Jaguar XK 2013 pix?
#2
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Barry Leftwich (10-17-2023)
#4
#7
Right now the top two gears are for MPG numbers. The ratios between the performance gears are too wide for ultimate acceleration. I find myself driving most of my winding roads in my XK in 2nd gear only, when I should be really using 4 gears for the same. I bet you that with a good 8 speed the XKR 0-60 numbers would easily drop below 4s and the 1/4 mile would improve by a bunch too.
Albert
Last edited by axr6; 08-05-2012 at 11:01 AM.
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#8
I agree that there could be improvements in the gearing. The xkr-s is essentially a 5 speed. 1st gear is useless-too much torque. The car starts off in 2nd gear in sport auto. I drive in manual sport most of the time and never use 1st gear. Seems like 1st gear should be 2nd gear and an extra gear could then be added (a tall 6th gear) to improve highway fuel economy
#10
I would be of like mind here. Being the abolute fastest 0 to 60 or the 1/4 mile is not really why I like or purchased the XK. Mind you, bragging rights may well be something else.
#11
In any race or performance car you get max performance by staying near the peak power band values. If your car develops max HP at 6000 RPM, you want to keep the revs near 5500-6500 for max performance. You have to check your actual dyno values to see how much HP you loose just by dropping 1000 RPM out of that range. Usually significant numbers.
In my XK I loose LOTS of power when I shift gears, because the RPMs drop too much between gears and fall way off the peak power range. As far as I know the XKR uses the same gear ratios as the XKs, so in that case, they could also significantly benefit from closer gear ratios. That could be done by leaving first gear unchanged, make 8th gear roughly what 6 is now (maybe a bit taller for improved MPG) and insert two more gears in between. The car would be a BEAST with those two gears. There are perfectly good reasons why more and more manufacturers are going to 7 and 8 speeds under the present cut-throat competition for performance supremacy while trying to deliver decent cruising MPGs at the same time.
To be fair; hardly any everyday driver needs the 8sp. But, then, hardly any everyday driver needs 510HP in their car either. However, to keep up with the Jones's, with the Nissan GTR's close(r) ratio tranny or the new BMWs, Benz's etc. it is simply a must have.
BTW - You should NOT be shifting in the middle of turns. Close ratio transmissions do not require such practice.
Albert
#12
The 5L S/C XKR is quite the opposite in that it's traction limited. Your same 2nd gear run would be done in 3rd gear where you'd have more torque to the wheels, and quite likely more than the tires could handle. I get wheel spin at 50 mph in 3rd when I put the spurs to it while going straight, never mind in the twisties. The ECU is actually limiting torque to the wheels, not looking for more. The practical way to improve 5L XKR acceleration would be with all wheel drive.
But an 8 speed will have the marketing types all geared up so it's sure to come, unless they decide to give us something truly useful like hybid power with electric drive to the front wheels like they were originally touting for the C-X16!!!
Bruce
#13
You are correct, the 4.2 XK is both torque and power limited. For max performance it really needs a close ratio tranny. However, max performance is NOT what the XK is about. That is why Jaguar made the XKRs.
I purposely included my example of the 640 RWHP, 2400 lbs race car as the example to show that even that car is NOT traction limited in skilled hands.
Today's top ultra performance tires are just about as sticky as the racing slicks were 10-20 years ago. It is only a matter of driver skill to handle the power and traction for those ultra high powered cars. You do not slam on the accelerator coming out of a tight corners but, treat that pedal as if it was an fragile egg and sink it only, and still gradually, when the car is fully hooked up. I suspect that a significant reason for the GTR's supremacy on race tracks or in the 1/4 mile vs. most of everything else is its close ratio tranny. Of course, no doubt, 4 wheel drive also helps a great deal.
Albert
#16
Albert,
My comment about traction was made only to illustrate that the XKR is not lacking in torque via the gearbox in the gears you've found lacking...not to suggest there's a problem with maintaining traction itself As you discover in your brief XKR test drive, the DSC steps in to assist when those limits of grip are easily exceeded.
I've been impressed with the XKR gear spacing under track conditions where any mis-match in gearing and powerband are obvious to the skilled driver, so no need for you to speculate about its effectiveness, or whether it uses the same gearbox as the XK, as that wouldn't help anyways since the powerband of the XKR is completely different. But regardless, all XK's will likely get the 8 speed with the 2014 redesign and be even better for it.
I can't tell from the photos, but do you feel the side skirts have the "visual" effect of lowering the car more than the 8 mm drop would do on its own? I wonder if the springs and/or skirts would be available to retro fit to 2010-2013 XKR's not so equipped. That could be a factory solution to those wanting to change the "stance".
Bruce
My comment about traction was made only to illustrate that the XKR is not lacking in torque via the gearbox in the gears you've found lacking...not to suggest there's a problem with maintaining traction itself As you discover in your brief XKR test drive, the DSC steps in to assist when those limits of grip are easily exceeded.
I've been impressed with the XKR gear spacing under track conditions where any mis-match in gearing and powerband are obvious to the skilled driver, so no need for you to speculate about its effectiveness, or whether it uses the same gearbox as the XK, as that wouldn't help anyways since the powerband of the XKR is completely different. But regardless, all XK's will likely get the 8 speed with the 2014 redesign and be even better for it.
Bruce
Last edited by Bruce H.; 08-07-2012 at 05:53 AM.
#17
#20
It sat in Baltimore for 2 weeks, but was finally put on the truck yesterday. Dealer thought he would get it either late today, or sometime tomorrow. After he gets it, he said he would need 24 hours to do his thing, which includes switching out the wheels and installing the Mina exhaust. So, I should be driving it before the close of business on Thursday.