Gen 5 boosted target AFR
Gen 5 boosted target AFR Anyone mess with gen 5/LT4 stuff or looked at a stock tune? I'm trying to understand how direct injection impacts target AFTER I for a boosted setup. I couldn't find much info searching online other than people saying it's leaner than port injection. An example would be port injected 93 octane ls1 may target 11.2 under boost, an LT4 direct injection on the same 93 octane may target 12.0 under boost. My understanding is that its due to cooling efficiency and that more of the fuel stays a liquid in DI as opposed to PI. Learn me.
Thanks. Do they typically handle more timing as well because of DI? Ps....not asking for anything GM related. I just posted on here cause guys like you that do this for a living would give me concise honest feedback.
We dont run alot of timing in them but 95% of the time when we re-tune something from another shop we run less timing and make the same power and go faster. They are sensitive to timing but I think that has more to do with the E92 ecm vs the DI.
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Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
The gasoline and spark plug don't really know it's DI vs PFI. You just get an extra cooling process inside the cylinder as the fuel evaporates, so think of it as running in a cooler ambient temp. I see a lot of village wisdom claiming that the DI engines need to run leaner under boost than the previous (LS3/7) engines and that's simply not true according to the tests I've run where we were able to keep conditions constant.
Thanks Greg, was hoping you'd chime in. I'm seeing other platforms outside of gm where people are running boosted setups upwards of stoich with DI and it just didn't make sense to me.
The gasoline and spark plug don't really know it's DI vs PFI. You just get an extra cooling process inside the cylinder as the fuel evaporates, so think of it as running in a cooler ambient temp. I see a lot of village wisdom claiming that the DI engines need to run leaner under boost than the previous (LS3/7) engines and that's simply not true according to the tests I've run where we were able to keep conditions constant.
^LSX- You said the plugs looked rich at .8 and made less power than .84....I assume that means the richer AFR didn't help with the heat soaking of the LT4? Sounds like the DI cools the charge enough that the impact of heat soak is minimized?
Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
The link above shows us on the same dyno, but it isn't the Lambda sweep. It's all in the disc though.