So as we embark on our racing program for the FRS/BRZ we knew oiling would become a major issue when running high RPM and high load cornering (Think 1.7+ G sustained). Much of what we've see on this engine compared to the EJ is very positive. Better head drainage, nice deep sump, and a 12mm pump gear.
With high oil temps on track people have already recorded oil pressure drop approaching the OEM redline. Clearly when boosting the first step is to run forged internals.
The powerband of this engine falls hard so we needed to pickup our powerband so big valve headwork was performed. Pulls like a freight train to 9k rpm now!!!!
Having faced serious cooling issues last year, it was straight to the racing parts I use on my STi and a serious radiator was fitted.
Now onto the issues but keep in mind we are running up to 9k RPM and running 325 Pirelli non DOT racing slicks with high downforce. We pretty much instantly oil starved the bearings under race conditions on a track known for tearing up motors due to long high G turns.
Look at the FA20 crank mains and the rod journals and you should spot something unique where I oil starved the rod bearing. The third main from right to left has a larger oil port. Why? Because it has to feed two rod journals where all others only feed one rod journal. What happens to oil pressure when you increase the oil port size? What happens to your oil volume requirements when you need to feed two journals with one main? Guess which one failed?
Now that's not to dissimilar to the EJ motors with how the mains feed the rod journals but the major differences are that on the EJ two oil ports in the block feed the mains where on the FA, one port feeds all the mains. On the EJ the oiling ports for the mains are opposed (two on each side) and on the FA you can see all oiling ports to the mains are inline. Now you would think on the FA, this is better and more direct as the EJ has to travel through the block farther even though it splits it's oiling.
Overall I think the FA has some major advantages but I think maybe we see on major difference which may lead to more pressure issues at the crank. On the EJ motors the oil pressure first feeds your crank and rods and then travels to the heads but on the FA the heads are feed simultaneously with the crank and rods. I'm not sure if Subaru needed more oil feed to the heads for the newer cam setup or they just wanted more direct flow to each.
My bearing failure is not black and white unfortunately. We know it's oil starvation but I was also running a ton more RPM than I was last year. We need to retest and note the pressures we are seeing and at what rpm they fall while on the dyno. This should show the merits of the oem pump which is 12mm. This will determine if we go with a 2 stage scavenge dry sump or if we need to go to a 3 stage pressure. In the racing environment g forces and aerated oil add to the demands a street car may never face.
Let me remind you 325 racing slicks and over 1000 lbs of downforce.
Many of you will never face this problem but should you choose to go with headwork you may have an issue purely based on RPM. Also note I was class limited to 390 whp so I wasn't running any crazy amount of power.
I figured I would share some of the issues we are facing with this engine and hopefully we'll come up with a solution or the other companies will. So far from what I'm seeing the pan designs out there aren't going to help as they are not concentrating the oil around the pickup, they are simply widening the oil pan which I think will only make it worse on track cars.
Thanks,
Phil Grabow