Here is what most don't understand. If your car started to feel like a dog down low after exhaust upgrade, that's actually good , and most likely it flows way better than stock, just needs an adjustment in the tune for the extra air.

 

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Would love to see what the standard xk 5l would do down the 1/4 mile .


There's nothing on dragtimes , the xf 5l is good for 13.9 with footage

 

I ran in the 13.4s, with my best pass being a.high 13.3. I don't have the time slips in front of me but I'd be happy to find them and post them. That might merit a separate post?

I used to drag race in a sort of informal "sleeper" street legal class, most of the cars were low 12s to high 11s. I had well over 500 passes in my car at the time which on it's best day did an 11.97, albeit with drag radials. When I took the Jag down the 1/4 I was unimpressed with the first 60' but at about the 1/8th mark it developed a serious amount of push, very different than I was used to. Jaguar obviously geared the car for high speed and the torque really doesn't seem to come online until you are above 50. In the three passes I made the car was still in 3rd by the end of the track meaning the it left a lot on the table. A 3.73 or 4.10 rear end swap would benefit that time substantially but I have no idea how you would accomplish the programming necessary to keep the car's systems from freaking out.

In case you are curious, this is what a 12.5 pass looks like outside and in:

 

Alright, I hobbled out to the Jag and pulled the timeslips out of the glove box. Here's the best pass:

60 ft - 2.0808
330 ft - 5.8039
1/8th ET - 8.8403
1/8th MPH - 81.46
1/4 ET - 13.3993
1.4 MPH - 107.40

I told you it was a very high 13.3.

Compared to what I am used to, the 60 foot time is slow. The Jag launches soft. I would like to see something down in the 1.8s. On the other hand that 107.4 at the top end with just a 13.3 says that the car is picking up hard on the long end. To put the into perspective most of my low 12 second passes were at 109mph. Basically the Jag is just not geared for the 1/4.

Post tune I'd like to see the number brute forced down to close to 13.1. The car is easily capable of it.

 

Good baseline numbers , it's faster than I expected! My car started out 13.4 in 1/4 as well, at 2300 DA my trap was also identical to yours at 107.
I'd love to see what your does tuned!

 

The true altitude around here is 1350 feet, I have no idea what the DA was that day. It was hot, and it's always humid here so aside from a few weeks in October it's generally always a bit on the slow side track wise.

 

That's a very strong mph (107.4) for a untouched n/a 5l I'm quite shocked actually !! Your on par with a 420hp xkr even thought your down alot of hp are you sure it's completely standard ??

My decatted and tuned 4.2 xk is dead on with yours at the 1/8 mile mark 8.8 @80mph and same 60ft , but by the end of the 1/4 mile I'm down .4 and a fair bit of mph (6mph)
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With diff ratio in the gen 2 we can go 3.58 (lincoln / thunderbird) without issues you have the gen 3 diff so your stuck with the 3.31 unfortunately no options there .

I'm yet to go down the strip with the new diff ratio 3.58 and enlarged throttle 81mm at best I'd be most likely 13.4-13.5 .

With a tune on yours , a X pipe and free flowing cats you'd have to be at 12.7/8 and 111-112mph

 

Steve how did you get the TB to 81mm? Is it same that's on Xkr?

 

Maxbore managed to increase sizing from memory 76 to 81mm a overall increased flow rate of 8%

 

Ahh ok I thought maximum that Maxbore could do from stock 75 to 78mm .

 

Stock 76mm
Maxbore 81mm

As the xkr has a different throttle body unsure how far it can be bored out

 

Thanks. with only 20K miles, I'd expect the trans fluid to be in good shape, but I'll check it out. Will also do a reset of the ECM. My car seems to take itself out of Sport mode if I drive it too long in a casual manner. Is that typical? it only seems to go back to sport if I click over to Drive and then back to Sport. The car will immediately down shift and resume the high-revving shift points as long as I continue driving it spiritedly... But if I get into traffic for any length of time, it seems to go to Drive and stay there though the selector remains in sport.

 

The first car I had with paddle shifters was a 2008 BMW 135i... Both paddles shifted up and down and that car worked wonderfully (it was also, with a JB4 tune, faster than my XK) (but it is in no way comparable... The Jag is a keeper)... I was shocked to find other cars shifted up one side and down the other like the XK, which to me is strictly a cost issue. Regardless, I rarely shifted the BMW or the XK manually, though the Jag requires it more often. Now, if the XK came with an actual manual, that'd be a different story.

 

I'd like to say that I'm just that awesome of a driver, but we are talking about a drag race here. I guess I could claim that I have an extremely heavy right foot. And yes mine is bone stock, verified as such by the local Jaguar guru before I purchased it and I certainly haven't done anything to it. I will say that the car really woke up at the 1/8th mark and developed some serious push. It was unlike anything I am used to. I made 3 passes that day and all of them were at 107mph, the other two were low 13.4 passes and I suspect those times reflected heat saturation in the engine as all I was doing to cool down between passes was prop the hood open.

That 12.7 goal is tempting but I also know that once that bug has bit it's a never ending push to just take another tenth off. I've been there. I'll be thrilled if I can break into the 13.1s.

 

For what it's worth mine acts exactly that same way.

 

Going off what I've seen the xf 5l do I was expecting yours to be around the 13.5-13.7 and 103-105 , nevertheless very very impressive for a stock 5L.

With a few tweaks a can see you easily dropping into the 12sec region . Nice going !

 

You should try mine then

 

Has anyone on here ACTUALLY tuned their 5.0L XK ?
I'd really like to hear some feed back, I still really want to do mine
but I can't get my LTFT to balance. must have a leak somewhere

 

Next level ^^^^^