alright, if not mistaken the XJ8 is limited to 149-150mph and the XJR is limited to 155mph.

Now anyone who have driven these cars know good and well these cars can go beyond that. But the question is what is the true top speed of the XJR and XJ8? Or maybe an estimate.

The 1988-1991 MBZ 560SEL top speed on paper 149 mph. Real life test (On the autobahn legally) was 155mph.

1991 BMW 750il (the V-12 of the e32) limited to 150 but a "flashed" (Limiter removed) was clocked at 180mph.

1995 Cadillac Fleetwood limited at 120 mph but I flashed it and it got to 150mph (NOT SAFE ON TURNS!!). Remember this is the one with the LT-1 corvette engine so no telling what is the limit on this car if the ECU and engine is tweaked.

Today most BMWs(V-12s included) , MBZs (Non-AMG V-12s)(1992-2006) , and Jags are limited to 155mph. 2007 up MBZ V8 limited to 130(curious about that decision.).
So given that many of these makers been making cars that have been capable to achieving 150mph since the 80s, I wonder what is the true speed of these cars today especially since a 1991 750il achieved 180 whose engine have about the same horsepower as the entry level 2006 XJ8 and and less than the XJR, MBZ S500/S550 and BMW 750li.

 

I've heard that with the limiter removed the XJR should reach 275km/h (about 171mph). The aerodynamics isn't as good as on the beemers and mercs. And I've also heard that it doesn't drive well at all when you start getting close to 150mph, also due to the aerodynamics. Apparently the nose gets very light. I've never taken mine over 130mph, so I have no personal experience...

 

I've done 150mph once in my XJ8 and it was all very nice for the 30 seconds or so I was there, but that was a silly thing to do...officer.

I've got it on very good authority that in development tests, an unrestricted XJR, in standard set up, touched inside of 200mph.

But lets be honest with ourselves, where in today's world of speed cameras, speed planes and a police force who have Jaguar XFR police cars can you do 155 MPH?

 

When running 1/4mile I can see end speed almost 190km/h ( 117-118mph ) on the speedometer, but it's officially just 170km ( 105.7mph ). . My car has 255/35/18 tires, which have 2.75% smaller circumreferences than stock 245/40/18.

Personally I would make the following upgrades if try to reach max speed ( in my XJR the speed limiter has been deactivated ):

1. Arden front spoiler
2. 25-30mm lowered spring set
3. " Selectable Steering Weight . Allows the driver to switch between normal and enhanced steering weight and feel. "
Jaguar Supercharger Upgrade | Jaguar Supercharger

 

Doesn't the steering go to the heavier setting automatically at high speeds?

 

If the more powerful and more aerodynamic E39 M5 can't do over 185mph (300km/h) unrestricted, it seems a bit strange that our beloved XJR would be faster...

 

Well I guess one of Jaguar's lead Test Driver is wrong. I'll get him on the phone now and tell him what he saw that day was not correct and that it was all wrong. I mean he was only involved with XJR test & development from 1997-2002 so there is a lot of space for error.

 

Whoa 150mph in a Cadilllac Fleetwood?!! What did that feel like?! How did it handle with those aerodynamics and soft suspension and how loud was the wind?

 

I guess the M5 is hitting it's rev limiter on sixth @185mph then...

 

Well the man in question is a family friend and I asked him all about the 308 when I had the chance. He told me what they (the engineers) wanted to do and what the accountants wanted were two different things. He hinted that if they'd been allowed to develop the 200mph saloon, it would've been game over for Ze Germans. However it wasn't seen that way and the direction it took changed.

The same man also told me they were toying with putting diesel engines into Jags back in the 90s but the Company were having none of it saying "There will never be a diesel engine in a Jaguar!" Well how wrong were they? If only they'd listened...

 

What is the mechanical max speed?

(rev limit X 5th-gear ratio X differential ratio, if not 1:1) = RPM at the wheels
then multiply by the tire rotational-length (outermost-diameter x pi) and then convert inches-per-minute of travel to MPH.

 

Straight line it was straight, a bit floaty. On one hand the steering feels very light but on the other hand you have to turn the steering wheel a bit in these cars in anysituation to get the front end to move. Lets say it was like driving a speed boat. And like a speed boat this bloody thing do not stop on a dime. It was fun to do but not something I would volunteer for again.

 

Potential Speed Calculator

 

Not so much stranger than the 91 BMW v-12 clocked 181 and it was no where near as aerodynamic as the E39, and less powerful and heavier but the e39 M5, the crown Jewel of BMW, only 185 aerodynamic limited to 185? That dont sound like much improvement overall. I mean even the brick front twice as heavy Arnage of that era was electronically limited to 155mph (with BMW V-8 twin turbo engine). Think the Red Label was limited to that one too or 160 with the 6.75 with the old 4-speed GM sourced tranny. Contiental GT goes 200mph+ with essencially is the same engine as the VW Phaeton and Audi A8 W12 which both are limited to 155mph.
I havent tested the limits of this XJ and probably wont be able to around here until I get to mid-nowhere Texas (between El Paso and Midland) where there is a good stretch of mostly unoccupied road where the speed limit is already 80 and some places 85. From what I gather, steering feel is the not going to be issue as the steering seems to get more hefty with speed. The 88 MBZ starts with hefty steering so some people find it "hard to turn" at low speeds and dont get it until I explain that when doing 130+ on the autobahn it comes in handy.

 

Haha Stu... is that sarcasm I'm sensing?

I can sort of buy that the X308 can go that
high... the E46 M3 can do 300kph, with 333hp,
and 265tq... although it may be more aero-
dynamic, the XJR is far more powerful, and
has longer gears.

Ihave always heard mid-170s were de-limited
tops on an XJR, but it's thrilling to hear that they
are near 200! Remember, the E60 M5 with no
limiter could do 206 with 502hp. (again, much
less drag though)

I do not believe, though, that the V12 '91 BMW
could do 181. Downhill, with a 30mph tailwind and
a 30 mile straight on a cold day, maybe... but
a standard XJ8 would rape one of those in a
straight line.

And Stu, from experience I agree, the X308
is rock solid at speed. My friend with an
E39 M5 said my car felt about the same as his
at high speed (except more wind noise), and
praise doesn't come much higher than that.

Ian

 

out in Arizona there a quite a few lonely stretches of road, and 150-155mph
can be reached pretty easily, The car is on standard size tires, and a K&N filter, so not really modified. She pull hard up to 155 and feels like there's more to go, trans was in sport mode, steering was normal and did not feel light.
99XJR with 198,000 miles.

 

ok, I'll bite. About this limiter removal...

 

Interesting stuff, and I don't doubt for one second that they reached 200mph (or close to) during development. It's the part about it being a standard production model that I find very hard to believe.

BTW, I read somewhere that the front wheel bearings of the X308 are different from the ones in X300, because they were designed to accept drive shafts... do you happen to know if a four wheel drive X308 was ever planned?

 

The ZF 5hp24 does come in AWD form. I think it is used in some kinda Audi and other vehicles. The seal kit I got when I did my A drum was for an AWD. I dont really remember splined holes in the front hubs though.

 

Originally it was designed to be AWD. Most ZF transmissions come in an AWD format and been so for long time. The old ZF4 used in the X300 was also used in BMWs, Porsche for RR setup and even Land Rover 4WD. Not sure about the current ZF 5 transmissions, but the old ones had removable bellhousings to fit different applications for just about any car that used the ZF transmission with of course changing out the output shaft for the specific car (BMW alone had four different output shafts for the ZF4hp22 (three prong, four prong, circle, and CV) that varied on model and even by specific production date) although making the 2wd fit 4wd took a little more work as you had to get the front 4wd bellhousing and transfer case. But essentially, the main body casing was all the same.
Ironically the idea was scrapped for the X308 very late in development hence the presence of bearings that would normally be found on 4wd vehicles. but I think the new ones can be had with AWD. I bet though, you might be able to make the X308 AWD but probably will change the dynamics of the car.