RB20DET - CAS Timing Issue

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Joined: Sun Aug 27, 2017 9:54 am
Car: 1990 R32 Skyline GTST

RB20DET - CAS Timing Issue

Postby TH1GTST » Sun Aug 27, 2017 11:34 am


I have a 1990 R32 GTST auto to manual swap. The swap was done in Japan and I didn’t realize it was a swap until after I bought the car...

Car has 52K kilometers, but considering it’s from 90’ I replaced the timing belt, tensioner, idler, and water pump with new OEM parts this winter. I marked the CAS before dissembling as my timing light wasn’t an inductive pickup type. Simply re-installed with the marks. I recently bought an inductive type light very similar to the one pictured in the FSM: http://www.esitest.com/130.html When I checked timing for the first time, I had also replaced the plugs.

My car still has the auto ECU, so I set timing at 20° BTDC @ 650 RPM
The FSM doesn’t mention anything regarding disconnecting AAC or TPS like some of the many forum posts I’ve read researching this, so I followed the FSM. To achieve 20° BTDC the CAS has to be rotated full CCW.

Things I’ve checked or tried:
- Verified correct orientation of inductive pickup on #1 ignition signal loop (reversing the lead results in a significant advance reading)
- Checked timing marks for the third time – cam & crank marks are in perfect alignment with #1 at TDC.
- Used DMM to set TPS to factory specs, operation checked out fine
- Replaced factory PFR5A-11 plugs with BCPR6ES-11 gapped down to 0.8mm as suggested by others on the internet
- ECU codes: 54 - A/T Control and 43 – TPS (was disconnected during troubleshooting, may be false code)
- CAS key is in good shape, no backlash, aligns well and fits tight.
- Gas has always been 93 octane

Modifications to car:

- HKS Super Turbo Exhaust (designed for GTR, but fit fine except for 1 rear hanger location)
- HKS Metal High Flow Cat
- A’pexi Downpipe (bolted to factory turbo elbow)
- A’pexi Drop in filter

Notes on drivability:

When CAS is centered (aligned to my own marks) off-boost partial throttle doesn’t feel linear, it feels like a surge of power right around 2000RPM, then feels more linear all the way to the top. Maybe this is just a characteristic of the engine?
I often will get a loud pop out of the exhaust when backing off anything over mid-throttle or light load high RPM. This isn’t constant, just occasional and I believe due to fuel overrun with the DP, exhaust & HF cat. Quite a scare the first time it did it though, including it in case it may be another symptom.

When CAS is fully retarded and at an indicated 20°BTDC, it had seemed to run a little hotter. When getting on it, it started to sputter and lose power, so I took it easy back home, went over everything again, and all checked out. This is the point where I had taken everything apart and tested as mentioned earlier. Put it all back together, reset ECU, & reset timing and took it for another drive. Ran great, so I went out of town and things were going fine. On the way back home, in some hilly areas it would violently cut out over 2000RPM with load causing the whole car to jerk, and the exhaust to pop. Had same problem very lightly accelerating through 2nd gear, did not seem to like high RPM's. Limped it up a few remaining hills with some angry traffic behind me, and that is where we are today. Popped the hood, and it seemed a little hotter than usual – I tried to see if the turbo was glowing, but it wasn’t, probably due to me babying it back. It was probably a good 10° cooler outside than the last time I had driven.

That seems to me like a tell-tale sign of too much ignition retard, I mean the CAS is all the way CCW, so duh! I put the factory PFR5A-11 plugs back in this morning and set the CAS back to the middle.

At this point I think I am going to spring for a PLMS cable and Nissan DataScan so I can have a better idea of what is going on, but I’m lost as to whether my timing light is reading artificially advanced or there is another problem elsewhere with the car.

I apologize for the novel, but I figured I would throw as much information out as possible. Any ideas on next steps?

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