After exchanging lots of PM and email with Drew, confirming that he is happy for me to post some of the info that we exchanged and finally having access to another engine, I would like to update this thread.
Hope I found the answer on why he managed to rotate the WP by hand so easily.
Additional info;
Drew managed to spin the WP with just one finger so easily when the crank pulley was at the blue marker.
He didn’t remove the cam shaft during the TB service and thus, the valve clearance was never touched.
I now have access to another engine and before start removing the internal parts, quickly took some videos.
It was recorded without changing anything on the engine so the internal parts/adjustments were exactly the same as they were when I test driven and parked this NSX last week.
Please note that while the cam timings were correct, the TB tension was bit low when I opened the engine.
Not sure who carried out the last TB service in UK but being told it was done at Honda main dealer with NSX experience…..
At the blue marker (9 cam teeth) after #1 TDC, there was no way I could turn the WP.
Please refer to the following video;
As you can see, I tried to even press on the TB to introduce some slack between the front and rear intake cams.
The WP is located between these two cams and when the crank is at blue marker past #1 TDC, both cams will try to rotate themselves towards exhaust side resulting in tensioning the TB around the WP.
Thus, there was no way I could even move the WP in any direction.
The friction from the TB was just too high.
As I was amazed by the fact that Drew managed to spin the WP so easily with just a single finger, I decided to rotate the crank 720deg slowly with my right hand while keeping the tension on the TB and at the same time kept my left hand on the WP to feel for it.
I found very interesting fact.
There were three windows while rotating the crank 720deg that you can turn the WP by hand if you apply enough force.
From about 2 cam teeth after #1 TDC until about 1.5 cam teeth before #4 TDC.
From about 1.5 cam teeth after #2 TDC until about 1.5 cam teeth before #5 TDC.
From about 1.5 cam teeth after #3 TDC until about 1.5 cam teeth before #6 TDC.
While exchanging PM and email with Drew, I even spoke with some of the most experienced NSX engine people in Japan and even they thought that there was no way one could rotate the WP by hand so thank you to Drew for highlighting this. I learnt something new even after knowing NSX for more than 20 years.
The last window is the most interesting one.
The 1.5 cam teeth after #3 TDC is when the blue marker on the crank pulley faces up.
This is 9 cam teeth after #5 TDC.
Please refer to the following video;
As you can see, initially, I couldn't rotate the WP.
However, when I pressed down on the TB around the WP using my three fingers, it introduced significant amount of slack and allowed me to rotate the WP fairly easily.
However, I still couldn't rotate it with just a single finger but probably, I was not strong enough like Drew.
So, based on these two videos and also what he wrote in the past in the email and in this thread, my conclusion is that he tried to rotate the WP at blue marker after #5 TDC instead of #1 TDC.
Or, he adjusted the TB tension at blue marker past #5 TDC instead of #1 TDC.
I hope this was the case and already sent the info to Drew.........
When removing the entire slack from TB just before adjusting the TB tension, the position of crank/cam doesn't really matter. You will be applying enough force to overcome the valve spring rate and all you are doing is eliminating the slack between the two pulleys and nothing related to the cam timing.
Even if you have misaligned the cam and jumped a tooth, you can still eliminate the slack and adjust the tension so needs to be very careful.
However, you have to be at the 9 cam teeth after #1 TDC and not #5 when adjusting the tension.
I’ll touch on this in the next post as it’s getting too long…..
Kaz
- - - Updated - - -
As a side note and for those interested in the timing and numbers........
When the crank is at blue marker past #1 TDC, it’s about 147deg ATDC #1.
The VTEC is not engaged obviously so the cam lobe is at the low speed side.
In this mode, the Pri Inlet valve opens at 7.5deg ATDC and the Sec Inlet valve opens at 12.5deg ATDC.
Both Inlet valves close at 25deg ABDC.
The Pri Exh valve opens at 25deg BBDC and the Sec Exh valve opens at 30deg BBDC.
Both Exh valves close at 7.5deg BTDC.
I won’t comment on the detailed cam lobe profile (symmetrical, asymmetrical, etc).
When the crank is at this position (blue marker past #1 TDC) and locked.......
The front exhaust cam is kind of locked or tries to rotate itself clockwise due to #6 exhaust phase past mid point.
The front intake cam will try to rotate itself clockwise due to #5 intake phase in final stage.
The rear intake cam will try to rotate itself anti-clockwise due to #3 intake phase in initial stage.
The rear exhaust cam is kind of resting due to #1 exhaust phase just about to start.
Hence, it is at ideal timing to adjust the TB tension considering the position of the tension adjuster.
When the crank is at blue marker past #5 TDC, it’s the same 147deg but ATDC #5.
At this position, if you press on the TB around the WP, both rear exhaust and intake cams will move clockwise resulting in passing any slack at the TB tensioner towards the belt between the WP and the rear intake cam.
Addition to this, the front intake cam will try to rotate itself anti-clockwise so because of the slack introduced above, it will relax the entire TB around the WP allowing it to be turned by hand.
Similar thing is happening at other two windows where you can turn the WP by hand.
Kaz
- - - Updated 27/DEC/12 - - -
As mentioned at the beginning of this post, I took above two videos on the engine with bit loose TB that covered some mileage and years since last TB service.
Now that I installed new TB, new WP and tensioned the TB properly, I took another video at 9 cam teeth past #5 TDC where it was possible to rotate the WP fairly easily on loose TB.
As you can see, again, initially it was not possible to rotate the WP.
After pressing on the TB several times like last time to introduce some slack on TB around the WP, I did managed to rotate it but this time, it required significantly more force to do so.
In fact, I couldn’t move it at all even using two fingers and just about managed by using three fingers.
This was similar at all three windows mentioned above.
So, as a final note, if the TB was new and properly tentioned, it would be still possible to rotate the WP at these three windows but with fair amount of force and not like spinning freely with ease.
Kaz
