RomRaider

Hi All,

I've had a WB O2 (innovate unit) for just over 3 months now. After spending ages dialing in the MAF scaling and getting it bob on for OL pulls and as close as for CL, the readings have now started to drift lean on pulls when compared to Final Fueling Base. However this seems to be intermittent.

The car is still running as it should and boosting as it was before, and I'm not seeing any substantial additional knock as a result of this 'apparent' leaning of the AFR. WB CL results are as you would expect, learnt fuel trims are sensible as you can see from the screenshot.

Things that have changed recently:
- fitted a turbo blanket about 1500 miles ago
- added both a boost gauge and the ARF gauges to the same power circuit as the innovate controller is attached - possibly creating a bad/dirty earth??
- changed to manual boost controller on 8th Jan

Things that I know / suspect that might be relevant, observations, and history:
- sports cat was fitted in Aug last year and the workshop that fitted it did not replace the turbo->downpipe gasket
- immediatetly after the turbo blanket was fitted AFR was bob on
- had a 600 mile blast around Scotland, with some 'spirited' driving, since then it appears the AFR reading is progressively drifting lean
- I calibrated the WB twice on 9th Jan with no apparent affect. It has always been fitted in place of the rear o2 sensor
- WB sensor was definitely torqued as per the rear o2 in the service manual
- occasional smell of exhaust fumes in the cabin, but this happened before fitting the turbo blanket, particularly noted by rear seat passengers
- no noticeable smell of exhaust fumes in the engine bay
- no noticeable change in engine or exhaust noise from inside the car
- no obvious sound of exhaust leaking at idle from under the car or engine bay
- there is a difference in cruise between front 02 and WB, with front 02 hovering slightly richer than stoich (not sure if this is normal?)

Log Files:
31-12-2016: just after fitting the Turbo blanket - AFR is bob on
03-01-2017: after the scotland trip - first sign of drifting, and I have reduced the timing in the knock areas
05-01-2017: further drifting?
08-01-2017: apparently OK on this day!? (MBC fitted before the pulls)
10-01-2017: 3rd and 4th gear pulls + some cruising logs - show it's drifted again

Previously the AFRs have been very consistent, and I've not seen this level of run-to-run to variation.

My thoughts are that the gasket between the turbo and downpipe is leaking, or that there is some earthing issue from fitting the gauages on the same circuit as the controller, do either of these seem reasonable places to start?
(or my worst fear is that fitting the turbo blanket has caused the turbine housing to crack....)

Any more thoughts or suggestions!?

Cheers!

-----------------------------------
Car is a 2006 Hawk STi
Mods: Sports cat downpipe, forged pistons uprated HG and bolts, samco inlet, RCM high flow fuel pump, sports cat centre res + pro drive back, Turbo blanket, MBC,
Map: my own tune, nothing has changed here other than tweeking the base timing map a little here and there, and setting target boost and WGDC = 0 to for using the MBC

have you tried cleaning the MAF sensor with MAF sensor cleaner? a little bit of film on the thermistor maybe?
have you calibrated it by free air lately?

as above, are you maf readings the same on "stable" vs "unstable" logs (filter out a few things so your looking at the same amount of boost pressure as before - that way the MAF readings should match fairly closely what you had before).

assuming you went for a fairly flat fuel target on boost, whats the EGT reading like - if your leaning out i'd be expecting things to start heating up. If you don't have a dedicated EGT gauge there's a post on here for using the front o2 sensor resistance values to see if your in the ballpark

could it also be intake temp based compensation (or lack of) seeing as how the outside temps have dropped a bit recently - maybe the MAF scaling needs adjustment again. This is assuming that you've firstly tried removing the sensor and doing a free air calibration on it of course.

Thanks for the replies. I had the thought about MAF cleaning as I was writing the post, so I've bought some cleaner and will take a look at it when it arrives.

As for MAF calibration in free air, I've not done this before, do you have any info on how it's done?

no no - calibrate the wideband in free air then stick it back in the car. the maf scaling i was thinking more atmospheric pressure comps or intake temp comps with the colder weather coming in.

Ah OK, thought I'd not heard of that before! Yes WB was calibrated in fresh air both times.

Do you think it's unlikely this is caused by exhaust leak? Intuitively I would imagine an exhaust leak pre sensor would cause a rich condition, unless the fast flow pulls air in?

does learned fuel trim D apply to open loop?

maybe you didn't spend as much time in 50 g/s+ as you should have, and the fueling error is being applied to open loop, but isn't as accurate as it should be? long drives and such, spirited or not, you should have spent more time in that range too.

edit: oh I see, you have it set really high. Do you ever see 80+ g/s in closed loop? Not having it effect open loop means you're sure your fuel from tank to tank has the same hydrocarbons and fuel density, as these changing can be the result of seeing seasonal LTFT D changes. Ideally D is somewhere around the top of closed loop cruise, something realistic. spend time in this area each tank of gas to ensure your tank to tank is being adjusted for by the ECU. running without learned trims applied to open loop is fine when you're scaling your MAF throughout a few logs of each tank of gas, or maybe tuning full open loop, but once the MAF scale is good, returning to stock MAF LTFT values is what I suggest.

I think this is a realistic, probable scenario in your case. It should be applying some learning to open loop, but it isn't. +/- 5% ethanol between tanks and open loop would be off by +/- 2% fueling error without compensations being added. Some fueling stations can use as much as 10% ethanol in their fuel and do not have to advertise it, depending on state/province/region laws.

80g/s is what it defaulted to when I followed the advise on one of the posts on here: http://www.romraider.com/forum/viewtopic.php?f=15&t=10778 but I agree I don't think I drive fast enough to see 80g/s in cruise!

The reason I did so was because in Sept last year I was struggling with dialing the MAF scaling in and found that by taking out the applied trim in OL it allowed me to hit it dead on repeatedly, so all seemed good at the time.

That's an interesting comment about the tank to tank fuel though - certainly over the course of the logs mentioned there has been fuel from totally different locations in the UK. I believe in the UK we have 'winter' and 'summer' grades of fuel or at least I've heard that mentioned before. I always fill up Shell with V power (99), but the change could be this summer --> winter thing.

My car is a daily and I use far too much fuel to adjust MAF scaling every tank, so I'll try your suggestion of reinstating the stock (or near to) fuel trim ranges. I'll apply it for the trip home tonight and see how it goes.

Thanks for the advice.

I don't think this would help matters...... the IAT was pretty gunked up, so I cleaned it carefully with some isopropyl alcohol and cotton buds. The elements inside look ok but will clean them with the spray when it arrives tomorrow.

That is MAF my friend (and IAT too) - anyways it looks really dirty - it sure might lean out the mix - it sees less air and thus adds less fuel.

After nearly passing out on my home from work yesterday due to exhaust fumes in the cabin, I've managed to resolve one of the issues I mentioned, at least! There was a crack in the exhaust gasket from turbo-->downpipe as I suspected. I've sorted that now, but it hasn't changed the lean condition I'm seeing.

I did try reverting to stock fuel trim ranges, but it was inclined to swing it more lean as the stock D range was ~-0.9%, so I changed back for now. The MAF cleaner will (hopefully) arrive, so I'll be giving that a try tonight to.

From tank to tank I'm seeing the same offset or thereabouts, so if the MAF cleaning does not resolve it, I might just tweek the scaling a little and keep an eye on it with the gauge. If the difference is due to the winter/summer fuel changeover it will probably be a few months before it switches back.

Another thing I find was the usual crack in the turbine house from the wastegate aperture, but from what I understand this is common and not something to be too concerned about.

To close this one out, the cause of the leaning off was a dirty MAF sensor. Now it's cleaned up it's swung slightly rich, so I'm happy to tweek MAF scaling back now. I'll be cleaning the MAF regularly now to!

Thanks for the advice.