C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Supercharging an LT4?

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Old Dec 20, 2005 | 09:35 PM
  #21  
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What would I be looking at for HP gains? I have a LT4/ hot cam, headers and side pipes and running an OBD1 reprogramed computer. Its in a 64 Corvette GS. I am thinking it may not be worth the investment???? Thanks
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Old Dec 20, 2005 | 10:19 PM
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Boost is fun. I haven't blown it up yet and I'm running approx 9.75 to 1 compression and full timing. The key is the alky injection.
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Old Dec 21, 2005 | 01:10 PM
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Default supercharged LT4 experience

Originally Posted by Zix
Are you speaking from experience?! But you'd have to admit, once it's done it's worth the effort!
I'am. My LT4 with 62K mi lasted less than 1K mi with an ATI prochager with 4 1/2 Lbs boost. Experts I have read say that you should not boost an engine with higher than 9.8:1 compression. My FMU failed/or was defective.The experta at EFI University say don't trust FMU's. Tune the ECM, and always use a wide band O2 sensor, and keep the a/f ratio at 11:1 for high boost, and 12.5:1 for light boost. Easier said than done, but worth the effort in my opinion.
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Old Dec 21, 2005 | 03:04 PM
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i know im new at forced induction but what is alky injection? is it part of an intercooling device for a blower? i looked at hte packages for the LT4 on his website and those are some impressive numbers. im assuming most of those are with forged pistons and reduced compression ect to run about 12lbs of boost but is that on a stock displacement? 349ci?
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Old Dec 22, 2005 | 02:04 AM
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Alky / water injection is added at high pressure about 100psi through a nozzle in the intake to cool the intake air coming into the engine, typically it is good for another 75 or so horsepower...

It is used either alone or in place of a air / air ntercooler... or both together, depending on what you are doing...

Most of the numbers you are seeing are from lt1 350's there are a few runing 383's and fewer 396's about the are supercharged...

Mo
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Old Dec 22, 2005 | 10:11 AM
  #26  
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Originally Posted by Mo_Bandy
Alky / water injection is added at high pressure about 100psi through a nozzle in the intake to cool the intake air coming into the engine, typically it is good for another 75 or so horsepower...

It is used either alone or in place of a air / air ntercooler... or both together, depending on what you are doing...

Most of the numbers you are seeing are from lt1 350's there are a few runing 383's and fewer 396's about the are supercharged...

Mo
DAMN! so if i got the kit for 600hp from that site and bored and stroked my engine to a 396 i could potentially see even more power?
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Old Dec 23, 2005 | 01:08 AM
  #27  
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no, it really is dependant on how hot the incoming air is enterng the intake, it is not like a shot of NOS...

The 75 hP is roughly the gains I saw..

Mo
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Old Dec 23, 2005 | 10:04 AM
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Originally Posted by Mo_Bandy
no, it really is dependant on how hot the incoming air is enterng the intake, it is not like a shot of NOS...

The 75 hP is roughly the gains I saw..

Mo

im sorry. i wasnt talking about alky injection. i meant if most of these guys are using kits from blowerowrks on stock discplacement motors and getting close to 600rwhp i should be able to get quite a bit more with a 396 motor
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Old Dec 24, 2005 | 03:01 AM
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Oh gotcha yes... sorry for the miscommunication...

Mo
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Old Dec 24, 2005 | 05:26 PM
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thanks when the time comes $$ will go into a rebuild and not supercharging my LT4.
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Old Mar 22, 2006 | 03:15 AM
  #31  
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Originally Posted by vstol
thanks when the time comes $$ will go into a rebuild and not supercharging my LT4.
Probably a wise choice, but I ran a intercooled procharger on a ls-1 camero with alky/water injection, comp cam, adjustable timing, special chip, etc. THERE IS NOTHING LIKE THE SOUND OF A SUPERCHARGER AND A GOOD EXHAUST SYSTEM. I ACTUALLY HAD TRAFFIC COPS TO WAVE ME OVER TO ASK WHAT I WAS RUNNING AND HOW FAST WOULD IT GO. DO MISS THAT CAR!!! Superchargers need: low compression, water alky injection, good timming. I had over 500rwhp and 20+mpg on the highway.
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Old May 11, 2006 | 10:41 PM
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IMHO the LT4 is built around old school normally aspirated HP hence the high compression ratio. For the cost of a supercharger, comp ratios changes, or a high dollar blower with low boost which defeats the purpose of the blower in the first place, you may be disappointed. You can build a reliable very quick car working with the platform you already have such as performance tires or drag radials, driving skill, a good clutch, sensible engine mods, programming etc.

If you must blow, leave the LT4 alone. Find an LT1 engine which is cheaper and more plentiful than the LT4. Take your time and build the engine on a stand for the boost you want. When done, swap your blower built LT1 where your LT4 used to live. Obviously pcm changes/programing will be required.
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Old May 12, 2006 | 01:20 AM
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bad tune or too much pwr kills ....but i do agree that too high of a compression make things tricky but it can be done.


alky injection is old school but it works ..if its not a daily driver nitrous works great on air inlet temps...
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