Compression Ratio
08-08-2003, 10:43 PM
#2
2nd Gear Member
Join Date: Apr 2003
Location: United States
Posts: 270
Compression Ratio
I've always read that 8.5 is great, 9.5 requires more tuning and 10.5:1 is a no-no. The s/c manufacturer will have all the spec's for each of their applications. (low psi vs. high psi, etc.)
08-09-2003, 12:34 AM
#4
5th Gear Member
Join Date: May 2003
Location: Norfolk, VA
Posts: 2,129
Compression Ratio
yep 9.0 or lower, the lower the better. to a point of course. that's why say a stock GT engine, like mine at 9:1, can handle a small boost ok, but alot of those high compression honda engines, mainly VTECs, don't hold up to boost very well. a guy i was in korea with has a friend who owns an import shop, and they turbocharged about 5 or 6 S2000's. just 6 psi kits. they quit doing it because they kept blowing head gaskets.
08-09-2003, 03:54 AM
#6
Join Date: Aug 2003
Location:
Posts: 7
Compression Ratio
The saying is the lower the safer. You can run more boost with lower compression but with lower compression it will take more boost to make the same power as someone running higher compression at low boost.
I run a 10.2:1 compression in my Honda and boosting 10psi with an 18G turbocharger and I haven't broken anything yet. It's all about proper fuel and tuning.
I run a 10.2:1 compression in my Honda and boosting 10psi with an 18G turbocharger and I haven't broken anything yet. It's all about proper fuel and tuning.
08-09-2003, 03:41 PM
#7
4th Gear Member
Join Date: Jun 2003
Location: B'ham, WA
Posts: 1,484
Compression Ratio
Key word - yet. Unless of course you've properly built the motor. Pretty much all of the Subarus that get 3-4psi kits are ok, but when they start running 6+ they all end up blowing up the motors. One guy ran his for 3 years before it puked. Others make it a matter of months or even weeks.
Even stock turbocharged motors can blow if the owner is an idiot. Some fool in Seattle slapped a manual boost controller on his WRX and cranked the boost up to 18psi and ended up sending the rod through the top of a piston. And then he drove it around even though "it made funny noises" and was down on power.
Stock 5.0 bottom ends are pretty tough. If you want to go for max boost, build the bottom end even more, and go low compression. They're right about it taking more boost to make similar power, but with lower compression you can throw even more boost at it.
Even stock turbocharged motors can blow if the owner is an idiot. Some fool in Seattle slapped a manual boost controller on his WRX and cranked the boost up to 18psi and ended up sending the rod through the top of a piston. And then he drove it around even though "it made funny noises" and was down on power.
Stock 5.0 bottom ends are pretty tough. If you want to go for max boost, build the bottom end even more, and go low compression. They're right about it taking more boost to make similar power, but with lower compression you can throw even more boost at it.
08-10-2003, 03:31 AM
#8
Join Date: Aug 2003
Location:
Posts: 7
Compression Ratio
Originally Posted by horatio102
Key word - yet. Unless of course you've properly built the motor. Pretty much all of the Subarus that get 3-4psi kits are ok, but when they start running 6+ they all end up blowing up the motors. One guy ran his for 3 years before it puked. Others make it a matter of months or even weeks.
Even stock turbocharged motors can blow if the owner is an idiot. Some fool in Seattle slapped a manual boost controller on his WRX and cranked the boost up to 18psi and ended up sending the rod through the top of a piston. And then he drove it around even though "it made funny noises" and was down on power.
Stock 5.0 bottom ends are pretty tough. If you want to go for max boost, build the bottom end even more, and go low compression. They're right about it taking more boost to make similar power, but with lower compression you can throw even more boost at it.
Even stock turbocharged motors can blow if the owner is an idiot. Some fool in Seattle slapped a manual boost controller on his WRX and cranked the boost up to 18psi and ended up sending the rod through the top of a piston. And then he drove it around even though "it made funny noises" and was down on power.
Stock 5.0 bottom ends are pretty tough. If you want to go for max boost, build the bottom end even more, and go low compression. They're right about it taking more boost to make similar power, but with lower compression you can throw even more boost at it.
08-13-2003, 11:19 AM
#9
5th Gear Member
Join Date: May 2003
Location: Norfolk, VA
Posts: 2,129
Compression Ratio
so this guy who lives in my building has got his jackson racing s/c now, running 8 psi non intercooled, on a completely stock except for cat back integra type R. i havent asked him too much about it yet, but i believe he bolted it on blind, w/o any dyno runs and tuning work. Almighty-Si.... or anyone else... care to comment on how this might affect engine reliability?
