Start of injection timing, cammed LT1 with +32% fuel lobe. Tuning strategy?

[mavericka70]

Has anyone had any verified gains with adjusting SOI on a cammed LT1, or is the stock table best left alone unless you're running out of fuel on a boosted application? If there are potential gains, what's the approach or process for optimizing these values?

My car has a tsp VVT-3 cam with the +32% lobe and flex fuel, for reference. Thanks for your input.

[Ben Charles]

SOI needs to be modded... it can be ran on stock SOI table, but nodding the table will help

[mavericka70]

SOI needs to be modded... it can be ran on stock SOI table, but nodding the table will help

I had a feeling this was the case. Has anyone noticed any trends with moving it closer to certain valve events, or is it just something you have play with on the dyno to get it dialed?

[GHuggins]

Gen 5 injection timing is real simple and can be overly complicated rather easily... Other than the exhaust - forget about valve events Your goal as simply as it can be put is to optimize timing enough to where the fuel is burning cleaner which is usually during higher cylinder pressure injections, but to not inject so late that it causes false knock from the injection window getting too close to the spark window... Typically you retard the injection timing by making the numbers less in the soi table which usually allows you to pull fuel from the air models due to cleaner burning cycles... This results in more power - have heard of 15 to 20 hp just in soi adjustments... When you retard it too much you'll know immediately from the knock the engine is suddenly adjusting for - this isn't real knock - it's just timing being pulled to avoid spark during the injection cycle... Shift the timing back from this and you should be good to go... Remember fuel is spraying into a pocket on the piston - the better you can "optimize" this, the better off things will be hint hint... Of course you still have a lot of things to work around - amount of fuel that can spray through the injectors for example - requires sooner soi's and so on...

[mavericka70]

That was very helpful, and will save me a lot of money when I go to book the dyno time. Thanks for your input, it makes a lot of sense to me now.