4.8L Performance upgrade options

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Mystical_Beast
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Re: 4.8L Performance upgrade options

Post by Mystical_Beast » 19 Jul 2018 21:36


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Michael
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Re: 4.8L Performance upgrade options

Post by Michael » 20 Jul 2018 06:02

Mystical_Beast wrote:
19 Jul 2018 13:16
The Dyno only measures torque
Within the software there is the ability to calculate the torque based on KW reading.
So obviously you have losses between the motor and the wheels on the dyno which effect the reading.
Hence the calculation factor to compensate for those losses. Using the factory specs as a reference base.
So although you are measuring the KW on the wheels, by calculating the correction factor you are able to get a reasonably accurate representation of the torque of the motor from the dyno and then the torque curve as such.

If your baseline is way off then you need to find out why
SAC Centurion's dyno takes abselutely no calculations into account. They just measure what is found at the wheels.

I have done many dyno runs there and had vehicles with similar KW curves and WAY different torque curves and visa versa so not sure exactly how they get both readings. Will ask them next time I am there
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Re: 4.8L Performance upgrade options

Post by Mystical_Beast » 20 Jul 2018 06:18

Sorry was a mistake
Dyno only measure Kw power not torque.
As I wrote earlier.

Internal software provides for a representation of torque.
To get that reading at the flywheel is where the calculation comes in based on factory spec.

How I understand it anyway

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Re: 4.8L Performance upgrade options

Post by Mystical_Beast » 20 Jul 2018 10:38

[/quote]
SAC Centurion's dyno takes abselutely no calculations into account. They just measure what is found at the wheels.

I have done many dyno runs there and had vehicles with similar KW curves and WAY different torque curves and visa versa so not sure exactly how they get both readings. Will ask them next time I am there
[/quote]

Michael it would be MATHEMATICALLY impossible for two of the same vehicles producing the same power at the same rpm on the same wheels diameter (speed) to present any meaningful difference in torque.

Its just not possible as the two are related.

Only place where variation would manifest is gear ratio would have to be different.. and that could be as simple as differing wheel diameters.

But same power, all else being equal, torque has to be the same.

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Re: 4.8L Performance upgrade options

Post by Michael » 21 Jul 2018 07:46

Julian, look Im not sure how their dyno works or calculate the torque, but have not found one Patrol producing the same graph as the next.

Will see if I can post two examples
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Re: 4.8L Performance upgrade options

Post by Michael » 21 Jul 2018 08:05

Ok so here are a cpuple of dyno runs from verious TD42's.
All were done in 4th gear.
I think all have a pre and post run.

The reason why I am not sure how they get their torque figure is because comparing two vehicles, the one makes 110kw and 350Nm at one stage where another makes 120kw and 557Nm....... does not have any relation.
Attachments
20180202_121944.jpg
20180202_121918.jpg
20180628_130139.jpg
20180628_130105.jpg
TD42_Dyno_Kw-2500.jpg
TD42_Dyno_Torque-2500.jpg
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Re: 4.8L Performance upgrade options

Post by Mystical_Beast » 21 Jul 2018 09:46

Michael

I wasn't saying all will be the same..

What I was saying is if for eg. one Patrol makes exactly the same kw at the same Rpm as another their Torque graph must be the same or very very similar.
It has to be.

Similar peak power must produce similar peak torque.

While these are all turbo charged 4.2 Diesels not one is the same, they are all over the place and I cannot provide any info as to why.

Is it different wheels that make it so random?

Normally, similar vehicle produce similar results, some a little better, some the converse.

The graph showing 180 kw at 3300 rpm on the wheels is questionable in my opinion and the torque drop off looks too severe.

On the other two at 3000 RPM they are within 5 kw peak but like you say there is no correlation as to the Torque curve.

How do you with such random results interpret anything?

Just a question, the one showing huge power, is that a completely different Turbo to the other two as that will account?

Whatever.. power on that one looks amazing.. Can it be believed though is the question?

Speaking to Steven, he will tell you that this certain car will make that..give or take a few.. anything out of that would be be suspect.

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Re: 4.8L Performance upgrade options

Post by Peter Connan » 21 Jul 2018 16:25

Power and torque on all the graphs above tie up exactly.

I calculated the torque of each engine from the power at two points, being 2000RPM and the point at which it makes the highest power on the tables rather than the graphs, and the results do tie up.

And for reference, 180KW at 3300rpm translates to 521Nm, which seems to be what the graph says too.

This is why N/A petrol engines tend to have higher power outputs than TDI's of the same capacity. They usually make their peak torques at higher RPM's, but more importantly, their torque doesn't drop off as rapidly as the TDI's...
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Re: 4.8L Performance upgrade options

Post by Mystical_Beast » 21 Jul 2018 18:18

Hi Peter
I am not sure what point you are making?

At the outset I stated that there is a relationship between KW and NM.
That if two vehicles are making the same KW at the same RPM the Torque must be the same.

You have just reinforced that, it’s a mathematical constant.

The question is this on two vehicles the figures are reasonably close, as they should be, but one is so far left field that it appears improbable.

How does one account for the difference?

I notice that the graph states 4.5 TD.
Is it fact actually a petrol motor, rather than TD 42?
Hence your comment on N/A petrol motors?

I thought Michael said they were all Turbo Diesels?

The KW/NM relationship will be there, regardless of the figures stated because of the mathematical constant.

That does not mean the figure stated is correct.

You can show 1000 kw on a 2 litre motor if you want to bullsh1t on a dyno.

The question remains, the figures shown for the stated 4.5 TD are so far removed from the others.

Why?

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Re: 4.8L Performance upgrade options

Post by Peter Connan » 21 Jul 2018 18:35

Sorry Julian, I was answering Michael's question, not responding to your comments.

Unless I misunderstood Michael's question, in which case I was just rambling nonsensically, in which case I apologize...

I am pretty sure these are all 4.2 TDI's, since the 4.5 turbo he is working on is not at the dyno stage yet?

:biggrin:
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