Rings don't seal. Low compression, oil in chamber. What's surprising?

These rings were some "race" rings from NPR sized for the JE pistons that were in the block, the only thing we could find that fit. "Race" in the parlance of the automotive aftermarket means designed for vacuum pump or dry sump, I.E negative pressure in crank case. You can run about 70% less ring tension with those systems. The bulk of the heat going into the oil is from ring friction in any engine, not combustion heat. That's one of the reasons a dry sump engine makes so much more power with no other changes, not hydraulic pumping losses as most people would guess. Run those rings in a wet sump that is chuffing along at .5 to just over 1psi and it's gonna get blowby. This particular engine burned a little from the very start and is now blowing a lot 40hrs later.

So yeah, built with our .5mm larger, .5 pt higher CR ST/XX piston package, it would make 185whp. We know that because we have made 169whp with a nearly stock but coated head and those pistons. The CNC head and cams here easily worth 15whp, thus the estimate.

 

Do you run oil squirters in you ST/XX engines?

 

We always retain the OEM oil squirters in every engine we build.

 

to clarify. I use a stock 99 intake manifold.
also, my oil squirters are removed and blocked.

My specs:
99 engine
.080" over 11:1 pistons with xx rings from Emilio
SCAT rods ( went beefy and heavy because my last motor pooped out Carillos)
Calico coated ACL race bearings: Rod and main
oil squirters removed
IJ crank scraper
BE Race oil pump shimmed for 80 PSI
Supermiata CNC head with +1 valves
stock 99 cams
stock 99 manifold with VICS left unplugged
Skunk2 TB
RB header
custom 2.5" exhaust
supermiata crank damper
E85
everything fully balanced
ACT prolite flywheel and 4 puck unsprung clutch (because Emilios race clutch was out of budget at the moment)

makes 178/146 unrestricted

 

^^^ Why block the oil squirters?
Was that power measured at the rear wheels?

 

We now offer bare CNC heads for those of you that just want the porting unicorns without any of the other bits.

SuperMiata CNC Miata Bare Head


New thread please

 

E, I noticed you recommended +2 for use with E85. Is that something specific to what E85 likes or is it more of a "go big or go home" kinda thing?

 

+2 for big cams and/or big CFM boost. IOW, 8psi out of a 2554 and +1 is fine. BP exhaust side flow is weak. It's essentially a BP05 head with 15% better intake flow, thus the imbalance.

 

Most excellent, that's why I went +2. Bottom end is back from the shop, now just waiting for the CNC head so I can button this build up. Thanks again for working with me

 

Thinking about updating to the NB1 or NB2 head and was wondering if anyone has found a fix for the NB2 intake cam harmonics problem at high RPM. I remember reading about it awhile back. I want to use the VVT since my ECU can control it and would also allow me to pick up 949 cams with the crazy 4.. Lift. Plus who doesn't like the added torque of the NB2.

 

The fix is valve springs or a better cam profile. The issue is not harmonics, but an aggressive cam profile and not enough valve spring.