LS2 compression ratio on 91 octane
10-06-2016, 04:37 PM
#1
LS2 compression ratio on 91 octane I am going to send in 243 heads to get ported and milled down and am not sure what compression ratio so I can still use 91 octane gas.
I am going with a 226-230@50 -113 lsa with 612-595 lift on a N/A Ls2 with Fast intake and 1 7/8 headers and would like to know what comp ratio and how much can be taken off heads.
I live in Canada so a hot day here is 85-90 degrees here.
I am going with a 226-230@50 -113 lsa with 612-595 lift on a N/A Ls2 with Fast intake and 1 7/8 headers and would like to know what comp ratio and how much can be taken off heads.
I live in Canada so a hot day here is 85-90 degrees here.
10-06-2016, 04:54 PM
#2
You can get away with a lot, but monitor the datalog and knock retard.
I ran a 12:1 402 that way and my stock engine which was modded w/decked TFS heads and 240psi static cranking compression.
The 402 I had to reduce spark in the midrange and the TFS headed engine needed both reduced top and mid range.
I ran a 12:1 402 that way and my stock engine which was modded w/decked TFS heads and 240psi static cranking compression.
The 402 I had to reduce spark in the midrange and the TFS headed engine needed both reduced top and mid range.
10-07-2016, 02:37 AM
#3
WHos "playin" with your heads? If its AI, ask Phil what he recommends.
10-12-2016, 02:32 AM
#5
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11.1
11.5 is pushing it.
Have you considered sending them into us:
http://www.americanheritageperformance.com/
11.5 is pushing it.
Have you considered sending them into us:
http://www.americanheritageperformance.com/
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10-12-2016, 01:23 PM
#8
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Spark Instant Accuracy The LS-2 can be fitted with a (OEM) 24ex OR 58x (my 60-2) crankshaft Target Wheel.
Thus the accuracy of the Spark Instant is vastly different.
The newer LS-2 or any LS-x when fitted with the 58x (59) TW can have a higher Knock Rating of .5 Compression Ratio increase in comparison to the lower tooth count TW. (24)
This case IS only true with OEM or other high quality (degree based) EMS
What one is fitted ?
Lance
Thus the accuracy of the Spark Instant is vastly different.
The newer LS-2 or any LS-x when fitted with the 58x (59) TW can have a higher Knock Rating of .5 Compression Ratio increase in comparison to the lower tooth count TW. (24)
This case IS only true with OEM or other high quality (degree based) EMS
What one is fitted ?
Lance
10-19-2016, 10:22 AM
#9
Maybe our elevation helps?
My combo:
stock bottom end LS2 from 05 GTO (24x)
ported 799 heads milled .015"
stock GM MLS LS2 head gaskets
ARP head bolts
LS1 knock sensors relocated to outside of block, ramped up sensitivity quite a bit
TR6 plugs gapped at .050"
I'm running the same timing curve as when the car was LS1 I just pulled 2* out around peak torque. Timing is at 27* in the upper RPMs.
Fuel is set to 12.4 around peak torque then leans out to 12.7-12.8 up top.
I try to run Shell non-ethanol 91 which seems to be the best I can get here.
My combo:
stock bottom end LS2 from 05 GTO (24x)
ported 799 heads milled .015"
stock GM MLS LS2 head gaskets
ARP head bolts
LS1 knock sensors relocated to outside of block, ramped up sensitivity quite a bit
TR6 plugs gapped at .050"
I'm running the same timing curve as when the car was LS1 I just pulled 2* out around peak torque. Timing is at 27* in the upper RPMs.
Fuel is set to 12.4 around peak torque then leans out to 12.7-12.8 up top.
I try to run Shell non-ethanol 91 which seems to be the best I can get here.