Originally Posted by Capricio
(Post 8098061)
Agreed. What I am surmising is DI depends a lot in very precise air velocity coming in and a lot of consistent air tumbling/turbulence. If you just start hogging out ports, putting in bigger valves, or forcing air in harder than the NA level expected, the whole thing goes to crap. Unlike port injection where the velocity of the air in the runner has it's own dissipative effect, the finely atomized fuel coming the concentric cones of spray from a DI injector don't suspend and reach every corner of the combustion chamber.
You make good points, and I'm not exactly sure how ported heads might affect the engine efficiency, but I will say (again, using the V6 as an example since its what I know, and has DI) we see positive results with a better intake, and a ported/better flowing intake manifold even without a tune. Of course a tune helps, as they can start to go a bit lean without it, but nothing so bad that you still couldn't drive it. So I don't see why the LT1 couldn't benefit from something similar.
There are a couple of C7 cams dyno'd on ls1tech, I'm not impressed. If what I said earlier holds true, then I don't see how adding duration or height to a profile can really do much besides slow down the air velocity and screw up the fuel dissipation. Now that the injector duty cycle doesn't depend on the intake valve being open, cam designers will have to rethink things.
With 2100 psi of fuel pressure, will a person ever really need a bigger injector? Or will it be more a matter of spray pattern?
I think its just a matter of supplying the stock injectors with enough fuel when you start to add serious power, but again I don't know the specifics. I don't think the pattern changes. I'll use "gretchens" V6 as an example. He pushed his LFX V6 to around 700 crank horsepower using a very special twin turbo build. But using stock components, typically once you try to surpass 550 crank HP or so, the AFR would go lean, and require more fuel since the stock components couldn't keep up. He swapped his in-tank pump with a ZL1 pump and the crank pump with one from the LF3.
I'd imagine the stock LT1 pumps would be good to go for regular forced induction applications and likely (just guessing) be good for 600 - 700HP or more, but for those wanting to really push the envelope they might have to find a different solution.
I think you're right but these engines are complete packages, and adding aftermarket FI to DI/NA in the future, I think it may require new piston tops, new injectors, new heads... everything required to maintain a very specific air intake velocity curve. (Which, once could argue, is about what it takes for current FI builds if they they are done "properly".) I think the difference will be with FI on DI maybe you won't be able to crank your boost up or down and tweak your fuel and timing a bit to compensate. Either that, or you just blast the injectors and run pig rich all the time.
I'm not sure of the compression ratio in the LT1, but it is pretty high in the V6, and serious forced induction builds seem to require different piston heads to lower the CR.
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