LS6, blower, compression question
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2004-2007 Cadillac CTS-V Performance Mods Discussion, LS6, blower, compression question in Cadillac CTS-V Series Forum - 2004 - 2007; I dont know why my last thread was closed on this issue, but here goes again. If a moderator can ...
  1. #1
    Hellride's Avatar
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    LS6, blower, compression question

    I dont know why my last thread was closed on this issue, but here goes again. If a moderator can contact me if I'm breaking some sort of rules, please let me know. I'm just looking for info on ls6's and blower combos. From what I've read, the compression is raised above pump gas friendly levels with a maggie/eaton blower on a stock ls6. Maybe if boost is held to 5-6lbs, then it will live. Put LS2 heads on the LS6 to drop compression, then bolt on the blower? Any input is appreciated. How about the stock LS6 bottom end with a blower? Thanks

    Is running a supercharger on a stock ls6 a bad idea due to the compression being too high? Stock is 10.5 to 1 and blower will only increase that. Is this a recipe for a bomb? Thanks

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    rand49er's Avatar
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    Re: LS6, blower, compression question

    Just as was replied to you on the last thread, dozens of us here have maggies on LS6 motors with no problems. Now, going beyond roughly, say, 8-10 psi boost could be a problem.
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    Re: LS6, blower, compression question

    No offense meant but I'm sure your other thread was closed for simply being retarded! Magnuson has been selling the LS6 blower since when our cars came out in 04' (or close to it).

    A lot of us run blowers on our LS6's with no issues. Compression is only a small piece of the puzzle, when you bolt on the blower you lower the timing and AFR and have fun!

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    Hellride's Avatar
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    Re: LS6, blower, compression question

    Ok, thanks. I'm looking at at buying an 04 v that has an Eaton on it with new carbon fiber shaft and pulley setup, 49k mi, cam upgrade etc. The guy said he had pinging when he first bought the car with the mods on it, then he had it retuned. So that had me researching on the LS6/ blower compression thing. And I came up with quite a few fellas, from another LS forum who advised against it. So I had to ask on here. LAst thing I want to do is spend 25k on a car that is on the verge of blowing up. Thats where this all started. Thanks for the reply
    P.S. Anyone have some serious miles on their proven LS6/blower combo?

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    Re: LS6, blower, compression question

    Quote Originally Posted by Hellride View Post
    Ok, thanks. I'm looking at at buying an 04 v that has an Eaton on it with new carbon fiber shaft and pulley setup, 49k mi, cam upgrade etc. The guy said he had pinging when he first bought the car with the mods on it, then he had it retuned. So that had me researching on the LS6/ blower compression thing. And I came up with quite a few fellas, from another LS forum who advised against it. So I had to ask on here. LAst thing I want to do is spend 25k on a car that is on the verge of blowing up. Thats where this all started. Thanks for the reply
    P.S. Anyone have some serious miles on their proven LS6/blower combo?
    I would still be leery if he openly admitted that he had some knock present. Very little knock will be avoided with knock retard by the PCM. If he was actually experiencing knock and not just having the PCM retard it then the motor could be in less than pristine condition.

    Do you know how much timing he is running at WOT?

    My advice is to have a qualified mechanic/tuner look over the car and tune. He can tell you if the tune is way fubared and the damage that may have been done by it. (Like if he sees stock timing then run away etc).

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    blackax is offline Cadillac Owners Member
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    Re: LS6, blower, compression question

    Well a stock LS2 is 10.9:1 and they take a lot of boost before you need to build it.

    Right now my forged motor is running 10.5:1 with 5 pounds on 91 (damn California gas) and it should be good up to about 10 or so before I need to run meth or something of that sort

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    Re: LS6, blower, compression question

    Your last thread on this subject, was closed, BY ME.

    You can do a little searching and find your ?'s are already addressed.

    There are plenty of superchargers and turbos and even NOX on LS series motors.

    Yes, you can blow them up.

    Yes they can be reliable.

    Depends on how close you skate to the edge of the pond.

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    Re: LS6, blower, compression question

    Most pinging is because at very heavy loading you run out of fuel.

    May need a bigger fuel pump or a (no flame) MAGNAVOLT.

    Quote Originally Posted by Hellride View Post
    Ok, thanks. I'm looking at at buying an 04 v that has an Eaton on it with new carbon fiber shaft and pulley setup, 49k mi, cam upgrade etc. The guy said he had pinging when he first bought the car with the mods on it, then he had it retuned. So that had me researching on the LS6/ blower compression thing. And I came up with quite a few fellas, from another LS forum who advised against it. So I had to ask on here. LAst thing I want to do is spend 25k on a car that is on the verge of blowing up. Thats where this all started. Thanks for the reply
    P.S. Anyone have some serious miles on their proven LS6/blower combo?

  10. #9
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    Re: LS6, blower, compression question

    Adding a supercharger has absolutely NO effect on compression ratio. Adding boost only increases the cylinder pressures. This means more oxygen molecules are in the cylinder allowing more power and increasing the stresses inside the motor. Crankshafts, rods, pistons, etc. can only handle so much before they break.

    Adding too much boost to a high compression motor can cause detonation which is when the air/fuel combination ignites prior to the spark because the cylinder temperature and pressure reaches the combustion point. The mixture then completely burns and produces it's maximum power before the piston reaches the top of it's stroke while the rods are still pushing up.

    Also, the LS2 has the same heads as the LS6. They are both 243 castings.

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    Re: LS6, blower, compression question

    I agree with all that's been said above, but just to add to the conversation, when guys put forced induction devices on their motors, sometimes they reduce the compression ratio down to 8:1 or 9:1. They then put some unGodly boost on those motors ... stuff like 30 psi or more. Going to one of the underlying points in this thread, I don't quite understand why they wouldn't want as much boost and and as high of a compression ratio as they could get assuming they've built the bottom end with every forged component they could get their hands on. It would seem to me that a 9:1 motor wouldn't need as much boost as, say, an 8:1 motor to achieve the same power. I mean, peak pressures more or less correlate with power output. What's the thought there ... anybody?
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    Stepside is offline Cadillac Owners Enthusiast
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    Re: LS6, blower, compression question

    Compression Ratio is not necessarily what it's cracked-up to be. It all depends on what the camshaft is doing with the valves.
    You do not have the theoretical ratio when the volume at BDC vs TDC is compromised by the timing of the closing of the intake valve.
    It is really all about cylinder pressure at a given Time/RPM. Valve Timing can make an 8 to 1 feel like a 10 to 1.
    Where do you want your power to occur? The cam/valve timing can increase of decrease cylinder pressure at a given RPM.
    There has to be a balance between theoretical compression ratio and the actual amount of air that is filling the cylinder and where in the RPM range this occurs so detonation does not happen.

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    Re: LS6, blower, compression question

    So, you're saying that valve timing (i.e. camshaft profile) plays a significant role with the flow dynamics of the gases and BTDC peak pressures and that there's some compromising done.

    Sounds to me like they need to throw some variable cam timing in there along with direct injection.
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    Re: LS6, blower, compression question

    Varible Valve Timing (VVT) with Direct Injection might be the near future for the big LS motors. How about 4 valve heads.
    Not to thread jack on a slightly different subject, though.
    To the original post-er . . The LS motors have a strong bottom end and can take about 8 to 9 pounds of boost max in 'stock' form.
    But, do not go beyond that unless there is a forged bottom end.
    That info I learned from Tommy at ECS when i picked up my car in Oct. '09.
    Of course the adjustment of "the nut behind the wheel" could change the outcome/results.

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    blackax is offline Cadillac Owners Member
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    Re: LS6, blower, compression question

    Quote Originally Posted by Stepside View Post
    Varible Valve Timing (VVT) with Direct Injection might be the near future for the big LS motors. How about 4 valve heads.
    Not to thread jack on a slightly different subject, though.
    To the original post-er . . The LS motors have a strong bottom end and can take about 8 to 9 pounds of boost max in 'stock' form.
    But, do not go beyond that unless there is a forged bottom end.
    That info I learned from Tommy at ECS when i picked up my car in Oct. '09.
    Of course the adjustment of "the nut behind the wheel" could change the outcome/results.

    Well thats mostly true...the bottom end of the LS motor is very very strong and you will most likely take out the top end before anything else breaks. The stock crank can take about 800 hp but the rods and pistons cant so you really only need to forge those.

    I run a high compression motor for FI (10.5:1) but I don't really fear breaking anything I just have to worry about detonation if I run alot of boost

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