Getting to the Bottom of Dropping OAR

[WarrenBoostit]

Hey all,
I'm trying to put a pin in the reason my OAR has dropped a bit lately. I'm on Gearhead's e30 Tune, at about 67k miles now (specs in sig), and for a while through this winter I was running at a very happy -0.99 OAR on roughly e35-e40. I know some positive KR is expected to counteract burst knock when going suddenly WOT at highway speeds, but about two weeks back I laid on the gas on the highway, felt a large initial hesitation in power and saw a large KR of something like +5 for a brief moment, large enough that it scared the OAR into dropping to -0.87. Not many days later, a similar scenario occurred again, dropping the OAR to -0.79.

Being winter in MN, I immediately assumed it was a bad tank of gas, and so to validate that burned about 90% of it off, and then filled mostly up with some pricy 98 unleaded unoxygenated, with a bit of e85 for good measure (ended up around e20). To my dismay, through the first half tank the OAR did not want to go any more negative, and even when I would try to cheat it by bogging the engine in sixth KR would not get very negative (I believe it has to be below -3 for the OAR to move). I reset my KAM, and reflashed the tune, just in case any bad habits had been picked up, and did the same cheating method of bogging the engine in 6th and giving it about 8 psi of boost. I got the OAR to very willingly go up to -0.75, but not any higher, and I'm seeing up to 2.5 on the KR on highway speed sudden WOTs. I'm not really comfortable trying to push it past this point, as the OAR is doing its job and I don't want to hear a ping once in the life of this engine.

All spark plugs (cold pregapped) and downstream o2 sensors were replaced as well as the rear pump module about 3k miles ago as part of a different parts cannon adventure.

This is a list of probable causes I could think of, I'd love to get any feedback or advice

1. It's just really cold right now
- MN has had an uncharacteristically warm winter, and this might be the first time it's been in the 0-20 degree range where the roads were good enough to go WOT. Maybe the cold air is just too thick on bursts, so it has to pull a lot of timing
2. Oil from the intercooler is causing preignition
- Though I think this is a bit early in mileage to be happening, I still haven't cut the hole to access the GH Intercooler's drain plug (I've only have a rough idea of where it is)
3. Leaking injector
- Outside of a slightly rougher idle that I can't tell if is just in my head, I haven't noticed symptoms for this, no CEL's (yet). AFR seems to be similar in both banks, though I would need to actually log to validate.

I know that if I really want to get to the bottom of this the next step in this is to actually get a laptop hooked up and do a log of some pulls, which I plan to do, but I'm also curious, is the amount of OAR I'm fretting over even enough degrees of timing to be concerned? Or is this a mountain out of a mole hill scenario?

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Black 2018 SHO Non-PP | GH e30 Tune | PPE Catted Downpipes | DG2 Trans Mount | M-12405-35T plugs at .026 | 170 Tstat | 3 bar | H&R Springs | XDI-35 | Badges removed | Chrome delete | Fuel-it Bluetooth ethanol analyzer | GH IC | EPP Gen2 CAI | Noisemaker delete | MSD coils | Ceramic coating | Window Tint | EPP Hot Pipes | Black AR924 w/ General GMAX AS 05 255/45r20 | MRT axle back w/black tips

 

[BradM]

I have read that negative OAR's are on the good end of the spectrum. https://www.motorsport-developments.co.uk/Understanding-Ford-Ecoboost-OAR-Systems.html

 

[WarrenBoostit]

Indeed, my issue is that my commonly negative -0.99 OAR has dropped a bit (technically increased), meaning it's advancing less/pulling more timing. I do know KR readings are manufacturer specific but I know for sure Ford does advances in the negatives.

 

[BradM]

FWIW, I looked at my logs from over the summer and across 3 modified tunes and my OAR is .96 and never moves. I only found one log where it was 0.615 and 0.82 on two passes. My knock sensor is only neutral or adding timing, never retarding. We moved the timing table to better center the timing and my current tune has 100% neutral knock sensor input on every pass (timing table is centered) and OAR doesn't move. I would pull some logs, learn what is happening, and not fret (no parts cannon!). Yes, knock sensor readings in the negative range means it's adding timing. BTW, your system appears to be working so you won't hear pinging. Go have fun.

 

[BradM]

To clarify, my OAR numbers are negative values.

 

[David Klopper]

Yeah the best OAR (most timing and boost) is -0.96.

From what I remember, Matt from Gearhead once commented that with the Auto Octane tune, a -0.80 OAR gives you full boost and -0.96 adds 2 degrees of timing. Not sure if the E30 tune is different.

One technique I’ve found to get OAR up is to brake boost. So basically put the car in drive, hold the brake and bring the rpm’s to around 2500. This seems to bring KR to -3 to -4 which is what’s needed to change the OAR.

 

[WarrenBoostit]

Yeah the best OAR (most timing and boost) is -0.96.

From what I remember, Matt from Gearhead once commented that with the Auto Octane tune, a -0.80 OAR gives you full boost and -0.96 adds 2 degrees of timing. Not sure if the E30 tune is different.

One technique I’ve found to get OAR up is to brake boost. So basically put the car in drive, hold the brake and bring the rpm’s to around 2500. This seems to bring KR to -3 to -4 which is what’s needed to change the OAR.

Interesting! I tend to avoid brake boosting, as on mine the nannies really come in after 2000 but I think I'll give that a try

 

[David Klopper]

oh forgot to mention that you mustn’t let go of the brake. Basically while stationary, but in drive, when I rev up to around 2500 I see a bunch of negative KR on my livewire which helps bring the OAR back up.

It doesn’t work when just revving in neutral so make sure you’re really holding the brakes well so you don’t push past them.

 

[WarrenBoostit]

From what I remember, Matt from Gearhead once commented that with the Auto Octane tune, a -0.80 OAR gives you full boost and -0.96 adds 2 degrees of timing. Not sure if the E30 tune is different.

Was wondering, how much boost do you read at full boost? I swear on this e30 tune I see 18-20 psi sometimes, and makes me wonder if that's correct or I have a misbehaving MAP sensor or something along the intake path.

 

[David Klopper]

Watch out to not interpret “boost spikes” as actual sustained boost levels. Most of the time on the auto octane tune I’ll see 14-15 psi sustained boost and 17-18 psi spikes around gear shifts.

The e30 boost levels seem to be 16-17 psi sustained but with more timing added.

Above that and you’re likely going to be outside of the stock turbos efficiency window.

Here’s a good post comparing the AO tune with the E30 https://www.ecoboostperformanceforum.com/index.php?topic=9707.0

 

[BradM]

My logs show 18.5psi dropping to 16psi during 4th gear pulls. I see peaks of 21psi. BTW, if you foot brake and hold 2500rpm for a few seconds, torque management will kick in and shut you down. Mine can hold 2300rpm longer and softer launches (~2000rpm) seem to give me better times because traction control doesn't kick in.

 

[WarrenBoostit]

Hmm, brake boosting it doesn't get to a high enough rpm to really get into boost or modify any timing, it sits at 0 KR (though OAR didn't start from 0). However, it was 50 degrees today (weird KR was when it was around 15) and I'm noticing the car altogether seems a bit less cranky. I believe the GH tune even modifies fuel pressure for temperature and such, so maybe the tune mappings are just a bit aggressive for certain variables in sub 20 temps. OAR still at -.75 unfortunately, but sounds like that is approaching peak boost anyway, so I'll just monitor it as temps warm up and see if the OAR begins to approach -96 again. I'd normally expect forced induction vehicles to love cold air, but for some reason this one always seems to get a bit upset when temps drop below 20

 

[kryptto]

My logs show 18.5psi dropping to 16psi during 4th gear pulls. I see peaks of 21psi. BTW, if you foot brake and hold 2500rpm for a few seconds, torque management will kick in and shut you down. Mine can hold 2300rpm longer and softer launches (~2000rpm) seem to give me better times because traction control doesn't kick in.

Does pursuit mode make any changes with brake boosting?