[SGDM]

Originally Posted by Raptor Jesus

This is 100% untrue.

I beg to differ sir but you are not correct. It is 100% true. Perhaps you need to do some research and ask yourself, why are so many LT1 engines having piston issues...compression and or bad tune. FACT!

[DaveC113]

Originally Posted by Raptor Jesus

This is 100% untrue.

Lowering CR should give you more margin for error and lower the chances for preignition type issues.

11.5:1 w/boost and pump gas seems a little extreme even with DI... maybe not w/E85 though.


edit: looked up ZL1's lt4, which is 10:1 CR

[wnta1ss]

Originally Posted by SGDM

I beg to differ sir but you are not correct. It is 100% true. Perhaps you need to do some research and ask yourself, why are so many LT1 engines having piston issues...compression and or bad tune. FACT!

Compression is not the problem at 10psi of boost. The main problem with adding a supercharger to the stock LT1 is not really the pistons themselves, but the fact that the ring gaps are sometimes extremely tight from the factory. When the ring gaps are too tight, the heat can make them butt together and THAT breaks the piston.

[Driski]

[QUOTE=JANNETTYRACING;10474972]Just finished another JRE Super Street Brawler package on 93 octane.

https://www.facebook.com/jannettyrac...1693976464327/[/QUOT

[KingLT1]

Originally Posted by wnta1ss

Compression is not the problem at 10psi of boost. The main problem with adding a supercharger to the stock LT1 is not really the pistons themselves, but the fact that the ring gaps are sometimes extremely tight from the factory. When the ring gaps are too tight, the heat can make them butt together and THAT breaks the piston.

True, but alternative fuels such as E85 does a great job at pulling the heat out of the cylinder which helps prevent the rings from expanding. You can run more timing, make more power on the same amount of boost, and keep the cylinder temps lower. the window for error is also larger compared to 91-93 octane.

[wnta1ss]

Originally Posted by KingLT1

True, but alternative fuels such as E85 does a great job at pulling the heat out of the cylinder which helps prevent the rings from expanding. You can run more timing, make more power on the same amount of boost, and keep the cylinder temps lower. the window for error is also larger compared to 91-93 octane.

What that stuff does is try to reduce the chance of breaking. But, it does not completely eliminate the chance. Different uses of the car, pot luck on whether your engine has an .007" gap while someone else's has a .015", etc come into play. Not to mention, you cannot run E85 on a supercharged LT1 without some extra work and expense. To be able to run E85 on a supercharged LT1 costs somewhere around $2000 (LT4 parts and flex sensor) just for the parts and that's the low end of the pool. Cannot turn it up very high and still have the fuel system supply enough E85. While I think E85 is a good idea, for the multiple reasons that you mentioned, what that extra expense does to the value equation cannot be ignored.

[EDFHOBBIES]

If you drop a piston what's another 2k down the line for a block and machine work(worst case) and you may get away with never needing the upgraded pistons.. Seems like a good gamble just make around 650 or 700 and roll the dice.

I been preaching this all along the zl1s are making more power with lower compression than the SS running the same LT4 fuel parts and the same blower..

Using the thicker Cometic head gaskets and Lt4 heads seems like the way to go.. Should get the compression to 10:1

granted you can make more power on higher compression but the need for more octane goes up so e85 and meth are needed. (and with known piston problems less compression seems smarter)

[Raptor Jesus]

Originally Posted by SGDM

I beg to differ sir but you are not correct. It is 100% true. Perhaps you need to do some research and ask yourself, why are so many LT1 engines having piston issues...compression and or bad tune. FACT!

I am correct. You said you MUST lower compression to run boost which is a truly ignorant statement. Hundreds upon hundreds run boost on bone stock engines with ZERO issues. You're using the old way of thinking that lower compression is a must for FI and that's not true and hasn't been for many many years. I remember 15-20 years ago we would build engines with 2 points lower compression because the tuning options were junk and we needed that margin for error. The engines ran like crap, no bottom end, and you had to run crazy boost levels to compensate. Then people learned to tune for the engines (well some did just not the OP's tuner) and people realized compression and boost is a good thing. The people who instantly say you MUST lower compression are stuck in the past.

If the ring gap is the limiting factor, fix it. But keep the compression.

[matt fe2o3]

[EDFHOBBIES]

Originally Posted by Raptor Jesus

I am correct. You said you MUST lower compression to run boost which is a truly ignorant statement. Hundreds upon hundreds run boost on bone stock engines with ZERO issues. You're using the old way of thinking that lower compression is a must for FI and that's not true and hasn't been for many many years. I remember 15-20 years ago we would build engines with 2 points lower compression because the tuning options were junk and we needed that margin for error. The engines ran like crap, no bottom end, and you had to run crazy boost levels to compensate. Then people learned to tune for the engines (well some did just not the OP's tuner) and people realized compression and boost is a good thing. The people who instantly say you MUST lower compression are stuck in the past.

If the ring gap is the limiting factor, fix it. But keep the compression.

Food for thought..

My car: zl1 Lt4 1.7L blower, ATI 9.2 balancer, CAI, and headers. Dynoed 659 rwhp

Wifes car: SS LT1, 2300 blower, Aux DSX, LT4 injectors, headers and CAI..

We had our cars worked on at the same time in feb.. dynoed with in 2 hours of each other both manual 6, both same fuel system, same dyno, she has a better blower. (Moves more air and iats where better since I was over spinning mine)

Lower compression wins when you can turn up the boost agreed..

Higher compression wins if you have a fuel system and octane.

But in the LT Direct injection running on 93 lower seems better..the blowers can out perform the fuel sytem.

Look at the Street Brawler by Jannety. 735 on a SS with cam and maggi2300, on zl1s it's in the 800s.

[Drsagacity]

Originally Posted by EDFHOBBIES

Food for thought..

My car: zl1 Lt4 1.7L blower, ATI 9.2 balancer, CAI, and headers. Dynoed 659 rwhp

Wifes car: SS LT1, 2300 blower, Aux DSX, LT4 injectors, headers and CAI..

We had our cars worked on at the same time in feb.. dynoed with in 2 hours of each other both manual 6, both same fuel system, same dyno, she has a better blower. (Moves more air and iats where better since I was over spinning mine)

Lower compression wins when you can turn up the boost agreed..

Higher compression wins if you have a fuel system and octane.

But in the LT Direct injection running on 93 lower seems better..the blowers can out perform the fuel sytem.

Look at the Street Brawler by Jannety. 735 on a SS with cam and maggi2300, on zl1s it's in the 800s.

Are you comparing the SS and ZL1 running the same boost level, or are you saying that a z running 15psi runs more power than the SS running 8psi?

I was in the 715whp range at 8psi with the super street brawler package...was over 800whp with 14psi...I am in the process of dialing my SS back down because I think that the 700range is perfect on the street. . .but will definitely run the SS over 800whp at the track this summer (super street brawler package).

I am also getting ready to get another super street brawler setup on my M7. Damn taxes seem to be slowing me down. I am really leaning toward forged drop in pistons on that setup too...

[EDFHOBBIES]

I'm saying you can make more power with lower compression with these LTs.. cuz you cant afford to fuel them yet correcly..ya some do and some go cheap using meth or mixing 93 and e85.. just do it right get the 5k fuel system.

Your ss made 700s w e85.. cam and whole shebang

My z made 701 with just swapping to a 2650.. on 93

15 psi to your 8 but u needed octane to do that.

I would bet the farm if you used the cometic head gaskets .77 thickness vs lt1/4's .40 something and LT4 heads lowering the compression almost a point and half you be 40 or 50 hp more.

I could care less about psi or boost numbers I'm talking the end number from the octane limit.

But ya 13.1 compression on c16 all time will make more power.. but good luck w that.

[DorkMissile]

For reference - I am making over 700wheel on a bone stock LT1 (stock intake, TB, stock headers, stock cam) with a centrifugal at 9.5lbs of boost. LT4 HPFP, LT4 injectors, secondary cat delete, pump E85 with meth injection turning on at 6lbs of boost. The meth isn't needed to fuel it, but is being used for octane / temp control. I can run it on strait E85 but we would be in the 630-640 range.

The misconception I am seeing in this conversation is people are relating boost with cylinder pressure, which higher numbers doesn't mean higher combustion pressure. The type of fuel and timing figure into that.

That being said - my tuner would have had no problem pushing my car into the 12lb area (and probably close to 800hp) on a stock LT1 had I had headers on the car. We were pulleyed for 14lbs with the stock manifolds and were making 745wheel at 5700rpm, but without the headers he was thinking the cylinder pressure was going to get us into DET issues. We may be going down that road mid-summer with headers and pulleys for 12lbs and try to hit 800hp on a stock LT1.

[Drsagacity]

Originally Posted by EDFHOBBIES

I'm saying you can make more power with lower compression with these LTs.. cuz you cant afford to fuel them yet correcly..ya some do and some go cheap using meth or mixing 93 and e85.. just do it right get the 5k fuel system.

Your ss made 700s w e85.. cam and whole shebang

My z made 701 with just swapping to a 2650.. on 93

15 psi to your 8 but u needed octane to do that.

I would bet the farm if you used the cometic head gaskets .77 thickness vs lt1/4's .40 something and LT4 heads lowering the compression almost a point and half you be 40 or 50 hp more.

I could care less about psi or boost numbers I'm talking the end number from the octane limit.

But ya 13.1 compression on c16 all time will make more power.. but good luck w that.

Got it. Yeah. Laynlo was running in the 700's on a completely stock LT1 with just Maggie. I get it. There are a bunch of ways to get it done. You ran 15psi to get there. I added a cam to get there on 8psi (or 10psi on 93).

Fwiw - My tune can use either e85 or 93. I would have to go back and look, but I know that I could run either 93octane at 10 psi or e85 at 8psi and have almost identical power. I like e85 because it's cheaper and I like less boost for same power. I dont use alky injection or my 12psi setup would be in the 830whp range.