Lean Cruise Questoin, how far can I go?

[truethinker]

I now have my VE tuning done and have Lean Cruise enabled and working. Now I am looking for some pointers on how far I can take a few of the settings.

I took the lean cruise setting from a holden tune and noticed that in the B3639 table at 0.32 grams/cylinder and 200rpms(my cruising sweet spot) the lean out was very low so I filled this cell with a rational number based on the surrounding cells. I'm hoping for some help as to how far I should be able to safely take this lean out setting on a factory engine and any pointers on adjustments to be made to get the most out of this.

Also, in B3638 the lean out rate is 0.0010. Can I make this a little faster or should I leave it alone?


Thanks!
Jesse


13409

13410

[macca33]

I, too, have been considering the implementation of the lean cruise facility. At present, I simply command COS3 SD semi-open loop stoich in my 'cruise' cells and to be honest, the mileage is not too bad - down to 9lt/100km on a good trip. I am considering using the factory Holden tables for lean-out rates, etc, but tidying the commanded EQ differentials to consistent values and not going so lean - I'd like to stay at around 15.4-15.6:1, to ensure that it is within a safe margin. I think that during initial set-up testing, WB monitoring is a very necessary thing.

Good luck with your testing

cheers

[Chevy366]

I now have my VE tuning done and have Lean Cruise enabled and working. Now I am looking for some pointers on how far I can take a few of the settings.

I took the lean cruise setting from a holden tune and noticed that in the B3639 table at 0.32 grams/cylinder and 200rpms(my cruising sweet spot) the lean out was very low so I filled this cell with a rational number based on the surrounding cells. I'm hoping for some help as to how far I should be able to safely take this lean out setting on a factory engine and any pointers on adjustments to be made to get the most out of this.

Also, in B3638 the lean out rate is 0.0010. Can I make this a little faster or should I leave it alone?


Thanks!
Jesse


13409

13410
I did the LC on my 6.0L and just used a Holden 5.7L settings like you, works fine. Thing with LC is any slight load (keeps it from knocking) and it drops out of it, so around where we live there are hills, load, my $.02 on LC.
Works, but benefits are minimal.
Know it does not answer your question, just don't go to lean.

[johnv]

I've seen the factory lean cruise tune run into the 16s afr at light cruise, but as said doesn't need much throttle to drop out of lean cruise with factory settings.
I would log to determine what cells you would normally cruise in at light load ,and massage them in the lean cruise table ,to give desired AFR.

[truethinker]

Thanks Johnv. That's pretty much what I've been doing. Based on the table, the most lean it can command is an afr of 16.5617(based on my 14.2 commanded stoich for E-10). I've seen it go as far as 1.1668 Lambda on the WBO2's so I'm pretty confident that everything is working properly. I'm just curious of the general consensus on how lean is too lean under light load.

[krisr]

What is the manifold pressure with and without lean cruise enabled. If the vacuum increases (kpa value goes down) then your engine is running more efficiently. Once you work out what the engine wants, then experiment with timing in those areas too. Lean mixtures burn slower and need more spark advance, again keep an eye on manifold pressure. It's the best way to work out if your motor is happy. This is what I found when I tuned my Megasquirted Pontiac 400 engine and I applied the same logic to my 2005 Holden Monaro CV8Z LS1 engine and seems to work great.

In my LS1, I cruise around 15.5-16.0 AFR with 38* spark lead. But the 400 can only take ~14.8 due to cam overlap.

[truethinker]

Thanks krisr, that makes a lot of sense. So decide on my desired lean cruise EQ ratio by logging MAP at different commanded EQ ratios.

It seems to me(and I could be way off) I should get my spark nailed down(B5914 Spark Low-Octane Table?) without lean cruise enabled and then adjust the timing for lean cruise via B5908 Fuel Mixture Spark Correction?

[krisr]

I dont use the Fuel Mixture Spark Correction table - but that's an interesting thought.... - I just use the high/low tables.

[johnv]

I also have a factory supercharged V6 commodore as a daily driver,
Put the wideband on it a few weeks back out of curiosity, and was quite shocked to see AFRs in the mid 17:1s at light cruise,
so I think you can lean em out quite a bit ,as long as you don't go crazy in higher MAP load cells.

[Chevy366]

15:6 is as high as I have seen mine but a few years ago someone was saying 16:1 in a Holden.
I found the Custom OS Speed Density worked just as well if not better than the LC.
Seems MAP is the key, never tried advancing timing, felt that the gains were so minute that any further experimentation was not warranted.

[truethinker]

thanks for all the input guys. I was considering a custom OS for this but just haven't decided if it is really warrented for a mostly stock daily driver. although I'm not over knowledgeable about the Custom OS's

[truethinker]

What is the manifold pressure with and without lean cruise enabled. If the vacuum increases (kpa value goes down) then your engine is running more efficiently. Once you work out what the engine wants, then experiment with timing in those areas too. Lean mixtures burn slower and need more spark advance, again keep an eye on manifold pressure. It's the best way to work out if your motor is happy. This is what I found when I tuned my Megasquirted Pontiac 400 engine and I applied the same logic to my 2005 Holden Monaro CV8Z LS1 engine and seems to work great.

In my LS1, I cruise around 15.5-16.0 AFR with 38* spark lead. But the 400 can only take ~14.8 due to cam overlap.

Can you expand a little bit on the best way to log MAP in a usable way. I'm not overly experienced at different uses of the scan tool. The most complicated thing I've done is autove and auto.VET.

Thanks!