Before I pull the Motor... again...
 

I wanted to just put this out there and see if anyone else had ideas or thoughts before I pull the motor (for the 2nd time)

Issue:
I recently was e-tuned with MotoEast. I have the Vortech Supercharger Kit with supporting mods, and on the etune, I made a pretty safe 251whp/204wtq on 91 octane (Mustang Dyno). Car felt great, and I had a 3 day race weekend at BIR that weekend. Did Road Course and Autox throughout the weekend, but towards the end I really started to notice power loss both just by feel and by times, my lap times were 3-5 seconds off my times from June. When I got back home, I took it to they dyno the next day and sure enough, I was only making 189whp.

No CELs, I have an AFR and did not notice any lean conditions, was always a healthy 11.x during WoT.

I've largely ruled out clutch and supercharger belt slip. I don't believe I have any spark or coil pack issues (would likely have CEL)

I have not touched the car yet to investigate. My guess is a piston / Ring / Etc issue, likely caused by our shitty, inconsistent 91 oct in the Minnesota / North Dakota area.

Backstory:

2 years ago I went to Full Blown Motorsports in Minneapolis, MN. Got tuned to 276whp, 201wtq on 91 octane. Made it two days till I bent a rod on the street, had smoke coming out of the exhaust, and it after it was all said and done I had scored cylinder 4. It was spring, so I just bought a used engine with 8k on it and swapped and went back to my safe, out of the box perrin tune, which I then ran no problems for the next two years.

So i've done this before, and I know now the answer is likely that I need to run e85 if i'm going to wail on this thing.

So - again - any thoughts or suggestions before I tear out the motor again would be great. Anyone done a compression test while everything is still in? Seems like a pain in the ass.

Mechanical engine issues usually have tell tail horrible clanky knocking noises or smoke out exhaust or bubbles in coolant or coolant/oil cross contamination.


Check for boost leaks, you should be able to log manifold pressure 1 bar is atmospheric so 1.5 bar is about 7psi boost


look at IAM ignition advance multiplier should be 1 and check for knock


check long term fuel trims should be below 10%

Edit: When I was at the track the first thing i did was compare boost. I think I ruled that out too. Both my good dyno run and the track log show a max of 1.58bar, which is 8.7PSI given my atmospheric pressure is 98kpa. The kit claims 9 psi max at redline so i'm pretty ok with that.

I'll check my logs real quick. I was able to take logs both on the track before I left when I noticed something was up (got a full lap in going 9/10ths) and again on the dyno both before and after. One sec.

Compression test, you might have melted a piston. Not on this car, but I've seen this on a few supercharged cars in tracks here. Altho they usually smoke a bit thru the exhaust (blue oil smoke usually, but not in huge amounts).

Edit: everyone else that makes you loose power (VVT, coilpacks, plugs, AFR) will create CEL as you already suspect, so its probably internal or boost leaks, but you seem to have ruled that out. These are all guesses, not based on my own but other people I track with (and on different cars for that matter).

Ok, checked the logs - Here's the snippet of both the good (right) and the bad (Left) logs.

https://s26.postimg.org/vj9wzbpd5/compare.jpg

Ok,


also have a look at the AVCS valve cam angles, make sure thay haven't defaulted to zero

I was kind of hoping for smoke, but nothing yet. It did get smoke last time. I am going to yank the header right away, so if there is any oil in there I should be able to see it.

You're IAM is super low on the bad log. Only .6 and even on the good run it isn't running great at below 1.0. This seems like some bad gas and the tune did it's job and pulled power. I could be wrong though:thumbsup:

Our gas in this area is notoriously shitty. It doesn't hold to 91 well at all, and its been a problem. So far, could be two motors worth of problems.

Second the low IAM.

The bad log also shows 3* of knock correction, which jives with the low IAM.

So what is IAM exactly and how does it relate to all this? Same with Knock correction, how does that work?

At a high level I can read, understand and compare the basics, but I haven't tracked really dug into those before.

So this is all just my understanding but the Subaru ECU systems use a decently complex Knock control system to try and protect the engine. The older EJ motors would fail a lot from the system reacting too slow but the newer systems are able to react much faster.

It's basically three parts, Ignition Advance Multiplier, Knock Control, and Fine Learning Knock Control. They all work together but also in different instances. The IAM is the most important one to keep good and steady at 1.0 if it is any lower it means the engine has seen more than just a random knock but it has occurred enough for the system to essentially say "we're gonna have a problem here" and it dials back timing in order to run in a detuned state. It also goes down in steps so the lower it goes, 0.6 is pretty low, it means it has seen the knock condition even after detuning to the previous step.

Knock Control is from my understanding the same but just not from a long term knock condition as it can pull timing and then add it back in relatively quickly if it seems to have gone away where as IAM will take a while to recover.

Then FLKC is a fine adjustment just like the name says. It takes care of very small adjustments that it learns over time like say in 3k-4k rpm it tends to knock a little bit it will pull some timing for those rpms.

I hope that this info was correct or at least close enough haha. Hopefully the ECU did what it's supposed to and it saved your engine:thumbsup: I'd fill it up with some new gas that is from wherever locals say has the best and then maybe dump one of the "better" octane boosters in. They don't do much but it could help get it closer to the ideal octane. Good Luck!

So what you're saying - there's a chance my motor might be fine, and that the quality of the gas I got (used the station outside of the track) might be to blame for the power loss?

That would explain why I am having no other symptoms except the power loss. No Smoke, No Cels.

I traditionally fill up with Holiday's 91 Non-Oxy - should I use that or go with the 91 that has 10% ethanol in it?

(Perk of using the non-oxy, I don't have crickets :) )

maybe a splash of race gas to up the octane? assuming the track has it available. good explanation above.