According from numerous tests the XK 4.2 can achieve a 1/4 mile in roughly 97/98mph at 14.4

I have achieved a officially time of 13.9 @101.5mph with only a custom dyno tune and 100 cell cats and an unofficial time of 13.7 @102.7mph with further exhaust modifications including the crossover x-pipe in place of the two resonators I had.

The next 1/4 mile test will be conducted very shortly as I have had my tune re-modified removing all torque limiters and increasing the flow of back pressure to account for the exhaust mods(100 cell cats + x-pipes)

After I have an offical time on the new tune my next mod will be installing the 3.58 gear ratios and if still not happy perhaps look at fabricating a set of headers I guess my goal at this stage is running a mid to low 13 e.t @103-105mph with the n/a 4.2

 

Sorry, another old thread revival but I am doing research for my new car

The build sheet for my 2010 XKR says that it has a 6HP28 gearbox (VIN B38274) and the press release for the 2010MY mentions the gearbox as well:

Jaguar’s acclaimed electronically controlled, six-speed ZF 6HP28 transmission offers an unparalleled combination of driver control matched to virtually undetectable gearshifts. With control either from steering wheel-mounted paddles or full automatic mode via the JaguarDrive Selector™, the new XK range delivers exhilarating performance.The supercharged V8 engine with 510PS and 625Nm of torque transmits power through an uprated version of the ZF 6HP28, additional clutch plates and an uprated torque converter having been added to the transmission to accommodate the extra power.

 

I don't think the VIN numbering is absolutely sequential. I helped another forum member local to me with my SDD setup earlier this year, his car has a VIN number about 8000 lower than mine, my car is identified as MY2008 and his as MY2009. His car has the slightly updated infotainment screen too, with the light blue colour scheme, mine has the earlier olive colour scheme.

I've also heard of owners of 5.0 cars with VIN numbers lower than the last 4.2s. I think Jaguar probably manufactured chassis' in batches and stamped them with VINs as they came off the line but didn't pull them in to the factory strictly in sequential order. Could be they had stocks of coupe shells and convertible shells ready to go and pulled them in as required to fulfill customer orders, but that's just one theory.

There's a member on the UK-based forum who lives in Finland I think, his car is B00031 if I remember rightly. According to the EPC and other service literature, the earliest production X150 had a VIN of B00379 or thereabouts so he maybe has an ex-press demonstrator or something. Sorry for the off-topic but thought it was sort of relevant given the above post.

 

One of the parameters that rarely is discussed when horsepower numbers are thrown around is weight.

While adding horsepower appears, on the surface at least, to be relatively simple, a performance gain is to be had by making the vehicle lighter. Despite the increase in horsepower, a combination of weight reduction and chassis tuning are required to extract the highest levels of performance. Included in that list are the tyres, which ultimately limit the amount of power that is transferred to the road/track.

As part of this discussion, it would be interesting to see if anyone has taken the approach of attempting to lighten their X150 as a means of improving performance.

 

having been down this road many times with both cars and motorcycles, the gains just aren't worth the effort unless you're willing to completely gut it. You can screw around with shaving five pounds off a wheel/tire combo or removing the spare tire and floor mats and while yes, it does make a difference on paper, you're just not going to feel it on the street. Consider too, a lighter wheel/tire combo is going to cost $3k+ and a 40-50 hp gain from a tune is under a grand.

But, I know plenty of people that'll spend thousands of bucks to save a pound or two when a couple hours a week in the gym would do the same thing.

That having been said... I do believe there's probably about a thousand pounds that could come out of a coupe if you went whole hog on the weight reduction. But at that point, it's not going to be very livable.

 

I agree with you and I ask the question to see if anyone has gone so far as to remove 'unnecessary' parts of the car.

 

Personally, all I've taken off my XKR has been the engine cover and front half of the front fender liners, but that was done in an effort to reduce under hood temps. The weight of those items is inisgnificant, anyway. The only other part on the car that I can think of that you could realistically do without and not affect the daily livability would be the fart box that pipes engine noises into the cabin. But that whole thing is under five pounds, so the gains won't be felt.

In my experience gutting other cars in a serious effort to reduce weight, you don't notice butt dyno improvements until you've taken several hundred pounds off. At that point, you've removed most of the interior and some sound proofing. If you're legitimatey racing the car for money, every ounce counts. But for a street car, unless you're willing to sacrifice all the amenities and comfort, there's nothing you can do that will make the same difference a simple tune will. At least in a straight line. Handling and braking are different stories, but the same still applies to them- unless you're willing to make the same sacrifices, a good set of tires and pads will get you more than a few pounds here and there.

On a related note, I've been trying to score a cosmetically clean flooded car to do this exact thing to (and more), but they're going for more than I can justify for something submerged in salt water that doesnt run and with a salvage title. When the 4.2L XK's start hitting $5-6k for high mile clean examples, I'll bite.

 

I threw a several $k bid at that 2013 XKR-S that was flooded and on a salvage site listed by another member on here, I didn't expect to actually win, but it'd been worth it. Lots of extra parts and a facelift front end for me. Last I checked the bids were above $14,000. It's been gone for a few days now.

 

At those prices you will come out ahead if you submerge your own car in brine.

Bbout that facelift, its not that much of a change. Would go to the Ftype lights and frontend if really wanting that modern look. They are very easy to find and inexpensive.

 

...... which is why I wouldn't have paid more than that $4k, including delivery. Just the blower itself is worth that. -S rear spoiler is how much? Wheels and tires... lots of worthwhile goodies on it. Plus, owning the VIN to an -S is worth something. I'm not stupid enough to pay $14k for a barnacle-covered hunk of aluminum. Also, I don't care much for the grafted-on F-Type front end. That looks sorta ghetto to me.

 

That car will be shipped to Russia, and made whole again- very easily btw.