[KingLT1]

Originally Posted by cmeJATT

Is it not recommended to run LT4 blower on 93 on LT1 car? I’m considering the swap along with doing LT4 fueling

Yes you can. Low boost(6-7psi) will be fine on 93. When you start pushing 8+ I feel meth or E85 should be considered.

Do the LT4 swap with LT4 fueling, flex sensor, and E60. Should net close to 600whp on 6-7psi with a M6.

[cmeJATT]

thank you .. currently i have FBO + FFK. thinking about adding boosy, but i really dont wanna dig into the motor.. some people are telling me to stay away from boosy as LT1 bottom end is pretty weak.. so i haven't decided what to do

Originally Posted by KingLT1

Yes you can. Low boost(6-7psi) will be fine on 93. When you start pushing 8+ I feel meth or E85 should be considered.

Do the LT4 swap with LT4 fueling, flex sensor, and E60. Should net close to 600whp on 6-7psi with a M6.

[KingLT1]

The LT1 bottom end is far from weak. The issue is knowing how to properly tune a direct injection engine. The injection timing to spray fuel is very short and it's easy for someone that is not accustom to tuning these platforms to pop a piston from a lean condition. When fuel is sprayed outside of the EOIT window, the cylinder goes lean but the wide band AFR still looks fine. So you can't tune these engine solely based on AFR. You need to keep a close eye on injector ms and rail pressure.

The LT4 is much more forgiving in this regard as it has lower compression and a different piston/ring pack which will take the abuse of 87 octane. This again doesn't mean the LT1 is weak, just means you need to know what you are doing.

[BlueCamaro6]

Originally Posted by KingLT1

The LT1 bottom end is far from weak. The issue is knowing how to properly tune a direct injection engine. The injection timing to spray fuel is very short and it's easy for someone that is not accustom to tuning these platforms to pop a piston from a lean condition. When fuel is sprayed outside of the EOIT window, the cylinder goes lean but the wide band AFR still looks fine. So you can't tune these engine solely based on AFR. You need to keep a close eye on injector ms and rail pressure.

The LT4 is much more forgiving in this regard as it has lower compression and a different piston/ring pack which will take the abuse of 87 octane. This again doesn't mean the LT1 is weak, just means you need to know what you are doing.

You know exactly why people have problems and I agree.

Injection timing is key. Less actual fuel is needed when done correctly, you get a better spray pattern, and also make sure you have the rail pressure to get the job done. There is a formula for the injection timing, but that's what sets an excellent tuner apart from an okay/good tuner. I bet most people wouldn't even need the booster pump they are running or meth injection if the injection timing was correct in the tune to begin with.

Remember, the piston isn't the weak part, it's actually the piston rings in relation to elevated heat. When you make a pull on the dyno or street, how much of a heat increase do you see with coolant temp in the motor? On the dyno, I see 2-4degrees maybe during the entire pull at 8-10spi boost and this is the same increase for a naturally aspirated vehicle that I typically see. I just looked a street log from this weekend in my 18 Camaro LT4 conversion A8. 2,500rpm pull in 4th to 5,600rpm (started getting loose on traction) so I shifted into 5th dropping to 4,300rpm and went to 5,500rpm before letting off. Started at 181 degrees and ended at 181 degrees of engine temp during the pull. It went to 183 once I got out of it and held 6th at 3100rpm for a little bit. (2,900-3,000psi rail pressure, 70psi low side all day long with LT4 fueling on 93 and 4.5ms at full boost) (E85 is roughly 70% here in Illinois currently. I do things a little different, but no meth or booster pump and under 6ms - just different parameter calculations on E)

I can tell you this was not the case before dialing in the injection timing. I would see an increase in engine temp during the pull and fast sometimes on stock SOI EOI. If you see more than 4degrees rise in coolant temp on a pull, time to tune injection timing sand get your inj ms down.

[FrostySS]

Doesn't the E85 help keep those temps down though?

[KingLT1]

Originally Posted by FrostySS

Doesn't the E85 help keep those temps down though?

It does and it is more forgiving far as how lean you can run the AFR and how high you can let the Injector MS get. Not saying to let it get out of the recommended tuning window, just that it has more of a buffer per se.

[BlueCamaro6]

Originally Posted by FrostySS

Doesn't the E85 help keep those temps down though?

It does, but on 93 it can have minimal effect on heat as well when tuned properly. I was on 93 that was sitting in the tank for two weeks when I drove the car and posted the info from the log. I bet if everyone sent in their tune that was in their car when the piston/ring lands gave out, I have a good feeling their SOI is stock or wrong for their modified tune. Or they had way too much boost to begin with and I know this is probably the case with some on here form the posts I have read which is a crap shoot at that point on reliability. I'm talking 10psi and down.

[GuywithL86]

I’ve cracked a lot of ringlands in my turbo honda days. It’s always the ringlands that go, and it always happens after many of thousands of miles of boost. Imo if I was a gambling man and had to guess when your ringlands would go from boost doing frequent spirited driving.

6psi = 60k miles
10psi = 30k miles

That’s long enough for a lot of people to tell you it’s safe, but obviously not even remotely close to the life span of oem design parameters.

On the brighter side, all 5 or 6 times I cracked my pistons, it was just an excuse to build the motor. It’s not like its that much more expensive to build it after the cracked piston. Twice I needed a new block because of cylinder wall hot spots, but the other times just needed a bore and hone, something you want to do with built motor anyway.