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Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.
I made a mistake when I was building my EJ205 for my Factory Five Kit car a couple years back. I am re-assembling the engine now. I am wondering about clearances and oiling for this track car.
I've heard 1.5 thousandths on the mains and 2 thousandths on the rods is what I should be aiming for. However, the plan is to rev this motor to 8k RPM in order to get the most of my Garrett G25-660 turbo. Do clearances change with a higher rev target? Would a clearance of 2.5 thousandths on the rods be okay? My machine shop weighed the rods and the small ends seem to be 1 gram out from each other. Same with the big ends. Is that alright?
In addition, would moving to the 11mm oil pump be necessary? What else would need to be done to get the EJ205 to get to 8kRPM safely for prolonged periods of track use? I have:
Stock non-crossdrilled crank
Eagle Rods w ARP 625+ bolts
ACL Race bearings
ARP2000 head studs
Crower Valvesprings + retainers (150lbs open pressure)
Conversion to shimless buckets
Thanks for the help.
The higher end of stock spec works fine on those.
That turbo requires less oil flow than stock, you don't have AVCS, but you'll need a significant oil cooler. Depending on your oil cooler and lines, and final clearances, you may or may not need an 11mm pump. Whether you go 10 or 11mm, it needs blueprinted, packed, staked or loctited.
The downside of the 11mm is pumping more wasted/bypassed oil, evacuating and aerating oil in the pan which is already a concern when you put that engine on track in a car with any grip.
I don't want to derail your post, but there's other info which is generally what makes those cars kill bearings. Aerated oil or lack of oil being in the pan because it's stuck elsewhere, resulting in bearing failure, rather than an assembly/clearance selection is what usually kills them. With that in mind I have some additional suggestions in case they are a help.
I really hope you have a way to immediately warn yourself of drops in oil pressure on track, perhaps a digital dash integrated with an ECU and oil pressure sensor so you can be alerted and apply ECU measures to immediately attempt to reduce damage. Typical gauges really aren't sufficient for this. I've had people tell me their gauge barely moved mid corner, then we log the car and oil pressure is dropping to near zero.
Getting oil back into the pan is an issue on that engine so air/oil separation and venting are key, plus the pan and pickup are not conducive to track use either, so a better pan, pickup, baffle setup is a must have, even if you just run the STI parts vs. something more costly.
Upgrading the pan and pickup does not guarantee avoiding oil starvation, and revving the engine high makes it more likely to starve because you're evacuating the pan more quickly. I have to short shift corners and corner less aggressively to avoid starving stock Subarus during track testing.
If you're set on high RPM power, stock cams will make HP roll over around 6000-6300 RPM. Plugging some used STI cams and installing is the cheap option to get power for another few hundred RPM, or GSC and Kelford have stage2/272 cams if you want to make power up to 7000-7300 RPM.
Alternatively you can ramp boost up with RPM to slam air in the engine to hold HP at high RPM, but that only works up to the shaft limit of the turbo, or other limits of your engine system i.e. intake, exhaust, intercooler, cooling systems etc. and is not the efficient way to do it. If your power target is low enough, this can work.
Even if you pay to have those Eagles balanced I'd stick to 300 tq, 7000 RPM if you use them. They tend to fatigue fail from use over those values just from time. They become two piece in the middle of the shaft. Stock STI rods will serve you better and they're cheaper if you get them from a place that takes them out of new shortblocks. I run the stock STI rods to 350 wtq, 7300 RPM in a road course application. If you want more than that, Manley I beams will handle whatever you throw at them.
I hope this helps. The FF cars are neat. Unfortunately they handle well so it's real easy to oil starve them. ;)
Thank you for your response Mike.
You're correct - Ball bearing turbo & no AVCS so I figured less oil demand. I do have:
External 13-row AN10 oil cooler
Remote Filter relocation
Killer-B oil pickup & windage tray
PLM oil baffle & stiffener (the one with all the viton one-way valves)
STI oil pan
Do you think those would be enough to combat oil starvation on the track? I understand that I might not make power all the way to 8K but I wanted that margin of safety so I could hold the gear a bit longer in Autox. However one day I plan to do BC 272 cams. Unfortunately I am running the stock ECU so I do not have a method of cutting power for low oil pressure. I simply have a gauge with an alarm.
Since I am running a stock 5MT I planned on keeping the torque very low - 250-300lb-fts and I wanted to rev higher to get the power up to 400hp. I also don't believe my intake, cooling, exhaust will be a bottleneck as they are all massively overkill. In addition, you truly believe that stock STI rods are better than Eagle forged H-beams? Honestly, I am surprised you say that as they are cast parts correct?
I am very concerned about clearances because the last time I assembled the engine I left the mains as-is and it suffered very low oil pressure - 10psi at idle, only 30psi at 5k - measured at the oil galley on the back of the head. Do you know the relationship between pressure measured there and pressure measured at the pump? I figured pump pressure is 5-10psi higher (still too low).
In my experience that oil cooler has been too small for customers, but airflow is a big variable, ambient temp and your driving are also very big factors, so it may work for you. As long as you're monitoring oil temperature and pressure, you can try it, then make changes only if the data shows you improvement is needed. Plotting oil pressure vs. RPM vs. oil temp is key, which means sensors and datalogging. Glancing at a gauge briefly once in a while is feasible, but you miss almost all of the data if you just have a gauge. Depending on location, airflow, ambient temp, your driving, session length, course layout (time on power), 24-32 row full width Setrab is more typical of that power/RPM level. EJs aren't terribly efficient and they make a lot of heat for their output.
One of, if not the biggest factor in: overheating oil or water, oil starvation, overheating the brakes, fuel starvation, is the driver. That factor cannot be overstated.
Much of the difficulty in getting consistent answers about what car X needs to survive on track comes from the driver variable. Almost any modern car in stock form can survive a first timer's first ever track session because they simply don't drive fast enough, and that's a great reminder. Depending on the vehicle, driver, track and conditions, maybe the car will be totally fine on the second session too. By the afternoon of their first track day though, most people I coach will push something on the car hard enough that I need to point it out to them. Usually they overheat the tires first, then perhaps the brakes. By afternoon of day 2, some of them are already going quick enough to starve things, while others aren't looking to drive that fast and they're having tons of fun, while only overheating the tires and maybe borderline on stock brakes. All this to say each driver's trajectory is different, where they plateau is different, so the mods one person needs to avoid oil starvation, overheating, etc. are unique not only to their vehicle, engine, tracks they drive, ambient temp, etc., but to them as a driver. I caution against seeing one person's success as the path to your success.
For items you are unsure you need, I suggest investing in the items to warn you immediately when you've found a limit. That way you haven't bought things you don't know you need, but also hopefully haven't killed multiple engines and turbos figuring out what parts to buy.
Gauges with simple warning lights generally can only warn you beyond one pressure value. If an oil pressure warning light is set to say 15 psi and you get 25-30 psi oil pressure when you should have 60-85 psi at 5000-8000 RPM mid corner and have no warning, that's an engine and turbo gone. Maybe it doesn't die in the moment, but it's just a matter of time once that happens. A proper setup with oil temp and RPM based oil pressure warning can alert you when you have less than normal pressure for that particular condition, or simply less than you deem required at a given RPM, depending on how you set it up. The light on a gauge really only works at hot idle, or after the engine is so severely damaged that you have little to no pressure while driving, at which point it's way too late already. You also have to see the warning light to do something about it, and many gauge lights aren't in line of sight or not super bright so that's another concern.
If someone doesn't have budget for digital dash sometimes I'll suggest a standalone ECU and sensors for now because safety measures are in place. You won't know why the engine cut out til you pit and view the datalog, but you know the engine cut power, you park it, figure it out after, and your engine hasn't been killed. Then you can add a dash later. I hope I don't seem pushy, just making a suggestion I've seen save people lots of engines.
I would skip the Accusump and focus on testing, logging, making changes to avoid starving the oil pickup in the first place. I've not seen an Accusump resolve oil starvation on that engine, only reduce the drop in oil pressure somewhat, and not enough to avoid damage. The Accusump system also requires a bunch of extra plumbing, extra weight, it's big, you add many failure points, it complicates oil level monitoring, you have to deal with opening and shutting the valve, etc.
The electronic valve isn't a viable option because it doesn't flow enough to do much and the manufacturer will tell you they fail if powered for more than a few seconds at a time. I've seen them fail in the field multiple times, they really die in a few seconds, too quickly for some corners.
I'd do stock STI pickup if using a stock STI pan. I'm not familiar with PLM so I can't speak to that. A good baffle should help.
Stock STI rods would be better than what you have, but if you really want 8000 RPM I'd get Manley I beams, however cheap rods might make sense til you're sure you have oil starvation avoided.
I understand your concern with clearances. Your past issue may have been due to a number of things including but not limited to bearing clearances. With clearances at the high end of the stock range, unless there's a mechanical fault, you won't have oil pressure that low as long as oil temp is reasonable and you're using an oil weight typical of stock clearance track use on that engine i.e. 5w40 or 10w40. The relationship you asked about is based on many places oil can spill out of so it's not a fixed value. On the other hand, the relationship between the main oil gallery ports and head at cam girdle and turbo feed is more consistent and I can tell you if you have 10 psi at idle in the main gallery, your cams are barely being oiled. 20 psi is a good minimum figure at idle for track use, increase idle speed if needed, and if you have less than 40 psi by 2000 RPM, I'd shut the engine down and diagnose.
***In case anyone is reading this, a lot of this is specific to this engine. Please don't feel you need to apply these values to another type of engine.***
And I suggest a low inertia clutch, light flywheel if you're going to try to make that stock trans shift at 8000 RPM.
As Mike suggests, normal electric oil pressure gauges are slow acting - it's a bit of faffing around, but mechanical ones normally react almost instantly, so may be worth the trouble.
With oil pressure switches, you can buy motorsport ones that can be set to come on at much higher pressure settings, and back in the day it was common to have one connected to a bright light on the dash - an indicator or tail-light worked well - to notifiy if there was even a relatively minor drop to the pressure setting.
Thank you for your responses.
I've looked into it and I think I can datalog oil pressure using my Cobb Accessport. That will at least allow me to plot data, as you were saying. Until I get a standalone ecu I will be stuck with that. I guess we will see how well the baffle works.
I chose the eagle rods based on recommendations from MotoIQ's "How to Build a Subaru EJ That Won't Blow Up," and Flatirons Tuning's rotating assembly guide. I figured they would be among the best.
I measured my main clearances and they were around 4-5 thousandths, which I think is where all the oil was bleeding off from, and is why my pressure was so low - It would top off at 30psi.
I am getting the block line bored and making sure the main clearance stays around 0.001-0.0015
I'm glad to hear you've found the source of the low oil pressure. It's always reassuring when you find a clear issue vs. just trying again and hoping for the best!
Logging on the Accessport will be much better than trying to watch a gauge while driving. The fewer items you monitor the better the rate will get, but there's likely other critical items you'll want to keep an eye on. Logging rate will be slower than what you'd want to watch for cavitation, but big pressure drops from loss of flow will still show up.
Well done and please let us know how it goes when you get it back together.