Compression Question regarding my elevation/ and high boost level
02-18-2004, 11:45 PM
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Car: 1992 Z28
Engine: 350 L98 w/ D-1SC
Transmission: POS 700-R4
Compression Question regarding my elevation/ and high boost level
Ive done the searches and homework on compression but I wanted to know how it would influence my potential build given my altitude/elevation.
I know lower is better for boost and generally a person who is boosting should shoot for 9.0:1 compression or lower.
However, I live @ about 5500-5600 feet. I'm going to be completely forging my bottom end and am going to be running 15 pounds of intercooled(cog driven) boost on my D-1SC.
I lose about 1 second for elevation @ the local track here and am shooting for (high tens/low elevens @ sea level).
Heres the plan for my L98
Eagle 4340 6" Rods
Eagle 4340 Crank (3.480"stroke)
AFR's 185cc 64cc 2.02/1.60
CompCam "Nitrous" (CL-12-415-8) .502/.520" 224/236
Holley Stealth Ram
Moroso Windage Tray
Now heres where I really need advice. I've been told by a few guys @ the local track here I'd be better off and keep the 9.75:1 stock compression because we're at a higher elevation. I know the rule of thumb is drop it down for high boost levels but @ my elevation can I/should I try to get away w/ the higher compression.
A buddy also made a point that if the procharger ever broke/got damaged my car wouldnt be a pig because I would still have stock compression and could throw a bottle on there. BTW I run 91 octane pump gas.
I have a lot of 4th gens who are talking smack down here guys help me make the right decision here.
All input and advice is appreciated and encouraged. What would you do?
I know lower is better for boost and generally a person who is boosting should shoot for 9.0:1 compression or lower.
However, I live @ about 5500-5600 feet. I'm going to be completely forging my bottom end and am going to be running 15 pounds of intercooled(cog driven) boost on my D-1SC.
I lose about 1 second for elevation @ the local track here and am shooting for (high tens/low elevens @ sea level).
Heres the plan for my L98
Eagle 4340 6" Rods
Eagle 4340 Crank (3.480"stroke)
AFR's 185cc 64cc 2.02/1.60
CompCam "Nitrous" (CL-12-415-8) .502/.520" 224/236
Holley Stealth Ram
Moroso Windage Tray
Now heres where I really need advice. I've been told by a few guys @ the local track here I'd be better off and keep the 9.75:1 stock compression because we're at a higher elevation. I know the rule of thumb is drop it down for high boost levels but @ my elevation can I/should I try to get away w/ the higher compression.
A buddy also made a point that if the procharger ever broke/got damaged my car wouldnt be a pig because I would still have stock compression and could throw a bottle on there. BTW I run 91 octane pump gas.
I have a lot of 4th gens who are talking smack down here guys help me make the right decision here.
All input and advice is appreciated and encouraged. What would you do?
02-19-2004, 09:20 PM
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Location: Rio Rancho,NM USA
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You could get away running 9.75 at our elevation but it still will kill your ablility to run higher boost levels at sea level. IMHO I'd just run a 8.5 :1 static compression ratio and turn up the boost. By dropping your compression ratio your leaving yourself room to grow. If you run a 9.75:1 ratio your looking at limiting the amount of total boost your gonna beable to run. Admittedly you can always just run more octane but I'll assume you'll want the most power outta pump gas and then turn up the wick on the good stuff. Anyways thats my 2 cents.
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