

[ringram]

with or without... it triggers on the lean cruise triggers, run time, min speed, low load etc.

[gto_in_nc]

Correct! (Sorry, bifster - didn't notice the post.) As ringram says, once the runtime & trigger speed conditions are met, lean cruise is enabled and the adjustments to commanded AFR are applied. It doesn't care whether cruise control is on or not.

Set {B3634} to some reasonable warm-up time (600 seconds, maybe?), {B3635} to the off-idle "cruise time" you want as a delay (setting this too short greatly increases the likelihood of engagement when you are NOT really cruising long-haul), {B3636} as the speed above which you must be travelling for the trigger to occur (hint, set it fairly high) and {B3637} for a speed not too far below that (this is the "turn-off" trigger and you want to be able to drop below it without becoming a traffic nuisance.) I recommend setting {B3638} at 1.0 to start. "1.0" gives a nice little stair-step that's easy to spot in a dash chart.

You also need to make sure {B3646} is not zeroed out. Unless you live in really cold climate, I'd just set it to 1.0 across the board.

Then comes the most important part - setting {B3639}. I would suggest either setting up a map of DYNCYLAIR_DMA vs RPM to get cell hit counts, or linking Scan Tool & Tune Tool and selecting sections of "cruising conditions" to see what part of "Lean Cruise Target AFR" really interests you. For me, it is focused around the 2000 RPM band at 0.24 & 0.32 g/cyl. I set those cells to a value that gave me the AFR I wanted (NOTE: A wideband O2 is CRITICAL and having already dialed VE in using AutoVE is, too!) and then I blended back to 0.0 over an area of 6x5 cells , centered on those two cells. For me, a value in those two cells of 0.088 works nicely BUT don't just take my values or my word!

Then go out and try it! Make certain, though that someone (preferrably you) is carefully watching realtime AFR readings! A small typo can command outrageous AFRs (the values in {B3639} are subtracted from the commanded EQ and AFR numbers are simply a resultant of what the PCM is really doing) so be prepared to back out quickly.

I'd recommend setting the two times to something short (like 60 & 30) for your initial tests so you don't have to drive all over God's green Earth while you are getting things the way you want, and then bumping those times up high enough that you are unlikely to trigger lean cruise except when on a trip somewhere.

BTW, you can always disable lean cruise by just setting {B3636} to 255.

Make sense?

[Garry]

B3639 is 14.63 on my base tune the whole map ... what would be good values, like, 15.2 or so?

[gto_in_nc]

Sorry! Lean cruise doesn't work on any US cars with the exception of 2004 GTOs. EPA doesn't like it because of NOx emissions (or something...)

[Garry]

Not even in a COS#5?

Feature Request !? :)

[gto_in_nc]

You can do different things with COS 3 or 5, I believe, to have a something of a commanded lean-mode for cruise conditions but the real "lean cruise" is not there, and the guys have clearly (and wisely) stated that they will NOT but it in a custom.

I remember someone (Tordne, maybe?) spending a few minutes in another "lean cruise" thread, talking about how he approached it.

At some point, I'll likely move to COS #5 but at this point the MAF still does it's job nicely for me - and since my '04 GTO has lean cruise, I figured it out and have made it work for me. I'll be the first to admot, though, that it's a little quirky...

[5.7ute]

You need to be careful using lean cruise with cos5. I have enrichment built into my B3647 table which can cause a rich cruise mode if the parameters are met during acceleration. It seems that load is not a factor with the custom os just speed & time.
I am just running a pseudo lean cruise at the moment until my wideband is fixed & I can nut out the best way to run the table.

[GMPX]

Not even in a COS#5?

Feature Request !? :)

This one has been beaten to death in the past. There is some US cars running LC, but don't ask me to do it, but, it is just a simple patch, it was talked about over at LS1Tech last year.

I'm sitting on the fence still with this one. Maybe I'll ask my old mate Vim Fuego to post on here how to do it.

Cheers,
Ross