Forged Shortblock

[serialk11r]

Originally Posted by cf6mech

I'm in process to going forged, waiting on Aria's custom pistons right now which will also lower compression from 12.5 to 9 to one,....track car and yes its for longevity with FI.

Dang, 9 is a huge drop, what kind of boost?

[cf6mech]

10 to 15 on pump gas.

[zohare]

...? 15? Running 20 on stock internals. Bottom end is *OK* for now, what we NEEED is heads XD (again ignore me for my lack of knowledge just my opinion ) Like s2k status 250hp and 9000rpm n/a heads. And hoping to see redesigned intake manifold sometime soon.

I feel like our manifold and cams are pretty mild. In terms of built na cars, worked on old Porsche 2.0 flat 6s in some race cars and Wed get 210 ish WHEEL HP at similar comp and sim. to stock rpm, not above maybe 8300 or so with old school air cooled non efi boxer 6s. I have a video if someone wants to see it or doesn't believe me.... S2k has vvt, but lower compression and makes 40 more HP? That alone says what our limiters probably are. Cams and everything pushing air into the heads, and the heads themselves.

Curious if the sti goes this direction. Looking like it'll be an intake manifold/tb and maybe more aggressive cam profile and some other small redesigns. and they're looking for 40 extra ponies. I'm OK with that because it only will make a BETTER boost candidate to me.

[serialk11r]

Originally Posted by zohare

...? 15? Running 20 on stock internals. Bottom end is *OK* for now, what we NEEED is heads XD (again ignore me for my lack of knowledge just my opinion ) Like s2k status 250hp and 9000rpm n/a heads. And hoping to see redesigned intake manifold sometime soon.

Uh, agreed on cams and manifold (the manifold is almost certainly tuned for low end and the intake cam could be a little bigger) but I would not fuck around with the ports on this. DI is very sensitive to the flow, grinding the ports bigger could destroy driveability.

Ever heard of fatigue? The stock internals are doing okay on 20psi boost and raised rev limiter, but that doesn't mean they'll last very long on it. Cutting the reciprocating mass by a little bit and using stronger rods will improve reliability. 9:1 pistons and 1 bar boost seems a bit conservative (and perhaps underutilizing the forged componentry) but it will certainly reduce stress on the components.

[zohare]

Thanks for info. Didn't know that about DI. What about that stupid torque dip around 4k... so annoying. I imagine the fatigue is an issue yes, but if its built, I feel like at 9:1 a LOT more than 15psi should be attainable. Buddies built/stroked 4g63 gsx, stock heads, has no problems at all at even 30+ psi. Out limits are tuning and spark blowout. Running e85@26 psi right now on an evo iii 16g but #6 ngks gapped .017. 8-0

[Captain Insano]

Don't try to compare to the 4G63. That engine is legendary for how stout it is. Besides that, in general, yes, with a 9:1 comp ratio you should easily be able to run 15+ psi even on pump gas (assume 91-93 octane region of residence dictating - I don't consider E85 pump gas as it's not commonly available everywhere). As long as the turbo is in its efficiency range and you aren't running crazy timing.

[cf6mech]

10 to 15 psi is a starting point,...want to drive it around like that for awhile,....then possible revisit for higher boost. It's about drivability on a road course and ability to put it to the ground with the tires and suspension components I have.

[Lonewolf]

Did anyone ever install one of these? Reviews?