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RE: Backfires on the N54

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Hi Guys,
I have owned the car for over a year now, It’s a 2009 E92 from the UK - picked it up with around 24,000 Miles on the clock
Within a few short months, the car was FBO and I was doing monthly track days. I spent quite a bit doing preventive maintenance as I knew I was going to be pushing the car with DD and doing track days
• Walnut blasting
• Replaced all coilpacks and spark plugs and now running the NGK plugs
• Oil change every 3000 Miles
Now the last 2 months I have had issues with car and bit of coin to get it all sorted.
• Failed front turbo seal – decided to replace both turbo’s as the car had done now 43,000 Miles

I had the workshop do an engine compression test as I was curious to see how the engine had been holding up since the tune/tracking etc

Results:
Compression was approx. 160 psi +/- 5psi (actually very even) on all cylinders on a cold engine.

After a month of replacing the turbo’s, I noticed that my whiteish smoke with a blue tinge was coming from the exhausts on deceleration.

Had the car sent back in to find out what was going on, and the shop came back with the following:

Check oil smoke coming out of exhaust, on overrun/back on throttle
Check oil level - ok, within min/max.
Check crankcase pressure - within tolerance at time of check.
Remove aftermarket oil catch can and check quantity of oil - very little at time of check, disconnect breather and run engine - no change.
Disconnect charge pipe from throttle body, check for oil - ok, run engine with charge pipe disconnected - no change.
Disconnect exhaust system at down-pipe connections and check for signs of oil at back of turbo's etc - ok at time of check.
Suspect that oil bypassing at valve stem seals - smoking occurs after (normal) vacuum present in manifold, then throttle opened again. Also, no smoking apparent when engine held at constant higher revs (part load).


So now it looks like I am going to need to replace the valve stem seals to fix the current issue

I was at the local BMW meet the other day and caught up with a new member who was commenting on how he had seen me on the track etc and how my car was spitting flames from the exhaust etc

So I was curious on why the valve steam seals had failed, as other people are pushing their cars way above my HP/tq etc

I then came across this video:

Which raised more questions :S

I noticed some comments on how backfires could damage valve steam seals etc – not sure how true that tho!

These vids are with me running the OFT with a wedge map for e50 – I have moved onto the JB4 recently – haven’t done a video yet to see if the car still spits flames with the IJOES E85 backend + Map7, probably will do this weekend to test

You can hear the backfires:




Now I know those are def not the burble from the exhaust(23 secs into my vid):


So , is backfires normal on FBO 335i’s on E85?

would appreciated the advice

thanks

My mod list:
| Stacked JB4 + Flash Tune | FFTEC In-line Fuel Pump | AR Downpipes | Active Autowerke Bov | Active Autowerke Exhaust | Active Autowerke Race FMIC | Active Autowerke Strut | BMS Dual Cone Intake | BMS Oil Catch Can | BMS Thermostat | WaveTrac LSD | Evolution Racewerk Sport Oil Cooler | Michelin Pilot Super Sport tyres | Lux Angel eyes | KW V3 Coilovers | Vossen CV3 Wheels | DEFIV lockdown kit | Cyba Air Scoops | Arkym front lip | carbon side splitters | M3 Front & Rear Suspension Conversion | Apex EC-7 Wheels | Toyo R888 tyres | NGK 5992 Spark Plugs |

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