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Keep 10.7:1 or drop it?

Old 07-12-2019, 06:49 AM
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Default Keep 10.7:1 or drop it?

I have to put new pistons in my LS3 and am debating on whether to keep the 10.7:1 or drop it to 9.0:1. I have a LSA blower running about 10-11 psi of boost with a meth set-up. I don't drive the car a lot, so I am leaning toward keeping the higher compression for better performance under normal driving. I doubt I am going to get a lot more out of the blower without upgrading to a larger one.

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Old 07-12-2019, 08:40 AM
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Itíll be fine with meth or e85.
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Old 07-12-2019, 09:30 AM
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yep if you can always spray meth or use say 40% ethanol or more = raise compression

don't want to depend on meth or high E = lower compression

blowers make alot of heat when they sit on top of an engine so be prepared to find all E85 stations
And I am not sure meth is reliable enough in this situation. It would work but it would be absolutely critical which I don't like so I wouldn't depend on it. Use the E version of our favorite alcohol

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Old 07-12-2019, 09:52 AM
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I would keep it unless you plan to up the boost more.
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Old 07-12-2019, 10:12 AM
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With the limited power output of the LSA I would keep the compression up. We put LSA's on 10.5:1 cars all the time with no issues and run more then 10PSI. 10PSI is nothing especially with a meth setup, even on straight pump I don't have issues even at 11:1 until over 17lbs. I wouldn't lower the compression to 9:1 unless you were planning on a power adder that moved a ton of air and you were going to run triple the boost.
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Old 07-12-2019, 10:25 AM
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Thanks for the replies! I ran it a few times with the stock pistons (10.7 CR) and the meth and the knock sensors never kicked in. My max psi is going to be 11 psi and I already have the meth set-up, so I will stay that route.

One other question. I noticed the oil ring on the higher compression pistons is 2mm, and on the lower CR pistons made for boost, it was 3mm. Will the small oil ring cause any issues under boost?
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Old 07-14-2019, 10:46 PM
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Keep it. Been running mine with boost for over 40k miles.
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