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Please be patient with me. I finally decided to go out and learn this instead of depending on others. Yes I've been doing my homework, searches and have played with numbers.
First off how do ya like to figure out compression ratio? Website, app or pencil and paper?
I've been using 2 different sites and get different dynamic & static results, being their different by a point or two.
I understand the tune is the key to keeping it together. So here goes my next question.
What compression ratio is ideal for boost?
Is it safe to say the following?
I've found the general consensus is anywhere from 8.X-10:1. Can run pump gas and plenty of boost and still be relatively safe.
11.X-13.X.1 is still possible but more often than not meth, alcohol, e85 is involved depending on the boost level. And its pushing the block to its limit again depending on the boost
So with these compression ratios in mind would a 8.X:1 be a little slower vs a 10.X:1 on the lower end without a turbo? Because at this level the engine is dependent on the turbo to make power and move right? But both will make great power at the top end?
Whereas 11.X-13.X:1 can still move well on the lower end because its not as dependent but co exists with the turbo?
Am I on the right track or did I get lost somewhere?
Any help is appreciated.
I have a lq4 im looking to put together soon.
Last edited by buicksWILD; Jun 13, 2021 at 11:17 AM.
You have not been doing nearly enough homework, and it sounds like the research you have done may have been some of the older 1980's stuff. The type of boost makes an enormous difference in how much compression you can safely use. I believe the old Callaway sledgehammers were something like 7.5/1 CR. Nobody in their right mind would suggest something that low today. On the other hand, there are a lot of 11/1CR motors running boost on premium pump gas, and I would not personally want to deal with that tiny tuning window. Read until your eyes bleed before dropping coin on hard parts.
You have not been doing nearly enough homework, and it sounds like the research you have done may have been some of the older 1980's stuff. The type of boost makes an enormous difference in how much compression you can safely use. I believe the old Callaway sledgehammers were something like 7.5/1 CR. Nobody in their right mind would suggest something that low today. On the other hand, there are a lot of 11/1CR motors running boost on premium pump gas, and I would not personally want to deal with that tiny tuning window. Read until your eyes bleed before dropping coin on hard parts.
The lq4 came with a 9.4-9.5:1 compression ratio and its been extensively documented to handle boost well especially with upgraded pistons.
Last edited by buicksWILD; Jun 13, 2021 at 12:38 PM.
Static compression is only 1 element of an engine recipe to meet a goal.
Here is a short list of questions to help provide direction:
What fuel?
What hp goal?
What rpm range do you desire to make power?
Intercooler - air, water or none?
Street or track?
Static compression is only 1 element of an engine recipe to meet a goal.
Here is a short list of questions to help provide direction:
What fuel?
What hp goal?
What rpm range do you desire to make power?
Intercooler - air, water or none?
Street or track?
These will allow folks to better help.
Pump gas
With boost 5-700 at the wheels
2-5/6k
Intercooler air to air
Street with the occasional trip to the track
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Compression ratio for boost. 
