Lets talk lambda...

[StealBlueSho]

So there are many threads talking about AFRs, carbon build up, cat temps, etc etc etc...

The stock Lambda desired when WOT goes as low as .68 which is super rich. However, Ford seems to think this is OK, and will CPO a car for 100K miles this way.

LMS is who is a well respected tuning company  leans this out to .74 at the end of the gears. This is leaner than stock, but at the same time still very rich.

Almost every other tuner is somewhere between .80-.82..

The latest dyno bake off between GH and LMS seemed to indicate that there is not much power difference between .74 and .82....

I'm leaving E blends out of this discussion to keep the water from getting muddy(er)...

The question is, with Ford running .68 at their richest and some tuners running .82 with LMS smack dab in the middle, what is the trade off?

Doesn't seem to be power based on the dyno information posted....

Thoughts?  I know I'm conflicted...

[802SHO]

I dont believe I have an answer or solution.  I would like to add more thoughts.....Ford is happy with .68 but the engine is highly detuned per say....and super rich....LMS steps in and develops tunes delivering more power and their at .74 but also very rich...and one if not the first to tune an Ecoboost ...perhaps .74 is a step in the right direction while playing it safe as much was still unknown or not tested enough at that point....then you have other tuners stepping in after the fact coming in at .80-.82 and theres more than one tuner or company using that lambda ....is that because it's been determined to be still safe?  Is it still not (very) lean?  We went from .68 (very rich) .74 (less rich) so now is .82 very lean or is it just right?  And is .82 adequate across the board for whatever mods you have in mind (upgraded turbos, internals?  So is the slight increase in power from .74 to .82 more or less in line with the extent of your modifications currently? 

[Gjkrisa]

I was watching a video of engineer explains and he said that di engines run richer so they can run higher compression and make sure you control pre detonation.

I believe it's in the one explaining difference of di and port injection.
And that actually combing the two is to help idle and low rpm gas mileage.
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[AJP turbo]

You are pulling the absolute richest scenario from the stock tune at .68 lambda. One of the benefits of Direct injection was the fact that they are happy to run much leaner than Port injection. And Ford actually put a lot of design into the shape of the piston to combat detonation.

Except for true WOT the SHO actually runs very lean. It doesn't even command open loop fuel enrichment until 90% pedal so you can run plenty of boost at 85% at 1.00 lambda.

Then even once you go WOT it will run about .90 lambda to about 3000rpm then .85 to about 4000rpm. It doesn't go really fat until over 4500rpm.

I've left catalytic and HEGO and valve temp protections at stock values and not needed temperature protection from fuel control to kick on. So even at leaner than stock AFR's EGT's were not at dangerous levels.

I think the biggest problem with leaning out the AFR's that people don't think about is NOX emissions that are produced.....OEM's tend to be more concerned and bound by those...Drivers of tuned cars tend not to be concerned with the environment as long as emissions tests are passed.

[StealBlueSho]

You are pulling the absolute richest scenario from the stock tune at .68 lambda. One of the benefits of Direct injection was the fact that they are happy to run much leaner than Port injection. And Ford actually put a lot of design into the shape of the piston to combat detonation.

Except for true WOT the SHO actually runs very lean. It doesn't even command open loop fuel enrichment until 90% pedal so you can run plenty of boost at 85% at 1.00 lambda.

Then even once you go WOT it will run about .90 lambda to about 3000rpm then .85 to about 4000rpm. It doesn't go really fat until over 4500rpm.

I've left catalytic and HEGO and valve temp protections at stock values and not needed temperature protection from fuel control to kick on. So even at leaner than stock AFR's EGT's were not at dangerous levels.

I think the biggest problem with leaning out the AFR's that people don't think about is NOX emissions that are produced.....OEM's tend to be more concerned and bound by those...Drivers of tuned cars tend not to be concerned with the environment as long as emissions tests are passed.

Thanks for the insight there Brad. Yes, I pulled those numbers from WOT at their richest, but generally when people talk lambda they are wrapping it around the context of the WOT and enrichment strategies.

My concern is longevity based on those different strategies. Some tuners say running too rich at WOT leads to excess carbon build up on the pistons which over time can cause major issues. Other seem to say running too lean (such as .82) can cause issues with excess heat.

Realistically .82 is still considered rich, and a lot of platforms outside of the Ecoboost world accept .80-.82 in a DI application to be plenty rich to protect the engine from lean conditions/detonation.

Just wonder why Livernois is soo adamant on running so much richer... what do they know that no one else seems to know?

Ultimately I suspect a torture test of the motor running .74 vs .82 over the course of many many many miles then a tear down/inspection would answer this?

If the stated differences were not so radically different then it could be written off as tuning style... but with such a difference in strategy on the lambda side, it has me curious...

[AJP turbo]

SBS I feel like you may be grasping at straws. The difference between .74 and .80 is only about 8% difference. There are SOO many factors that would go into engine wear that there is no way you could control all variables and create a test where the 8% change in air fuel ratio was the only variable.

Attached is the fuel curve a WOT for a stock SHO. It actually only commands .73 at richest. But much leaner with lower coolant temps.

I just don't feel like the differences are "radical"

But WOT is not just a single AFR value there is a curve.

But to address the heat part: Like I said before there are protections that are invoked in the tune when valve, flange, cat and EGO's get hot the ECU will take over fuel control and adjust the AFR's to control those temps. I have not seen those temps exceeded or the ECU use fuel control at .80

Just some thoughts.