safe WOT AFR for stock 2014 5.3 sierra

[ayousef]

How lean can you go on a direct injection motor before you have to watch out? This is on 93 octane and stock everything. Also considering you don't want to kill the cats in short order.

Plus, is there any reason why the PE table looks so weird on stock vehicles? more so on my direct injection truck.

[SultanHassanMasTuning]

they all have weird values as you can see its a bit richer in peak torque as well. DI engines can go leaner depending on your fuel quality

[thewrx]

Have you tried e85 yet, nice little kick for a stock tune and stock truck.

[sunny]

Great question! It sure would be nice if someone answered it.

[Higgs Boson]

most go to 13:1, I personally would leave it at 12:8 or so, no point in leaning out a stock or bolt-ons truck. it's still going to be slow, so why not be safe about it?

if you are going for some kind of track record you might lean it out more but no one is going to tell you an exact number. if you blow it up they don't want you saying it's their fault! after all, here in the US, you can get sued for having bad breath, much less giving bad advice....

[thewrx]

what would you say if you were boosted? safe afr? I target around 11.0 right now.

[Higgs Boson]

12.2 on a direct injection engine

[thewrx]

I think that would not be safe for a boosted application, DI or not, unless you are running alcohol or something.

-D

[Higgs Boson]

you can run it even leaner than that. that's why you are breaking up, we have been through this many times....just do a search if you want.

[thewrx]

you can run it even leaner than that. that's why you are breaking up, we have been through this many times....just do a search if you want.

Actually the reason it was breaking up was the gap in the plugs was too wide, factory was almost .040. I regapped the plugs and now its not breaking up. I am sure search will tell me lots of information both useful and not useful, but DI engine or not having boosted motor with pump gas and 11.5 compression on a brand new truck 12.2 is a little to lean for my comfort. I am sure my tune is on the rich side but will make small incremental changes as I start put more timing in it and pulling more fuel out.

[Higgs Boson]

why did you ask the question in the first place then?

[Higgs Boson]

http://www.hptuners.com/forum/showth...7-Weird-issues

[mowton]

Actually the reason it was breaking up was the gap in the plugs was too wide, factory was almost .040. I regapped the plugs and now its not breaking up. I am sure search will tell me lots of information both useful and not useful, but DI engine or not having boosted motor with pump gas and 11.5 compression on a brand new truck 12.2 is a little to lean for my comfort. I am sure my tune is on the rich side but will make small incremental changes as I start put more timing in it and pulling more fuel out.

You aren't injecting against a closed valve where you also have to compensate for evaporation, puddling and impact factors. FI in the previous injection methodology also needed to be richer to help cool the charge to preclude detonation. From my reads, injecting directly into the chamber at much higher Fuel Pressure PSI's (2000+) provides adequate charge cooling at a lower fuel to air ratio. As HB stated, there is a lot of reads out there.

Ed M

[thewrx]

why did you ask the question in the first place then?

We'll didn't know at first then started checking the obvious, appreciate the discussion regardless.

[thewrx]

http://www.hptuners.com/forum/showth...7-Weird-issues

good read, left me with blue balls though. The lean theory was not proved or disproved in this thread.

Andy had a badass trailblazer back in the day.