Quote:
Originally Posted by Megahurtz
King is absolutely right. Boosted LT1's live on pump gas when the boost pressure is lower than 9psi and a bunch of timing is pulled to be safe. The number one danger on a boosted LT1 is detonation. It will break the weak LT1 pistons real fast. Second is the heat the top rings are exposed to. Too hot and you break a ring quickly. To mitigate this, boosted stock piston LT1's are usually run rich and low on timing. They make good torque but lay over up top. Pushing past this on pump gas, and your risks greatly increase.
As the blower heats up, the ECU pulls more timing, keeping things safe but also lowering the power. So a dyno pull might show 570 rwhp, but then on the street the car gets slower when things are heat soaked or the blower is hot. You can mitigate this with meth or flex fuel and make more consistent power. But on pump gas, you're stuck with this timing logic.
You can push an LT1 harder if you're spraying meth or using Flex Fuel extract more heat from the combustion chamber, reducing detonation chances and keeping the rings cooler. What King has been saying is not "1 car example". It's be proven time and time again on the LT platform.
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I can attest to this based on my car as well. Initially I had only a blower with a single low side fueling enhancement (JMS), it made 560 rwhp on the dyno at 7.5 psi of boost, but at the drag strip it started "dying off" past 110-112 mph, I could literally feel the "oomph" go away once I hit 5th gear (the big rpm drop in the 8L90 doesn't exactly help there either). Nothing wrong with the setup or the tune, it was a compromise I understood.
Then, once we moved to the current setup with headers and a forged bottom end (leaving nothing but the LT1 block as stock), full LT4 fueling, flex fuel capability and a smaller pulley for 10-11 psi of boost with the appropriate tune, the car is now pulling like a banshee even at 140 mph, with no knock retard or any audible knock whatsoever even on 93 pump gas. Needless to say, it runs even better on E50-60, it's close to scary, which is exactly how I want it.