Very unfortunate dyno session

[ric342]

A background of the build: 2013 Scion FR-S manual 98900k miles
IAG closed deck 12.5 to 1 built short block
GSC titanium valves and springs
lifter retainers
killer bee oil pickup
oil pan baffle
5W-30 euro full synth oil
1050 cc injectors
greddy light weight pulleys
verus AOS with cooling integrated
HKS spark plugs
Harrop supercharger with the 70 mm pulley
Perrin crank pully
X clutch chromoly clutch kit
Cusco motor mounts
4 bar map sensor
CSG flex fuel kit
upgraded fuel pump with trap door
Running on E85
ARP head studs
Jackson racing dual rad/oil cooler setup
Mishimoto fan shroud and hoses
FBM thermostat
So let me start with saying that this is in no way the tuners fault.

I am the first and only owner of this car and in 2022 the motor was a victim of the dreaded valve spring recall/ blowup afterwards due to silicone clogging up an oil gally(83k miles). I put build together with a friend and this was indeed my first attempt at rebuilding a motor. I put the engine together and left it NA for 2 years and about 10k miles, I saved up enough to get the supercharger and a tune along with the supporting power mods. While starting the tuning process a few issues arose.

We found that the wiring harness had started to go bad along with the mass airflow sensor, replaced both and proceeded with data logs. We then ran into cooling issues at high loads, fixed them and proceeded with the data logs. I found that after I introduced the supercharger there was a very small leak coming from the cam cradle and was already planning on installing the lifter retainers per the tuners suggestion. When I took the heads off I noticed on the passengers upper cam journal there was scoring, bad enough that I could feel it with my nail. I did some research and found no similar cases and proceeded to reseal the engine. Car drove great with no major issues so we set up a date to do a dyno session.

Fast forward to the day of the dyno, I met up with the tuner and by coincidence there was an engine builder present at the time. I shot the shit with him and the topic of the cams came up and I asked him what his professional opinion was on the subject. He told me that it was most likely a cam sprocket going bad, causing oil to drain from it stating that if I was going to track the car that all 4 sprockets should be replaced. The tuner agreed with the assessment and mentioned that my light weight crank pulley was a concern as well, stating that the harmonic balancer is an integral part if the engine dealing with all the vibration at high rpm.

We proceeded with the dyno session with me stating that I would buy the fluid damper crank pulley and install it ASAP. First few pulls were looking good, but on top end we were getting random dips. The tuners deduction was that the engine was vibrating so much that the timing was being pulled back at high rpm.

Now on pull 6, we were getting a great power graph but the moment we hit 7600 rpm there was a 1 second metal on metal boom. The tuner immediately shut the car off and we looked at the data. We found that when we hit redline the car misfired 80 times in cylinder 4, the tuner stated that he had never heard a sound like that and the engine builder stated that it sounded like a piston kissed a valve. That noise ended the dyno session, not only to prevent further damage, but because I was 175 miles from home.

The drive back home was something that Id never wish on anyone, not because the car was having drivability issues, but because of the anxiety that came with all the possible problems that could arise. I had a 3 hour drive home and had the Ecutek app open the whole time looking at the misfire counter. The car drove fine but at random points while in traffic the counter for cylinders 3 and 4 would go anywhere from 2-20 misfires then reset. The car never popped a CEL and I could not feel the misfires as the counter went up. At speeds of 70-80 the cars misfire counter never changed, I got it home and am beginning to tear it down. Why does the car have the random spikes on the misfire counter at slow speeds in cylinders 3 and 4?

Where did I go wrong? Not replacing the heads on the initial build? Wrong oil viscosity? Or is this a common issue with the FA20. All I know is that im in too deep and need to see this build to its completion, I bought a used head on Facebook but now I dont trust it. Should I replace the timing cover again due to it having the oil pump integrated?

Im biting the bullet and getting everything that was not replaced the first time brand new. Looks to be close to 6000 in parts alone. Any input would be great.

Thanks for reading
Ric

[EndlessAzure]

You let the magic smoke out of the FA20. Happens a lot when you crack Subaru boxers open for a rebuild.


Someone else might have a better idea, but it's important to take a moment to consider that although we often think of cars as uncomplicated adult Legos, some aspects like engines are elements that exist, hidden, with exacting precision - every piece we touch along the way may affect that.

[DarkPira7e]

Azure is spot on. I think the build was a little ambitious for the power goals and the more you touch, the more you are rolling the dice.
I can't comment on lightweight pulleys, but I have a Fluidampr on mine and rev to 8k, no weirdness.

No telling where the misfires came from, it could be vibrations causing issues but I'm not going to blame something on a concept I don't understand well enough.
Definitely replace the cam gears. There's so much on the internals of those that can hold debris. The internal flaps the control engagement can become loose or go bad (I had a couple like this., No symptoms when my 3rd recall failure engine replacement spun a bearing, but it would've caused issues later)
After my rebuild, we had a noise like this. The dowel on the cam was loose. A cam sprocket had a loose bolt and it slipped on the cam, causing a super loud bang noise. We had no idea what it was until we took the timing cover off and removed the cam gear to replace all 4 of them like I should have done initially..

Did you get a new timing cover? If I could give anyone who is undertaking a build like this advice, it would be to replace the timing cover, and ALL cam sprockets on a rebuilt. Just get it over with, it's not worth it! And have a second person check your torque on every bolt connecting the cam sprocket to the cam itself. If I had someone check, we could've caught my loose bolt and saved ourselves hours and hours of scare.

Sorry to hear you had issues. The only people who don't have issues are people who document their builds on Youtube and conveniently omit the problems.

[KeishaMurch]

Any update?

[ric342]

Originally Posted by KeishaMurch

Any update?

Update: Found aluminum in the oil pan and continued to disassemble the long block. What I found was that a valve did indeed float, no damage to the piston, no bent valve.
What was found was that all but the drivers side intake cam journal had substantial scoring due to what I believe to be loss of oil pressure(sprockets failing). I ended up buying new heads, cams , sprockets, valves, springs, bearings and cradles.
The car is about ready to go, just dealing with an evap code at the moment(p0458). Purge valve is fairly new, Ill connect the smoke machine to the car and verify if there is a leak.
One unpleasant surprise was that the UEL FT86 speed factory headers had gone bad due to a dislodged comb. Part has less than 30k miles and I had to go back to stock. In doing so the car now has a (P0031). I ordered a new bank 1 sensor.
Ill add pics of the damage asap.

[ric342]

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