Wanted: Series 1 V6 24v

[jorgy]

Hi John

I don't need to even say that that's not your doing (or anybody's else) at all so, please, don't feel upset, all these threads are quite entertaining and educational normaly !!, now, this went beyond cars sadly, that's the problem and nothing else, I still don't see how I have offended anybody to deserve such an answer and be treated various names out of the blue, and among people I respect; and at the end it's not a constructive way to come on to somebody, no matter how angry one feels to start with, justly or not that's a whole other issue. The last thing I expected though is to be told by somebody "look pal, the day we met all my behaviour to you was acted, kind of, and everything I thought, I said the opposite; I just didn't take u seriously". wt..?

Anyway, I won't expand more on this here, will not poison the forum, enough said from me.

cheers
George

ps. not sure what u mean about David's cars, I'm out of the loop, has he got 24v XMs from Europe??

[jorgy]

Woah....... This has gone a bit off topic..........

Since opening the thread I have managed to locate a Series 1 and a Series 2 V6 that I am pursuing.

David.

Hi David, good for you, are they what you wanted -I guess one's a PRV the other an ES9J? Manuals?

I tried to sell my girlfriend your nice Xantia but listen what she thought: "it's too old!" (translation: too old looking, compared to her Fiat Coupe). So seems we'll keep the go-kart-with-a-roof for now! sorry.....

cheers
G
ps. and *I*, am looking for a plain 2lt manual XM! Working at Strathclyde Uni now so daily commute needed -are u still in Caly or done with it?

[andmcit]

Well, as you asked George:





Andrew

[jorgy]

Perfect fit! Thanks!

Could u now do one where the torque scales are fitted?

G

[andmcit]

Right you are: must admit, I laid it out quickly and didn't clock the differing scales for torque
(the whole point of the discussion I realise!) - back in a short while then.

Andrew

[andmcit]

[jorgy]

Thanks very much Andrew,

still a little juggling needed I think, not sure what's the problem though, one thing I can see is u used the mkg so the PRV torque should move up to 24.5kg from 24. Still this doesn't explain the following:

If u go by mdan, their torque curves need to cross at exactly 4,000rpm, PRV makes about 23mdan and 2.5 about 22.5mdan (see also how horsepower by hp is same at 4,000rpm, about 130hp)

Also, I now remark, on the 2.5 graph about 22mdan correspond to 25mkg, while on the PRV 22mdan correspond to 22.75mkg, what's going on here, different mdan and/or kgm standards used between the 2 graphs?

Another thing I now note is, on the PRV graph the last interval's lenght of mkg is reduced, i.e. should really read "24mkg" where it reads "24.5", why did they do this?

If u go by KWh, graphs seem to agree as they both make 94.5-95kw at 4,000rpm, this confirms that something is wrong with the torque graphs, torques should cross at exactly 4,000rpm.

So not sure what's need done here Andrew, bring the PRV torque curve up or the 2.5td down, but they need to meet at 4,000rpm it seems, 2.5 appears higher than it should as is.

cheers
George

[andmcit]

TBH, I don't believe either original graph is 100% reliable or be the means of basing a
comparison with any chance of accuracy. Having gone over them all I noticed the Mkg
scale on the v6 graph and the discrepancy with the 24 (or is it 24.5) which would
inflence the crossover point of both graphs most likely at 4000rpm. I'll see if I can turn
up any better reference in my manuals. I am a sad stickler for diagramatical accuracies
and cobbling these graphs together in any kind of order is difficult with the poor quality
of the draghtsmanship it's very "trying".

I'm not sure myself where to go with the graph; its not due to my photoshop abilities.
I can and do all manner of impossible things to pictures in my work and if they're done
properly, nobody ever even notices!! Not that I ever would, but I could make the nicest
pictures ever to sell a car on ebay!!

Would you still buy a used car from this man based soley on the pictures!?
I guess you can trust me, I work in advertising...

Andrew

[DerekW]

I'm not sure if I'm missing something here, but as has been intimated already what matters in performance terms is not torque at the crankshaft but torque at the roadwheels. So the curves for the two engines should be plotted against miles per hour, not rpm and that involves factoring in the individual and final gear ratios and the rolling tyre radius.

This means that to get a true performance comparison it's necessary to produce torque curves for each gear in turn on the same plot for both cars. The result will be very instructive, the graphs will show the ideal road speed for gear changes for each car and which car has better acceleration in which gear throughout the range.

The final part of the puzzle is to calculate the power required curve - should be near enough the same for all XMs. Power required is of course made up of aerodynamic drag and rolling resistance. Convert it to torque required and then plot it against the previously obtained torque curves.

The surplus of torque available versus torque required gives a direct indication of acceleration and the point where the torque required curve crosses the torque available curve in top gear gives the maximum speed.

Make sure you're always using the same units. Anybody fancy coming up with a definitive answer?

Derek

[xmexclusive]

Hi DerekW

Thought you would be interested.
I too am looking at what has been produced with some suprise at how good the 2.5 appears in the lower half of the graph.
Taking the published 0-60 times into account the standard 2.5 is much the slower of the two.
Your suggested changes would almost certainly show this as a clear difference.
It would be quite a bit of work for Andrew and a few itterations till everyone was happy.
Not really sure that it would be worth all that effort though because we might then be disputing gear change points/2.5 chipping etc.
Will see if I can put together a 0-60 table for all XM's.

Hi Andrew

Thanks for your efforts.

Hi All

I suspect that there is just one simple reason why 2.5 owners find their car to be an equal performer to a V6.
That is that we compare them in normal driving and not in a standing start race.
Usually when you call for maximum or extra power the 2.5 was trotting along somewhere between 1500 and 2000 rpm.
Engine nicely warmed up and you floor the pedal.
That is just the point where the 2.5 curve is rapidly getting better than the V6 one.
There is loads more torque too.
There is even an added bonus as you leave the surprised potential overtaker in a cloud of your black smoke.
Hence the belief that the 2.5 is much the better car uphill pulling a heavy load.

John