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RB25 gt3582 Fury ecu strange missfire

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Hello, the engine runs a 36-1 crank trigger pattern with bosch VR sensor and on exhaust cam 1 toot triger with hall sensor. Max voltage on vr sensor is around 35-40 v , filter for triggering is around 7V, no sync errors , no trigger errors. Changed about 5 sets of coils ( r8 audi coils, hgk coils, desno yaris coils...any imaginable spark plug from denso and ngk, diffrent fuels...battery..alternator..), engine exhibits same strange misfire fenomenon as soon as the boost reaches 0.8bar ( ewg spring is 0.5bar) and around 4500 5000rpm . Any ideas? Valve float? Wastegate flutter , ewg flutter? Trigger problem on crank?(Compresion is around 10bar , all cylinders under 15 % leak and all within 5% from each other).

Attached Files

Ps. Is it possible that the vibration of VR crank sensor would generate a erratic signal and is not picked up by ecu as sync or trigger error? Anyone know how Link decodes?

Hi Claudiu,

It sounds like you have covered most of the basics well.

Even though there are no trigger errors showing, lets start by confirming that the trigger looks good.

Can you do a couple of trigger scope captures and attach them here (best to save as log file rather than .jpg). Do one at idle and one with engine at about 4500RPM.

Will do as soon as the car comes back to the shop. We suspect the problem is cranck sensor vibration

changed the VR crank sensor sheet metal bracket with a billet bracket , the problem has moved now to 1.3 bar, seem to be crank sensor related. any ideas? idle voltage is 12v at idle with 2mm gap( sensor is VW 1.8t Bosch crank senor) a bit high I believe. on internal scope nothing to see, I attach logs. idle , 4500 constant and 1.3 bar pull, any recomandation regarding trigger wheel size, tooth size? with this sensor. or different sensor recommended? I don't belive the internal ecu scope is fast enough for this problem. any ideas are welcome.

thank you

Attached Files

Hi - Im just going to add this because i didnt see it come up but what about coil dwell times ? Excuse me if im well off base . Also 2 mm gap on the VR sensor seems wide to me . When i set mine up the recommendation was 1mm .

I dont see any sign of trigger error in your log and the trigger scopes look good. Usually dwell will start to scatter if there are any trigger errors but yours is a nice solid flat line, so I would be quite confident the trigger system is fine.

Your reported trigger voltages are quite normal too.

Around the area that you report this misfire occurs you are very rich and with retarded ignition. At only 1.3Bar you have lambda ~0.735 with only 8deg timing, this wouldnt give very favorable combustion conditions... Have you tried it leaner and/or with more timing?

Tried a lot o variables afr advance this was very safe.Mr. Adam you seem to have discovered the small bug in the plug ii base pcl that we have used regarding peak and hold, i hope is the solution, we wait for the car to return to the shop and report ( my mistake not to check the pcl seting , althrough the oem.i injectors are also high, i usually configure from scratch but this time i just took the plugin pcl ...).

Ps. We also went from 0.5-4mm with the gap, 2 mm seems to give best result with our trigger wheel material and tooth shape

Regards

Solved , it ripps peak and hold seems to have caused all the problems and vR sensor vibration due to bracket. Question is why was it boost dependant?