RB28 with EFR8374 Turbo surging

Good evening y‘all

I just started to map a Haltech Elite on a Skyline with RB28 and an EFR8374 Turbo as the following problem occured:

Staying for several seconds at 3000 rpm on part-throttle, the turbo started to surge very hard. It kept surging at different PSI, AFR-levels and ignitiontimings (afr always stayed okay before the surging starts). Also when i tried a dynorun from 1500rpm-5500rpm, the engine fighted with very hard shuffle at 4500rpm. At the moment we fitted the efr bov block plate, tial bov and hks 272° cams. The timing from the cams was adjusted. EFR says, we should remove the internal bov because we use an external bov. maybe this could be a problem?

Has anyone an idea where the surging could come from or we can solve that problem?

Greetings

You shouldn't be having any trouble with an 8374 on an RB28. There are plenty of people running that exact combo with great results. The first question however is what A/R housing are you running? My second question is where are you taking the pressure feed for the wastegate from? You can have part throttle surge issues if the pressure source is taken from the inlet manifold as opposed to the compressor outlet. What boost pressure are you seeing this surge occur at 3000 rpm?

Hey Andrew

Thanks a lot for your feedback. We use the 1.05 AR exhaust housing with a full race manifold and two external 44mm tial waste gates. The pressure feed is taken from the Turbo compressor housing. I reach around 0.8-1.0bar at 3000rpm (WG-Duty is 0% for the RPM vs THR map). Maybe i should advance the intakte cam? I can upload a video, if this will help.

The tune is based on E85, by the way.

Upload a video if you can please.