Quote:
Originally Posted by KingLT1
That is on NA applications that is not limited by fuel system. On Boost applications it's a different ball game. Yes these cars do need port injection for supplemental fueling because the DI system cannot keep up with builds pushing 1100whp+ on full E85. Why do you think GM made the LT5 dual injection and also why Ford went dual injection on the Coyote.
The caveat with direct injection is that the window to inject fuel is very small vs port injection. So you need huge injectors that only can use 30% of their capability vs port can use 80-90% of the injector. The problem with really large injectors is the idle quality suffers due to really low injector pulse widths. So, there is a point where it makes more sense to add a secondary port injection system to only activate under boost that way you can use a smaller DI injectors for better drivability.
The good news is that you don't need either a 2650 nor Port Injection for 750whp. If you have been paying attention over the years, you would see that a Ported blower, 38% lobe cam, and low side would get you 750whp on E60 all day.
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So, which is cheaper, port injection or tearing the motor down to add a cam, spring, lifters, etc. I can't see that being cost affect compared to PI, just the labor cost for the cam swap is going to be more than the port injection would be, plus the blower porting is at least 1500.00 plus shipping back and forth. If I can make 707 with a 2300 and stock Lt1 motor with basically a stock fuel system except JMS voltage booster with port injection on E65, an Lt4 should be able to make it with the forged internals short block. After all I'm only on 10.5 lbs of boost, we aren't pushing mine because of the cast pistons and higher compression, plus we are just on the edge of our low side running out, I agree you don't need a 2650 to do it but for future mods I'd rather it than a 1740 if nothing else just for lower IATs. But it's not my money and people can spend it as they please. King I know you may disagree but put a pencil to it and it will be more expensive to go your recommended route.