KV6 2.5: power & torque loss?
 

I would appreciate very much to know whether some of us owners of a KV6 2.5 have tried to get some figures from a test bench?

I presented my car last Thursday to such a test and the figures were appalling:

- Power 140.5 bhp --> 35 bhp loss! 20%!!! :eek:
- Torque 146.5 ftlb --> 30 ftlb loss! 17.3%!!! :eek:

They complained they had difficulties to make the test because of the auto box which was systematically downgrading in gear even in the 4, 3, 2 gears! :confused:
I'd never thought that the auto box could downgrade to the immediate gear below even in a 'stuck' position as 4, 3 or 2! https://www.the75andztclub.co.uk//fo...s/confused.gif
But if so I have the feeling that the tests couldn't have been done in the 5th gear... May it be the secret of those weird and bewildering figures?
Would somebody explain where lies the flaw or the mystery?

Because my engine is very responsive, I've no difficulty to accelerate very quickly uphill even on hard slopes, I can very easily overtake with an immediate kick down that gives me a real kick in the ass, every service had been done, VIS motors swapped in 2017, brand new iridium spark plugs since the end of 2017, belts pulley & pump swapped 6 months ago, oil & filter changed once a year and the like. And TOAF detection of errors gives absolutely nothing wrong: every bit is in perfect order. Even my tyres are slightly over inflated.

So why such a ginormous discrepancy between the theoretical figures indoors and the real efficiency in the real life??? :eek:
I know that impressions & feelings don't give any evidence: but all the same I'm not a beginner, I hope I'm not schizophrenic either but nonetheless the gap looks utterly unbelievable at least for me.

Thank you for your wise comments & reactions. :bowdown:

Firstly you should know what figures you have been quoted. Are these figures on the wheels or figures off the crank.?
There is always a loss through the box and the diff. In the Auto box the losses are higher than through a conventional box.
The car gears down very easily, that means that the torque converter in play at all times and that affects the torque measurements.
It becomes difficult to maintain revs and load, and you need to do that in order to get proper readings.
If these are the results on the wheels I would not complain.

But it is of course not a V8!:getmecoat:

Thank you @kaiser for you quick reaction and comprehensive & astute explanation.
They didn't tell me where the results came from.
Had the figures come from the wheels would a projection be made even approximatively to find out the equivalent off the crank? :confused:

When initially Rover gave 175 bhp & 177 ftlb, from which did it come?
Don't you think the mystery could be explained because they never were able to use the 5th gear to make their tests? :shrug:

I'm not at all a petrol head as you may guess. ;)

Thanks to enlighten my knowledge. :bowdown:

Don’t forget different dyno’s can give different readings, I was speaking to a bmw owner who ran his car on two dynos a week apart, one showed 530bhp the other showed 590bhp!

They normally apply a correction factor to compensate for losses, in order to give you an estimated output on the crank. So if you use 0,15 or 0,2, it will make a lot of difference. Many owners will happily walk home with a curve that shows a number of ponies more!

As for testing in 5th gear, that is totally impossible in the automatic 75, unless you can hold 5th, somehow?

The tendency is to gear down immediately there is load, even a light load.
So in an auto it will give you the whole spiel, in all gears.

in a manual, you select and it stays there, until you change your mind!

At the "flywheel" Arnaud, in other words it's the engine maximum output before the gearbox. When you have your car tested on a dyno, it is measured at the driving wheels so there will always be a reduction.

Dyno sessions always result in dissatisfaction so are best avoided. Just enjoy your leather seats, thick carpets and burr walnut trim and ... r e l a x! :D

Simon

I love your very true and positive philosophy Simon! ;)
Unfortunately for me I'm born curious: that'll be my misfortune! :D
Nevertheless thanks to your crystal clear statement I understand much better where were lying my useless worries.
So no longer any complain: I'm happy, you've saved my day! :bowdown:

Thank you very much Arnaud! :bigsmile:
(Curiosity is good though and I too have been through the dyno experience.)

Best wishes,

Simon

BTW it wasn't a sorry experience after all (I'd asked for a remap as well, even for a rather modest - not to say mean - benefit, but I was fully conscious I had neither a diesel nor a turbo engine:duh:) .
My pride & joy was praised for her very good condition & maintenance by the pros. Likely a more gratifying exam than the MOT... :shrug:
And as I'm badly suffering of perfectionism since a while ;) I'm rewarded to see my comfy girl running at her best. :cool:
Maybe an expensive tantrum? But let's not get bored with trifles, it's only money as they say... :D
Hence I can enjoy even better if possible my burr walnut trim, fine leather seats and thick carpet, hey Simon? ;)