How high C/R is too high for forced induction?
07-29-2009, 10:16 PM
#1
Staging Lane
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How high C/R is too high for forced induction? I'm looking at buying an LSx powered vehicle and wondering what my options are.
Currently it's a 99 LS1 shortblock with GTP ported 5.3L heads with the bigger valves. Stock sized GM MLS (ls6/7?) headgaskets were used. I was reading that this should yield around a 10.5:1 C/R. It currently has a TSP 226/226 112LSA cam.
I know there are lots of modern late model factory cars running 10.5:1 C/R on turbocharged setups bost most of them are direct injection.
Would I have to use thicker head gaskets to even consider going FI besides nitrous? Consider that the car will be tuned on 93 octane, and quite possibly E85.
Thanks.
Currently it's a 99 LS1 shortblock with GTP ported 5.3L heads with the bigger valves. Stock sized GM MLS (ls6/7?) headgaskets were used. I was reading that this should yield around a 10.5:1 C/R. It currently has a TSP 226/226 112LSA cam.
I know there are lots of modern late model factory cars running 10.5:1 C/R on turbocharged setups bost most of them are direct injection.
Would I have to use thicker head gaskets to even consider going FI besides nitrous? Consider that the car will be tuned on 93 octane, and quite possibly E85.
Thanks.
07-29-2009, 10:22 PM
#3
Staging Lane
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I've been tuning turbo cars (mostly 4cyl.) for a long time and the average C/R is about 8.8:1. When built, we usually do a 9:1 and they take fine to as much boost as you want to throw at them (everything else being right).
I've seen some Integra GSR's that had their stock 10.5:1 motors boosted and they just couldn't take any timing because of it. Timing is where the power is, FME. I'm curious if the LSx is the same way, or can you make big power on a no-timing tune, if necessary.
I've seen some Integra GSR's that had their stock 10.5:1 motors boosted and they just couldn't take any timing because of it. Timing is where the power is, FME. I'm curious if the LSx is the same way, or can you make big power on a no-timing tune, if necessary.
07-29-2009, 10:34 PM
#4
That compression is fine if the boost level is moderate. No reason not to run a higher CR if you're going to run E85. I'd run that or pump & methanol injection.
In your particular situation the problem is that you have higher compression than is normal and (I'm guessing) stock pistons. I wouldn't push it past 8 psi.
In your particular situation the problem is that you have higher compression than is normal and (I'm guessing) stock pistons. I wouldn't push it past 8 psi.
07-29-2009, 10:50 PM
#5
I've been tuning turbo cars (mostly 4cyl.) for a long time and the average C/R is about 8.8:1. When built, we usually do a 9:1 and they take fine to as much boost as you want to throw at them (everything else being right).
I've seen some Integra GSR's that had their stock 10.5:1 motors boosted and they just couldn't take any timing because of it. Timing is where the power is, FME. I'm curious if the LSx is the same way, or can you make big power on a no-timing tune, if necessary.
I've seen some Integra GSR's that had their stock 10.5:1 motors boosted and they just couldn't take any timing because of it. Timing is where the power is, FME. I'm curious if the LSx is the same way, or can you make big power on a no-timing tune, if necessary.
