XK slower than the outgoing model

[voituer]

When my Xk Coupe was on order a good friend of mine argued that it is actually slower than the outgiong model and Jaguar had fudged some figures to get a good result. BAsically his argument was with the gear ratios and diff ratios. If the new car had the same ratios as the old car it woudl actually be slower. Anyone knowledgable on this one?

[Phil Hopkins]

Can't see it personally. The weight difference alone would suggest that with the same ratios the new XK would still be quicker.

I'm not an engineer however and could well be wrong.

[a8hex]

The new car is lighter and fractionally more powerful, they'd have to try hard to make it slower.

[triple7]

I had a race in my loaner with a mate in an 4.2 XKR, no concerns that the new XK was quicker, be interesting to see how the new XKR holds up.

G

[a8hex]

triple7 said:

I had a race in my loaner with a mate in an 4.2 XKR, no concerns that the new XK was quicker, be interesting to see how the new XKR holds up.

G

It will be like when you buy software. When you take delivery of one you will have to sign and agreement never to compare the performance with the AMV8

[job38]

I've driven plenty of XK8, XKR, XJR, new XK.
The XK is seriously quicker than the XK8.
(and the handling and brakes are in a different leauge)

[hendry]

voituer said:

When my Xk Coupe was on order a good friend of mine argued that it is actually slower than the outgiong model and Jaguar had fudged some figures to get a good result. BAsically his argument was with the gear ratios and diff ratios. If the new car had the same ratios as the old car it woudl actually be slower. Anyone knowledgable on this one?

But it doesn't have the same gear or diff ratios. So what sort of statement is that?

Tell him this: If cars still had to have a bloke waving a red flag walking in front of them, the Model T Ford would be just as quick as the Focus ST. Dumb ass.

[voituer]

hendry said:

voituer said:

When my Xk Coupe was on order a good friend of mine argued that it is actually slower than the outgiong model and Jaguar had fudged some figures to get a good result. BAsically his argument was with the gear ratios and diff ratios. If the new car had the same ratios as the old car it woudl actually be slower. Anyone knowledgable on this one?

But it doesn't have the same gear or diff ratios. So what sort of statement is that?

Tell him this: If cars still had to have a bloke waving a red flag walking in front of them, the Model T Ford would be just as quick as the Focus ST. Dumb ass.

Dumb Ass???? No you're the Dumb Ass Ha....

Anyway back to the subject, you ask what sort of statement is that. Did you read the post? I know it does not have the same ratios and that is in the post. The point is that if it did have the same ratios it might not be quite as quick as it should be. Jaguar made a big point of the improved performance being down to the fact that so much weight had been saved. It may be possible, however, that the performance has been helped by using lower gearing diff ratios. If the same ratios were applied to the old XK8 then it could be able to achieve the performance figures of the new XK.

Result is that the XK might not have any real performance improvement over the outgoing model.

This is purely speculation until someone comes up with real maths but I did think it was worth discussing

Dumb A... Oh yes we have done that!!

[a8hex]

voituer said:

Result is that the XK might not have any real performance improvement over the outgoing model.

This is purely speculation until someone comes up with real maths but I did think it was worth discussing

Dumb A... Oh yes we have done that!!

Acceleration = Force / Mass

New XK has lower mass and higher force, so...

[aeroresh]

Its no more powerful (still 300bhp) marginally lighter (100 lbs, the weight of a passenger!))...so not enough to make any difference in the real world unless there's some gearing wizardry somewhere along the line, which indicates it'll loose out it some other way.

[job38]

Its 100kg lighter, (NOT lb) which is a considerable improvement (especially in a world where every new model is seriously heavier than its predecessor).
Feel free to join me in the gym to do some 100kg bench press if you don't believe me.

The XK8 always 'felt' like a very heavy car, the XK is the opposite.

[hendry]

voituer said:

hendry said:

voituer said:

When my Xk Coupe was on order a good friend of mine argued that it is actually slower than the outgiong model and Jaguar had fudged some figures to get a good result. BAsically his argument was with the gear ratios and diff ratios. If the new car had the same ratios as the old car it woudl actually be slower. Anyone knowledgable on this one?

But it doesn't have the same gear or diff ratios. So what sort of statement is that?

Tell him this: If cars still had to have a bloke waving a red flag walking in front of them, the Model T Ford would be just as quick as the Focus ST. Dumb ass.

Dumb Ass???? No you're the Dumb Ass Ha....

Anyway back to the subject, you ask what sort of statement is that. Did you read the post? I know it does not have the same ratios and that is in the post. The point is that if it did have the same ratios it might not be quite as quick as it should be. Jaguar made a big point of the improved performance being down to the fact that so much weight had been saved. It may be possible, however, that the performance has been helped by using lower gearing diff ratios. If the same ratios were applied to the old XK8 then it could be able to achieve the performance figures of the new XK.

Result is that the XK might not have any real performance improvement over the outgoing model.

This is purely speculation until someone comes up with real maths but I did think it was worth discussing

Dumb A... Oh yes we have done that!!

XK8
Final Drive 3.06:1
1st 3.57:1
2nd 2.20:1
3rd 1.51:1
4th 1.00:1
5th 0.80:1


XK
Final Drive ?
1st 4.17:1
2nd 2.34:1
3rd 1.52:1
4th 1.14:1
5th 0.87:1
6th 0.69:1

This suggests that only 1st and 2nd are lower, which won't have much bearing in real world driving, unless you live at the start of the Santa Pod strip and work at the end. So as everything suggests that the new car would always be faster (lighter, more powerful), maybe the onus should be on you or your mate to show us the maths to prove the claim...?

And David Brent has the best answer for "if it had this if would be that" type statements: "And if my aunt had bollox, she'd be my uncle".

[schmooveboy]

Am I the only one who doesn't care about the answer to this?

They changed the gear ratios to make it faster. So what? Isn't this part of the engineering processes that all manufacturers will look at to determine hte acceleration of a vehicle vs the top speed? Surely 'if they had the same gear ratios it would be slower' is like saying 'if the new car had less power it would loose a drag race'.

It hasn't got less power and it has different gear ratios.

It's called vehicle design.

[avos]

I read somewhere that the final drive ratio of the XK is 3,31, that with the new gear ratios for the 1st and 2nd gear, is probably one of the biggest factors in improving acceleration speed, and not the weight reduction as jaguar sells it.

[Phil Hopkins]

hendry said:

voituer said:

hendry said:

voituer said:

When my Xk Coupe was on order a good friend of mine argued that it is actually slower than the outgiong model and Jaguar had fudged some figures to get a good result. BAsically his argument was with the gear ratios and diff ratios. If the new car had the same ratios as the old car it woudl actually be slower. Anyone knowledgable on this one?

But it doesn't have the same gear or diff ratios. So what sort of statement is that?

Tell him this: If cars still had to have a bloke waving a red flag walking in front of them, the Model T Ford would be just as quick as the Focus ST. Dumb ass.

Dumb Ass???? No you're the Dumb Ass Ha....

Anyway back to the subject, you ask what sort of statement is that. Did you read the post? I know it does not have the same ratios and that is in the post. The point is that if it did have the same ratios it might not be quite as quick as it should be. Jaguar made a big point of the improved performance being down to the fact that so much weight had been saved. It may be possible, however, that the performance has been helped by using lower gearing diff ratios. If the same ratios were applied to the old XK8 then it could be able to achieve the performance figures of the new XK.

Result is that the XK might not have any real performance improvement over the outgoing model.

This is purely speculation until someone comes up with real maths but I did think it was worth discussing

Dumb A... Oh yes we have done that!!

XK8
Final Drive 3.06:1
1st 3.57:1
2nd 2.20:1
3rd 1.51:1
4th 1.00:1
5th 0.80:1


XK
Final Drive ?
1st 4.17:1
2nd 2.34:1
3rd 1.52:1
4th 1.14:1
5th 0.87:1
6th 0.69:1

This suggests that only 1st and 2nd are lower, which won't have much bearing in real world driving, unless you live at the start of the Santa Pod strip and work at the end. So as everything suggests that the new car would always be faster (lighter, more powerful), maybe the onus should be on you or your mate to show us the maths to prove the claim...?

And David Brent has the best answer for "if it had this if would be that" type statements: "And if my aunt had bollox, she'd be my uncle".

Hendry, not sure if I'm reading this correctly but the outgoing 4.2 XK8 had a 6 speed ZF box so that would make your figures applicable to the 4.0?

Or am I mistaken?

[hendry]

Maybe Phil. I am not sure I care that much - as has been said elsewhere, there is much different between the two cars so a statement like "it's slower" doesn't mean much withoiut some evidence, which hasn't been forthcoming.

Let's all forget it shall we?

[Phil Hopkins]

I'm not agreeing with the initial poster, on the contrary.