XJ8 top speed
 

Greetings. I'm sure this has been discussed but I haven't found a definitive answer. Top speed of US and Canadian 2004+ XJ8 is limited to 121. Quite disappointing given the cars potential. Curiously, I saw that the new 2011 base XJ is also limited to 121. Assuming properly rated tires, I'd like to be able to override the limiter. Plenty of programmers available for other vehicles, and in fact have successfully used a Superchips Flashpaq on my F150 to change this parameter(I know, I know...not the same thing). However, I haven't found anything of a similar ilk for the Jag. Anyone gone down this road with any success? Thanks in advance.

Sorry, posted to wrong area
 

Sorry. I just realized I should have posted this in the 2004-newer section.

Well, unless I am sadly mistaken and my eyes crossed, I do believe I had mine well over 120mph just a cpl weeks ago.

I am quite confident I have read that the car is limited at 155mph but I won't swear to this, nor do I ever intend to find out if it will make it, lol.

My 06 is limited to 129.. reason is simple, the US-Spec cars come from the factory with H speed rated tires. Reason is, if Americans need to replace the rubber on their $65K+ car in less than 20k miles they go bananas...

Idrovemy 04 xjr cross country, in montana where the speed limit is 75 but really I was averaging 110 90% of the time, I got my car up to around 137 mark. quite exhilarating...

You guys need to try riding motorbikes for some real thrills! ;)

Ya, did 90 MPH on my 01 Shadow. That was fast enough in the open wind for me. I do believe the earlier x350 are limited to 155 MPH.

The 2011 XJ Supercharged top speed is limited to 155--it has ZR rated tires.

I have a 2005 Jaguar XJ8L model with the 4.2L engine that I purchased in January 2014. It was originally a Florida vehicle, and it came with Pirelli P235/50 ZR18 97W tires. Does anyone else know what the top speed would be for that vehicle in the United States?

Well, I did take my 2005 Jaguar XJ8L on a trip along the expressway to Indiana last May to pick up some specialized fireworks. I didn't set the transmission in Sport Mode at the time, but I did clock 110 MPH briefly on the way there. Unfortunately, I had to take my foot off the accelerator at that point because of approaching traffic up ahead.

My hands were a little greasy at the wheel too so I'm not sure if I would have dared to open up the throttle much more anyway. What I can tell you is that 110 MPH is fast enough for anyone.

Has anyone else taken their Jaguar XJ8s (with the standard 294 HP engine) out for a spin? I'm just curious as to what the top speed of that vehicle is (in the United States).

I have an 05/XJ8L and no where do I see where it is limited to 121 MPH. It says in the book that it is electronically limited to 155. If your using the speed limiter to try to get above 121, I haven't even thought about that but, the limiter it's self may have a top speed of 121. I believe if you forget about the limiter and just go out and punch it, I think your hands will be a little greasy too. Mine were as the speed-O passed the 130 tick, so I backed off too. The car just sat there as the air suspension lowered it down to the road as designed. An important feature one looses when he switches to plain old springs.
121? Never heard of such a thing.

Interesting point about lower speed rated tyres (tires,sorry) I know that my old 308 is limited to 249 KPH and because of that the tires needed to be 300 KPH rated to appease the road registering folk,should they check.

To lower the limited speed because the factory fitted lower speed rated tires should be easy to bypass for the right person. It also points to some-one got cheap seeing little 4 cylinders stuff achieving 120mph.

X350 for North America is limited to 121 MPH for all naturally aspirated vehicles. This is well documented. All supercharged vehicles (Super V8, XJR, and 06 Portfolio) are limited to 155 MPH worldwide. Anyone saying otherwise has either a modified vehicle or is misinformed. This information is readily available. In fact here is an exerpt from Jaguars press release for the then new X350:

JAGUAR INTRODUCES ALL-NEW 2004 XJ RANGE FOR 2004

Embargo release date: 21st December 2002 00:01:00

This Press release has to be one of the longest Jaguar has ever put out! Here it is in its entirety. Note that this is a USA originated document and that some details may not apply to other markets such as the UK.

"The new XJ is both quicker and more economical across the board than the outgoing generation – and many of its competitors. As an example, the quickest model in the new XJ range, the XJR, dispatches the 0-60 mph sprint in just 5.0 seconds and has a top speed electronically limited to 155 mph. The XJ8 records 6.3 seconds 0-60 mph and has a top speed electronically limited to 121 mph."

http://www.jag-lovers.org/x350spec2112.php

So for anyone who wants to argue the point, this is an official Jaguar Cars Ltd. document. I find anything else on the internet subject to interpretation, including Wikipedia and various non-instrumented reviews.

PS. I have had my 06 XJ8L up right at the limiter several times. There is no fuel cut off as in rev limited japanese cars. The engine was turning around 3400 rpms ( I beleive I was in 5th gear, but have no way to know for certain.) My hands were quite steady and dry and the car was planted, stable and quite comfortable at that speed. I believe as long as the road allowed, it would happily have run at that rate all day long. I felt no need to "back off" at all except for knowing my luck to have the road to myself for much longer was limited as well. The only noticeable sensation other than speed was some wind noise around the sunroof. I doubt I would be able to ride at the XJR's limited 155 mph for more than a very brief time. I am not THAT crazy.

top speed
 

Yes that is correct Blaireware, thanks....

It did seem to me that I may had been approaching the limiter when I briefly reached 110 MPH on the way to Indiana, but I did not have the transmission in 'Sport Mode' (if that means anything in this case) at the time.

What I do know is that the vehicle had Pirelli "W" rated tyres when I acquired it last March, and those are good for up to 150 MPH.

With the coil/spring suspension that I have on the vehicle, will that tend to make the front end 'light' at speeds above 110 MPH?

RICKKK
Since you do not have the air ride suspension, I would say yes. The car as it came had air suspension and that has the feature of lowering the car at higher speeds. This causes less wind interference, helping the car "hug" the road. With just coil springs, it doesn't have that feature , thus allowing wind to better get under the car, thus lighter front end. Lower speeds are your best safety bet.

Thanks for the info. My XJ8L is plenty fast for me, especially in Sport Mode.

What's the idea of putting speed limiters in the Jags sold in the United States to begin with? I wouldn't imagine that it would be in Jaguar's interest to do so. Is this federal law?

If the limiter was removed from my 2005 XJ8L, I wonder what the top speed that the 4.2L would be capable of delivering.

I keep reading comments made by forum members about the [Sport Mode]. Some must think that if they have selected the Sport Mode, it has an affect on car speed---that is, the car will go faster if in the Sport Mode.
The Sport Mode does basically one thing: If the driver selects the sport mode, what ever gear he is in--left or right side of the "J" gate--from a stop, the longer he holds his foot down the longer the transmission will stay in (left side of J gate) 2nd, then third, then fourth, then 5th gear. IE; If he has the shift lever in 4th gear and mashes the gas pedal, the transmission will not shift up to fifth until either the driver backs off on the gas, or the engine reaches an RPM it deems necessary to up shift. Same reaction if on the right side of the J gate, except here from a stop the transmission starts in 1st gear. With the selector in the drive slot (D), from a stop it will go from 1st to 5th. When he lets up on the gas then it will go into 6th--if your car has a 6 speed. Nothing else! It won't make the car go any faster at top speed. The Sport Mode will just allow the driver to possibly get to that top speed (what ever he thinks his car is limited to) somewhat faster, depending on how hard he wants the engine to work. IE; How high he wants that engine RPM to get.

From what I could gather, the speed limiter for the 6-speed XJ8's can easily be overridden by simply staying in 'Sport Mode', and J-gating in 5th. Apparently, as soon as the engine has reached a certain RPM in 5th, the vehicle will automatically switch over to 6th. At that point, a few more mph will be attained.

That "Jaguar Document" about top speeds is a good read if you have a 2002 straight XJ8, but I see nothing that mentions anything younger then that. Those were good cars, but to compare a document put out by Jaguar referencing 2002 cars, to say, an 04 or 05 XJ8 or XJ8L car, is a bit off the track. These cars look a lot similar, but once pass the looks there is no comparison--with the exception of maybe some mechanical issues--. Just to mention one aspect, the 05 cars, with the exception of a few under body suspension parts, are ALL aluminum--built like an airplane--with rivets and adhesives. Nuts and bolts used only to hold on finders etc. Yes sir, quite a different CAT. So the comment that all US Jaguars are limited to 121 MPH, is a mute statement.

2004 XJ8 & Sport mode - one man's opinion
 

In my personal experience with my 2004 XJ8, also an aluminum bodied car, I found that the real world action of the selection of Sport Mode mirrored what the driver's handbook stated.


If I chose Sport Mode on EITHER side of the J-gate the upshift RPM's in full auto were extended to about 6600-6700 (based on tach readings). To the extent that such an increase keeps the car closer to it's horsepower and torque peaks it would in each gear give a higher speed that it would have attained had it shifted at it's more normal 6000-6100 RPM's,. and it would get there quicker. The shift points are slightly more aggressive but still very smooth in each gear all the way through to 6th with a similar run to 67-6800 in each successive gear.


Since both 5th and 6th gears are in fact overdrive ratios designed for higher mileage and quieter cruising they wouldn't be my choice for a top speed run. I'd pick 5th and maybe even 4th as that would certainly keep the engine nearer it's power peak in the RPM range. With maximum HP (293) coming at 6100-6150 RPM's and torque peaking at just about 400lbs. at 4200-4300 RPM's you can see that keeping it limited to about 3400 RPM's in either 5th or 6th as was seen by Blairware in a post on 12/21/2014 is well short of the motors potential even given an increase in aerodynamic drag as the speed picks up.

I'd think that if the speed were NOT electronically limited the XJ8 would be capable of something near 135. Given that in 2004 the standard 17" and optional 18" wheels came fitted with "H" rated tires with a speed rating of 130mph a limit of 122mph makes sense. Oddly enough the 19" & 20" wheels came equipped with "Y" rated tires that max out at 186 mph!

Not really Chuck as electronic speed limiters don't care if the car is 3800 libs or 4000 lbs. as they are calculated to react to the computerized speedometer's speed reading. The fact that the car weighs some 200 lbs. less than a similar steel bodied car (that's all the difference there is) just makes it a slightly faster accelerating car and more fuel efficient.

Both 5th and 6th are overdrive gears and thus don't allow the engine to operate at it's full potential. If anything 6th gear would reduce the top speed in a speed unlimited car although maybe not in our limited XJ8's.

When I took possession of my 2005 Jaguar XJ8L last March, it was equpped with Pirelli P235/50 ZR18 97W tires. What I also know is that the original owner sold the car to a Florida woman with roughly 40,000 miles on the odometer. It had about 78,400 miles on the odometer by the time that the woman traded it in to a Florida dealer in the Fall of 2013. I believe that she decided to peddle it some time after air suspension problems started developing (and attacking her pocketbook). Well, enough with the history.

After changing the air suspension over to coil/shocks, I purchased a set of Bridgestone "W" rated tires for the vehicle a week later. I'm guessing that the Pirelli tires were still the originals so I can't help wondering why that particular vehicle with a speed limiter on it would be equipped with 150 MPH rated tires.

According to the Jag literature I have the standard tire for a 2005 XJ8L was"


2005 XJ8, XJ8L 235/50 HR18 All Season Dynamic 8-Spoke 8x18

Well, apparently either the original owner or the Florida woman requested the higher rated tires. It seems plausible that the car is capable of attaining nearly 135 MPH, and that sounds about right to me.

Huh? That is the press release for the X350 so is very relevant!

The non supercharged 4.2L X350 in the rest of the world was limited to 155mph so the US version should be able to at least achieve that with the 121MPH limit removed as it is only 6bhp down on those cars.

As a guide the UK 3.0L V6 X350 had a top speed of 145mph and the 3.5L 150mph. The 4.2L XJ8 and XJR were limited to 155mph.

Would the non-supercharged versions of the 4.2 liter have enough horsepower to overcome the air resistance in attaining 155 MPH?

The 4.0L XK8 had 290bhp and that was also limited to 155mph so I don't think it is out of the question. I had my 1996 XJ12 up to an indicated 150mph and it still had some more to go.

my 1994 xj12 would only do 130 it had 4 speed, as for xk models they have always been governed at 155.

124 mph or so
 

My 04 xj8 will do

200 kmh or 124 mph or so....

Limiter takes over and holds the car back, she is still accelerating nicely intill the limiter kicks in.

Have had it there MANY times.... I will try in 5 the gear next time and see what it does. I doubt it will override the limiter!

Tom

This reminds me of USA S-Types apparently being limited whereas non-USA ones are not (by way of example my STR came with ZR tyres). I suppose it would be some sort of geographically-based marketing/etc reason.

Can you not simply program in one of the software versions from another region? Quite cheap to try.

Just Might Be 155 MPH
 

I’ll Gladly Be That Dare Devil. I Once Had A 2004 XJR & It Did Every Bit Of 170 MPH . 155 is nothing I’ll Be Getting a XJ8 VP (vanden plas)

Well, when I did reach 110 MPH at the time, I also began to smell fumes. It seems that I also smell fumes sometimes when I really step on the gas. In any case, the 2005 Jaguar XJ8L was earlier converted over to coil/springs so I'm not sure that I would have wanted to take the car over 130 MPH anyway (as the front end would likely begin getting light). In addition, I was rapidly approaching traffic down the expressway so I had to back off on the accelerator. Yes, my hands began feeling 'greasy' too.

Top speed with limit is 155

Have yet to see what top end is, i know a hundred is nothing when passing someone if your not watching just how fast you are going.

100+ is just a tap of the pedal on a SV8

Top speeds are computer limited
 

I've seen repeatedly over the years that the non-SC cars are limited to the low 120's while the SC cars are limited to 155, at least here in the states where we have the space in some areas to really let them rip.

Why that may be so is up for debate but I suspect it's tied to liability, tire ratings and durability, and most importantly (and tellingly) the governments not wanting the roads flooded with cars that can easily outrun the state troopers whose cars generally top out at 150.


That doesn't mean that some tuner somewhere can't 'hack' the system but I suspect for the vast majority of original Jaguar buyers speeds over 100 are generally not high on their list of priorities. Besides if they wanted a land based missile their are any number of foreign and domestic offerings that offer such thrills for less money.

In any case 100mph or more is easily achievable by both the SC and non-SC models with either 4.0 or 4.2 V8's and getting their is probably achievable in under 15 seconds or less. Next time you rocket by some lane lizard who is doing 60 in the passing lane consider what would happen if he, or she, were to suddenly switch lanes as you approached out of fear...which over rides thought.

The thought of it is bad, just bad.