[ZL1Atlanta]

Originally Posted by Joshinator99

Have you heard anything about the +90’s that King referenced? What confuses me about those would be what will LPE do on the HPFP side. The +52 and +65 injectors out there pretty much max out their existing Big Bore HPFP.

That is the first I've heard of them that large, but agree that it seems pointless unless you do one of those XDI belt driven pumps perhaps.

[KingLT1]

I agree that it would likely take a seconday HPFP to fully utilize the 90's. I believe you still need one to max the +65's. This is based on running full pump E. On E60 the +65's, LPE HPFP, and a 32% lobe is enough DI only for 1000-1100whp. Not sure how far you could go with a 42% lobe. My guess is this is when you might finally need more octane then E60 provides. I haven't ventured into those waters yet so only speculating.

[Evansa22]

Originally Posted by KingLT1

yes, I have had to do that with +65 injectors, and they work fine. These require lower rail pressure across the board vs LT4 stuff. 2500psi max

LPE supposedly has some +90's coming out...not sure how those will be to tune.

I prefer to fuel the engine DI only, but with the price increases on DI fueling, PI starts to make a lot more sense.

For sure, the cost now for pi stuff seems to be quite a bit cheaper than upgrading di and you get more fuel. Adjusting the rail pressure and pulse widths at idle was something I saw from a Greg Banish video. Wanted to see other people's opinions about it. Wouldn't be dropping rail pressure too low or pulse widths too high, just finding the sweet spot Radz was referring too for a nice clean burn and smooth idle.

[laynlo15]

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.

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.

[KingLT1]

I think you took my post out of context. I am advocating Port Injection in my post. I am just saying it's not hard to make 750whp with a ZL1, so let's not over think it. I probably should of just said that instead.

[laynlo15]

Originally Posted by KingLT1

I think you took my post out of context. I am advocating Port Injection in my post. I am just saying it's not hard to make 750whp with a ZL1, so let's not over think it. I probably should of just said that instead.

Sorry, at my age I'm just trying to make complete sentences. Haha, missed your point, guess this one good eye misses stuff sometimes.

[KingLT1]

No biggie!!

[RobZL1]

Originally Posted by laynlo15

Sorry, at my age I'm just trying to make complete sentences. Haha, missed your point, guess this one good eye misses stuff sometimes.

This made me literally LOL, which I needed after a long day. Thank you.