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I have been having a detonation problem in high gear (both with a manual and auto trans) starting around 19 to 20psi with my GLHS Charger.
The GLHS engine is a turbo 1 shortblock(9cc dish pistons) with a swirl head (48cc combustion chamber). With my calculations this works out around a 9.05 compression ratio!! In my past experiences I have found a safe effective commpression ratio (under boost) to be about 16 to 1 for a swirl head and 18 to 1 for a G head on 93 octane with proper tuning, give or take a little.
On the Daytonas combo I was running T2 mahles 14.5 cc dish with a 53cc G head. Compression ratio was around 7.98. I was able to run 26psi with no problems on 93 octane. Effective compression ratio was around 18.39 to 1.
On the GLHS's combo, I was at the limit starting with as little as 18psi. That explains why I could not tune out the detonation with the boost I was running (23psi) at least on 93 octane with 104+ race octane boost!
Iam going to put a stock G head on the GLHS and this will lower the compression ratio to around 8.4. That coupled with the G head's slower burn rate, I should be able to run 23psi on 93 octane and 25 to 26psi with race gas. We will found out. When I build a dedicated engine for the GLHS I plan on shooting for a mid to high 7 for a compression ratio, as that seemed to work great for fairly high boost (26 to 28psi).
 

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26 PSI??? Wow!! Man seems you gotta love that G head!! Everything I have heard about them has been pretty good. Thats why I went with one for my van. Need mucho boost to get the box movin lol

Who did your cal for that 26 PSI??


Jeff
 

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Discussion Starter #3
My96z said:
26 PSI??? Wow!! Man seems you gotta love that G head!! Everything I have heard about them has been pretty good. Thats why I went with one for my van. Need mucho boost to get the box movin lol

Who did your cal for that 26 PSI??


Jeff
Stock cal with 4.3v diode and aux. injectors. The compression still has to be right to run that kind of boost on 93 octane even with a G head.
 
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