[KingLT1]

Originally Posted by ArthurJGuy

Not really.

Mod for mod the LT cars consistently make less power than the LS cars, when you would expect exactly the opposite. My ZL1 made less power than my CTS-V, and the ZL1 has a more efficient supercharger. Oh and my ZL1 is a M6, it should have been over 100whp more than my CTS-V was.

Not sure I agree with this at least up to the point where you reach fuel limitations of DI as Josh pointed out. You can go to RPM or LMR youtube channel and watch hours of footage of H/C LS9 stuff vs H/C 2650 LT4 stuff and see that isn't really true. I see LT4 stuff making more power on average then LS9. The LT cars are generally heavier so it makes the power advantage moot. Sure when you want to start pushing north of 1500hp then yes LS has the advantage but that is going to change here in the next couple years. The new Holley system with DI control will be a game changer and with PI added for dual injection you will start to see some big power LTx builds still using DI. Probably still not going to be very popular until the cost comes down some because LS is cheaper to work with.

[gtfoxy]

So you used a stud in the crank snout & jam-nutted it so you could turn it over for degreeing... or is this a tool kit you picked up?

I like that. I have an LS at the shop I have to degree & this will work slick. Thanks!

[sschons74]

Originally Posted by ZO6Ted

Maybe I misunderstood but I thought that DI gave a huge improvement in lowend torque and hp. Not that that's relevant in this scenario. There was a vid from some Katech engineer that I saw, I thought? Or maybe too many Corona's....

Yeah I heard same about DI, is good at low end torque. I was following the GM Direct Injection motor development in the news just before Corvette got the LT1, and trucks got DI V8 early.

https://media.gm.com/media/us/en/che...mallBlock.html

they mention halfway down article: delivering great low-end torque and excellent high-rpm horsepower

but I understand from you guys that you need either supplemental fuel injection above certain hp as DI fueling time window is limited, or just remove DI, plug it off and just use port injection and Holley computer.

I won't go to that kind of speed, I want to keep mine a nice driver, maybe 600hp.

video about centri vs. PD, I'm still learnding. - Ralph Wiggum.
but I know now, that I would like PD.

[ArthurJGuy]

Originally Posted by KingLT1

Not sure I agree with this at least up to the point where you reach fuel limitations of DI as Josh pointed out. You can go to RPM or LMR youtube channel and watch hours of footage of H/C LS9 stuff vs H/C 2650 LT4 stuff and see that isn't really true. I see LT4 stuff making more power on average then LS9. The LT cars are generally heavier so it makes the power advantage moot. Sure when you want to start pushing north of 1500hp then yes LS has the advantage but that is going to change here in the next couple years. The new Holley system with DI control will be a game changer and with PI added for dual injection you will start to see some big power LTx builds still using DI. Probably still not going to be very popular until the cost comes down some because LS is cheaper to work with.

A 2650 car made more than an LS9 car? Tell me more....

Originally Posted by gtfoxy

So you used a stud in the crank snout & jam-nutted it so you could turn it over for degreeing... or is this a tool kit you picked up?

I like that. I have an LS at the shop I have to degree & this will work slick. Thanks!

It's a tool that they sell, but you can easily make one with a long bolt or a piece of all thread and a coat hanger/welding wire.

[toohighpsi]

Originally Posted by KingLT1

Not sure I agree with this at least up to the point where you reach fuel limitations of DI as Josh pointed out.

King you are correct, DI makes more power than port - it can support higher compression ratio with lower octane fuel resulting in better fuel economy and more peak power. Now at the highest power levels with enough octane there seems to be a benefit to having both as we can end up with a more homogeneous charge mixture in cylinder and still have the added cooling benefits of DI - something lost if we go entirely back to only port injection.

Many OEMS have dual systems (ford, toyota) but apparently GM was able to achieve the designed performance of the vehicle without adding the extra expense of the dual system - with the exception of the ZR1.

[95 imp]

That makes perfect sense.

The higher pressure/finer particles from the DI system light and propagate faster (hence more power/less emissions). The DI heat burns the "bigger chunks" of fuel from the PI system for a quicker, cleaner, burn than PI alone.