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Static vs Dynamic CR & Boost

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Old Oct 29, 2004 | 04:33 PM
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Default Static vs Dynamic CR & Boost

Ok so I have a 9.80:1 static compression ratio and 7.27:1 dynamic compression ratio.

How does this effect the amount of boost I can run? I'm trying to figure out if I need to get lower compression pistons to run good amounts of boost on race fuel.

To start with my goal will be 10psi on the streets and around 20psi at the track.
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Old Oct 29, 2004 | 11:02 PM
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you will probably get better responces than what i am going to throw out there but i might as well give it a shot. my info mostly comes from what someeone else told me.

i have a 6.0 with a 234/232 115+1 cam. my static compresion is 9.4 and i was told my dynamic is around 8.0.

with that set up i was able to run an intercooled 10psi on pump gas and got up to over 16psi on a 92/118 mix(105 octane). i may have been able to go higher but that is all the higher i tried. i pulled 630rwhp and 630rwtq at that boost and have a power robbing driveline.

i was going to run a higher % of 118 and really crank up the boost but ran into other problems before i got a chance to try it.
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Old Oct 30, 2004 | 03:14 AM
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Thanks for the info Parish, when detonation happens how bad is it? Will I start to see knock retard or will I just blow **** up?
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Old Oct 30, 2004 | 09:42 AM
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Originally Posted by term
Thanks for the info Parish, when detonation happens how bad is it? Will I start to see knock retard or will I just blow **** up?
i watch my scan tool closely. start low on timing and boost and creep up. i started at 7psi and 16deg. i added about 1psi at a time and drove it loging and listening. when i got above 10psi on pump i started seeing KR on the scan tool. at 10psi i tried adding timing and i got KR then also so i stuck with 10psi and 16deg.

then with good gas i creeped up again. i got up to 16psi and 20deg and still never heard any detonation. i did get some on the scan tool and that is what sucks. i have some exhaust touching frame so i am not sure if it was false or real. once i saw some KR on the scan tool i stoped turning it up and if i couldn't hear it and it wasn't too extreme on the scan tool i kept it at that setting for awhile to get a feel for it.

i can't remember my set up but there was one run i remember i could hear 3 distinct pings during the run and when i looked at the log there were 3 times when the KR kicked in. if you know what it sounds like and dont keep in it there is a very good chance you will have time to let off before you kill the motor. i really think the people that are melting plugs and breaking pistons have some prety extreme detonation and are just not aware of what it sounds like so they just keep it to the floor.
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Old Oct 30, 2004 | 04:23 PM
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how do you figure dynamic compression?
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Old Oct 30, 2004 | 04:26 PM
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never mind...google

http://members.uia.net/pkelley2/DynamicCR.html
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