VCU Torque test results

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GrumpyGel said:
Are you not mistaking reliable for accurate - and is the 5kg test not accurate enough? We have seen many results with 5kg, and they appear reliable.

Your graph shows 8kg at 16 seconds and 5kg at 35 seconds. So the 5kg test is 218% of the 8kg test.

The tests by @dfossil in post #112 come out at ...

8kg 13s and 5Kg 30s - so 5kg is 231% of 8kg
8kg 12s 5kg 28s, so 5kg is 233% of 8kg
8kg 12s 5Kg 24s, so 5kg is 200% of 8kg

So his findings are roughly the same as your graph.

@kernowsvenski tests 16 months ago (post #1171) shows 8kg at 23 seconds and 5kg test of 41 seconds (both first thing cold and frosty). So the 5kg test is 178% of the 8kg test. They are nearer, but not earth shatteringly so.

@kernowsvenski latest tests shows 8kg at 32 seconds and 5kg test at 44 seconds. So the 5kg test is now only 137% of the 8kg test.

I agree, something is wrong here.

However - what is wrong? The 2 5kg tests both gave very similar times. They were a couple of seconds longer than the previous test, consistent with a bit of aging on the VCU, but well within "the time to replace" that gets used of 60 seconds. Only 1 8kg test is shown and it is much slower than the previous one.

Would the sensible advice therefore be that the 5kg tests indicate that the VCU is past its best but not dangerously so - however the 1 8kg test is alarming, so test again at 8kg, as it is possible that this latest test gave an erroneous result?

If the test comes back again at 32 seconds, then one has to consider whether that is OK or the 5kg "time to replace" of 60 seconds needs revising.
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There's two reliability issues. The first is momentum needed to turn the wheel. 8kg and above gives roughly the same time. It does increase slightly as you add more weight. 8 to 9kg isn't that much difference in time when compared to 5 to 6kg difference, which is. Weights on the straight line linear section get the vcu turning as it should, shifting with a reasonable pace during test. Past a point of optimum force needed to turn at a reasonable pace. If it's aged and won't allow the usual pace... that's a concern.

The second it applying the weight before 45 degrees. The sooner it's applied and the quicker the tester lets go (drops), the faster the test will then complete. You can vary the result by giving it an unintentional 'kick' in this way that can vary times by up to 15 seconds using 5kg. At 8kg it's not as noticeable as it's got the power to turn where results are linear and the unintentionally kick effect not as noticeable.

We also have a number of factors like the weight of the bar. If it's 1kg heavier than what someone else uses, then the test time will be quicker. 8 to 9kg time difference is minimal but more significant at 5 to 6kg. So comparison between test bar used can impact results. We always knew this but it's minimised at 8kg or above so it was ignored. It is a factor but there's only so far we can go for accuracy.

I try to avoid vcu freds normally. I can remember the arguements 11 years ago when all this kicked oft, like it was yesterday. Someone will be along soon with two large screw drivers...

On this occasion I see someone with an 8kg test result which to me looks slow. More worryingly it's on the move when comparing past test results, by an amount that concerns me. Hence my comment about lifting rear wheels to see if the brakes catch when spinning.

I use tracing paper on the screen to put lines against my video's to time results. As 8kg is roughly at the end of the linear straight line, a change in resistance across the vcu can trigger a noticeable time difference as the result time creeps round/up the curve. An increase of 10 seconds roughly being what you would see if applying 2kg less weight.

A happy vcu will consistently give the same time with 8kg. Even with a vcu which hasn't turned for months. If that's the case then turn the vcu one complete revolution to mix the fluid round the plates inside. Then it will give consistent results. The fluid does drop slowly to the bottom when they're not in use.
 
Hippo said:
Please do. It could be giving you the early warning the test is designed to provide.
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So just trying to take in some of the finer points of the discussion above, am I okay starting the test with the bar vertical so its already moving, and start timing as it reaches 45 degrees, or should I be starting with the bar as close to 45 as I can get it and letting go? Just wondering about the "momentum" issue.
 
kernowsvenski said:
So just trying to take in some of the finer points of the discussion above, am I okay starting the test with the bar vertical so its already moving, and start timing as it reaches 45 degrees, or should I be starting with the bar as close to 45 as I can get it and letting go? Just wondering about the "momentum" issue.
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When I've done the test, I start it above the 45 degree mark and start timing when it gets to the 45.
 
kernowsvenski said:
So just trying to take in some of the finer points of the discussion above, am I okay starting the test with the bar vertical so its already moving, and start timing as it reaches 45 degrees, or should I be starting with the bar as close to 45 as I can get it and letting go? Just wondering about the "momentum" issue.
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If the bar is vertical like 12 o'clock, it won't turn. The bar needs to be on a diagonal to get the weight turning it.

Copy the video below. 8kg starts about 5 minutes in.

One Wheel Up Test Results video = https://www.youtube.com/watch?v=L0ytdkWyEsQ

Put yer ratchet on the centre nut. Turn it anti clock wise so it goes past 45 degrees. Then lower it clock wise untill the weight is applied to the ratchet, then let go. It will then start travelling before 45 degrees.

In general... 1 litre of liquid is 1kg.

Do the test 3 times to check yer get consistent results.
 
Hippo said:
If the bar is vertical like 12 o'clock, it won't turn. The bar needs to be on a diagonal to get the weight turning it.

Copy the video below. 8kg starts about 5 minutes in.

One Wheel Up Test Results video = https://www.youtube.com/watch?v=L0ytdkWyEsQ

Put yer ratchet on the centre nut. Turn it anti clock wise so it goes past 45 degrees. Then lower it clock wise untill the weight is applied to the ratchet, then let go. It will then start travelling before 45 degrees.

In general... 1 litre of liquid is 1kg.

Do the test 3 times to check yer get consistent results.
Click to expand...

Thanks. When say vertical, I suppose I meant near to vertical, but enough for the weight to start the bar moving. Unfortunately I don't have a big enough ratchet so I'm using a bar and had to get it on the nut at the right point for the weight to be balanced so that the socket stayed on. Anyhow, I'm pretty sure I was doing it correctly so hopefully with dry weather this weekend I'll do the test definitively.
 
kernowsvenski said:
Thanks. When say vertical, I suppose I meant near to vertical, but enough for the weight to start the bar moving. Unfortunately I don't have a big enough ratchet so I'm using a bar and had to get it on the nut at the right point for the weight to be balanced so that the socket stayed on. Anyhow, I'm pretty sure I was doing it correctly so hopefully with dry weather this weekend I'll do the test definitively.
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Yer bar looks ok. As long as the wheel can move freely it's ok to test like that.
 
Just got home and done a few 8kg tests at 1.2m. An average of 21s, but that's with a warm VCU.
I'll do a few more tonight or tomorrow morning to see what it's looking like cold.
 
kernowsvenski said:
Just got home and done a few 8kg tests at 1.2m. An average of 21s, but that's with a warm VCU.
I'll do a few more tonight or tomorrow morning to see what it's looking like cold.
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I think that shows that you can get false bad readings (recent 8kg test) - but not false good readings. Also the importance of doing a few repeat tests while you've got the car raised.

That time is about what you would expect given the 8kg & 5kg tests you did last year and the recent 5kg tests.

Were they all similar times?
 
GrumpyGel said:
I think that shows that you can get false bad readings (recent 8kg test) - but not false good readings. Also the importance of doing a few repeat tests while you've got the car raised.

That time is about what you would expect given the 8kg & 5kg tests you did last year and the recent 5kg tests.

Were they all similar times?
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Yes. All there or there abouts. I'll see what difference it makes when cold. Probably won't be able to do a cold test until Monday though now.
 
So with the car having stood overnight I did few more tests this morning. Admittedly it's a warm day but with the 45 to 90 angles marked out as accurately as I can the 8kg results were as follows;
25s, 22s, 19s, 20s and 18s.

I did a couple of 5kg tests after. These were both 37s.

The conclusion I have come to is that i was misjudging the 45 angle when doing it by eye. I feel more comfortable with the current VCU now.
 
kernowsvenski said:
The conclusion I have come to is that i was misjudging the 45 angle when doing it by eye. I feel more comfortable with the current VCU now.
Click to expand...

It's difficult to judge angles, when there's no datum to compare it too.
So marking out is the way to go.

Those times seem fine to me. ;)
 
kernowsvenski said:
So with the car having stood overnight I did few more tests this morning. Admittedly it's a warm day but with the 45 to 90 angles marked out as accurately as I can the 8kg results were as follows;
25s, 22s, 19s, 20s and 18s.

I did a couple of 5kg tests after. These were both 37s.

The conclusion I have come to is that i was misjudging the 45 angle when doing it by eye. I feel more comfortable with the current VCU now.
Click to expand...
The reducing times are due to the settled fluid mixing round. The 18 measurement should repeat consistently thereafter.

I always film mine and watch it back with tracing paper on the screen with angles marked.

There's also the Turnip test you can do. After being stationary for a few hours, take it for a drive of 3 or more miles. The vcu will feel warn to touch, but not hot. You can also measure it with an infra red thermonitor if you have one. Or a normal thermonitor held parallel against the vcu with a tissue to trap the heat in, after you have stopped.
 
One of the cars I had was so tight it took something like 2.5 minutes to do the test. I can't remember if it was 8kg or 5kg but your results are excellent by comparison.
 
This is one of the tests I did on Monday. The bit of tape above the mudflap is the 45 mark, and the bar is at at 90 just before the weight touches the ground.

When looking back at my earlier vids, I'm definitely judging the angle wrong and starting the timer too early.
 
kernowsvenski said:
This is one of the tests I did on Monday. The bit of tape above the mudflap is the 45 mark, and the bar is at at 90 just before the weight touches the ground.

When looking back at my earlier vids, I'm definitely judging the angle wrong and starting the timer too early.
Click to expand...


I'd have no worries about the condition of your VCU. ;)

It's worth changing the IRD and rear diff oil though. ;)
 
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