I added a 100+ horsepower modification today - relative to what a Jaguar XKR is


http://www.dfwx.com/jag.htm



The XKR as a performance road car is an illusion. So then work the illusion.


Learning that apparently Jaguar permanently crippled their XKRs with 1970s rear gearing used to get mileage out of 2 1/2 to 3 ton luxury cars ended my love affair with this car. No matter what performance mods I add, it is relatively speaking carrying a 1/2 ton steel plate under it in terms of acceleration.

However, it continues to serve the illusions purpose that was a main reason I bought it. And it's still a "nice" car. A "work" utility vehicle. Not a night prowler. A weekend cruiser with the Mrs.

Not today, though. We live on a road that is very popular for car and bike clubs to cruise on weekends. Thousands of them if the weather is good. Getting ready to leave I saw about a dozen late model Vettes go by the way we were headed - a small Vette car club. So the Jag not suitable. Too inferior.



Last night I tired having to find excuses to pull over or find ways to make certain a car was in front of me at redlines when there were late model Mustangs, Cudas, Chrysler 300Cs, Mercedes etc coming along side. While it still could be built to 500 horsepower, doing so would be a fool's play giving the terrible handicap it comes with. It would be easier to contend with a 5,000 curb weight than 3.03 rear gears in terms of acceleration.

As a parked car it completely serves the illusion of being a sophisticated performance car as most people can't even guess what brand it is unless they read the front growler emblem or rear deck stamping.

Since, the few comments of people who walk up to it has changed from "great looking car" to "how fast it is?" and "how many horsepower does it have?" For which I answer I don't really know how fast it goes and "a little over 500 horsepower." No one doubts it.

I didn't research enough before buying. I had figured 450 horsepower would cost $10K and 500 from $20K to $25k. But only a fool would figure upping a Jag would be cheap. It never occurred to me that Jaguar would have built into the computer unchangeable software to make it impossible to turn the XKR into a real semi-performance car in relation to other cars in the same weight, displacement and power class via their differential. Somehow knowing that, of performance potential in its class, the XKR is the slowest of them all has soured my respect for it. Rather, for me it is now a utilitarian car for appearances and it still works for that purpose.

Like the Beach Boys song, it's a "no go show boat." You can't "have your cake and eat it too" with a Jaguar. Vettes, Lotus Esprit etc all have the wrong appearance so weren't optional. An old guy in a Vette or an Esprit is not distinct around here -as common as Mustangs - and an Esprit too strongly would hint of later-mid-life crisis.A Jaguar XK8/R looks both sophisticated and performance oriented of someone who can sling some money around. In short, an accurate reflect of myself.


Had I know this, I would have saved $15K and gone for an XK8. There is no difference between being slower and a little less slower. Still, the illusion value of the Jaguar pays for itself. It's like one of the finer suits in my closet. Suitable for only certain occasions but all wrong for others.

I'll give an overseas call to Paramount this week to see if there is any way around the 3.03 half-ton lead weight differential gearing issue before giving up on the XKR as a personal enjoyment car. It appears to have been built to please product liability lawyers and government regulators. Customers exist for the car, rather than the other way around though. You buy the illusion, not a reality, of performance.

I like the emblem. That supercharger (R rather than 8) costs $15K added to the price. So show it off. The emblem appears OEM. No one knows what "R" stands for. They do know what "supercharged" means. "Keep it simple."

 

deaf ears here, but I understand. its marketing, if Jagaurs were as prevalent as a Corvette there would be alot of power to be had in the aftermarket as well. there is NOT enough demanding $$$ for companies to crank the factory ecu and rewrite software. On my Nissan we got Uprev in Auston to do Frontier,(they do 300/350/370Z's Titans and Infinities, But it took 20 people at $750 each for them to even consider and do Frontiers.
So if there was a better market for true performance upgrades to Jaguars, companies would do it. We build alot custom and more and more manufacturers come in. Ive got custom wheels being made now, and took a stock Stillen supercharger kit and modifyed to up power even more.(Plans are to machine a adapteer and install a much larger Whipple super charger to put out alot more power. Speaking of a Whipple, contact Avos on here about them, he's built his XKR into a 600 hp Jaguar useing one.

 

Well, it is unclear to me exactly what you are looking for, perhaps some sort of good looking, classy hot rod. As you said yourself, the XK8/R was not engineered, designed or built to be a high performance vehicle. This car was engineered as a GT, or Grand Tourer, a good looking, smooth riding, refined and classy vehicle with above adequate performance. The original XKE was actually a derivation of a Jaguar race car and was, early in its inception, more of a sports car. The XK8/R was never meant to be a sports car. I hope that you enjoy it, nonetheless. I just thought that I would mention, even though you may have considered it, that an alternative to gain that lower gearing ratio that you seek would be a smaller real tire circumference, effectively reducing the gear ratio. You could get smaller diameter wheels and or low profile tires, or some sort of combination (all around, of course). Anyway, you could calculate the gear ratio that you are looking for by the circumference of the rear tires now, to what you could change them to.

 

Hi, thanks for the comments.
If the computer reads lower gears I would think it would equally read smaller circumference tires, wouldn't it?

What irks me so much is that it appears a deliberate goal of keeping the XKR slower than it's counterparts solely for the sake of doing so. Gearing it for a 234 mph top speed with a 155 governed limit - thereby also then slashing it's acceleration ability - has no rational purpose other than making American lawyers and EU regulators happy. No one buys a $100K concerned about 3 mpg fuel economy one way or the other. Only G-men care about that.

Maybe they should put Ralph Nader's stamp of approval on it. The green-nish of my XKR is appropriate as in a Green Party grand touring car. Sure, everyone else's is faster, but ours gets 3 mpg better fuel economy so therefore is more friendly to polar bears.

Note: I was very seriously considering the Whipple etc route - ultimately a total upgrading I figured would run $20 to $25K. But 3.03 gears is such a horrific handicap it just seems a fool's play. To always have to make 20% more power just to be equal. 550 bhp and 3.72 gears is about all possibly useful in a rear wheel drive car weighing 2 tons (fuel and driver) on street tires for the 0-70ish contests. Any more power would just literally be spinning your tires. Accordingly, if that goal could have been obtained, my XKR would always be viable regardless of what else comes out next year. To go faster would then mean softer tires or finding weight reduction, not more horsepower.

I also don't like what long gears do in terms of corners, but that is a sense-impression thing. Long gears not only affect performance, they also affect the sound and feel.

This all just seems bizarre to me. Even if no company made performance parts for the motor, that can be gotten around anyway. If nothing else, just go wet NOS as a desperate course. But 3.03 gears? Why not 2.87? Ford made those too for their 3 ton Lincolns.

I understand Jaguar's logic but think it foolish. The Japanese are not as afraid of American lawyers and EU regulators. The Nissan GTR has 3.70 rear gears - allowing it to blow away every other car in it's weight, horsepower and price class (actually much cheaper) plus all wheel drive. That little thing, 3.70 gears, pushes the Nissan 1 1/2 seconds faster in the quarter and out accelerating everything as though it a brilliantly designed car.

I could understand Jag not having the $$ to keep up design wise. But gearing isn't a design challenge. So I am questioning their decision to keep their cars deliberately slower than the actually are in design, weight and horsepower.

I doubt there will be a single person who will not buy a GTR because it gets 4 mpg less than it's counterparts for the 3.70 rear gear nor 1 person who buys an XKR because it gets better gas mileage. So I believe it is a terrible marketing blunder. How many videos are going up to prove up other models are superior at much lower prices by their acceleration ability specifically in relation to the XKR? Their brands and models are fast - because they are faster than $100K Jaguars? Not a good rep for Jaguar. That is likely to worsen.

It may be the Jaguar's future is solely dependent on their 4 doors and the XK8/R (2 door sport models) are a vanishing breed.

Then again, that might be the result of having to beg a transmission off of Mercedes. Mercedes might have conditioned the sale on Jaguar agreeing to allow the transmission to slow down Jaguars.

How do the few Jaguar racing teams get around the computers? Do their XKs get thrown into the limp mode while racing?

 

Sorry for being so "down."
I'm not convinced (yet) this is incurable. I don't know if the computer can be altered. Some aspects possibly might be able to be made irrelevant or tricked. If all the instrumentation, cruise control etc, wasn't also tied into it, I'd consider just seeing it as a motor and transmission and try to go from scratch on engine management with an old school stand-alone engine management system to run the ignition and fuel injection system. I'm going to guess that is what racing teams do - just make the ECU, TCM etc irrelevant as in not connected?

 

OK, here is your last resort to try to turn your touring car into a street racer.
Good luck.

http://www.eurotekdesigns.com/main.html

 

Jaguar racing teams getting around the computers? Apparently, you think that a Jaguar, as set up by a Jaguar racing team, has some relation to the Jaguar that the public buys. If that is your perception, then, I don't really know what else to tell you, other than contacting the company that I told you about.

 

I don't mean to be so down on Jags and I do understand the difference between setting up a track car and a street car as in totally different creatures. However track cars need ECUs, speedometers etc too.

I presumed cams, cranks, rods, pistons, essentially anything internal, or any other substantive changes of any kind, would be either totally unavailable or totally cost prohibitive for a Jag. All that could be dealt with relatively easily as my goal would be at most a 20-25 percent power increase, though certainly it require compromises and much higher costs. I just never figured "impossible" in relation to gearing.

For example, with an XJS it requires replacing the motor, transmission, total suspension work and differential work. But it can be done.

"Can't be done" is a new one for me in the world of cars. It was "very costly and challenging" with Porsches, but never "can't be done."

I'm just surprised - as in totally caught off guard - about the differential gearing being totally tied into the computer system via the transmission and therefore unchangeable. Being an old guy I had no idea how much cars, or at least this one, is fly by wire and inalterably so.

If I can't find a way around the gearing limitation, I'd put performance money into a different car rather than the XRK - probably a generic US model (likely new Camaro) as those are what parts are most available for and any mods would start a second faster than the XKR in 0-70mph - though will research that in terms of the total drivetrain and computer challenges for Chevys now too first. I suspect about anything that goes on a Vette goes on a V-8 Camero of same vintage, but again I would check that first.

I'll make some calls and if there is a solution around the differential challenge I'll post it. It seems the real question is can the "limp mode" be killed and maybe if the automatic can be changed to manual shifting only. Probably not but I won't accept "can't be done" until I've run the course with it.

 

well the diffs being install as of mid year last year I beliec are now Quaife engineering units. and all replacements. You need new prop shaft, half shafts and the diff. and theyre very performance oriented.
http://www.quaife.co.uk/
when we were building the 07 XK for the Koni chakkenge series, we were gonna used a motec management system. Manual gearbox, no tcm.
But if you really are looking for more, why not buy the new XKR for 2011 with a limited speed of 175mph and 510hp(for now)
One of the things Tata(motors and owner) are looking to do is to take the XK into supercar status, this has been pushed around for awhile, but not under Ford managment was this gonna happen....

 

Did you see THIS??????


http://www.eurotekdesigns.com/main.html

 

Yes, I looked it over. Thanks.

 

$100K is over my budget and I'd run up against the same wall. 5s0 can be had out of the 4.2 and the 05 Coupe could shed an equal amount of weight or very close to it easy enough. It'd cost bucks, but I'd still be $40 to 50K ahead.

I hoping Paramount can put together a Quaife unit work with my 05 somehow in relation to the TCM - and I was planning exact that until this new insight. Overall, what I was looking at was a Whipple setup, larger intercooler and pump, headers, performance CATS and redoing the remainder of the exhaust, Aqua Mist water/alcohol injection, low temp theromostat and 3.73 gears. Don't carry the spare, 1/2 tank of fuel, save a few pounds on the exhaust.

That'd give it around a 3700 curb weight, 525 horsepower (I under-estimate) on 3.73 gears and 11 inches of rubber on the ground. That'd have done everything I need it to do, while still being fully streetable, non-hotroddish and still everything else that is "nice" about it.

If it can't be done, I guess I'll just have to come to terms with having a beautiful car that is "nice" to drive.

Understand my other Jag (I still have it) is an XJS with a 454 in it (NOT an SBC) - and that was my slow toy. The fast one was an early 928 with a custom turbo set and TEC stand-alone engine management system. Early model because the 16v 4.5 v8 models were lighter weight, had much lower rear ratio and stronger dual disc clutch. The latter 32V 5.0s are superior motors, but in inferior chassis for weight and those awful 3.0ish rear gear.

My fishing boat is a Pickle fork (tunnel) with a 502 that I have a Gale Banks dual turbo setup to put on it for this summer, with it replacing the old modified V with an old school tricked out L88 427. The XKR was to replace my XJS as my toy as it is outdated and is too hotroddish. I now sort of regret selling off the Whipple/water/air intercooler/fuel injection setup I had for the old XJS. I haven't driving it probably in a year and a half so figured time to get rid of the extras never put on it.

The only reason to mention any of that is that it should tell you that while I accept truly serious performance machines will best me (there will always be someone faster), it is never acceptable that something off-the-shelf and mass produced can best me 0-75mph unless it one of those truly super pricey machines - that you rarely see on the road and when you do they are babying them.

Someone pulling off the lot in a new Mustang or Chyrsler that is OEM and still besting me 0-75 is troubling. I'm not used to that with my best toy car - so it will be something new to accept. That's just how I am. If it's a Vette with turbos or a newish ZR1 or a Lambo, well that's just a different machine.

I'm just disappointed - mostly in myself. I thought I had carefully checked out the XKR before buying it in terms of performance and everything seemed perfect about it for all my goals. So I was particularly pleased. I had done the inquiries into lining up all the components. Figured it'd take about 6 months to pull all together. Then this insolvable glitch, if it is.

I didn't look into differential ratios because the wrong rear end was always replaceable in one way or another if necessary. I just didn't see a computer issue potential in that regards to rear end gearing. So it's my fault in the end.

A minor build up isn't really of interest going up against that wall. 390 horsepower and 450 horsepower are the same result on a 3.03 rear in relation to who would be beside me. 500 would make a difference, but not enough to justify the costs for benefit return. There is exactly no difference between being slower and slower-er than the other guy.

Where I'm at is 0-75 heaven for those who like that sort of thing. Its just how the roads are laid out and who cruises around here. Divided 4 lane state highways marked 55 to 60 that have redlights every few miles leading out to zero population. 0-70 contests won't even get you a ticket. Of course, low gears are the most critical modification - and one most don't make. It'd take well over 500 hp for an equal weight car to match the XKR if it had 4.10. 3.73 and mods, though, would be more multi-purpose suited.

With a 4.10 rear and upwards to 600 horsepower (that is not easily done with a 4.2 so I tend to more think in terms of 550), if I went non-DOT on the rear tires it could give a new ZR1 a good run to 75. Hey, if he wants to risk 100+ with 100 sheriff's deputies out there, he wins because I'm shut it down. 80 is about tops for me doing the redlight thing. If I go over 80, I do it alone on the road way out there somewhere. That is very rare and then only if the road is curvy.

Around here it's old guys who have the time and can afford expensive cars - but don't modify them much. OEM except maybe an exhaust and tires upgrade. They can be arrogant because they have $80, 90, 120K in their cars that leave kid's old hotrods and marginally upgraded little rice burners behind (the wanna-be fast-and-furious kids). Those old guys should have been easy marks.

Few things are more enjoyable than besting some old guy showing off his money in his costly late model car in something that cost much less. Somehow, it seems I just became put on the other teamp of being that old guy myself. So I'm not happy about it. I've been doing the 0-75ish redlight thing for over 4 decades. It's "just my thing."

This O5 XKR is a nice car. No question about that. Just look at the pictures on my first post above. Most people can't even hope for such a car - new or used. Most my life I couldn't either.

More power than you need for driving. And it looks fantastic. For most people it likely ideal. The convertible is a car women would love to drive or ride in. (Mine a coupe.)

If I have to accept that as the car's inherent limitations, then I do and will come to terms with it. But it's like people who resisting accepting retirement. I'm too young to retire from the redlights yet. I'm mid in my 50s, not mid 70s. Its too early to slow down. So I'm protesting that possible fate. The ragingness of my bloggish messages on this topic probably are more about myself than the Jag.

 

If there was an edit or delete feature, I'd use it. I had NO IDEA I rambled on that long. Don't bother reading it. (SORRY, SORRY)

 

I think if you check you will find the replacement diff kits Jaguar are using now are Dana units.

 

yeah i dont know about if theyre danas or quaife units since theyre not marked. But they do look like quaife units and theyre big in other areas of the world not in the US like Dana. So its a pressumption...
And Dfwx, I understand completely, no ramble, and not something I have grown out of either.
Nothing like gearing for quick of the line short burst action to show em up
the new 5.litre in the new Jaguars is a totally different engine. direct fuel injected into the cylinder with upto 2500psi fuel pressure. and alot of other changes that make the normally aspirated engine put out the same power your SC 4.2 does.

 

and you CAN edit you're own post...lower right corner of your post.

You are truly the master blogger.

 

I really have mixed feelings about the overall tone of the complaint here. On the one hand, I have had all sorts of cars within my particular budget fast ones (1970 RoadRunner 383, 1995 Corvette) and slow ones (1979 Toyota Supra, 2001 Audi 5000 Turbo, 1986 BMW 325 ES). I have never been disappointed with any of these cars while I owned them since I knew what I was getting. Going from my muscle-car RoadRunner to the Audi 5000 was disappointing in terms of performance but, at the time, the look and classiness of the Audi sedan was more important. Similarly, I knew that going from my Covette to the 2005 XKR would be a big stepdown in sheer fun and brute force but I had no illusions that the Jaguar was a Corvette.

If you feel somehow diminished by having all those rich guys around your neighborhood blowing the doors off your Jaguar, then spend about $25,000 or so and get a Suburu WRX and spend another couple of thousand and stick in a nitrous shot and you will be blowing their doors off--it that is what you want.

Doug

 

You don't need to spend so much, for less than half you already get so much more out of the car with a TS setup.

The amount of low end torque with the twin-screw is so much (pending on the pulley you choose), that you will have traction issues in 1st and 2nd and that is with LSD (standard 285 width tires). So changing gearing would not be needed for the 0-75 range imho, as the DSC would be working overtime giving you even a handicap.

 

Paramount says they'd have a Whipple set up for me in 2 months on a $7K pre-pay. A fair deal in your option? Anyone else offering to do it?

 

ok you two(Avos and Dfwx) time to hook up
Avos heres some interest ready to go and others have expressed as well. I think you can write a cnc program to make your pieces? sell as a kit for the above avg DIY and at the very least recoup your time and research putting it together......sounds to me like we finally have some people serious about getting out of the less than satisfying intake and exhaust mods, and doing something more substantial with a far greater bang for the buck