UK vs US VVT Cam Timing
 

Hey all, wondering if anyone has input
I built a UK-spec VVT engine to swap into my '93. While doing some light break in, I kept the VVT deactivated so it would stay 0 degrees advanced. After a couple hours total run time, I started to stepping through VVT duty cycles to find the min and max absolute angles. Even at 100% duty, the cam stayed at 276 degrees. I narrowed the problem down to the actuator on the cam. Car is running a MS3PRO PNP

I had a second actuator on hand, so I took both apart to compare them and found the locking dowel was implemented differently, and the second actuator looked like it would work better with heavy oil (glossing over some details here). Way back I bought a second actuator from a US car. While parts sat around during the build, I lost track of which actuator originally came with the engine (my research to this point suggests they should be functionally the same)

Fired the car up on the second actuator and now I've got 45 degrees of actuation stroke, but the minimum angle is 293 degrees; almost the exactly what it would be if the intake cam was 1 tooth. I took off the belt covers to check the alignment and it looks dead on and belt tension is good. Oddly, the car also revs/idles much better now. Havent been on a drive to see if its down on power or anything

Anyone have VVT absolute angle settings I can compare to? I guess a good starting point would be to know if a UK BP-Z3 engine, with VVT at 0% duty cycle, has around 276 or 293 degrees absolute minimum angle

I've got a UK VVT head on an NA block - my min is set as 272, max 325 degrees.

From a couple of other maps I've got lying around from other UK cars, they are about the same range (~270 - ~ 320)

Mine (EU) also does about ~272 degrees at 0% duty.

Thanks everyone for the info. I'm not surprised it's the same for US and UK engines...

Another variable that occurred to me is that I changed the cam sensor to the improved one from Ballenger Motorsports. If the output from this new sensor is inverted from the old one, it might be sensing the trigger on the opposite side of the pulse. I doubt this is the case however

Well, thats not what I would expect. I made a janky adapter to swap back to the old cam sensor, and my timing was 273 degrees absolute. To double check it is the sensor, I switched back to the Ballenger sensor and the minimum absolute angle changed to 293. I'll have to take a look at the logs in a bit

I noticed that the design of the sensor element is reversed:

https://cimg6.ibsrv.net/gimg/www.mia...b355a88305.jpg

Did you recheck your base timing in your ECU after swapping the sensors round?

I think nearly everything is derived from the base & cam timings, so if the sensor is in a different place and 10 degrees base becomes something else, then your VVT timings would also be offset.

My understanding is that the base timing is derived from the crank sensor primarily, with the cam sensor feeding into VVT control and injection timing, if the latter is set to change with the VVT in the tune

Either way, I would not expect a "compatible" sensor to change cam angle feedback by 20 degrees, especially if there is no way to correct for it independently on a stock ECU

Apologies - I misread that you had put a baller crank sensor on, not cam sensor.

But agreed yeah, a like for like replacement shouldn't make any changes like that...

I made a separate thread for investigating the cam sensor. Turns out the polarity between the OEM and Ballanger sensor is inverted, changing what waveform edges are rising and falling
Ballenger Cam Sensor Changes VVT Timing