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
