is lean cruise bad for the engine

[Garry]

I was under the impression,

lean-cruise raises cylinder head temps and thus raises ECT?

Lean condition raises the burn temperature, so yes, anything will heat up more. Anyway, as someone else stated, under low load, this usually isn't a real problem. The only thing to watch out for is the cats, if you still have some ... IIRC, cat protection will add additional fuel when it kicks in to lower exhaust temperatures ...

lean cruise actually makes, don't think it's going to turn a 6.0L in to a Honda Civic!

Well, I sincerely hope not! J/K

[vzsv8]

I don't aggree that leaning the mixture ( from stoich ) will increase temp. If we are running lean at cruise than the load is clearly low, so if we go lean we are going lean from 14.7. Therefore less fuel than optimum, giving less temp.
This is not a guess, pilots regularly run 75% throttle at cruise and 50 degrees Celcius colder than stoich, for best safe economy.
On the other hand, if we start at 12.5 or so at full load and start to lean off temps will certainly increase, toward 14.7.
Does anyone have an EGT gauge and the ability to run lean cruise? There would be some interesting data to be gathered.
I think that PLX will be getting an order for Fathers' day
Cheers, Steve

[Boost]

Thanks for the interesting info, vzs. Care to explain why you think that occurs? By the way I love the sig!

[kbracing96]

I have a log with Tech Edge WB installed and a pyro. This is all at highway speed. Load increases temp, but lean cruise doesen't let me know what you think.

[vzsv8]

I have a log with Tech Edge WB installed and a pyro. This is all at highway speed. Load increases temp, but lean cruise doesen't let me know what you think.

Your log is exactly what I have been looking for. I have mapped your EGT vs Throttle Position, filtering out transient throttle, low throttle, cold ECT and cell counts less that 10. It shows that as AFR leans off EGT drops. Not sharply, just a big, wide, fat curve.
My take is that 14.7:1 represents exactly the correct proportions of reactants (obviously), and so gives the hottest flame, if we vary from stoich then the flame cools and burns more slowly.
This means that a rich or lean mixture needs more timing, sort of explains B5908 (Fuel mixture spark correction) and its use for lean cruise.
More timing should compensate for the slower burn and lower temps even more.
The OEMs can't use this approach because a lean mixture gives good economy, controls CO and CH but fails NOx badly.
BTW your drive home from work is about 100Kph faster than mine
Cheers, Steve

[kbracing96]

I'm glad you found it useful. I have had the EGT prob installed for quite some time, just have never really put it to good use.

Oh, and that was my drive home from the track this Sunday. My truck ran a best of 12.21@110.5mph, not bad for a 5300# pig at 4800' elv. (DA was 7000') :lol: And our interstate speed limits here are 75mph

[GMPX]

All this talk of lean cruise reminds me. I was sent an Email a month or so back stating that on a Torrent download site there was some cax files posted that allowed lean cruise on all GenIII's from 2001+, US vehicles included.
If someone can find them please let us know what it's all about. I've had no luck in my searches.

Cheers,
Ross

[Chevy366]

Hmmm , does it really work ? : http://thepiratebay.org/torrent/4303...ll_ls1_engines
Tried DLing , nothing .

[GMPX]

Thanks for the link, from what I see yes that would do the trick. If you dig back far enough on our forum (or it was LS1Tech), there was some guys that figured out what needed to be done.

Cheers,
Ross

[Chevy366]

If someone can get it to download , would they post the file ?
I have tried several times and will not download .
Thanks