8V TS Variator Adjustment

[MD]

Does anyone have information about the degree value of each tooth position on the variator. Would appreciate the info if you do.

[jla987]

Not sure I understand the question properly as I've had no experience with the 8V variator, but if I do:

Count the number of teeth, divide 360° by that number.

[MD]

Yep agreed on procedure. I am trying to avoid doing that if there is a published figure. The reason I say that is because I suspect we are (possibly) going to arrive at fractions of degrees as well as avoiding to take my engine apart just to make the count.
I was also hoping to discover a technique of fine adjustment if there is any opportunity at all to do that. I have yet to pull the variator apart and see just how the sucker works and what you can and cannot do with it.

On a separate note but related to cam adjustment, does anyone know if you can fit a conventional sprocket in place of the TS variator to turn it into a "standard" camshaft like the exhaust cam?

[jla987]

Ahh I see what you mean. It's a nice little mechanism. A solenoid controls oil pressure inside the variator depending on engine revs. A hydraulic piston pushes against the camshaft which is mounted in a helical spline. So that linear movement from the piston turns the cam however many degrees relative to the sprocket (25° rings a bell).
But that's really all I know - which is based on the 156 variator which is a little different (no dog clutch on the sprocket for one thing)

As for fitting a fixed sprocket, anything is possible with a large machining budget. It might also be possible to block the oil galleries in the variator and disconnect the solenoid but I have no idea which position that would lock the cam in.

[LukeC]

Mike: I thought you had a lathe? Not  difficult job, just need an old Nord cam, lathe, press and maybe if you are not sure of your interferance fit withstanding the torque of driving the cam a drill press and a tap to fit a grugscrew (or maybe a rolpin...  )

What are you trying to achieve?

Reprofiled cams dialed in to you specific needs... ?

When I put a TS engine in my 67 Junior in 1998 (running on carbs), I made a unit to hold the variator in the advanced position at any time when the oil pressure was high enough to drive the piston to the advanced position. On 45mm dellortos, and the distributor I made with twin points and proper bearings on the shaft (Bosch & Nissan parts),The engine would idle dead steady at 800 rpm. Went like a cut cat!

[MD]

jla987,LukeC

Thank you for your contributions.

Luke, you and I know what you mean but perhaps other readers following this may be misguided a little so I will clarify what I believe you meant.. I think you meant to say..just need an old Nord sprocket and not a Cam" . The simple reason is, Nord and TS cams are not interchangeable.

To get to the heart of it so this post may help others, I have counted all the adjustment positions which total 90. Therefor the increment of adjustment is calculated from 360*:- 90 teeth =4* There is no possibility that I know of to make smaller adjustments than this unless a conventional sprocket is fitted to replace the variator.

Just to complete the info, the TS exhaust cam minimum adjustment value is 3*.

To obtain the lobe centres that I need, this level of adjustment will be just fine.

Feel free to ad to this if you factually know more.

[LukeC]

Just thought I would expand on this significantly for the greater good.

As Mike and other people have found, the adjustment on the variator is not fine enough to get the timing perfect at times (you can be up to 2* out), so you have to choose either 2* advanced or retarded (most will choose the advanced position). This is fine for street engines, but not for performance and race engines with non-standard cams.  In these engines, cam timing is set using a degree wheel and dial indicators on the followers. In this way, the cam timing can be set to the cam manufacturer's actual recommended valve opening and closing timing (usually at .050", to get lobe centre correct). I aim to get the timing within around 1* of the recommended valve events. This typically takes me around 1.5 - 2 hours rather than 5 minutes when building a standard engine.

The original Nord and TS exhaust cam timing adjustment is adjusted using "Vernier adjustment". The sprocket and drive flange on the cams have a different number of holes (around 18). By multiplying the number of holes on the driven flange by the driving flange you calculate the number of adjustment positions (around 320). Then you divide 360 by this and gain the incremental  adjustment in degrees (around 1.25*). Halve this and you will find the maximum error of cam adjustment on conventional Nord engines and the exhaust cam on a TS (~.075 degrees).

I have raided some images from around the InterWeb to explain the challenge (thanks to those that posted these).

The first one shows the cam drive flanges of both the TS exhaust and a Nord engine.

This image shows a pair of Nord cams.

The third image shows a pair of performance TS cams.

And finally, the business end of a TS intake cam with the variator disassembled. Note difference of the top (inlet) to the performance cam.  As an aside, I have disassembled a couple of these, one with 350,000 km on it and found no discernable wear or faults. A very reliable unit.

One of Mike's questions was if it is possible to install the conventional Nord type Vernier adjustment to the inlet (am I right in saying that that inlet cam has been reprofiled, Mike?). The answer is no: I have not done it, but I am willing to bet a bottle of Single Malt that I can. I someone supplies me with a TS inlet and a Nord cam: I will tell you when I am finished and what Whiskey I am in the mood for (I will keep it under $150 to make it cheaper than commercial machining). I reckon it will take me about 2 hours.

From looking at a couple of sites, TS performance cams without the variator are around $1400 - $1500 AU a pair. Not sure what the going rate for profiling is locally these days, But it shouldn't be more than a $700. Add to that commercial rates for machining (last time I got something machined it was $135/h) and you can save probably 450-500 beer tickets over buying from the usual suspect overseas.

How would I do it? In a lathe, machine the end of the TS inlet cam off to the front of the journal. Drill and bore the camshaft to a depth of 40 mm (dia. - ~10mm less than the journal). Do some calcs to ascertain the length Nord cam end to fit into this bore. Cut end of Nord cam off. Machine rear of Nord cam stub to suit bore in TS cam (I would say.0005"-.00075" interference). Machine starter step on stub to assist pressing. File flat on stub to relieve any hydraulic pressure while pressing stub into cam. Use EP (Gear) oil and press in. Drill through variator supply hole and insert a roll pin (cut to size) to ensure the stub will never move. Check Journal for expansion and polish as required. Use the Nord drive and driven flange... Voila! I can taste that Single Malt already!

Using the front of a Nord cam would save the machinist several machining steps (thread-cutting, milling in a woodruff key etc) rather than making the drive stub from scratch.

As always, when accuracy is at stake: I would measure up and draw on Autocad first to ensure the sprocket sits in the right place.

[AikenDrum105]

Hi Luke,  thanks for posting all that info - really interesting to read.

I wondered if you chose to time the camshaft:chain  such that worst case it was 2 deg. advanced at rest, and then fit a shim/spacer ring inside to the helical drive section to limit it's travel.  ie the VVT now only advances 24 degrees instead of 26 - to get the timing accuracy back at the most advanced position ? 

I've probably misunderstood something there and am parading my ignorance    

appreciate you taking the time to post.

Cheers,



Cheers,

Scott.

[MD]

Top contribution Luke !

No Buddy I don't have a lathe but a I do have access to to a few which is almost as good.

I like to know stuff for future reference hence my conversion question which you have answered so admirably.

The present engine that I am using will not require superfine cam timing so I will not take up this work for now however it will come in handy if and when I build another one or change my current plans.

Thanks for taking the time. Appreciated.

[LukeC]

I wondered if you chose to time the camshaft:chain  such that worst case it was 2 deg. advanced at rest, and then fit a shim/spacer ring inside to the helical drive section to limit it's travel.  ie the VVT now only advances 24 degrees instead of 26 - to get the timing accuracy back at the most advanced position ?

That would be a way to do it. Smart thinking! But it gets back to the fact that if you are running the variator, the engine is not a real performance engine and this level of accuracy is probably not really required. However, there is a guy in the States that runs duel variators on his spider and produces serious power.

Over on the US BB, which you trawl on, Richard Jemison just posted recently to use compressed air in the variator supply hole in the front journal to help set the timing on the older Nord engines with variable cam timing... He may be a bit crotchety, but knows his stuff.

I don't presently have my own lathe, but it is coming as soon as I have finished a 3 month project that has been taking up an enormous amount of my spare time and shed space.

[AikenDrum105]

which you trawl on...

Cast that net as far and wide as I can  

Richard certainly knows some things - was reading a thread recently where he demonstrated ways to further optimise flow through a set of weber 45s... 

Cheers,

[LukeC]

Not my birthday, but I bought me a pressie! And the first job I am doing on it.