Any help or advice appreciated! I'm in misfire purgatory. Currently in the process of custom tuning (via Wedge) my 2009 E89 Z4 35i with N54 and running into misfire troubles only with Eldor coils. I suspect my MSD81 DME is the culprit, maybe it can't supply enough energy to run the Eldors? Do IGBT's on MSD81's fail? Is there any way of logging/testing to check DME condition? I also suspected poor ground for the coil(s) because this can cause them to fail prematurely and lead to misfires.
Results on 3rd gear and 4th gear pulls (7 speed DCT) WOT from about 2800-7,000rpm:
1. Used Eldor coils (8,000km) from FCP: Runs relatively well when targeting 15psi (in 3rd gear using boost limit by gear). Completely falls apart when targeting 16psi with misfires randomly reported on all cylinders. CEL and limp mode. Car feels like it is surging through the RPM until limp mode kicks in. Lambda readings are quite erratic from about 4,000rpm when the surging starts. Worse in 4th gear than 3rd gear.
2. New Eldor coils from FCP: slight misfires at redline at 20psi actual boost. Falls apart from 3800rpm when targeting 22psi, even when boost has barely reached 15psi. Misfire fault codes are random cylinders accompanied by CEL and limp mode. Car feels like it is surging. Equally bad in 3rd gear and 4th gear. Erratic lambda readings during the surging.
3. Used Bosch coils (came with the car and suspect they may be the original ones): sometimes triggers a CEL (and misfire fault code) right at redline after I've let off the throttle on 16, 20 & 22psi maps. On a few occasions there hasn't been a CEL but there was a misfire reported. The misfire generally seems to follow one specific coil. The car doesn't surge at all on the Bosch coils - it feels strong right through the RPM. 50% of the time there is no misfire at all. The Lambda readings are very smooth.
DME: MSD81
Engine mileage: 58,000km (35,000miles)
RB2+ turbos with silicone inlets, 2" outlets & catless DP's.
New genuine HPFP (FCP Euro)
New Walbro 535 LPFP (Walbro dealer)
New Bosch pre cat O2 sensors (FCP Euro)
New 2 step colder NGK 97506 gapped to 0.016" - 0.024" (FCP Euro)
Applied dielectric grease inside the coil boots (not on the electrical connection points)
No signs of carbon tracking on plugs
E85 fuel (tested >e80)
Tried a set of brand new index 12 injectors (FCP Euro), but reverted back to my index 05's (bench tested to 2500psi). Same results on either.
Tried flashing the MHD custom tune with OEM coil option and B58 coil option (no difference)
Checked engine earth strap and resistance between coil ground points and chassis (all good)
Added extra grounding wires between chassis and each coil ground point (Valve cover bolts)
Added extra grounding wire for the DME ground point.
Logged battery voltage during some pulls using Protools to confirm battery voltage >14V the whole time.
Log: Old Bosch coils. 0.017" gap. 22 psi target. No misfires.
Log: New Eldor coils. 0.017" gap. 22 psi target. Misfiring from about 3800rpm.
Results on 3rd gear and 4th gear pulls (7 speed DCT) WOT from about 2800-7,000rpm:
1. Used Eldor coils (8,000km) from FCP: Runs relatively well when targeting 15psi (in 3rd gear using boost limit by gear). Completely falls apart when targeting 16psi with misfires randomly reported on all cylinders. CEL and limp mode. Car feels like it is surging through the RPM until limp mode kicks in. Lambda readings are quite erratic from about 4,000rpm when the surging starts. Worse in 4th gear than 3rd gear.
2. New Eldor coils from FCP: slight misfires at redline at 20psi actual boost. Falls apart from 3800rpm when targeting 22psi, even when boost has barely reached 15psi. Misfire fault codes are random cylinders accompanied by CEL and limp mode. Car feels like it is surging. Equally bad in 3rd gear and 4th gear. Erratic lambda readings during the surging.
3. Used Bosch coils (came with the car and suspect they may be the original ones): sometimes triggers a CEL (and misfire fault code) right at redline after I've let off the throttle on 16, 20 & 22psi maps. On a few occasions there hasn't been a CEL but there was a misfire reported. The misfire generally seems to follow one specific coil. The car doesn't surge at all on the Bosch coils - it feels strong right through the RPM. 50% of the time there is no misfire at all. The Lambda readings are very smooth.
DME: MSD81
Engine mileage: 58,000km (35,000miles)
RB2+ turbos with silicone inlets, 2" outlets & catless DP's.
New genuine HPFP (FCP Euro)
New Walbro 535 LPFP (Walbro dealer)
New Bosch pre cat O2 sensors (FCP Euro)
New 2 step colder NGK 97506 gapped to 0.016" - 0.024" (FCP Euro)
Applied dielectric grease inside the coil boots (not on the electrical connection points)
No signs of carbon tracking on plugs
E85 fuel (tested >e80)
Tried a set of brand new index 12 injectors (FCP Euro), but reverted back to my index 05's (bench tested to 2500psi). Same results on either.
Tried flashing the MHD custom tune with OEM coil option and B58 coil option (no difference)
Checked engine earth strap and resistance between coil ground points and chassis (all good)
Added extra grounding wires between chassis and each coil ground point (Valve cover bolts)
Added extra grounding wire for the DME ground point.
Logged battery voltage during some pulls using Protools to confirm battery voltage >14V the whole time.
Log: Old Bosch coils. 0.017" gap. 22 psi target. No misfires.
Log: New Eldor coils. 0.017" gap. 22 psi target. Misfiring from about 3800rpm.
