05-08-2005, 08:50 AM
|
#1
|
  |
|
Too much compression!
|
|
Naturally Aspirated
Join Date: Jul 2003
Location: Woodville, Alabama
My Ride: 87 GLHS
Engine: 2.2 8Valve
Induct: Turbo
1/4: 0.000
|
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).
|
|
|
TurboDodge.com 
